Virus structure classification and replication Viruses defined Obligate

Virus structure, classification and replication

Viruses defined Obligate intracellular parasites

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

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

Basic virus structure DNA or RNA + Capsid protein Nucleocapsid + Nucleocapsid Lipid membrane, glycoproteins = Naked capsid virus Enveloped virus

Capsid symmetry Icosahedral Helical Naked capsid Enveloped Matrix Lipid Glycoprotein

http: //www. ncbi. nlm. nih. gov/ICTVdb/Images/Ackerman/Animalvi/Adenovir/799 -16. htm Adenovirus Electron micrograph Foot and mouth disease virus Crystallographic model http: //virology. wisc. edu/virusworld/ICTV 8/fmd-foot-and-mouth-ictv 8. jpg Icosahedral naked capsid viruses

Helical naked capsid viruses Protein Caspar and Klug, Adv Virus Res. 1960; 7: 225 -325 http: //www. ncbi. nlm. nih. gov/ICTVdb/ICTVd. B/em_tmv. gif RNA Tobacco mosaic virus Electron micrograph Tobacco mosaic virus Model

http: //web. uct. ac. za/depts/mmi/stannard/emimages. html http: //virology. wisc. edu/virusworld/images/herpescapsid. GIF Icosahedral enveloped viruses Herpes simplex virus Electron micrograph Herpes simplex virus Nucleocapsid cryo. EM model

http: //web. uct. ac. za/depts/mmi/stannard/paramyx. html http: //web. uct. ac. za/depts/mmi/stannard/fluvirus. html Helical enveloped viruses Influneza A virus Electron micrograph Paramyxovirus Electron micrograph

Taxonomy of the Order Mononegavirales a V, vertebrate; I, insect; P, plant. Fields Vriology (2007) 5 th edition, Knipe, DM & Howley, PM, eds, Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia Table 2. 2

Classification of Human Viruses Fields Vriology (2007) 5 th edition, Knipe, DM & Howley, PM, eds, Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia Table 2. 1

Major diseases caused by human viruses

Virus replication: general

Virus replication: variations on theme • • ds. DNA ss. DNA (+)ss. RNA (-)ss. RNA ds. RNA retro DNA retro

ds. DNA virus replication (+)m. RNA ds. DNA

ss. DNA virus replication (+)m. RNA (+) ss. DNA ds. DNA

(+)ss. RNA virus replication (+)RNA (-)RNA (+)RNA

(-)ss. RNA virus replication (+)m. RNA (-)RNA (+)RNA (-)RNA

ds. RNA virus replication ds. RNA (+)m. RNA ds. RNA

(+)ss. RNA retrovirus replication (+)m. RNA (+)RNA ds. DNA ss. DNA (+)RNA

ds. DNA retrovirus replication (+)m. RNA ds. DNA (+)RNA ss. DNA

Virus growth 1, 000 – 100, 000 viruses/cell, 5 – 24 hours From Schaechter’s Mechanisms of Microbial Disease; 4 th ed. ; Engleberg, Di. Rita & Dermody; Lippincott, Williams & Wilkins; 2007; Fig. 31 -8

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