Hi chickeny- I like your thinking- you’re thinking like a scientist!
The thing about viruses is that they need a host to be able to multiply. This is because they don’t have the machinery to be able to divide in the way a cell does- they’re pretty simple really, almost not alive.
This means that it would be impossible for a virus to counteract another virus directly, because they only target cells. However, if a virus could be used to reduce the chance of HIV attaching to cells by changing the cells behaviour- that would be good!
Hope this helps P.S. I like the good/ bad bacteria bit- spot on!
I might be wrong about this – but I think a big part of good bacteria being able to counter bad bacteria in your gut has to do with them crowding the bad bacteria out, so that they can’t get a foothold to start growing! And the thing about bacteria is that many of them are upstanding, self-respecting living things in their own right – they might rely on your gut for food, but they also help break down some of the things we eat so that it’s easy for us to absorb, so it’s a win-win situation.
Viruses, on the other hand, can’t really live like that. To a virus, all a cell really is, is a baby-making factory! Whatever virus you inject into your blood, as long as it is able to get into human cells, it will use that cell to make lots and lots of new viruses and then kill that cell in the process – and it can either do that immediately upon infection, or after hiding in that cell for a long time (which is what HIV does). In theory it might be possible to engineer a virus that specifically hunts down and kills cells that have been infected by HIV, before it can produce more baby viruses and infect more cells – but this would be really difficult because HIV hides inside the cell like a ninja and tries really hard not to show anything different on the outside of that cell.
On the other hand, we can use viruses in other ways – some people in my old lab are actually trying to use a different kind of virus to cure HIV! But not by getting this new virus to attack HIV directly. Viruses specialise in sticking their own genetic material (DNA or RNA) into cells, and changing the instructions that tell a cell how to behave. These scientists have made a virus that sticks a bit of DNA into your muscle cells, that tells them to make antibodies against the HIV virus! This is a really clever idea – usually muscle cells are NOT the cells in charge of making antibodies – but the reason why HIV is so scary is because it attacks and cripples your immune system, and at the same time has many strategies to stop your body making good antibodies against it. So we can use specially engineered viruses to side-step the immune system altogether, and tell a part of your body that’s still healthy to make the antibodies we need!