[mortonman1]

how does a HiV virus mutate. Im not asking what it mutates, only how. Any answers are fine with me, including what happens, what changes, but try to stick to how. Thanks guys. all answers appreciated

[dttom]

Doesn't it just mutate, but without much concern on repair so the observed mutation rate is high?

[mortonman1]

I don't know! ha Thats what i want to know. what I know is that glycoproteins change, most like gp41 and gp120. I know not much more

[CharonY]

Error prone replications system.

[mortonman1]

Okay, so somehow the DNA sets itself up to mutate, without making mistakes in other areas besides glycoproteins. How? and what changes? please be specific

[cypress]

Other mutations are made but they generally damage function and the variations do not compete. The mutations that do compete are the one of which you speak these are the ones that lead to adaptations that happen to defeat/confuse immune response. Non-conserved mutations occur throughout the RNA. Recognize that HIV is a retrovirus with its genetic code stored as RNA as opposed to DNA. Once inside the cell the virus uses its enzyme reverse transcriptase to generate DNA which is then transported to the host cell machinery to be duplicated.

GP120 and GP41 are the proteins that bind to the host cell and provide the mechanism for entry into the host. Alterations to these proteins impact entry efficiency but do not seem to impact internal viral function. Alterations to systems performing internal function seem to be mostly deleterious and thus the present configuration is highly conserved.

[dttom]

DNA sets itself to mutate... not so correct.
mutation will occur, but the virus has trace mechanism to repair, so they appear to mutate.
In other organisms (so called more stable ones), again mutations do occur, but be repair to a larger extent, they just don't appear to be so much mutated...
So mutation is not a result of an active mechanism, but from passive ones like error in replication, environmental mutagens.etc.

[CharonY]

Most polymerases have a proof reading element, which the HIV polymerase lacks. As mentioned, it already lacks other DNA repair mechanisms Note that errors are everywhere not only in specific proteins. However, those that are defective are simply not infectious and those that do not provide any selective advantages (as the receptors) vanish or are not detected. As viruses do not have to maintain metabolism and reproduce in huge quantities, it can allow itself to produce a lot of crap.

This post has been edited by CharonY: 21 June 2010 - 12:19 AM

[mortonman1]

Ok all of that made sense luckily, even though I don't have much knowledge of it. i was wondering however, that if the gp41 and/or gp120 proteins changed, that would reduce efficiency of getting into host cell?

[CharonY]

Depends on which regions change. If the binding to the surface receptor of the host gets diminished in the process, then yes.

[qwasi]

Hi,

HIV mutations occur a lot and are completely random.
HIV has a RNA genome which, during replication, it must convert to a DNA genome. The enzyme involved is called reverse transcriptase and, unlike other enzymes involved in DNA replication, it has no proof-reading activity. This means that when copying the RNA to DNA it makes a lot of mistakes that go uncorrected. Therefore, when the DNA copy of the HIV genome is made it is different to the original RNA copy. Many different HIV genomes can be generated.

The mutations are completely random and so any region of the virus' structure can be changed. However, only those mutations that benefit the virus will be retained. This means if a mutation occurs in a region the virus uses to adhere to cells, the virus will be unable to adhere efficiently and will be unable to enter cells and replicate. These viruses will be selected against. A mutation in a region that is not involved in essential stages like adherence etc. may be useful to the virus and enable it to evade the host's immune system. Viruses with these mutations will therefore survive so this mutation will be retained.

Hope this helps.