Virology
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	Spring, 2004 Lecture Outline 2/26 PICORNAVIRIDAE, CALICIVIRIDAE, & NODAVIRIDAE TOBAMOVIRIDAE Picornaviruses: prototype of group- polio other members of grp: coxsackie (& polio)- enteroviruses encephalomyocarditis (EMC)- cardioviruses common cold- rhinoviruses foot-and-mouth virus (FMDV)- aphthoviruses hepatitis A considerable variation between genera variation c/in genus: more than 100 serotypes of rhinovirus enteroviruses- many serotypes found, even sans Dz or Sx Examples of diseases: Polio- 3 type strains: marked Ag stability man- only natural host; lab strains adapted to infect animals cytopathology; transmission Foot-and-mouth Dz: Aphthovirus of cattle: world wide problem structure: 27 nm icosahedron; RNA 2.4 x 106 daltons polio RNA infectious forms: ss plus strand (native); ds RF; ds cDNA of some isolates **ss complimentary RNA (minus strand)- noninfectious infection: receptor substance on cells- polio protein affinity uncoating begins following attachment RNA ENTERS CELL, little protein enters translation: 1. plus strand translated 2. polyprotein produced- 247 K beginning from near 5' end 3. polyprotein cleaved during translation replication: replication complex: viral RNA, VPg(3B), pol(3D), HF(host factor) assoc. c smooth membranes 1. 1st product may be RF- minus strand produced 2. many RI- multiple plus strands produced / mother minus strand assembly: 1. 5 whole P1 aggregate, split to form aggregate of 1AB,1C,1D 2. 12 aggregates crystallize forming icosahedron = procapsid 3. procapsid can hold RNA = provirion 4. 1AB's further split to 1A,1B- stabilizes particle release: mode not well known in polio Caliciviruses veterinary importance & Norwalk viruses (gastroenteritis in children); Hepatitis E RNA 2.8 x 106 daltons- naked is infectious *translation: different from picornaviruses- resembles togaviruses & some plant viruses Nodaviruses: most are insect viruses; similar to picornaviruses in size, shape, stability bipartite like some plant viruses- 2 RNAs/particle   Intro to [+] strand RNA plant viruses structure: isometric or helical- rigid rods or filaments genome: RNA 1.3 x 106 daltons divided genome & satellite viruses Egs: comoviruses- 2 components, both essential tobraviruses- 2 components, largest req for infection another e.g.: tobacco necrosis virus TNV + STNV (satellite TNV)- 2 unrelated viruses Tobamo grp: TMV is prototype structure: may be unique, very stable- may be why 1st isolated helical, narrow rigid rod 18 x 300 nm assembly of TMV co-translational disassembly translation of plant viral RNA: all plus strand RNAs are inherently mRNA *general assumption: translated into proteins before replication replication of plant viral RNA: all plants contain RNA-directed RNA polymerases *capable of in vitro transcription of viral RNA Next week: Enveloped [+] strand RNA viruses; Toga-, Flavi-, Coronaviridae- see CRC, ch 7 & appropriate parts of Wagner, including ch 15; on-line [-] strand RNA viruses; Rhabdo-, Paramyxo-, Orthomyxovirdae- read Wagner, ch 16; other reading & prep: same as above
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