Is HIV slowing down?

[ARV-man]

i heard the rate of mutation in some strains of HIV is decreasing. but since drug use increases the level of mutant strains of HIV why is this happening???

[Ed_330i]

i have only heard that the European strain was slowing down, just alittle bit.

[Jarryd]

Although this may seem like somewhat of a harsh way of saying it, but wouldn't those who have HIV be more easily detected and 'quarintined' (sorry for spelling). This alone you could say would slow down the rate of mutation because their is a decrease in population size of a virus, therefor the chances of a mutation occuring at a given time would decrease. Also with a condition such as HIV you tend to either be doing great (because of drugs working correctly) or not doing well at all which may result in death which would kill the mutant strain anyway.

[Mokele]

This alone you could say would slow down the rate of mutation because their is a decrease in population size of a virus, therefor the chances of a mutation occuring at a given time would decrease.

 

Actually, the rate of new mutations appearing is pretty much constant regardless of population size; that's the basis behind the 'molecular clock' used in phylogenies. We actually did the math behind it in Evolution, and the terms for population size drop out of the equation. Basically, in small population, a mutation will be a bigger fraction of the total genepool, but in a large population there's more individuals to mutate.

 

As for HIV, from what I understand it's simply evolving. In societies where there's a substantial time between sexual partners, those variants which take longer to become AIDS will be more likely to be transmitted than their less restrained brethren. However, they pay the price of having to remain 'dormant' longer. On the other hand, those variants in an environment with numerous potentials for transmission have no such pressure, and thus the fastest-reproducing virus wins. This has cumulated in the recent discovery of an HIV variant which is immune to 3 of the 4 drug cocktails and all but one of the nearly 20 anti-retroviral drugs, and goes from infection to full-blown AIDS in less than 6 months, iirc. It was found in NYC, and the health officials were pretty much shitting bricks over this, since it was in (as would be predicted from the above) and *extremely* sexually active individual (hundreds of sexual partners in that time frame).

 

Mokele

[LucidDreamer]

i heard the rate of mutation in some strains of HIV is decreasing. but since drug use increases the level of mutant strains of HIV why is this happening???

The terminology gets a little confusing when we use the words rate of mutation. DNA mutation rate in the same environment is constant, but the variables in the environment are numerous (including the method of replication). The anti-HIV drugs actually reduce the amount of overall mutations in the population because there are fewer viruses to mutate. If we are determining the rate of mutation of a virus by how many different forms or clades that we observe in a population over a period of time, then we would conclude that the rate of mutation of HIV has decreased after the introduction of the drugs. But if we were to study the rate of mutation by factoring in the total amount of virus, then the mutational rate would be the same. Drugs don't increase the mutational rate; they only provide a selection process that leads to a form of virus that is more resistant to drugs. At the same time, with the cocktail there is very little chance that a virus will be able to mutate into a viable form because it will have to triple mutate.

[ARV-man]

To clarify, yes, i did mean HIV-1, the european and north american strain, (group M) and i'm only talking about the wild-type form (i.e. no exposure to drug treatments) in lab studies.