Jun 9, 2009
Hi, I'm a medical student studying in the uk and i'm hoping you can help me clear up a rather confusing question. hiv when it enters the body targets cd4 t cells of which they can be active or resting, enters the cells and incorporates itself into it's DNA. hiv can only actively reproduce in active t cells, yet 95% of these cells are mostly resting. So if the virus enters the body of a previously uninfected individual and happens to only infect resting cells, does this mean that the virus can lay dormant indefinately or until the cells are activated by another virus? If so what difference would pep treatment make if these cellshave already been infected?
Response from Dr. McGowan
Thanks for your question and good luck with your studies. You raise an escellent point.
While HIV preferntially infects activated CD4 cells, it can also infect resting cells. It is the long-lived memory cells in the resting pool that is the "archive" of virus that makes it currently impossible to eradicate HIV once established.
The purpose of PEP is to effectively abort an HIV infection before it can get established. The early dynamics of HIV infection are now undergoing intense scrutiny. Work done by Dr Bruce Walker and others have shown that for PEP to be effective it has to be started as soon as possible and continued for enough time to be effective. The goal is to suppress HIV levels enough to allow stimulation and development of specific anti-HIV immune responses (CD8) that would eliminate the infection before it can spread systemically through the lymphatic system (Ref: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1687192). So, we are not relying fully on the ARV to stop viral replication (which would be most effective on the activated cells), in addition we are recruiting the immune system (while keeping the virus in check with meds). This would avoid the usual problem where the predator (CD4 cells) become the prey (for HIV).
Best of luck,
Rash with Bactrim/Atripla
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