Download 06vir2

Biology 331
Virology II
Class IV and V Viruses
RNA/RNA Pol (1 error/50,000 bases)
Class IV Poliovirus
GI mucosa/diarrhea 99%, neuron/paralysis 1%
Unenveloped capsid, NO enzymes in virion
ss(+) RNA - 3 proteins from ONE reading frame
Host ribosomes translate into POLYPROTEIN
Protease autocleavage - coat, RNA/RNA Pol
Special Issue - Polio History in the US
Pre-1900, polio/fecal water everywhere…
Infants exposed while still passive IgA-protected
Post-1900, sanitation delayed exposure
So - US epidemics 103-4/year, 1910-55
Now, polio vaccines - close to eradication
Class V Influenza
Mammalian lower respiratory, pneumonia
Envelope with H and N proteins - bind, virulence
8 helical gene segments, RNA/RNA Pol in virion
(+) copies - host translates; (-) copies - genomes
Ag shift (coinfection/reassort) vs. drift (mutations)
“Shift” and “Drift” coined to describe influenza
but relate to ANY virus.
Class VI and VII Viruses Use RT
RT Pol (1 error/12,000 bases)
Class VI Retroviruses
Tumors/HTLV, immunodeficiency/HIV
Envelope/surface protein around capsid with…
Reverse Transcriptase (RT), Integrase (IN)…
Diploid/2 ss(+) RNAs genomes - to DNA (RT)
INT inserts DNA into genome, host expresses
Retrovirus Genes
LTR - long terminal repeat promoter, CIS!
GAG (capsid/protease) and POL (RT/INT)
ENV - surface protein and tat (TRANS activator)
HIV/AIDS
STD, blood, perinatal (in utero and breastmilk)
Phagocytes - spreads inside, “Trojan Horse”
T cells - kills, decline = AIDS, opportunists
MALT - kills, GI wasting, opportunists
Brain Phagocytes/Microglia - dementia
AIDS Cases - US Distribution
What most of the
world looks like
Class VII Hepatitis B
STD/blood/perinatal - chronic liver, cancer
Envelope/surface protein around capsid…
Partial dsDNA, encodes BOTH DNA Pol and RT
DNA Pol finishes DNA, host - RNA/proteins
RNA partly copied to DNA by RT - packaged
Contrast with A - acute, no envelope, food-water
acquired (Section 34.12)