host pathogen evo: PtERV and HIV vs TRIM5a

[Guest guest]

I read this article on HERV in the NYer a few weeks ago. Most

interesting was a hypothesis for why HIV-like viruses are

hypervirulent in man yet pretty harmless for the other apes. It seems

that dozens of copies of an ERV called PtERV are present in other

great apes, and humans don't have any of these. The human version of

the antiviral protein TRIM5a offers high protection in vitro against

PtERV, but is ineffective against HIV - vice versa for the TRIM5a of

the chimp (which is slightly different from the human TRIM5a).

The surmise/guess is that early humans were free of viruses from the

HIV lineage, leaving their TRIM5a free to evolve towards effectiveness

against viruses of lineage PtERV. Pressure on TRIM5a to evolve towards

excellent anti-PtERV function, in the total absence of any pressure

from HIV-lineage viruses, would of course be not unlikely to promote

significant (or total) loss of anti-HIV function.

Then the HIV lineage spreads back to man circa 1940-1970 or whenever,

and we end up with the AIDS epidemic. Perhaps other human-chimp

differences are necessary for HIV-like viruses to end up acting

hypervirulently (AIDS), or perhaps our TRIM5a differences are enough

all by themselves.

http://www.newyorker.com/reporting/2007/12/03/071203fa_fact_specter?currentPage=\

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