Unique Genetic Regions
There are at least two regions of the HTLV-III virus—called sor and 3’ orf—that have no direct counterpart in any other retrovirus studied to date. According to the Nature report, sor may be a remnant of a former envelope gene; 3’ orf may not be a gene at all, since only one of the two HTLV-III isolates that were sequenced contained such a region.
The nucleotide sequences of two isolates studied by the American group differed by about 1 percent, Dr. Haseltine told GEN. Similarly, the genetic analysis of the LAV isolate by the French group—which appears in the January issue of Cell—differed from either of the American sequences by about 1 percent.
“I think the fundamental thing is that they [HTLV-III and the LAV] are the same agent—there’s no doubt any longer,” said Dr. Haseltine.
Chiron Corporation has analyzed a virus known as ARV (AIDS-Related Virus) and expects to publish their results in the February 1 issue of Science. Dr. Haseltine said, based on discussions he has had with members of the Chiron group, that the ARV is yet another isolate of the HTLV-III virus.
In related work, the American team claims that the HTLV-III virus, like the other HTLV viruses, alters cells by affecting the mechanism by which genes are transcribed, a phenomenon called trans-acting transcriptional regulation (TAT). They suggest that the common structural and functional features of the HTLV viruses—the presence of the lor gene and the TAT phenomenon—set the HTLV family of viruses apart from other retroviruses.
8,000 AIDS Cases
Nearly 8,000 cases of AIDS have been reported in the United States since 1981, and more than 45 percent of the victims have died.
Although government agencies and the scientific community have been criticized—particularly by members of the major risk group, male homosexuals—for not gearing up to study the problem quickly enough, many investigators in the field now feel that research has progressed at an astonishing pace.
“The whole series of experiments that have been done so far have been accomplished in record time—from first recognition of the HTLV-III virus to complete nucleotide sequencing in less than nine months,” Dr. Haseltine said.
“This particular effort represents a very good cooperation among a number of research groups that one might otherwise think would be competitive—and I think it represents the recognition that AIDS is a very important problem that needs an immediate solution,” he added.