Virology

Prepared by Perlie Harriet Mata, RMT

Small size: 0.01 -0.3 um FILTERABLE AGENTS Virion- viral particle Capsid – protects the viral nucleic acid

Virion- the whole viral particle, that is the neocapsid w/ its outer envelope (if present)

1. Capsid – protein coat of a virus; made of of numerous capsomere

2. Nucleocapsid- the complex of protective protein and viral nucleic acid

They possess only one nucleic acid: Either DNA/RNA (NEVER BOTH)

a. Helical- rod shaped b. Icosahedra – cube like c. complex- non conforming symmetry

1. Type of nucleic acid

2. Number of strands of nucleic acid and their physical construction (single or double stranded, linear or circular, circular w/ breaks, segmented)

3. Polarity of the viral genome – RNA viruses in w/c the viral genome can be used directly as messenger RNA are by convention termed “positive-stranded” and those for which a transcript has first to be made are termed “negative stranded”

4. The symmetry of the nucleocapsid 5. Presence or absence of a lipid envelope

w/o outer membrane – non-enveloped/ naked resistant to ether ether stable

w/ outer membrane – enveloped sensitive to ether ether labile labile viruses Enveloped – derived from nuclear

membrane or host cell Composed of Lipid Soluble to ether because of

thelipid component

I. DNA viruses – replicates in the nucleus

*dsDNA *icosahedral

Parvoviridae – ssDNA

All are icosahedral symmetry except for Poxviridae – Complex; replicates in the cytoplasm

Pox viridae – Largest virus complex symmetry

ENVELOPED: Hepadnaviridae, Herpesviridae, Poxviridae

NAKED: Papovaviridae, Adenoviridae, Parvoviridae

ssRNA except Reoviridae : dsRNA

Helical except Picornaviridae, Caliciviridae, Reoviridae, Togaviridae, Flaviviridae : Icosahedral

Enveloped except Picorna, Caliciviridae, reoviridae : Naked

Replicates in the Cytoplasm except Retroviridae, Orthomyxoviridae : Nucleus

Storage: 4°C Transport medium: -70°C

1. Light microscopy

Viral inclusions Negri bodies – inclusion in Rabies virus –

cytoplasm

2. Electron Microscopy

Most rapid way of detecting viral infection Most common rapid EM method: Negative

staining

3. Culture a. Chick embryo b. Tissue culture Medium A549 cells – lung carcinoma HeLa cells – cervical carcinoma Hep2 cells – human epithelial cells from laryngeal

carcinoma Human Fibroblast Cells– preferred tissue culture medium

for CMV ** We do not look for colonies, we look for CHARACTERISTIC CPE

CPE (cytophatic effect) – morphological change in cells associated w/ viral proliferation

4. SERO Test:

Neutralization Complement fixation test Hemagglutination Inhibition (Abs against

influenza/ rubella)

BSL1 Non pathogenic for healthy individuals

B. subtilisM. gordonae

BSL2 Common agents of infectious disease including HIVEither result of bioterrorism/ natural method

B. anthracisY. pestis

BSL3 Organism grown in large quantities

Culture for MTBSystemic Fungi (Mold form)Francisella tularensisBrucella spp.

BSL4 ArboviridaeArenaviridaeFilovirus (Ebola virus)Small pox (last case 1997)

Virus Family

Arthropod – borne viruses

1. Bunyaviridae 2. Flaviviridae 3. Togaviridae

EBV: Infectious mononucleosis Burkitt’s lymphoma Target cell: B cells (CD21) IM: Atypical/ Reactive lymphocytes (Downey

cells) T cells reacting to B cells

infected w/ EBV

infections Toxoplasmosis Rubella CMV Herpes Syphilis

CMV: most common congenital infection

Blood Transfusion (leukocytes)/ organ transplant

CMV aka Salivary Gland Virus > 40 day fever Culture: human fibroblast cells Inclusion: OWL’s eye inclusion

HHV6 and HHV7: Roseola (Exanthem subitum)

6th childhood disease

HHV8: Kaposi’s sarcoma Most common malignancy observed

among AIDS patients

Pa = papilloma virus : WART’s Po = Polyomavirus Va –vacuolating virus of monkey

Parvovirus B-19 Slapped cheek Rash Erythema infection 5th disease

Guarheiri body Vaccinia – cow pox virus Variola major – small pox Variola minor – Alastrim

Caliciviridae: Hepa E- fecal oral route

Water contamination Increased fatality : pregnancy

Coronaviridae – common colds SARS

Yellow viruses **Dengue

Hepa C – most common cause of post transfusion Hepatitis

Hepa C 80% Hepa B <10%

Orthomyxoviridae: Genus influenza Enveloped have spikes Composition of spikes:

hemagglutinin Ag Neuramidase

Infected cell is identified by HEMADSORPTION Abs: Hemagglutination inhibition

a. Measles – rubeola b. mumps c. Parainfluenza d. RSV – respiratory syncytial virus

Smallest RNA virus

Hepa A virus: genus enterovirus type 72 Short incubation heap 15-40 days incubation period   Differentiate Enterovirus: Acid resistant Rhinovirus: Acid Sensitive

children: gastritis/ diarrhea adults: asymptomatic *common cause of gastritis and diarrhea in

winter

Reverse trancscriptase: unique enzyme RNA-> DNA Genus: Lentivirus HIV1: AIDS in US and Europe HIV2: AIDS in west Aftrica Target cell CD4+

HTLV I HTLVII – associated with hairy cell leukemia

– Bullet shaped Rabies/ Lyssa virus

Rubella – German

Measles Aka RUBIVIRUS

Pox viridae – Largest virus complex symmetry

Picornavirus - Smallest RNA virus