HIV-1 vs HIV-2

[RYBICKI, ED]

> To:            virology at net.bio.net
> From:          "Patrick O'Neil" <patrick at corona>
> Subject:       Re: HIV-1 vs HIV-2
> On 15 Mar 1995, RYBICKI, ED wrote:
> 
> > > The most parsimonious scenario of all has an HIV ancestor 
> > 
> > Whaaaaaaaat?  Says who?!  All of a sudden, HIV has been in 
HUMANS 
> > for a thousand odd years, and gets BACK into simians??
... 
> Not really.  More jumps are required, based on sequence 
homologies, if 
> one starts with SIV (as seen in chimps) and then assumes a jump to 
humans.
...
> Low pathogenicity within a host doesn't necessarily a "better" 
adaption. 
> If selective pressures within a natural host population favor 
rapid
> transmission and pathogenesis, then it will develop in that 
direction
> regardless of how long the virus has been floating around within 
the host
> population. 

This seems to be a new "current wisdom" - which does not necessarily 
invalidate the old, which held that the milder a virus was in its 
host, the better adapted it was.

But two excellent replies to my followup, sorry I have to do this 
thru the group, but the address for Patrick (note: not O'Neil B-)) 
doesn't work from my server.  Thanks Patrick!

> Low pathogenicity within the host might just as well indicate a 
recent 
> move into that population, meaning that the virus hasn't quite 
developed 
> for maximum efficiency within that host, just as an overly high 
> pathogenicity could mean the same thing IF it reduces the rate of 
> successful transmission.
> 
> 
  _____________________________________________________
 | Ed Rybicki, PhD          |  (ed at molbiol.uct.ac.za)  |
 | Dept Microbiology        | University of Cape Town  |    
 | Private Bag, Rondebosch  |   7700, South Africa     |          
 | fax: xx27-21-650 4023    |  tel: xx27-21-650 3265   |  
 |       URL: http://www.uct.ac.za/microbiology        |
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