Favourite Virus Assignment: Parvovirus

Favourite Virus Assignment

Samantha Bray

BIOL 4904 – Virology

December 1st, 2015

Q1-1: What is your favourite virus?

My favourite virus is Parvovirus. This assignment will be answered mainly in the context

of canine parvovirus. If information about canine parvovirus could not be found the question will

be answered in the context of other parvoviruses such as adeno-associated virus, human

parvovirus B19, and minute virus of mice parvovirus (MVMp).

Q1-2: What type of genome does your virus use?

Canine parvovirus genome consists of a roughly 5000-nucleotide long linear strand of

either positive sense or negative sense single stranded DNA as their genome. However, the

negative sense stand may be favoured for packaging.1

Q1-3: Using http://viralzone.expasy.org/ (or similar resource), find a virion diagram of

your virus and explain its structure.

Figure 1. Parvovirus virion structure shows general capsid arrangement with T=1

symmetry and a ssDNA viral genome.2

Parvovirus has a spherical, icosahedral, self-assembling capsid that consists of 60 copies

of two types of capsid proteins, VP1 and VP2. The capsid has symmetry of T=1 and it encloses

the single stranded DNA genome. CPV is very small and is only 22 nm in diameter.3

Q2-1: What capsid structure does your virus use?

Parvovirus has an icosahedral capsid structure with a T=1 symmetry.3

Q2-2: Is your virus enveloped?

Parvovirus is a non-enveloped virus and is therefore called a naked virus.4

Q2-3: What is the typical ratio of infectious virus to viral particles produced during

infection with your virus?

http://viralzone.expasy.org/

When KB cells are infected with adeno-associated virus (AAV) they produce many

classes of particles that differed in the buoyancy is CsCl. They formed AAV particles that had

densities of 1.450 g/cm3, 1.410 g/cm3, 1.350 g/cm3, and 1.320 g/cm3. The only AAV particles

that were infectious had a density of 1.450 g/cm3 and 1.410 g/cm3 and they contained standard

full-length genomes. The AAV particles that had a density of 1.350 g/cm3 and 1.320 g/cm3

contained deleted or snap-back genomes and were therefore non infectious.5 Although I was

unable to find the typical ratio of infectious virus to viral particles I was able to find the particle

to infectivity ratio. For the 1.450 g/cm3 infectious particle is 20-100 fold higher than the 1.410

infectious particles that has a particle to infectivity ratio of less than 100:1.6

Q2-4: What host proteins are found in your virion?

The parvovirus virion is an extremely small virus therefore it carries genes for what is

absolutely necessary. Parvovirus encodes only what is absolutely necessary. They encode for

about 2-4 capsid proteins, mainly making VP1 and VP2 as well as NS1 and NS2 non-structural

protein.7

Q3-1: With the aid of the side diagram, explain each basic step of the viral replication

cycle of your virus. Indicate what steps apply to your virus (3A, 3B, 3C and 5A, 5B).

Step 1: Attachment to host receptors.8

Step 2a: Does not apply

Step 3a: Does not apply – parvovirus does not fuse with plasma membrane.

Step 3b: Mediates clathrin-coated endocytosis.

Step 3c: Virion penetrates host endosomal plasma membrane via pH drop to ~6.0 causing

permeabilization to gain entrance into cytoplasm.8

Step 4: Virion transported to nucleus via microtubule system. ssDNA penetrates into nucleus and

is converted to dsDNA by cellular polymerase. dsDNA is transcribed to give viral mRNAs, and

genomic DNA

Step 5a and Step 5b: Do not apply – virion exits through cell lysis.

Step 6: New virions are released into extracellular medium until they encounter a new target

cell.8

Q3-2: What type(s) of cellular receptors does your virus use for viral entry?

In dogs, parvovirus binds to host transferrin receptors to mediate viral entry through

dynamin dependent clathrin-coated endocytic vesicles.9

Q3-3: Find a research article figure depicting the replication of your virus over time.

Explain.

Essentially, the researchers inoculated CPV-2b strain into canine A-72 cell line that was

maintained in Dulbecco Minimal Essential Medium with 5% FCS in order to asses the kinetics

of canine parvovirus mRNA and viral DNA production during the course of infection. They took

samples of A-72 supernatants and criolysates at 24, 48, 72, and 86 hours post infection. They

extracted the RNA and DNA from the supernatants and criolysates with extraction kits. They

extracted RNA extracted from mock-infected A-72 cells as negative controls. They found that

they were able to detect viral NS2 mRNAs in the criolysate as early as 24 hours and at 38 hours

in the supernatant. They were able to detect DNA at 0 hours in the criolysate and 24 hours post

infection in the supernatant. Both viral mRNA and DNA loads increased in all of the trials.10

Q4-1: What type of polymerase replicates the genome of your virus? Explain how this

affects viral evolution. What are the main forces contributing to genomic variation in the

family of your virus?

Host cell DNA polymerase is responsible for replicating Parvovirus single stranded DNA

genome through a rolling hairpin mechanism. Parvovirus is able to improve its genetic economy

by utilizing host cell DNA polymerase. This affects viral evolution making a more efficient virus

that does not need to waste resources encoding their own viral polymerase.11 The main forces

contributing to genomic variation is recombination of NS1 genes and VP2 genes as well as the

fact that parvovirus even though it is a DNA virus has mutation rates similar to that of RNA

viruses.12

Q4-2: Find your favourite virus in the ICTV website taxonomy tree. Is your virus a type

species? Has the classification changed since the 2005 release?

My virus is not from an assigned order, but it is from Family Parvoviridae, Subfamily

Parvovirinae, Genus Parvovirus and Species Canine Parvovirus. The classification has not

changed since 2002. 13

Q5-1: Research another Bacteriophage. Make a table using 6 criteria describing the

similarities and differences between T7 and this virus.

Table 1. Similarities and differences between Bacteriophage lambda and Bacteriophage T7.

Criteria Bacteriophage lambda14 T7 Bacteriophage14

Capsid

Structure

Non-enveloped,

Icosahedral (T=7).

Non-enveloped

Icosahedral (T=7).

Genome Linear double stranded DNA with

cohesive ends (single stranded

extensions on either end).

Circular single stranded DNA.

Genome

Expression

Sequential Expression, early

genes, middle genes then late

genes. 14

Sequential Expression, early genes,

middle genes then late genes.

Genome Entry

Into Cell

Transcription via RNA

polymerase pulls the genome out

of the virion into the cell.

Requires mannose permease, a sugar

transport system. Is poorly

understood.

Viral Genome

Integration into

Host Genome

Not observed. Integrates viral genome into host

genome creating what is called a

lambda lysogen, which is capable of

turning off all host gene expression.14

Lytic or

Lysogenic

Lytic only. Capable of lytic or lysogenic cycles.

Q5-2: Describe a therapeutic use for phages in humans.

Oncotis, or ear infections are often hard to treat. Researchers created a bacteriophage

cocktail that consisted of five podoviruses and one myovirus. The viruses they selected

specifically target bacteria that are often found to cause ear infections. Using less than 1 million

phages, which is a relatively low dose, they were able to effectively treat the oncotic and provide

their patients with therapy.15

Q6-1: Research another Archaeovirus. Make a table using 6 criteria describing the

similarities and differences between SSV-1 and this virus.

Table 2. Similarities and differences between Sulfolobus Spindled Shaped Virus 1 and

Sulfolobus islandicus filamentous virus.

Criteria Sulfolobus Spindle Shaped Virus 1

(SSV-1)

Sulfolobus islandicus filamentous virus

(SIFV)

Genome Circular supercoiled dsDNA16 Linear dsDNA with modified terminal

end structures.17

Envelope Yes. Yes.

Viral

Genome

Integration

Into Host

Cell

Genome

Yes, carries integrase along in the

virion.16

No, does not carry integrase along in the

virion.17

Host Infects Crenarchaeota that are

hyperthermophilic, liking temperatures

above 80 C.

Infects Crenarchaeota that live in hot

springs.

Virion

Structure

Lemon shaped with short tail fibres at

one end.

Filamentous/rod shaped and each end has

three terminal tails.

Adsorption

Strategy

Virus attaches to host cells using their

tail fibres.18

Virus attaches to host cells using their

terminal tails as claws that fold upon

interaction.18

Q6-2: Does your favourite virus co-replicate with a satellite virus?

Dependoparvoviridae such as adeno-associated virus 1 and 2 (AAV-1, AAV-2) are able

to function as satellite viruses that do not have negative effects on the virus it co-replicates with.

AAV-1 and AAV-2 adeno-associated viruses have replication cycles that depends on the

coinfection with adenovirus or herpesvirus.19

Q6-3: Could your virus be inhibited by the natural or a synthetic CRISPR system?

Exhaustive literature research has resulted in no findings for inhibition of parvovirus by a

natural or synthetic CRISPR system. In a very general comparison however some researchers

have been able to inhibit the replication of other ssDNA viruses although they infect plants not

animals. Specifically they inhibited replication of beet severe curly top virus with

sgRNACRISPR-Cas9 through the introduction of mutations at target sequences.20

Q7-1: Research two other ssRNA+ viruses from different families. Make a table using 6

criteria describing the similarities and differences between Poliovirus and these viruses.

Table 3. Similarities and differences between Poliovirus, Cucumber Mosaic Virus, and

SARS (positive sense single stranded RNA viruses).

Criteria Poliovirus

(Family

Picornavirodae) 22

Cucumber Mosaic Virus

(Family Bromoviridae) 21

SARS (Family

Coronoviridae) 22

Virion

Structure

Non-enveloped,

Icosahedral capsid

(T=1), Small (30 nm).

Icosahedral capsid (T=3),

non-enveloped, Small (29

nm).

Very large (120-160 nm),

Sphere, enveloped,

studded with clubbed

spikes, Helical

nucleocapsid.

Genome

(all are

+ssRNA)

8 kb in length, 5’ end has

a viral protein (VPg),

and a polyadenylated

segment at the 3’ end.

9 kb in length, Segmented

genome into 3 RNA

molecules, 5’ end is capped

and 3’ end has tRNA like

structure.21

27-32 kb in length has a

5’ terminal cap and a

polyadenylated 3’ tail.

Pathology Poliomyelitis (paralysis). Sometimes is

asymptomatic,

Catastrophic Crop Loss

(because it infects plants)

In humans causes severe

acute respiratory illness,

fever, pneumonia,

hypoxemia, and death.

Fun Facts Translated all expressed

genes into a single

polyprotein that gets

cleaved into functional

units by viral encoded

proteinases. 22

The segmented genome is

not all packaged into a

single virion rather it is

packaged into many.

Allows a large genome to

be packaged into a small

particle.

Has the largest known

RNA genome that

encodes for over 20

proteins.

Viral

Entry

Virus binds to cell with

CD155 poliovirus

receptor mediating

causing a conformational

change that creates a

pore through the host

cell membrane allowing

the genome into the cell.

Virus enters through

natural wounds in the plant,

and then uses cell to cell

spread through junctions

such as plasmodesmata to

infect other cells.21

Spike protein binds to

host cell receptor

mediating fusion of

envelope with the host

cell membrane. 22

Proteins Encodes for 3-4 capsid

proteins, 1-3 proteinases,

and 6-8 proteins

associated with

replication.

Encodes for a genome

capping enzyme, a RNA

polymerase, a silencing

suppressor, movement and

capsid proteins.

Encodes for

approximately 12-16

replication proteins, 3-4

envelope proteins, one

nucleocapsid protein, and

4-6 other proteins.

Q8-1: Research two other -ssRNA viruses from different families. Make a table using 6

criteria describing the similarities and differences between Pneumoviruses and these

viruses.

Table 4. Similarities and differences between Pneumoviruses, Rabies Virus, and Ebola

Virus (negative sense single stranded RNA viruses).

Comparison

Criteria

Pneumoviruses 23 Rabies Virus 24 Ebola Virus 25

Taxonomy Order: Mononegavirales

Family: Paramyxoviridae

Genus: Pneumovirus

Order:

Mononegavirales

Family: Rhabdoviridae

Genus: Lyssavirus

Order: Mononegavirales

Family: Filoviridae

Genus: Ebolavirus

Clinical

Symptoms

Respiratory tract infection

Inflammation of the

brain (encephalitis). 24

Hemorrhagic fever

Replication

Strategy

Virus binds to host cell

with HN glycoprotein and

fuses with host cell

plasma membrane

releasing nucleocapsid

into cytoplasm. Genome

replicated by sequential

transcription.


with G glycoproteins,

mediates clathrin-

mediated endocytosis.

Virus fuses with

endosomal membrane

releasing nucleocapsid

into cytoplasm.

Genome replication

sequential transcription.


with GP glycoprotein

mediating pinocytosis

uptake of virus, virus

fuses with vesicle

membrane releasing

nucleocapsid into

cytoplasm. Genome

replication by sequential

transcription

Genome Linear -ssRNA, 15 kb,

encodes for 11 proteins

(NS1, NS2, N, P, M, SH,

G, F, M2, L)

Linear -ssRNA, 11 kb,

encodes for 5 proteins,

plus 4 more via

alternative initiation.

(N, M, G L, and P1 –

and through alternative

initiation P2, P3, P4,

and P5).

Linear -ssRNA, 18-19kb,

encodes for 7 proteins

(NP, vp35 vp40, GP, L,

vp30, vp24)

Viral

Transmission

Coughing releases viruses

hanging on respiratory

droplets that get inhaled

by others. 23

Transmission is

zoonotic, and through

animal bites.

Zoonotic, Person to

person infection is

through contact with

infectious body fluids.25

Virion

Structure

Enveloped and spherical

shaped virus.

Enveloped and bullet

shaped virus.

Enveloped and

filamentous shaped.

Q9-1: Identify a virus that can undergo genome reassortment. Draw a diagram that

explains which genome segment exchanges are most likely to promote virulence in a new

reassortant strain of this virus.

Influenza viruses have an ssRNA genome and are classified into types A, B and C

depending on core proteins. Type A viruses are further subdivided according to their envelope

glycoproteins with haemagglutinin (HA) or neuraminidase (NA) activity. The use of NA and HA

for classifying strains shows that these segments are important for the virus. Thus showing that

genome segment exchanges in these regions are important. Influenza virus can undergo genome

segment exchanges that cause major changes in the type A influenza HA and NA surface

antigens. This major reassortment event can promote virulence and may cause large pandemic

outbreaks. HA genome segment exchanges promote virulence because HA is the major antigenic

target of neutralizing antibodies. The host will have neutralizing antibodies that are specific for

the HA antigen and specific for the last strain of influenza encountered. The protective effect of

neutralizing antibodies by one strain of influenza may be reduced, lost, or ineffective against the

new strain of Influenza. This is why new strains are able to cause large pandemic outbreaks.26

Figure 2. Reassortment event with two strains of Influenza. Influenza A and Influenza B.

HA and NA gene segments reassortment leads to increased virulence in Influenza Strain C.

Original artwork by: Samantha Bray

Q9-2: Explain what components of reovirus are recognized by the innate immune system.

What is the cellular sensor responsible for initiating this signalling cascade?

Rotavirus viral genomic dsRNA acts as a PAMP for TLR 3, TLR 7 and TLR9.

Endosomal TLR3 recognizes dsRNA and activates downstream signalling to induce the

production of NFκB, IRF3 and IRF 7 that activate the transcription of Type 1 interferons.

dsRNA can also be recognized in the cytoplasm by PKR or RLRs (RIG-I and MDA5). PKR

responds to dsRNA and through some unknown mechanism promotes the secretion of IFN-β.

Most viral dsRNA is sequestered in viroplasm however in an imperfect process some may be left

in the cytoplasm.27

Q10-1: Research one other small DNA virus from a different family. Make a table using 6

criteria describing the similarities and differences between Parvovirus and this virus.

Table 5. Similarities and differences between parvovirus and nanovirus (small DNA

viruses).

Criteria Parvovirus 28 Nanovirus 29

Virion

Structure

Non-enveloped capsid, round

icosahedral T=1 symmetry made of

only 60 identical capsid proteins. 18-26

nm

Non-enveloped, round capsid with

T=1 icosahedral symmetry. 18-19 nm

Genome

Structure

Linear ssDNA, 4-6 kb genome with

terminal hairpin ends that promote

replication.

6-8 1 kb circular segments of ssDNA

genome, approximately 4 satellite

genome segments that encode

accessory replication proteins. Each

circular segment encodes only one

protein.

Genome

Replication

Strategy

Rolling hairpin mechanism to make

dsDNA transcription templates and

ssDNA genomes to package into

virions. 28

Rolling circle replication to produce

ssDNA genome that can be packaged

into virions, converted to dsDNA

transcriptional templates, or

transported out of nucleus via

movement proteins and into neighbour

cells via plasmodesmata. 29

Associated

Symptoms

Canine parvovirus causes

gastrointestinal upset, and GI tract

damage mainly in puppies. Human B19

Parvovirus causes Fifth disease (cold-

like symptoms, fever, headache, rash,

and skin lesions. 30

Growth stunting, plant death, plant

tissue necrosis.

Host Humans (B19 type), Canines (CPV2

type), and others.

Legume plants.

Transmission Transmission by respiratory/oral

droplets or fecal-to-oral.

Aphid vectors transmit viruses

between plants.

Q11-1: Human papillomaviruses also can transform cells. Using a diagram, explain the

differences and similarities in cell signalling pathways that contribute to oncogenesis

during polyomavirus and papillomavirus infections.

Polyomaviruses have large T antigen. Large T antigen induces separation of pRb protein

from E2F allowing transcription of cellular genes and entry into the S phase of cell cycle. T

antigen binds p53 that blocks the cell cycle and p53-mediated apoptosis. T antigen also binds

p300 and controls the levels of transcription of cellular genes. Cell transformation and tumour

formation occur when parts of viral DNA is integrated into non-permissive host cell genome.

The cell can then express viral early genes expressed (T antigen) that turn on the cell cycle and

block apoptosis, leading to increased growth in the cell and its progeny cells. Oncogenic cells do

not produce virions, only early viral proteins are express. 31

Papillomaviruses have E7 protein that binds to pRb. Like polyomaviruses T-antigen,

papillomavirus E7 protein induces pRb separation from E2F promoting DNA synthesis through

entry into the S-phase of the cell cycle. Unlike T-antigen, E7 protein can induce ubiquitin-

mediated proteolytic degradation of pRb. Papillomaviruses use a different protein (oncogene) E6

to stimulate p53 protein, unlike polyomaviruses that use only 1 viral oncogene (large T antigen)

to stimulate both pRb and p53. E6 binds p53 protein causing its proteosomal degradation. E6

binds PDZ domain on proteins inducing cell proliferation control in later malignancy. These

outcomes from E6 and E7 stimulation predispose the cell to cancer and tumour formation.

Similar to polyomavirus transformed cells, papillomavirus transformed cells are also unable to

prohibit viral replication.31

Q11-2: Find a product sheet for an SV40 transformed cell line on the American Type

Culture Collection (ATCC) website: http://www.atcc.org/

Figure 3. Product sheets for SV40 transformed endothelial cell isolated from axillary

lymphnode/vascular epithelium from Mus musculus.

Q12-1: Do other large DNA viruses other than the Herpesviridae exhibit viral latency?

Give an example or counter-example.

There is likely a large DNA virus other then Herpesviridae that exhibits viral latency,

however it is not common based on the fact that I have searched exhaustively through many

articles trying to find one. I think the reason for this lack of research on other potential latent

DNA viruses is because the majority of funding goes towards studying Herpesvirus and

retrovirus latency because many people are infected with these viruses. Thus, other large DNA

viruses that exhibit latency they are ignored.

The other major virus that exhibits viral latency is HIV retrovirus that has an RNA

genome. It has a clinical latency period that lasts an average of about 10 years (or more if on

antiretroviral drugs). During this time HIV replicates at low levels causing no symptoms. After

the latency period reactivation of the virus leading to AIDS.32

Q12-2: Larry has a cold sore on Valentine’s Day – this makes him sad. There exists a

negative cultural stereotype surrounding Herpesviridae. Make Larry feel better by

explaining why this stigma is unjustified considering the prevalence of these viruses in

society and current therapies.

http://www.atcc.org/

Larry should not be sad because the stigma that surrounds Herpes virus is unjustified

because essentially everyone gets infected by Herpes virus at one point in his or her life and

becomes latent carriers. For example, the seroprevelence of HSV-1 is 50-70% in healthy adults.

Meaning that 50-70% of healthy adults have pathogen in their blood serum. Herpes virus is so

common that the seroprevelence of VZV is 85-95% in adults.

Treatment/management of the viral infection is through the use of oral or intravenous

drugs such valacyclovir, acyclovir and famcyclovir. When taken daily the antiviral drugs reduce

severity and length of breakouts, and prevent viral spread.33

Q13-1: What are the key viral enzymes of a retrovirus and how do they promote viral

replication?

The key viral enzymes in retroviruses are reverse transcriptase, integrase, and protease.

Generally, without these key enzymes retroviruses cannot replicate in their host cell. Reverse

transcriptase transcribes the viral RNA genome into a double stranded DNA genome promoting

integration into the host’s double stranded DNA genome. Integrase is the enzyme responsible for

integrating the transcribed proviral dsDNA genome into the host genome where it can then be

replicated by along with the host genome. Protease becomes activated when virions are

assembled and start exocytosing from the cell. It is responsible for cleaving the Gag/Pol viral

proteins into functioning structural (capsid, matrix, nucleocapsid) and enzymatic (protease,

integrase, reverse transcriptase) proteins. Without protease, these Gag/Pol proteins would not be

able to reassemble into infectious mature virion.34

Q13-2: What are the major differences between HIV and HTLV-1 infection? Make a

table comparing at least 6 main points.

Table 6. Major differences between HIV and HTLV-1 retroviruses.

Criteria HIV HTLV-1

Replication

Levels

Extremely high levels of active

replication.35

Minimal levels of active replication

once infection is established.35

Gene Expression Encodes 3 accessory proteins Vif,

Vpr and Vpu. Spliced mRNA

encodes Rev, Tat, and Nef.36

Spliced mRNA encodes Rex and Tax

(transcriptional activator) and 4

accessory proteins made through

alternative splicing (p27, p12, p13,

p30). HBZ encoded through antisense

transcription.36

Protein that

escorts unspliced

mRNA from cell

nucleus.

Rev protein.36 Rex protein.36

Associated

Diseases

AIDS.37 Adult T-cell Lymphoma.37

Clinical Signs It is characterized by a significant

decrease and loss of activity in

CD4+ T cells.37

It is characterized by a significantly

increased white blood cell count that

is mostly made up of leukemic T

cells.37

Acute Symptoms Rash, small appetite, fever, Normally Asymptomatic.37

headache, fatigue, malaise, a

general unwell feeling, sore

throat, and night sweats.38

Q14-1: What accessory proteins does your virus encode?

Human B19 parvovirus encodes the NS1 protein. The NS1 protein is a nonstructural

regulatory accessory protein.39

Q14-2: What do your viral accessory proteins do and how were they discovered (described

the experimental approach, not the history of the discovery)

They used human hematopoietic cell lines K562, Raji, and THP-1 as transfectants that

are able to produce the parvoviral NS1 protein upon induction with a bacterial lactose

repressor/operating system. These three transfectant cell lines produced interleukin 6 (IL-6),

which was detected by analyzing cellular supernatant by ELISA. The researches were able to

show that a NF-κB binding site in the IL-6 promoter region mediates the NS1 effect. This means

that regulatory NS1 protein functions as a trans-acting transcriptional activator on the IL-6

promoter. The researchers are using this data as a support for the relationship between human

B19parvovirus and the polyclonal activation of B cells in rheumatoid arthritis, which in turn

means that the NS1 protein plays an indirect regulatory role in the pathogenesis of human B19

associated arthritic disease.39

Q15-1: Write a 200 word summary of the documentary, The Lazarus Effect.

http://www.youtube.com/watch?v=HrJN1_axMEM

The Lazarus Effect is a heart-wrenching documentary about antiretroviral treatment of

HIV in Africa. It aims to show the effects that HIV and AIDS has on the people infected as well

as their loved ones. It scrutinizes the drastic amount of un-necessary loss/deaths of human life

caused by HIV that could be controlled very easily with the help of ARVs. The documentary

highlights the struggles that HIV positive patients go through. For example, many have a hard

time adhering to taking the ARV’s because it is a time-dependent, life long process that is

expensive and inaccessible for many. The Lazurus Effect shows the impact of HIV on mothers,

children, people that have to life with HIV.

The Lazarus Effect highlights the social relations that contribute to poor HIV control in

Africa, putting the blame on embarrassment, and lack of support. This documentary shows the

progress of making HIV, something people tend to be embarrassed about, into something that

people recognize, are aware about, and can talked about. The documentary shows the hard work

of people committed to combatting the problem of HIV, the progress of Africa getting free

ARVs for a small proportion of the people infected, as well as support groups for people that are

infected with AIDS.

Q15-2: What are the major differences between HIV diagnosis and treatments in North

America versus Africa?

In Africa, the main form of HIV treatment is the use of ARVs. Despite genetic

differences or differences in disease progression people infected with HIV in Africa are all given

basically the same treatment. In America ARVs are usually not even considered as a treatment

option. In North America the standard treatment is called HAART (highly active antiretroviral

therapy) that uses a minimum of 3 antiretroviral drugs in combination to suppress HIV

http://www.youtube.com/watch?v=HrJN1_axMEM

replication. These drugs are customized to the patient depending on a variety of factors such as

patients viral load, strain of HIV, CD4+ T cell count, disease symptoms and other factors. 40

Q16-1: Could your favourite virus endogenate into the human genome? Why or why not?

Due to exhaustive literature search, to date, canine parvovirus cannot endogenate into the

human genome. However, researchers have shown using PCR analysis that canine parvovirus

endogenated into chromosome 5 of the rat genome. Endogenated Parvovirus (EnPV) amino acid

sequences in the rat genome were most similar to sequences of canine parvovirus. EnPV has

amino acid sequences that are share 65%-75% of the same amino acid sequence as the capsid

and non-structural proteins of CPV.41

Q16-2: What are the major differences between exogenous and endogenous retroviruses?

List 5 main points of comparison.

Table 7. Major differences between exogenous retroviruses and endogenous retroviruses.

Comparison

Criteria

Exogenous Viruses 42 Endogenous Viruses 43

Genome

Integration

Genome integrates as proviral

DNA. (not into germ-line cells).

Genome is integrated into the germ-line.

Is virus

active?

Proviral DNA is active and Integrated genome has many mutations

so that most ERVs are rendered inactive.

(Usually loses env ORF).

Genome

Characteristic

Static Genome42 Dynamic Genome: retrotransposition

Cell

Replication

Limited to only the cells that get

infected by the virus or cells that

replicate from a infected cell

(provirus). 42

ERV is replicated in all cells of the body

(because its in germ-line cells) 43

Lifecycles Retrovirus infects cell, RT

transcribes viral RNA into DNA it

moves to nucleus and integrates via

integrase and replicates with the

cell to make genomic RNA and

viral mRNA that can be translated

to make proteins and then packaged

into virions with genomic RNA.44

Retrotransposition: integrated DNA

transcribed into RNA template then RT

into DNA and reintegrated into a new

genomic site.

Complementation in trans: Endogenated

RV can replicate forming a virion in

trans that can be incorporated into new

progeny virions.

Reinfection: Viral replication carries out

like normal retroviral replication to make

mature virions that go on to re-infect the

cell.44

Q17-1: Can your favourite virus be infected with a virophage?

Due to exhaustive literature search I conclude that Canine parvovirus cannot be infected

by virophages to our knowledge. However, Dependoparvoviridae such as adeno-associated virus

1 and 2 (AAV-1, AAV-2) can function as satellite viruses that do not have negative effects on

the virus it co-replicates with. AAV-1 and AAV-2 adeno-associated viruses have replication

cycles that depends on the coinfection with adenovirus or herpesvirus.45

My hypothesis for why Parvoviridae cannot be infected by virophages is because of their

size. Parvoviridae are some of the smallest known viruses, 18-26 nm in diameter46 and the

sputnik virophage is 50 nm.47 This comparison shows that Sputnik is larger than Parvovirus.

Thus virophages would have to be extremely small in order to infect the extremely small

parvovirus.

Q17-2: What are the major differences and similarities between viruses, viroids and

satellite viruses?

Table 8. Similarities and differences between viruses, viriods and satellite viruses.

Comparison Viruses 49 Viriods 48 Satellite Viruses 50

Genome Encode

Proteins

Yes, encodes capsid

proteins

No Yes, encodes capsid

proteins

Genome RNA or DNA RNA RNA

Genome

Encoded

Polymerase

Yes No No

Causes of

Disease

Viremia,

blocking/modulation

of host immune

defenses.

Small interfering RNAs Modulation of Helper

Virus

Viriods are naked, circular, ssRNA molecules that do not encode any proteins or viral

mRNA and replicates autonomously relying on host proteins (RNA polymerase). Viriods mainly

infect plants and cause disease with small interfering RNAs that silence host genes.48

Viruses may be naked, they may have circular or linear genomes, their genome can be

DNA or RNA. They infect both plants and animals. They do encode viral proteins that makes up

its capsid structure and viral mRNAs that. Viruses sometimes rely on the host for viral

replication but can also encode its own proteins that promote viral replication. Viruses cause

many diseases through many mechanisms including viremia and blocking of host immune

defenses, etc.49

Satellite viruses replicate in the presence of a helper virus and are able to modulate

(increase severity or decrease severity) the symptoms caused by the helper virus. They do not

encode their own RNA polymerases for replication. They replicate along with the helper virus

and modulate (increase/decreases) the amount of viral RNA to increase or decrease the severity

of infection by the helper virus. Satellite viruses are able to encode their own capsid proteins that

encapsidate their RNA genome.50

Q17-3: Explain the ecological implications of virophages.

Virophages negatively affect virus replication/viral load in a host, thus virophages act in a

positive way for the host. Thus they decrease virus abundance, and increase host abundance.51

An example of this is the Organic Lake Virophage. The Organic Lake Virophage infects

phycodnaviruses infected cells (algae) and impairs the replication of phycodnaviruses and thus

helps the algae. Thus, according to researches, the introduction of Organic Lake Virus increases

the frequency of algal blooms by reducing algal mortality due to phycodnavirus infection.52

Q18-1: Is infection with your favourite virus associated with changes in the expression

prion proteins?

Through exhaustive literature searching it can be concluded that infection with

parvovirus has not yet been associated with changes in the expression of prion proteins. In one

study researchers wanted to determine if addition of random peptide sequences would modulate

the formation of protein kinase resistant PrP (PrPres) from PrP. To do this researchers used a

random sequence (DGAVQPDGGQPAVRNER) from canine parvovirus. Upon addition of the

peptide PrP was not modulated to form PrPres indicating that the canine parvovirus sequence does

not modulate or change the expression of prion proteins.53

Q18-2: What are the major differences and similarities between viruses and prions?

Viruses have nucleic acid genomes, are enclosed in a proteinaceous capsid and

sometimes have an envelope structure, in comparison prions do not have nucleic acid genomes,

rather they are only composed of proteinaceous infectious agents. Viral proteins are typically

virally encoded whereas prion proteins are host encoded. Viral genomes are infectious agents,

are infectious agents. Viruses usually require host proteins, or their own virally encoded

replication proteins to replicate themselves, whereas prions can replicate themselves without.

Both viruses and prions are able to cause pathologic effects in humans.54

Q18-3: What scientific arguments are made against the prion hypothesis?

One scientific argument against the prion hypothesis is that a small virus could be

responsible for transmission of prion disease by infection neurons in the brain causing changes in

the cell leading to conformational change in PrPc to PrPSc. This goes against the prion hypothesis

that states prion disease results from increased stability or the aggregation of mutated PrPSc.54

Q19-1: What is the route of entry of your favourite virus?

CPV infection is initially acquired through oral/nasal contact with feces that contain

infections virions. CPV enters the lymphoid tissue in the oropharynx by binding to the transferrin

receptor then disseminates hematogeneously into the rest of the body.55

Q19-2: What cell, tissue and species tropism does your favourite virus exhibit?

Canine parvovirus has the ability to bind to the transferrin receptor on host cell surfaces.

This receptor binding interaction is what determines CPVs specificity for dog cells that express

the transferrin.56 According to Merck Veterinary Manual CPV prefers to infect tissues that have

cells that are rapidly dividing, such as the intestinal epithelium, lymphopoietic tissue, as well as

the bone marrow.57

Q19-3: What is the clinical presentation of an infection with your favourite virus?

Dogs infected with Canine parvovirus often stop eating, have a fever, are lethargic,

vomiting, and have severe diarrhoea leading to dehydration, and sometimes death. (A) CPV

causes myocarditis and gastric enteritis leading to bloody diarrhea.58

Q19-4: Elaborate on a mechanism of viral pathogenesis caused by your favourite virus.

In the intestine, CPV infects and destroys active, dividing enterocytes that line the

intestinal crypts. The destruction of enterocytes causes intestinal lesions to form. A dog that has

many lesions leads to mucosal surface collapse, mucosal and serosal haemorrhaging,

malabsorption and maldigestion, as well as bloody diarrhea.59

Q20-1: Tell a story of viral pathogenesis in a 200-word paragraph

Transmission of Ebola is usually introduced into new hosts through contact with

infectious bodily fluids with open wounds or mucosal membranes. Ebola virus has GP that can

either be secreted or attached to Ebola viruses cell surface via a transmembrane domain. Ebola

GP binds to and facilitates entry into epithelial cells (lining blood vessels), monocytes and

macrophages. The exposure to Ebola virus or the damage caused by Ebola virus causes the

release of pro-inflammatory cytokines (TNF a, IL-6, IL-8) that are associated with inflammation,

fever, and damaged vasculature. The secreted GP inhibits neutrophil activation. Ebola replicates

at high rates, and during infection both host and viral proteins contribute to viral pathogenesis.

During infection there is an increase in IFN-y, IFN-a, IL-2, IL-10, and TNF-a.60 These pro-

inflammatory cytokines are associated with systemic inflammatory syndrome, and often lead to

fatality. TNF-a may even contribute to the necrosis, epithelial cell leakiness leading to the

characteristic haemorrhagic symptoms. The products released from necrotic cells also stimulate

further release of pro-inflammatory cytokines contributing to further pathogenesis. Chronic, fatal

infections are typically characterized by necrosis in multiple tissues such as the liver and spleen.

Ebola virus also impairs the adaptive immune response by impairing the function of dendritic

cells and by causing lymphocyte apoptosis. Loss of adaptive immune response may inhibit

antibody production against the virus impairing some hosts (but not all) from fighting off the

virus.61

Q21-1: Tell a story of an emerging virus and its contribution to viral pathogenesis in a 200-

word paragraph.

Hendravirus (HeV) is a newly emerging negative sense single stranded RNA virus that

mainly infects horses. It was first observed in 1994 and is found only in Australia. It is postulated

that HeV originally spread to horses via direct contact with bodily fluids from a flying fox.62

HeV was first recognized in 1994 as a virus that spreads horse to horse via direct contact with

infectious bodily fluids, making it seem as if HeV had limited infectivity to horses. In 2011, a

dog living on a property with horses become infected with HeV showing the virus is not so

limited.64 In horses HeV has a vascular tissue tropism preference that causes a lot of HeVs

signature respiratory disease with symptoms such as epithelial edema, large syncytial cell

formation, haemorrhage, destroying of alveolar epithelium and macrophages. HeV also is also

neurotropic, causing neural necrosis and gliosis.64 In horses these virally associated diseases lead

death in horses 70% of the time.62 In humans HeV causes mild flu like symptoms or respiratory

and neurologic disease that is often fatal.63 HeV in humans has a 57% case fatality rate.64 Horses

infected that recover will always be carries of HeV as they exhibit dormancy thus in Australia

they have laws that enforce euthanization of the animal.62

Q22-1: What PRRs can detect your favourite virus?

Researchers were able to demonstrate that oncolytic parvovirus H-1PV is detected by

TLR3 and TLR9 in human embryonic kidney cells. TLR3 and TLR9 stimulation led to activation

of NFκB. Researchers were also able to show that human dendritic cells when infected with H-

1PV induce both NFκB activation and TNF-α production. One thing important to note about this

study is the fact that these results are seen in vitro and may not reflect real PRR stimulation in

vivo.65

Q22-2: Name an ISG is turned-on in response to infection with your favourite virus. What

transcription factor or IFN regulates the expression of this gene?

Researchers used mouse embryonic fibroblasts (MEFs) and infected them with

parvovirus minute virus of mice. Upon infection a Type I interferon (IFN) response is turned on.

The IFN then binds to membrane bound receptors and turns on the JAK/STAT interferon-

signaling pathway. The pathway involves the phosphorylation of STAT1 and STAT2 transcription

factors as well as the activation and the up regulation of ISGs that encode for PKR, STAT1,

STAT2, and 2′-5′-OAS.66

Q22-3: Name a viral restriction factor that limits the replication of your favourite virus.

Explain its mechanism of action.

The Adeno-associated virus (AAV) is a member of Parvoviridae. It requires co-infection

with a helper adenovirus and carries out replication in the nucleus where they form a nuclear

replication center. The researchers transfected some cells with APOBEC3G, some with

APOBEC3A, and some with C106S then infected the cells with wild type AAV and adenovirus.

They found that only APOBEC3A viral restriction factor was able to inhibit the formation of the

nuclear viral replication centres. They then analyzed why APOBEC3A was the only restriction

factor out of the ones used to restrict viral replication. Using immunofluorescence techniques

they found that it was because APOBEC3A was found in both the cytoplasm and nucleus,

whereas APOBEC3G and C106S were only found in the cytoplasm. Although researchers are

unsure of the mechanism one belief is that APOBEC3A directly binds to single-stranded viral

DNA inhibiting the completion of DNA synthesis.67

Q22-4: Does your virus employ viral evasion strategies to avoid the innate and intrinsic immune

response? Elaborate on one specific mechanism.

Yes. Parvovirus migrates to the nucleus via the cellular microtubule system before

uncoating their ssDNA genome. This allows parvovirus to avoid detection of the genome by

innate DNA sensors such as AIM2. 68

Q23-1: Identify an innate immune evasion mechanism carried out by your favourite virus.

Write a 200-word summary of the mode of action, along with an original diagram.

Murine parvovirus minute virus of mice induces an IFN response in mouse embryonic

fibroblasts although not a great enough response to induce an antiviral state. MVMp can block is

known to block the innate immune response. MVMp infected cells down-regulates the secretion

of IFN and IL-6 from Poly (I:C) stimulation. One mechanism used by MVMp to avoid detection

by innate immune sensors is trafficking to the nucleus. The MVM genome coordinates the

movement of the virion from the cytosol to the nucleus. The virion only uncoats its genome one

it has reached the host cell nucleus during the host cells entry into the S-phase. This virion

trafficking avoids MVMp genome detection from cytosolic DNA sensors such as DAI,

LRRFIP1, IFI16 and ISD that could detect viral genome in the cytosol and mount an antiviral

response against them. Another mechanism used by parvovirus to evade host innate immune

response is the interference with interferon stimulating genes that has antiviral activity. The

researchers postulated that MVMp interferes with ISG activity that restricts viral replication.

Although the exact inhibition mechanism is still unknown, it is indicated that MVMp infected

cells block the stimulation of poly (I:C) which results in the down regulation of IL-6 and IFN

antiviral cytokine expression.69

Figure 4. Cell infected with MVMp that avoids recognition of host innate immune system

by blockage of Poly I:C stimulation as well as migration and decapsidation at the nucleus

to avoid cytoplasmic DNA detection. Original Artwork by: Samantha Bray

Q24-1: Describe the adaptive immune response against your favourite virus?

The main adaptive immune response used against parvovirus is the production of

neutralizing antibodies by B cells.70 Parvovirus B19 produces IgM and IgG antibodies. IgM

antibodies are produced first within the first or second week of infection then declines. IgG

antibodies are then produced to provide long-term adaptive immunity. IgG levels increase during

active infection and levels off as the infection subsides. Individuals that are exposed to

parvovirus B19 will have some IgG in their circulation for the rest of their life.71

Q24-2: What T cell subsets are activated during an infection by your favourite virus?

During infection by human parvovirus B19 CD8+ T cells become activated. These CD8+

T cells are increased and sustained over many months during resolution of acute parvovirus B19

infection.72 Human B19 parvovirus also activate CD4+ T helper cell responses for the production

of IFN-γ.73 Human B19 parvovirus activates Th1 and Th2 helper T cell responses.74

Q24-3: Does your favourite virus encode a virokine or other viral proteins that mimic host

molecules? Explain their role in immune evasion.

Human parvovirus B19 has regions in their viral structural protein VP1 and VP2 that are

homologous to GATA1 a transcription factor that plays a key roll in hematopoietic development,

megakaryopoiesis, steady-state erythropoiesis and red blood cell expansion during anemia.

Additionally, peptides in VP1 were identified that are similar to human cytokeratin. Molecular

mimicry is one of the ways by which parvovirus can induce the production of cross reactive

autoantibodies that contribute to auto immune disease.75

Q25-1: Describe how viral escape mutants affect the replication and spread of your

favourite virus?

Historically feline panleukopenia virus is a parvovirus that used to only infects cats. It is

hypothesized that FPV mutated, and gained the ability to infect canine cells. The ability of FPV

to infect canine cells is associated with the virus’s ability to bind the host cell transferrin

receptor. In the past, FPV could only infect feline cells. However, researchers found that two

mutations in the FPV virus allowed spread of virus from a feline host to a canine host. The two

mutations at residue 93 from Lys to Asn and residue 323 from Asp to Asn allowed FPV to bind

the canine transferrin receptor, gaining the ability to infect a canine host.76

Q25-2: How does your favourite virus influence cellular apoptotic pathways?

To access how viral NS1 influences cellular apoptotic pathways researchers used HeLa

cells and transfected them with pcDNA.CPV2.NS1, some were left uninfected as controls. They

used flow cytometry and real time PCR techniques to analyze the activation of caspase-3, Bcl2,

and the p53 apoptotic pathway. The researchers found that caspase-3 was activated and

upregulated in the cells that were transfected with pcDNA.CPV2.NS1 whereas Bcl2 and p53

were not activated. In short this study found that increased apoptosis in CPV2 infected cells is

caspase-3 dependent and p53 independent.77

Q25-3: Identify and explain one additional viral evasion strategy performed by your

favourite virus that was not covered in this course.

Human parvovirus B19 has a NS1 protein that is a transcriptional activation that

modulates STAT signalling. B19 NSI expression leads to the activation and dimerization of

STAT3, the STAT3 dimers translocate to the nucleus. The activation of STAT3 is associated

with the up regulation of antiviral genes such IL-10Rα, IL-2Rα and IFN receptor proteins (IFNG

and IFNAR). B19 NSI expression suppresses promoter activity of SOCS1 and SOCS3. STAT3

suppression followed by PIAS3 activation is a viral mechanism that promotes viral persistence

and chronic inflammation. Viral B19 NS1 is hypothesized to blocks the phosphorylation and

activation of STAT1 by suppressing TYK2 (a Janus kinase) which contributes to reduced Type 1

antiviral IFN response.78

Q26-1: Is there a vaccine against your favourite virus? If so, describe.

Yes there is a vaccine called Nobivac ® Canine 1-DAPPV that is widely used in dogs

to protect against canine parvovirus as well as adenovirus type 1 (hepatitis), adenovirus type 2 (respiratory disease), parainfluenza and canine distemper. It is a combined modified live virus vaccine and is given as a subcutaneous injection. It can be given to healthy dogs starting at the age of 6 weeks and is given in 2-4 week intervals until the puppy is 12 weeks old. It must be boostered annually to stay effective.79

Q26-2: Is there antiviral regimens against your favourite virus? If so, describe.

Yes there are antiviral regimens against canine parvovirus infection in dogs. Once

infected the main goals of treatment are restoration of fluid, electrolyte and metabolic

abnormalities as well as the prevention of secondary bacterial infections that occur when bacteria

translocate across intestinal epithelium that was disrupted by the virus. Most dogs are put on IV

fluids to correct fluid levels. Antibiotics such as ampicillin or gentamicin are given to combat

bacterial translocation across intestinal epithelium. Antiemetic therapy is given to stop vomiting,

which also combats water loss (dehydration). Dogs with parvovirus infection suffer from

extreme diarrhea, however it is not appropriate to give infected dogs antidiarrheals because it

could cause retention of intestinal contents may increase the risk of bacterial translocation across

the gut. Generally after infection that dog is low on many nutrients, so after vomiting has

stopped the dog should be fed and watered. Oseltamivir can be given to infected dogs to reduce

the amount of weight loss and to increase the white blood cell count (in respect to dogs not given

Oseltamivir). With appropriate supportive care, which in turn helps the dogs immune system

fight against parvovirus infection, 68%–92% of dogs with CPV enteritis will survive.80

Q27-1: With a partner from BIOL4904, decide who has the most pathogenic virus and

justify your answer in terms of transmission, viral replication, viral pathology and clinical

presentation. You must present information comparing and contrasting both viruses. 300-

word minimum.

Compared to Human parvovirus B19, SARS coronavirus is more pathogenic to humans.

SARS Coronavirus spreads between hosts through direct contact with respiratory droplets in

aerosol form, through the fecal-oral route, or through contaminated surfaces.81 Similar to SARS,

Human parvovirus B19 can also be spread by respiratory secretions, but not through the fecal-

oral route.82 Human parvovirus B19 replicates only in human erythroid progenitor cells and it

typically replicates in the nucleus of the cell until virion levels are high enough to cause cell

lysis.83 SARS Coronavirus replicates in host epithelial cells that line the lungs and intestines.

Similar to parvovirus B19 SARS virions also replicate in the host cells until the level of viruses

is so high that it causes the cell to lyse releasing thousands of virions.84 Human B19 parvovirus

only causes mild symptoms called Fifth disease.82 Initial symptoms include fever, runny nose,

and headache, it then progresses into a face and body rash forming a characteristic “slapped

cheek rash” that is common in children.82 Parvovirus B19 may also cause painful swollen joints.

The infection resolves itself usually without treatment and only progresses into more serious

complications in people that have weakened immune systems.82 unlike parvovirus B19, SARS

usually requires treatment or else the infection will persist. SARS symptoms include cough,

breathing difficulties, fever, chills/shaking, head and muscle aches.81 SARS infection had a death

rate of over 50% in people over the age of 65. The death rate from SARS was 9 to 12% of those

diagnosed. In people over age 65, the death rate was higher than 50%. Throughout history SARS

has caused more pathogenesis especially in the 2003 outbreak that caused +8000 deaths

worldwide according to the World Health Organization.85 Human parvovirus B19 infection

rarely causes death in adults, but it has been associated with causes fetal deaths.86

Bibliography

1. Leppard, Keith., Dimmock, N., & Easton, A. (2007). Introduction to Modern Virology.

Blackwell Publishing Limited. pp 450.

2. “Parvoviridae.” ViralZone. ExPASY SIB Bioinformatics Research Portal. n.d. Web. 20

Sept 2015.

3. “Capsid Protein VP2.” Uniprot. 7 Jun 2004. Web. 25 September 2015.

4. “Canine Parvovirus Type 2.” Microbewiki. n.d. Web. 25 Sept 2015.

5. Linden, R. M., & Berns, K. I. (2000). "Molecular biology of adeno-associated viruses.

Parvoviruses: From Molecular Biology to Pathology and Therapeutic Uses. 68-84.

6. Laughlin, C. A., Myers, M. W., Risin, D. L., & Carter, B. J. (1979). Defective-interfering

particles of the human parvovirus adeno-associated virus. Virology, 94(1), 162-174.

7. “Protoparvovirus.” ViralZone. ExPASy SIB Bioinformatics Research Portal. n.d. Web.

28 Nov 2015.


Nov 2015.

9. Suikkanen, S. (2003) Cell biology of canine parvovirus entry. University of Jyväskylä,

13-14.

10. Elia, G., Cavalli, A., Desario, C., Lorusso, E., Lucente, M. S., Decaro, N., ... &

Buonavoglia, C. (2007). Detection of infectious canine parvovirus type 2 by mRNA real-

time RT-PCR. Journal of virological methods, 146(1), 202-208.

11. Ducani, C., Bernardinelli, G., & Högberg, B. (2014). Rolling circle replication requires

single-stranded DNA binding protein to avoid termination and production of double-

stranded DNA. Nucleic acids research, 42(16): 10596-10604.

12. Shackelton, L. A., Parrish, C. R., Truyen, U., & Holmes, E. C. (2005). High rate of viral

evolution associated with the emergence of carnivore parvovirus.Proceedings of the

National Academy of Sciences of the United States of America, 102(2), 379-384.

13. “Virus Taxonomy: 2014 Release.” International Committee on Taxonomy of Viruses.

July 2014. Web. 9 Oct 2015.

14. Acheson, Nicholas H. (2011) Fundamentals of molecular virology. Hoboken: John Wiley

& Sons, Inc. 77-96.

15. Kutter, E., De Vos, D., Gvasalia, G., Alavidze, Z., Gogokhia, L., Kuhl, S., & Abedon, S.

T. (2010). Phage therapy in clinical practice: treatment of human infections. Current

pharmaceutical biotechnology, 11(1), 69-86.

16. “Alphafuselloviridae.” ViralZone. ExPASy SIB Bioinformatics Research Portal, n.d.

Web. 9 Nov 2015.

17. “Betalipothrixvirus.” ViralZone. ExPASy SIB Bioinformatics Research Portal, n.d. Web.

9 Nov 2015.


& Sons Inc., 97-103.

19. “Dependoparvovirus.” ViralZone. ExPASy SIB Bioinformatics Research Portal. n.d.

Web. 10 Nov 15.

20. Ji, X., Zhang, H., Zhang, Y., Wang, Y., & Gao, C. (2015). Establishing a CRISPR-Cas-

like immune system conferring DNA virus resistance in plants.Nat Plants, 1, 15144.

21. “High Tunnel Disease Facts: Cucumber Mosaic Virus.” The Ohio State University. n.d.

Web. 30 Oct 2015.


& Sons, Inc., 112-171.

23. “Pneumovirus.” ViralZone. ExPASy SIB Bioinformatics Research Portal. n.d. Web. 9

Nov 2015.

24. “Lyssavirus.” ViralZone. ExPASy SIB Bioinformatics Research Portal. n.d. Web. 9 Nov

2015.

25. “Ebolavirus.” ViralZone. ExPASy SIB Bioinformatics Research Portal. n.d. Web. 9 Nov

2015.

26. ”Influenza.”World Health Organization. 2 Oct 2014. Web. 27 Nov 2015.

27. Arnold, M. M., Sen, A., Greenberg, H. B., & Patton, J. T. (2013). The battle between

rotavirus and its host for control of the interferon signaling pathway. 1-8.

28. “Protoparvovirus.” ViralZone. ExPASy SIB Bioinformatics Research Portal. n.d. Web. 9

Nov 2015.

29. “Nanovirus” ViralZone. ExPASy SIB Bioinformatics Research Portal. n.d. Web. 9 Nov

2015.

30. “Fifth Disease.” Wikipedia. 20 Oct 2015. Web. 9 Nov 2015.


& Sons, Inc., 247-271

32. “HIV/AIDS Basics: Stages of HIV Infection.” Aids. 27 Aug 2015. Web. 27 Nov 2015.

33. Coen, D. M., & Schaffer, P. A. (2003). Antiherpesvirus drugs: a promising spectrum of

new drugs and drug targets. Nature reviews Drug discovery, 2(4), 278-288.


& Sons, Inc., 345-351.

35. Brites, C., Sampalo, J., & Oliveira, A. (2009). HIV/human T-cell lymphotropic virus

coinfection revisited: impact on AIDS progression. AIDS Rev, 11(1), 8-16.

36. “Human immunodeficiency virus 1.” ViralZone. ExPASy SIB Bioinformatics Research

Portal. n.d. Web. 21 Nov 2015.

37. “Human T-lymphotropic virus 1.” ViralZone. ExPASy SIB Bioinformatics Research

Portal. n.d. Web. 21 Nov 2015.

38. Dock, E., & Boskey, E. “Acute HIV infection.” Healthline. 16 Jul 2012. Web. 21 Nov

2015.

39. Moffatt, S., Tanaka, N., Tada, K., Nose, M., Nakamura, M., Muraoka, O., Hirano, T., &

Sugamura, K. (1996). A cytotoxic nonstructural protein, NS1, of human parvovirus B19

induces activation of interleukin-6 gene expression. Journal of virology, 70(12), 8485-

8491.

40. “What is HAART.” National Institute on Drug Abuse: The Science of Drug Abuse and

Addiction. July 2012. Web. 27 Nov 2015.

41. Kapoor, A., Simmonds, P., & Lipkin, W. I. (2010). Discovery and Characterization of

Mammalian Endogenous Parvoviruses. Journal of Virology, 84(24), 12628–12635.

42. Retrovirus - Characteristics, Reverse Transcriptase, Retrovirus Replication Cycle,

Consequences Of Retroviral Infection, Retroviruses And Cancer. Medicine JRank. n.d.

Web. 27 Nov 2015.

43. Griffiths, D. J. (2001). Endogenous retroviruses in the human genome sequence. Genome

Biology, 2(6), 1017.1-1071.5

44. Douville, R. (2015). BIOL 4904 – Virology. Lecture 16: Genome-Endogenated Viruses.

21 Oct 2015. Powerpoint. 27 Nov 2015.

45. “Dependoparvovirus.” ViralZone. ExPASy SIB Bioinformatics Research Portal. n.d.

Web. 10 Nov 15.


Sept 2015.

47. La Scola, B., et al. (2008). The virophage as a unique parasite of the giant mimivirus.

Nature, 455(7209), 100-104.

48. Racaniello, V. “Viroids, Infectious Agents That Encode No Proteins.” Virology Blog

About Viruses and Viral Disease. 14 Jan 2015. Web. 27 Nov 2015.

49. Waggoner, B., Speer, B. R. “Introduction to Viruses”. University of California Museum

of Paleontology. 14 Aug 1995. Web. 27 Nov 2015.

50. Hu, C. C., Hsu, Y. H., & Lin, N. S. (2009). Satellite RNAs and satellite viruses of

plants. Viruses, 1(3), 1325-1350.

51. Taylor, B. P., Cortez, M. H., & Weitz, J. S. (2014). The virus of my virus is my friend:

ecological effects of virophage with alternative modes of coinfection..Journal of

theoretical biology, 354, 124-136.

52. Yau, S., Lauro, F. M., DeMaere, M. Z., Brown, M. V., Thomas, T., Raftery, M. J., &

Cavicchioli, R. (2011). Virophage control of antarctic algal host–virus

dynamics. Proceedings of the National Academy of Sciences, 108(15), 6163-6168.

53. Rigter, A., Priem, J., Timmers-Parohi, D., Langeveld, J. P., van Zijderveld, F. G., &

Bossers, A. (2009). Prion protein self-peptides modulate prion interactions and

conversion. BMC Biochemistry, 10(29), 7.


& Sons, Inc., 387-395.

55. “Canine Parvovirus.” The Merck Veterinary Manual. Feb 2015. Web. 9 Nov 2015.

56. Hueffer, K., & Parrish, C. R. (2003). Parvovirus host range, cell tropism and

evolution. Current Opinion in Microbiology, 6(4), 392-398.

57. “Canine Parvovirus.” The Merck Veterinary Manual. February 2015. Web. 9 Nov 2015.

58. “Canine Parvovirus.” The American Veterinary Medical Association. n.d. Web. 9 Nov

2015.

59. Maclachlan, N. J., & Dubovi, E. J. (2010). Fenner's Veterinary Virology (4th Edition).

Saint Louis, MO, USA: Academic Press.

60. Sullivan, N., Yang, Z. Y., & Nabel, G. J. (2003). Ebola virus pathogenesis: implications

for vaccines and therapies. Journal of virology, 77(18), 9733-9737.

61. Bray, M., Hirsch, M. S., & Mitty, J. (2015). Epidemiology and pathogenesis of Ebola

virus disease.

62. “Hendra virus.” Australia Veterinary Association. n.d. Web. 9 Nov 2015.

63. “Emergency, Preparedness, Response: Hendra Virus (HeV) Infection.” World Health

Organization. n.d. Web. 9 Nov 2015.

64. “Overview of Hendra Virus Infection.” The Merck Veterinary Manual. Oct 2014. Web. 9

Nov 2015.

65. Sieben, M., Schäfer, P., Dinsart, C., Galle, P. R., & Moehler, M. (2013). Activation of the

human immune system via toll‐ like receptors by the oncolytic parvovirus H‐1. International Journal of Cancer, 132(11), 2548-2556.

66. Grekova, S., Zawatzky, R., Hörlein, R., Cziepluch, C., Mincberg, M., Davis, C.,

Rommelaere, J.,& Daeffler, L. (2010). Activation of an Antiviral Response in Normal but

Not Transformed Mouse Cells: a New Determinant of Minute Virus of Mice

Oncotropism. Journal of Virology, 84(1), 516–531.

67. Chen, H., Lilley, C. E., Yu, Q., Lee, D. V., Chou, J., Narvaiza, I., ... & Weitzman, M. D.

(2006). APOBEC3A is a potent inhibitor of adeno-associated virus and

retrotransposons. Current biology, 16(5), 480-485.

68. Acheson, Nicholas H. Fundamentals of molecular virology. John Wiley & Sons, Inc.,

2011. 240-241.

69. Mattei, L. M., Cotmore, S. F., Tattersall, P., & Iwasaki, A. (2013). Parvovirus evades

interferon-dependent viral control in primary mouse embryonic

fibroblasts. Virology, 442(1), 20-27.

70. Kurtzman, G. J., Cohen, B. J., Field, A. M., Oseas, R., Blaese, R. M., & Young, N. S.

(1989). Immune response to B19 parvovirus and an antibody defect in persistent viral

infection. Journal of Clinical Investigation, 84(4), 1114.

71. “Parvovirus B19.” Lab Test Online. 13 May 2014. Web. 27 Nov 2015.

72. Norbeck, O., Isa, A., Pöhlmann, C., Broliden, K., Kasprowicz, V., Bowness, P.,

Klenerman, P., & Tolfvenstam, T. (2005). Sustained CD8+ T-cell responses induced after

acute parvovirus B19 infection in humans. Journal of virology, 79(18), 12117-12121.

73. Lindner, J., Barabas, S., Saar, K., Altmann, D., Pfister, A., Fleck, M., Deml, L., &

Modrow, S. (2005). CD4+ T‐ Cell Responses Against the VP1‐ Unique Region in

Individuals with Recent and Persistent Parvovirus B19 Infection. Journal of Veterinary

Medicine, Series B, 52(7‐ 8), 356-361.

74. Isa, A., Lundqvist, A., Lindblom, A., Tolfvenstam, T., & Broliden, K. (2007). Cytokine

responses in acute and persistent human parvovirus B19 infection.Clinical &

Experimental Immunology, 147(3), 419-425.

75. Lunardi, C., Tinazzi, E., Bason, C., Dolcino, M., Corrocher, R., & Puccetti, A. (2008).

Human parvovirus B19 infection and autoimmunity. Autoimmunity reviews, 8(2), 116-

120.

76. Parrish, C. R., & Kawaoka, Y. (2005). The origins of new pandemic viruses: the

acquisition of new host ranges by canine parvovirus and influenza A viruses. Annual

Reviews of Microbiology, 59, 553-586.

77. Saxena, L., Kumar, G. R., Saxena, S., Chaturvedi, U., Sahoo, A. P., Singh, L. V., Santra,

L., Palia, S. K., Desai, G. S. & Tiwari, A. K. (2013). Apoptosis induced by NS1 gene of

Canine Parvovirus-2 is caspase dependent and p53 independent. Virus research, 173(2),

426-430.

78. Duechting, A., Tschöpe, C., Kaiser, H., Lamkemeyer, T., Tanaka, N., Aberle, S., Lang,

F., Torresi, J., Kandolf, R., & Bock, C. T. (2008). Human parvovirus B19 NS1 protein

modulates inflammatory signaling by activation of STAT3/PIAS3 in human endothelial

cells. Journal of virology, 82(16), 7942-7952.

79. “Nobavic® Canine 1-DAPPv.” Merck Animal Health. n.d. Web. 21 Nov 2015.

80. “Canine Parvovirus.” The Merck Veterinary Manual. Feb 2015. Web. 21 Nov 2015.

81. Hadjiliadis, D., Harron, P. F., Zieve, D., & Ogilvie, I. “Severe acute respiratory syndrome

(SARS).” Medline Plus. 2 Feb 2015. Web. 28 Nov 2015.

82. “Parvovirus B19 and Fifth Disease.” Centre for Disease Control and Prevention. 2 Nov

2015. Web. 28 Nov 2015.

83. Meštrović, T. “Parvovirus Replication.” News Medical: Life Sciences & Medicine. 14

Apr 2015. Web. 28 Nov 2015.

84. “Severe acute respiratory syndrome (SARS).” Environmental and Health Sciences

University of Minnesota. n.d. Web. 28 Nov 2015.

85. “SARS Basic Fact Sheet.” Centre for Disease Control and Prevention. 2 Jul 2015. Web.

28 Nov 2015.

86. “Morbidity and Mortality Monthly Report: Current Trends Risks Associated with Human

Parvovirus B19 Infection.” Centre for Disease Control and Prevention. 8 May 1998.

Web. 28 Nov 2015.