Chimps, AIDS, And Immunity

Anonymous Coward writes "Researchers at the Biomedical Primate Research Center in The Netherlands have come up with a theory as to why modern chimps don't develop AIDS and its variants. The chimps in the study were found to share a usually uniform cluster of genes in the area that controls their immune systems' defenses against disease. This lack of genetic diversity suggests that a lethal sickness attacked chimps in the distant past. The theory postulates that approximately 2 million years ago an AIDS-like epidemic wiped out a large portion of the chimpanzee population. Those that survived developed an immunity to AIDS and its variants. If this theory holds true it may explain why some humans who are repeatedly exposed to HIV don't get sick."

unusually uniform cluster of genes

[non]

the poster got this part wrong. it is an unusually uniform cluster. from the article : "Chimps show more genetic variation than humans in all areas - with this one exception, which is seriously condensed," said Dr. Ronald Bontrop, who led a Dutch team that worked with statisticians from the University of California.

Rather simple

[praedor]

It is actually rather simple why certain people can be repeatedly exposed to HIV and not become productively infected. HIV requires its target cells have two cell surface proteins in order to infect it. One is the basic CD4 T cell receptor. The other is one of two different types of chemokine receptor. There is the CXCR4 and CCR5 receptors. The names derive from a common amino acid motif found in these receptors in most people: for CXCR4 it is cysteine-any amino-cysteine-arginine. For CCR5 it is cysteine-cysteine-arginine. Most of the people who appear immune to the infection contain a mutation in the CCR5 receptor (I'm not familiar with the CXCR4 receptor vis a vis mutations and infection resistance). Thus, HIV can bind to CD4 but because of the mutation in CCR5 it cannot complete the process and fuse with the cell. No fusion, no infection.

This common form of resistance doesn't require any cluster of genes nor any mysterious genetic variation or evolutionary alteration.

Re:How Does It Explain Human Immunity?

[Lshmael]

I think the article means that because humans and chimpanzees have incredibly similar DNA, a minority of the human population (just like a minority of the pre-epidemic chimp population) has immunity, just like those chimps that survived.

Perhaps some misunderstanding...

[broken_down_programm]

"Those that survived developed an immunity to AIDS and its variants. " ...Uh, IANA genetecist, but I THINK the way it works is that those that ALREADY had the peculiar genetic combination that would equip them to survive SIV where the ones that SURVIVED. Through their offspring this combination came to prevail in the population today...

I worked at the NCI

[muyThaiBxr]

About 5 years ago I worked at the National Cancer Institute, which is part of the NIH in the US. (Ft Detrick, Frederick, MD if you wanted to know) While I was there, my boss, (I was a labtech) did some analysis, and found out that a gene called CCR5 could be in people with a 32 base pair deletion. When this deletion was present from both the mother's chromosome and the father's, the person with the mutated form of the gene was basically immune to HIV even through repeated exposures. This was about 5 or 6 years ago, so I'd say OLD NEWS!

4-7 millions years ago. not 2.

[theirpuppet]

best estimates are 4-7 million years ago, our ancestors split off from the ancestors of modern apes.

2 million years ago, something happening to the ancestor of modern Chimpanzee isn't going to affect us, unless our ancestors were also involved.

duh! i wish these people would do more research before making such crap as 'it may explain why some humans who are repeatedly exposed to HIV don't get sick.'

Re:Rather simple

[Lurkingrue]

This paper sorta contradicts what I'd been hearing about simian models for HIV transmission. I'd understood that infection & incorporation of the retroviral sequences into the host genome takes place, but CD4 cell apoptosis is somehow avoided. nb: Dalgleish, O'Byrne: AdvCanRes 84:231-76 (2002) [nih.gov]

Virology is admittedly not my area of research, but I'd think that there seem to be two divergent opinions here on simian resistance. Anyone here working in the area care to explain the (seeming) contradiction?

Re:Monkey skin condoms!!

[Anonymous Coward]

I don't know what is sadder that someone said it or the fact that they are right. Just think about it. AIDS right now is killing off several types of "undesirables." First it is killing off the gay/lesbian and other sexual defectives. Next it is killing off intravenous drug users and such. Then it is kill off the so called "free bleeders." This removes thier defective genes fom the pool.

Now sometimes it does kill off a child or other innoccent but that is the way it goes. Mother nature doesn't worry about civilian casualties. Besides some of those children are nothing more than the defective offspring of a infective drug user or the like. They will be nothing more than a drain on socitiety anyway.

Possiblly most important is AIDS is striking with great efficency in the so called third world. Entire generations are being elminated in Africa and India. One estimate is that AIDS could claim as many as a billion by 2015. One can only hope those numbers are set concervitly low. In the space of a 15 years almost one sixth the excess drain on the Earth can be removed.

To get a added bonus, these figures are only for Africa and India. There is supposed to be a explosive outbreak in China. It is almost impossible to guess the size of this outbreak but excess population eliminated by 2010 could be as high as two hundred and fifty million.

Stick around, this will be a great thing indeed.

Re:AIDS, mortality, and timing.

[Mr.Ned]

AIDS is not something that just kinda turns up in your system one fine morning; is an epidemic that can be effectively prevented with some very basic safeguards.

Rape is a huge problem in Africa, especially in the kwa-Zulu Natal area that has been described as the 'epicenter of AIDS' now that Uganda has gotten things under control. AIDS really can just kinda turn up in your system one morning without you having any choice in the matter - for many people, it's often not as simple as wearing a condom and not sharing a needle.

Re:QUESTION FOR THE BIOCHEMISTS

[bluGill]

I'm not a biochemist, but I can answer the second one: Sometimes. Gene mutations are belived to be random. The chimp doesn't have a SIV specific gene, it has a gene that causes certian types of protiens. The protien then allows certian immunities. It might happen that the gene only affects SIV, more likely it affects several things, which might or might not include HIV.

One of the early vacinations for small pox was bassed on cow pox, once infected by cow pox you were immune to small pox. So yes, one infection can make you resistant to a different one. However there are many different viriues. Most people get the flu every year, and each time they get one strain they become resistant to that and several other, however appearently not the one that strikes the next year.

There are too many random factors in immunities and genetics to really answer your second question, but I tried.