From: KARYPM%SJUVM.BITNET@VM.USC.EDU (Paul M. Karagianis)
Newsgroups: sci.med.aids
Subject: Strains, subtypes and lethality.
Date: 28 Jul 92 19:17:41 GMT
Organization: UCLA, Computer Science Department
Note: non-commercial reproduction.
Archive-Number: 5799

The following source:

> From: matthew@ooc.uva.nl (Matthew Lewis)
> Subject: Conference Newspaper -Tuesday, 21 July - part 1
> Date: 21 Jul 92 20:06:46 GMT
> Organization: Center for Innovation and Cooperative Technology,
>               University of Amsterdam

  ...contains the following excerpt...

> A great deal of effort has already been invested in studying the
> variability of HIV. Dr Gerald Myers, of Los Alamos National
> Laboratories in the US, described a wider spectrum of HIV genetic
> diversity than had been originally observed. There are at least five
> major subtype lineages of HIV-1, and each subtype changes about
> 1% of its genes each year.
>
> Myers said that an HIV-infected individual soon becomes host to "a
> swarm of distinguishable variants" differing from each other by about
> 5%. He raised the possibility that infection by one subtype of HIV
> may actually prevent infection by another subtype. No one has ever
> been found who is infected with more than one subtype (not to be
> confused with variants of subtypes). It might be possible to harness
> this apparent inhibition, protecting people against lethal subtypes
> by inoculation with a less deadly one.  Myers said this theory might
> lead to a prophylactic vaccine but doubted that the world was "quite
> ready" to risk using an infectious agent, even a defective virus, to
> protect against AIDS.

  ...The Thursday edition contains...

> Two Thai subtypes identified
>
> Further insights into the mysterious ways of HIV subtypes have
> come from Dr Chin-Yih Ou and Dr Bruce Weniger of the Centers for
> Disease Control HIV/AIDS collaboration project in Bangkok.  Ou
> reported that two viral subtypes have been found in Thailand. One
> type is in patients likely to have contracted HIV via sexual
> transmission, while the other is confined largely to intravenous
> drug users.  None of the Thai patients had contracted HIV through
> blood transfusion.  As in related data presented previously by Dr
> Gerald Myers, no one has been found to be infected with both
> subtypes.
> The subtype found in female prostitutes, their male clients and the
> pregnant wives of those clients closely resembles the HIV subtype
> most prominent in Africa, including strains Uganda 455, Zaire Z6,
> NDK and MAL.
> The subtype found in drug users is essentially the same as that
> found in the North American and European strains LAI and ADA.
> The Thai data show a 22% genetic divergence between the two
> subtypes, indicating that HIV-1 was introduced twice into Thailand
> and that the current subtypes did not evolve from a common
> precursor virus after initial introduction into the country, Ou said.
> He added: "We do not fully understand the reasons for this
> segregation.  It could be that there is little high-risk contact
> between intravenous drug users and prostitutes and that the HIV
> epidemics are quite separate between these groups."  Other
> theories are that there may be biological differences in how easily
> the two subtypes can be transmitted, or that infection with one
> viral subtype may block infection with another.
>
> The Thai programme researchers are currently trying to determine
> whether the subtypes differ in pathogenicity.  They are running
> cohort studies, in prostitutes, young men and pregnant women, and
> they are now going back to determine the viral subtypes in each of
> these patients. This work should reveal some useful information
> about the relation of HIV subtypes to the progression of the disease.

  If I read these correctly a "strain" is a subset of a larger entity
known as a subtype, and infection by a single strain blocks infection
by other strains within different subtypes?  Furthermore, there is a
suspected difference in lethality between different subtypes or strains?

  The obvious conclusion (or gross oversimplification by a layman) is
that in the (near?) future, someone who discovers they are HIV+ will
follow the initial test with a strain or subtype analysis and be given
some idea of what the expected progression of their disease will be?

  Furthermore, there might currently exist HIV+ asymptomatic patients
who will discover that they apparently will not develop AIDS, are
essentially immune to other more lethal strains (or more likely strains
within other subtypes only?) and (in my final ignorance-based leap into
the wild blue yonder) are essentially walking live virus vaccines?

  I realize I sound like I'm hallucinating, but that's what the above
quotes suggest to me, so taking the time to shoot me down now may come
in handy later when the National Enquirer or somebody jumps to the same
conclusions.  Thanks for the time and consideration....   -Kary.
Newsgroups: sci.med.aids