Why can we get HIV to a viral load of 0 but can’t get rid of the virus?
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Because the viral load never gets to actually zero it just gets so low that it’s not detectable. The virus still lives in small reservoirs in your body where medications can’t get to.
When HIV infects a cell, it basically hijacks the cell. It fuses together with it. Then it hijacks the machinery to replicate. All the drugs do is interfere with this replication. It’s much harder to get rid of HIV from those cells, and you don’t want to get rid of all those cells, because those cells are your immune system.
HIV actually has mechanisms for integrating itself into its host’s DNA. It’s a long, complicated explanation for how it achieves this, but every time HIV-infected cells reproduce, so too does the virus.
The way I see it is like a garbage can. It needs to be emptied on a regular basis. If you don’t, then the trash would accumulate and cause a mess.
Antiviral and antiretroviral drugs we currently have are virustatic. They do not destroy virus instances. They merely interfere in the reproduction and growth of these viruses.
The issue lies in the very nature of HIV. It’s a retrovirus, so it sticks its genetic material into the host’s DNA. So in order for scientists to “permanently uninstall” HIV, it needs to be removed from the host’s DNA once and for all.
We already have tools that can theoretically do this, and the best one is CRISPR. But we’re in the early stages. Only mouse trials have been shown to work, and that doesn’t necessarily translate to humans, so we’d need to test on animals next.
Additionally, there’s worry of what are called “off-target effects”, which means CRISRP might by accident remove non-HIV DNA from the host’s DNA, so we should be absolutely sure a potential treatment will be safe. Some scientists worry that even after some CRISPR components finish its job, others might linger and remove DNA unpredictably, but that’s lesser of a worry.
In short, current anti-HIV drugs only control the infection. They can’t cure HIV completely because HIV is constantly getting made, all because it has become integrated into our very own DNA. We have a tool that can excise the HIV parts from the host’s DNA, but we still don’t have a safe and functional model for humans.
Okay every answer so far is some degree of wrong, so here goes.
To put it simply, HIV writes its own genome into the host genome after it infects a cell. From then on, every time the cell copies its genome to divide, the viral genome gets copied along with it.
Currently we have no way of getting the viral genome out of the host genome. The best we can do is block the production of new infectious viruses.
Source: I’m in med school and we just had a lecture on HIV a few weeks ago.
The term is “reservoir” – HIV lives in cells. The ways of attacking it interfere with its reproduction, they don’t actually kill it. Small numbers of it infect tissue outside the immune system and can live there for years until inexplicably multiplying.
Source: Wrote my senior thesis on AIDS mortality trends.
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)
I wanted to talk a little about this because I’m currently working in an HIV lab and kind of know the basics of this!
Essentially, HIV does this thing where it gets into the DNA of cells and can stay there indefinitely. It won’t always be expressed, which is why you can get the viral load down to 0; the virus isn’t being produced when it’s not expressed. However, because it stays inside your cells, it can start producing virus at any time (I’m not too sure about the specifics of this but that’s essentially what happens). That’s why there is no cure, because we currently have no way of isolating cells in your body that have this HIV DNA and getting rid of them. Not only does it get into random immune cells, it can also put itself randomly at any place in the DNA, which makes it a lot harder to target.
I hope this makes sense! And if anyone wants to correct me please do, I’m still learning 🙂
HIV infection creates reservoirs of virus in the lymphatic system adjacent to the gut, where meds and the immune system can’t work very well.
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