Immune Control of HIV Replication
Bruce Walker, M.D., Provides an Update
July 21, 2009
There's nothing like hearing the results of studies directly from those who actually conducted the research. In this summary, you'll hear Bruce Walker, M.D., discuss his plenary paper, "Immune Control of HIV Replication." To view a video of Dr. Walker's talk, click here. To view his slides, click here.
Bruce Walker: I presented data from our studies that we've been doing collaboratively in KwaZulu-Natal, the heart of the epidemic, regarding how the body tries to fight HIV infection, and attempts to understand why some people develop AIDS within six months of becoming infected1 and other people actually do well and seem to be able to survive without the virus ever causing disease. We've had some clues thus far from those studies indicating that partly it's the immune system forcing the virus to become something it doesn't want to be. And particularly if one directs immune response against the CAPSID program protein, the gag protein, one can force the virus in that direction.
One of the key points I would like as a take-home from this is that we're still a long ways away from a vaccine. Working at the heart of the epidemic in KwaZulu-Natal, one gets a perspective on where the problems are. In screening pregnant women coming into the clinic that we work out of there, and stratifying by age, we discovered this really horrifying statistic, which is that up until about age 15 women are not infected. But in this particular location now, today, by the time those kids are 22 years old, 66% of them are HIV infected.
To me what that says is there's this incredible window of opportunity with adolescents and we're a long ways away from a vaccine. We need to do everything we can to try and prevent those kids from becoming infected. As an immunologist talking about vaccines and immune responses, I ended up by talking about a soccer program to teach life skills to kids to try and help prevent them from becoming infected.
Craig McClure: Bruce, during your talk, you talked about ongoing HIV replication and HIV mutations caused by post-immunity over time that are then being transmitted. What do you think are the potential implications of that in terms of possibly a more virulent virus in the future?
Bruce Walker: We're seeing that to some degree in mother-to-child transmission -- where the virus learns from the mother's immune system how to avoid that immune system and is then passed to the child. The child gets part of its immune system from the mother, and so we've seen circumstances where you would expect somebody to be a slow progressor with appropriate HLA allele, when in fact they're not able to use that HLA allele to fight the virus. So there are implications.
I think though that the other implication is that some of these resistant strains that are getting transmitted are less virulent, so they're causing less damage in the critical, early stages of infection. And so how this is exactly going to play out, I think, still remains to be seen. We presented some data yesterday -- Toshi Miura did -- on a bunch of individuals who became elite controllers or HIV controllers -- people able to suppress the virus to very low levels without treatment.2 What we found in those individuals was that there was an enrichment for those people becoming infected with these mutated viruses that don't replicate as well, where the immune system's left its mark on the virus. So the virus, even though it got transmitted, it actually causes less damage in its recipient. So it can sort of go both ways. It depends on to what extent having that mutation cripples the virus versus to what extent the mutation, if it's not a crippling mutation and it gets passed on, is a problem because then you don't have an ability to see that virus.
This transcript has been lightly edited for clarity.
This article was provided by TheBodyPRO. It is a part of the publication The 5th International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention.