Virology
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	Spring, 2004 Lecture Outline 3/2 ENVELOPED PLUS-STRAND RNA VIRUSES   Togaviridae: *envelope c short peplomers (spikes) vs. Corona- long peplomers *most transmitted by insects; replicate in insects 2 major genera: rubivirus- not insect transmitted alphavirus- insect transmitted E.g.: equine encephalitis- 3 species; reservoir: birds Sindbis- widely distributed in world alphavirus structure: spherical, 42 nm; 60-65 nm "spike to spike" RNA- single molec 4.3 x 106; naked is infectious capped 5'; poly(A) 3'; ends are complimentary capsid- nonglycosylated, 30 K envelope- 2 major proteins 50 K + 1 protein 10 K General Envelope Structure- true of most enveloped viruses proteins c both hydrophilic & hydrophobic regions: amphipathic * glycosylation- only by host enzymes * appears that proteins displace host membrane proteins * cause variety of biological effects on host lipids derived from host membranes- endoplasmic reticulum, Golgi, plasma membrane translation & replication: 26 S RNA produced early from 49 S RNA (genomic) 1. 49 S- primary translation of polyprotein: yields RNA polymerases, protease 2. full length minus strand transcribed 3. 26 S- transcribed from minus strand 4. translation of structural proteins from 26 S Rubella virus: 2 glycoproteins E1, E2- similar to Sindbis E2, E3 similar strategy of replication & production as alphaviruses 1 Ag strain; E1- hemagglutinin cytopathology & disease course transmission- primarily nasopharyngeal persistence- congenital infection may continue up to 3 yrs Flaviviridae: similar appearance, structure, transmission to Togaviridae different transcription process 3 major genera: Hepatitis C virus; pestiviruses; arboviruses Egs of arboviruses: Yellow fever- prototype; dengue (Caribbean islands); Japanese encephalitis pathology; transmission via bloodsucking arthropods birds & other animals- can be intermediate hosts Coronaviridae: cytocidal, organ specific, persistent respiratory & GI diseases, among others responsible for common colds in man (besides rhino-) assoc. c multiple sclerosis- not yet proven structure: 80-150 nm c large peplomers 12-24 nm- "corona" buds from ER & Golgi helical nucleocapsid; spherical overall transcription: plus-strand from minus strand- starts at several sites & continues to end; 7 "nested" mRNAs   Midterm 1: Material through today Next up: [-] strand RNA viruses- an extra step is required, what is it?
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