Why can we get HIV to a viral load of 0 but can’t get rid of the virus?
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So a good bit of answers here but what you’re looking for is the reservoirs. While people are getting that it’s a retrovirus and inserts its DNA into cells to infect them, it’s not like cells have infinite life.
Effectively we have antiretroviral medications that target different steps in the process where HIV binds to and hijacks our cells. That includes preventing it from attaching to cells, keeping it from insert its DNA, etc. these drugs fall into different classes and generally most cocktails (most people take three drugs in one pill but there’s some exception). The standard backbone targets reverse transcriptase, then that’s paired with a protease inhibitor, a fusion inhibitor, an integrase inhibitor, etc.
Eventually after we keep it from replicating long enough you reduce the amount of free virus in the blood below the level that our current PCRs can detect them. That’s where we get the term undetectable.
BUT that refers to the blood. The cells within the blood will die off eventually and get recycled by the body so eventually you’ll really have a tiny amount in the blood. That means eventually you’ll also deplete the HIV infected white blood cells, which when they get recycled means you’ll reduce it in things like semen and other bodily fluids. That’s why undetectable people can’t transmit HIV (we now say that with the weight of fact behind it, we don’t say “reduces the chance” anymore).
But there’s part of the body where reservoirs can live like lymph nodes and microglial cells. Antiretroviral drugs don’t generally pass through the blood/brain barrier so while you’re eliminating HIV from the blood, there’s virus still elsewhere in the body that can reseed the body should the medication go away. We used to hope that we could eradicate after long enough treatment (in the order of 20 years) but that’s how we learned about these reservoirs.
(I’m an epidemiologist and work with HIV pretty exclusively)
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