Study Suggests AIDS Virus Did Not Come from Monkeys
NEW YORK (AP) _ The AIDS virus probably did not jump from monkeys to humans but could have infected the common ancestors of humans and monkeys millions of years ago, researchers say.
That conclusion comes from Japanese biologists who have determined the entire genetic code of the AIDS virus that infects African green monkeys. Some researchers have suggested that these monkeys may have been the source of the human AIDS virus.
The Japanese team found that the African green monkey AIDS virus differed from the two known human AIDS viruses in several important respects. If the virus had jumped from monkeys to humans in recent times, the viruses would be identical or nearly so.
The Japanese scientists’ findings appear in Thursday’s issue of Nature, a British scientific journal.
In an accompanying commentary, Carel Mulder, a biologist at the University of Massachusetts Medical School in Worcester, writes that the Japanese findings mean that ″the human viruses cannot have originated from African monkeys in recent times, as had been predicted by many people.″
Studies of these AIDS viruses and of AIDS viruses in other species of monkeys suggest that each species has its own AIDS virus. The two human AIDS viruses probably evolved in isolated populations in different places, the Japanese researchers said.
Humans and monkeys are both descendants of primitive primates that lived 20 million to 30 million years ago. The Japanese researchers, led by Masanori Hayami of the University of Tokyo, believe that an AIDS-like virus infected those primitive primates. As the primitive creatures evolved into humans and various species of monkeys, the parent AIDS virus evolved into the different forms seen today, the researchers speculated.
However, no AIDS virus is known in apes, which are more closely related to humans than are monkeys.
Norman Letvin, a physician and primate specialist at the Harvard Medical School, said of the Japanese research, ″This is yet another piece of data in support of what I think should now be accepted - that a jump of the virus did not occur.″
Asked why the virus has only recently been observed to cause disease, Letvin said that it could have existed until recently only in isolated populations, and that it might also have evolved into its present virulent form in comparatively recent times.
The virus that Hayami and his colleagues studied was isolated from a wild African green monkey obtained in Kenya, in East Africa. Their determination, or ″sequencing,″ of the virus’s genetic code shows that it lacks some genetic material carried by the human AIDS viruses.
The two human AIDS viruses are HIV-1, which is almost exclusively responsible for the worldwide epidemic of acquired immune deficiency syndrome, and HIV-2, which is mostly limited to West Africa but is now slowly beginning to spread.
The African green monkey virus lacks the so-called ″R″ gene present in HIV-1 and HIV-2.
In addition, it appears that the African green monkey virus does not make monkeys sick. It is conceivable, therefore, that the missing genetic material is required to make animals - or humans - sick. At this point, however, the function of the R gene is unknown, researchers said, although work is going on to determine this.
Letvin noted, however, that the only a very ambitious study of wild African green monkeys could conclusively establish that the monkeys do not get sick from AIDS.
Mulder, in his commentary, said part of the confusion over the source of the AIDS virus came from studies by Dr. Myron Essex and Dr. Phyllis Kanki of the Harvard School of Public Health that showed that HIV-2 and the monkey virus identified in rhesus monkeys are closely related.
In February, Essex and Kanki said some of their virus samples might have been contaminated and that the HIV-2 and the rhesus virus might not be as closely related as they had appeared to be.
In a telephone interview, Kanki said the research had no bearing on the question of where the AIDS virus arose. She suggested that differences among AIDS viruses in different species of monkey might not be as important as the Japanese researchers and Mulder speculate.
She noted that there can be more differences between different strains of HIV-1 than there are among the various monkey AIDS viruses. ″I’m not convinced that splitting the hairs about these species differences is useful,″ she said.