Why can we get HIV to a viral load of 0 but can’t get rid of the virus?
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When testing viral load, it is only looking at blood. However, the virus will also infect cells in other areas that can’t be detected.
HIV is a DNA retrovirus. That means that it alters the DNA of cells that it infects with the sequences needed to make more HIV.
So zero viral load means that no HIV is in your system, but there are still cells in your body that have DNA that codes for HIV and that cell can make more at any time. HIV drugs prevent cells from making new HIV, but if you stop the drugs your infected cells will just start pumping it out again.
There are a few things different about HIV that together create this situation.
First, every test for something in the body has a limit of detection. For example, your average viral load test might be able to detect a few viruses in a small vial of blood (in reality it’s not this sensitive). However, this level of sensitivity still isn’t good enough to detect a very small amount of viruses hiding within hidden reservoirs in the body.
The above situation in particular can occur because the hiv genome is capable of integrating itself into cells in the body, and then lie dormant without producing any viruses. The drugs that we use to attack HIV only stop the virus from infecting new cells. We rely on the virus production process itself along with the natural turn over of cells to kill infected cells. If the virus isn’t being produced in a cell that’s long lived, the viral reservoirs can remain for a long time even when the virus itself is undetectable in your blood.
Once you stop treatment, some of these reservoirs will wake up and start making viruses again. Since HIV is a virus that attacks the immune system itself, the immune system can’t really deal with even a small number of hiv viruses, and so the viral load will go back up again.
Its like a whack-a-mole…. the drugs keep hitting the box, so when the virus pokes its head out, it gets whammed, but we can’t get inside the box….. and when medication stops, it happily propagates.
HIV is a tricky virus because it hides inside certain cells in your body, like immune cells, making it hard to completely get rid of. Medications can reduce the amount of virus in your blood to very low levels, almost zero, which is called an undetectable viral load. However, the virus can still hide in these cells and might come back if you stop taking the medication. So, we can control it very well, but getting rid of it completely is challenging because of these hiding spots.
Yes the DNA answers are correct but the *main* reason is that HIV lives in reservoirs within the body where ARVs don’t reach. So while the viral load circulating in the blood is zero or close to zero – HIV still can exist within these reservoirs. If HAART is stopped – the virus will start to reproduce and spread. That’s why we are close to a functioning cure with current treatment options – but we can’t fully eradicate HIV from a person – yet. So we are careful to say that HIV is *treatable* and *manageable* but not curable.
However despite these reservoirs folks who are undetectable (viral load of less than 40 copies is usually the standard) CANNOT transmit HIV. Even if they have sex without a condom. That’s why getting treatment to folks as soon as they are diagnosed is so important because 1) it effectively gives positive folks their lives and health back and 2) *prevents* new infections. There’s an individual and a collective benefit to treatment.
HIV PrEP/PEP and newly diagnosed counselor here.
“Viral load” refers to the amount of the virus in the blood. If the virus is dormant in a cell and not reproducing, then there is no virus freely flowing around the blood.
That is an excellent question, and the concept of latency (which is responsible for this) is the main reason why we cannot cure HIV at the moment.
Think of your body as composed of millions of small independent factories (your cells).
Each factory (cell) has access to the same schematic but only produces certain parts from the blueprints. This means that the products produced, although different, look very similar and can be recognised as “self” (by your immune system), they belong there. If the factory at any point fails this inspection it is immidiately shut down and destroyed.
What HIV has the ability to do is place it’s own set of blueprints into the schematic and cause your factories to produce HIV parts, which can be recognised as foreign. However, each factory has to decide what blueprint to produce, this means that factories can go on for a long time without producing any HIV parts.
With the current drugs (ART) we have the ability to stop this process, both the production of new HIV and the integration of the blueprints and therefore remove all chance of transmission. BUT ART doesn’t remove the blueprints already integrated, they remain there until the factory is destroyed.
If the factories with HIV blueprints don’t produce anything that labels them as infected they avoid destruction (by the immune system). They then remain and act as a reservoir ready to produce HIV if ART is stopped.
This is of course very simplified and there are lots of aspects that can be a elaborated on, so feel free to ask any questions.
Maybe an analogy helps:
It’s like fighting racism: you can remove every poster, outlaw all speech, and ban every content promoting it, but that won’t get rid of it inside the heads of the people.
Just with cells’ DNA instead of heads.
Usually HIV drugs are huge and cannot enter the Blood Brain Barrier , and thus there is still viral reservoirs in the brain/spinal fluid.
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