9-13 1 PM Structure, Classification & Replication

7/30/2019 9-13 1 PM Structure, Classification & Replication

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Virus structure, classification andreplication


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Viruses defined

Obligate intracellular parasites


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(From Medical Microbiology, 4th ed., Murray, Rosenthal, Kobayashi & Pfaller, Mosby Inc., 2002, Fig. 65-1.)

Under attack!


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From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Fig. 6-4.

Structures compared


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Basic virus structure

Capsidprotein

NucleocapsidNaked

capsid virus

DNA

RNA

or =+

NucleocapsidLipid membrane,

glycoproteinsEnveloped virus+


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Capsid symmetry

Icosahedral Helical

Naked capsid

Enveloped

Lipid

Glycoprotein

Matrix


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Icosahedral naked capsid viruses

Adenovirus

Electron micrograph

Foot and mouth disease virus

Crystallographic modelhttp://www.ncbi.nlm.nih.gov/ICTVdb/Images/Ackerman/A

nimalvi/Adenovir/799-16.htm

http://virology.wisc.edu/virusworld/ICTV8/fmd-foot-and-mouth-ictv8.jpg


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Helical naked capsid viruses

Tobacco mosaic virus

Electron micrograph

Tobacco mosaic virus

Model

RNA Protein

http

://www.ncbi.nlm.nih.gov/ICTV

db/ICTVdB/em_

tmv.gif

Ca

sparandKlug,AdvVirusRe

s.1960;7:225-325


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Icosahedral enveloped viruses

Herpes simplex virus

Electron micrograph

Herpes simplex virus

Nucleocapsid cryoEM model

htt

p://web.uct.ac.za/depts/mmi/

stannard/emimages.html

http://virology.wisc.edu/virusworld/images/herpescapsid.GIF


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Helical enveloped viruses

Influneza A virus

Electron micrograph

Paramyxovirus

Electron micrograph

http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html

http://web.uct.ac.za/depts/mmi/stan

nard/paramyx.html


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Properties of enveloped viruses

Envelope is sensitive to Drying

Heat

Detergents

Acid Consequences

Must stay wet during transmission

Transmission in large droplets and secretions

Cannot survive in the gastrointestinal tract Do not need to kill cells in order to spread

May require both a humoral and a cellular immuneresponse

Adapted from Murray, P.R. Rosenthal K.S., Pfaller, M.A. (2005) Medical Microbiology, 5th edition, Elsevier Mosby, Philadelphia, PA Box 6-5


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Properties of naked capsid viruses

Capsid is resistant to Drying

Heat

Detergents

Acids

Proteases

Consequences Can survive in the gastrointestinal tract

Retain infectivity on drying

Survive well on environmental surfaces

Spread easily via fomites Must kill host cells for release of mature virus particles

Humoral antibody response may be sufficient to neutralizeinfection

Adapted from Murray, P.R. Rosenthal K.S., Pfaller, M.A. (2005) Medical Microbiology, 5th edition, Elsevier Mosby, Philadelphia, PA , Box 6-4


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Taxonomy of the OrderMononegavirales

Order Family Subfamily Genus Type Species Hosta

Mononegavirales

BornaviridaeBornavirus Borna disease virus V

Rhabdoviridae

Vesiculovirus Vesicular stomatitis Indiana virus V, I

Lyssavirus Rabies virus V

Ephemerovirus Bovine ephemeral fever virus V, I

Novirhabdovirus Infectious hematopoietic necrosis virus V

Cytorhabdovirus Lettuce necrotic yellows virus P, I

Nucleorhabdovirus Potato yellow dwarf virus P, I

Filoviridae

Marburghvirus Lake Victoria marburgvirus V

Ebolavirus Zaire ebolavirus V

Paramyxoviridae

Paramyxovirinae

Rubulavirus Mumps virus V

Avulavirus Newcastle disease virus V

Respirovirus Sendai virus V

Henipavirus Hendra virus V

Morbillivirus Measles virus V

Pneumovirinae

Pneumovirus Human respiratory syncytial virus V

Metapneumovirus Avian metapneumovirus V

a V, vertebrate; I, insect; P, plant.

Fields Vriology (2007) 5th edition, Knipe, DM & Howley, PM, eds, Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia Table 2.2


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Classification of Human Viruses

"Group" Family Genome Genome size (kb) Capsid Envelope

dsDNA

Poxviridae dsDNA, linear 130 to 375 Ovoid Yes

Herpesviridae dsDNA, linear 125 to 240 Icosahedral Yes

Adenoviridae dsDNA, linear 26 to 45 Icosahedral No

Polyomaviridae dsDNA, circular 5 Icosahedral NoPapillomaviridae dsDNA, circular 7 to 8 Icosahedral No

ssDNA

Anellovirus ssDNA circular 3 to 4 Isometric No

Parvoviradae ssDNA, linear, (- or +/-) 5 Icosahedral No

Retro

Hepadnaviridae dsDNA (partial), circular 3 to 4 Icosahedral Yes

Retroviridae ssRNA (+), diploid 7 to 13 Spherical, rod or cone shaped Yes

dsRNA

Reoviridae dsRNA, segmented 19 to 32 Icosahedral No

ssRNA (-)

Rhabdoviridae ssRNA (-) 11 to 15 Helical Yes

Filoviridae ssRNA (-) 19 Helical Yes

Paramyxoviridae ssRNA (-) 10 to 15 Helical Yes

Orthomyxoviridae ssRNA (-), segmented 10 to 13.6 Helical Yes

Bunyaviridae ssRNA (-, ambi), segmented 11 to 19 Helical Yes

Arenaviridae ssRNA (-, ambi), segmented 11 Circular, nucleosomal Yes

Deltavirus ssRNA (-) circular 2 Spherical Yes

ssRNA (+)

Picornaviridae ssRNA (+) 7 to 9 Icosahedral No

Calciviridae ssRNA (+) 7 to 8 Icosahedral No

Hepevirus ssRNA (+) 7 Icosahedral No

Astroviridae ssRNA (+) 6 to 7 Isometric No

Coronaviridae ssRNA (+) 28 to 31 Helical Yes

Flaviviridae ssRNA (+) 10 to 12 Spherical Yes

Togaviridae ssRNA (+) 11 to 12 Icosahedral Yes

Fields Vriology (2007) 5th edition, Knipe, DM & Howley, PM, eds, Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia Table 2.1


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Major diseases caused by human viruses

"Group" Family Human pathogens (disease)

dsDNA

Poxviridae Variola (smallpox); Orf (pustular dermatitis); Molluscum contagiosum (pustular dermatitis)

Herpesviridae Herpes simplex 1,2 (oral, genital herpes); Varicella-zoster (chickenpox); Epstein-Barr (mononucleosis);

Cytomegalovirus (neonatal abnormalities); HHV6 (roseola); HHV8 (Kaposi's sarcoma)Adenoviridae Adenovirus (respiratory infection, conjunctivitis)

Polyomaviridae Polyomavirus (benign kidney infection, respiratory disease, leukoencephalopathy)

Papillomaviridae Papillomavirus (warts, genital carcinoma)

ssDNA

Anellovirus Unknown

Parvoviradae B-19 (fifth disease, fetal death)

Retro

Hepadnaviridae Hepatitis B ("serum" hepatitis)

Retroviridae HIV (aids); HTLV (leukemia)

dsRNAReoviridae Rotavirus ( infantile gastroenteritis)

ssRNA (-)

Rhabdoviridae Rabies virus (rabies)

Filoviridae Ebola virus (ebola)

Paramyxoviridae Parainfluenza virus (respiratory infection); Mumps virus (mumps);

Respiratory syncytial virus (respiratory infection); Measles virus (measles)

Orthomyxoviridae Influenza virus (influenza)

Bunyaviridae Hantaan virus (hemorrhagic fever with renal syndrome)

Arenaviridae Lassa fever virus (hemorrhagic fever)

Deltavirus Hepatitis D (fulminant acute hepatitis)

ssRNA (+)

Picornaviridae Poliovirus (polio), rhinovirus (URI), Hepatitis A ("infectious" hepatitis)

Calciviridae Norwalk (gastroenteritis)

Hepevirus Hepatitis E (acute hepatitis)

Astroviridae Astrovirus (gastroenteritis)

Coronaviridae Coronavirus (respiratory infection)

Flaviviridae Yellow fever virus (yellow fever); Hepatitis C (hepatitis)

Togaviridae Eastern Equine encephalitis virus (encephalitis); Rubella virus (rubella)


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Virus replication: general


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dsDNA

ssDNA

(+)ssRNA

(-)ssRNA

dsRNA

RNA retro

DNA retro

Virus replication:

variations on the theme


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dsDNA virus replication

dsDNA dsDNA

(+)mRNA


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ssDNA virus replication

(+)mRNA

dsDNAssDNA(+)


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(+)ssRNA virus replication

(+)RNA (-)RNA (+)RNA


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(-)ssRNA virus replication

(+)mRNA

(-)RNA

(+)RNA (-)RNA


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dsRNA virus replication

(+)mRNAdsRNA

dsRNA


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(+)ssRNA retrovirus replication

(+)RNA

dsDNA

ssDNA

(+)mRNA

(+)RNA


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dsDNA retrovirus replication

dsDNA

ssDNA

(+)mRNA

(+)RNA

dsDNA


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Virus growth

From Schaechters Mechanisms of Microbial Disease; 4 th ed.; Engleberg, DiRita & Dermody; Lippincott, Williams & Wilkins; 2007; Fig. 31-8

1,000 100,000 viruses/cell, 5 24 hours


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Summary: structure,

classification & replication

Structure

Nucleic acid in a protein shell, +/- lipid envelope

Structure impacts on biological properties

Classification Many virus families, organized by structure and

biology

Replication

Generic scheme

Varying strategies depending on nucleic acid

Documents

9-13 1 PM Structure, Classification & Replication