Biology 331Virology II

Class IV and V VirusesRNA/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)