New virus, growth factor found for AIDS.

New virus, growth factor found for AIDS

Yet another virus that apparentlycauses AIDS--along with a growth factor in the AIDS-associated Kaposi's sarcoma and a role for leukemia viruses in the AIDS scenario--were among the new findings presented by scientists during this week's Third International Conference on AIDS held in Washington, D.C.

According to Robert C. Gallo of theNational Cancer Institute (NCI) in Bethesda, Md., his research group and other collaborators have recently found the following:

In addition to the previously describedHIV-1 (also known as HTLV-III) and HIV-2 viruses, there appears to be a third, distinct retrovirus capable of causing the fatal disease. The scientists found the virus in blood samples from 10 Nigerian patients with AIDS or AIDS-like syndrome. Tests using the patients' serum and known AIDS viruses showed that the newly isolated virus is a separate human retrovirus that causes AIDS, says Gallo, who expects more such viruses will be found. He says the discovery increases the risk of infection by an AIDS-causing virus, but that "we shouldn't panic' since the virus seems to be less virulent than the other AIDS viruses.

Although the bluish or reddish skinnodules of Kaposi's sarcoma are frequently associated with AIDS, NCI scientists have determined that the syndrome probably is not directly caused by the HIV virus, says Gallo. And, he says, his group has regulated the growth of Kaposi's sarcoma cells in the laboratory for the first time, by manipulating the one or more growth factors released by retrovirus-infected lymphocytes. The factors, which cause new blood vessel growth and support longterm cultures of sarcoma cells, were produced in vitro by lymphocytes infected with HTLV-II, a retrovirus that does not cause AIDS. Despite the dramatic effects of these growth factors on the sarcoma cells, the same cells do not respond to other, well-known growth factors as do normal cells, says NCI scientist Shuji Nakamura.

Based on the data, Gallo says thesarcoma "is not a true malignancy, and should be easily controlled by interrupting the growth factor effects.' Although it is found in only 40 percent of AIDS patients and is not in itself life-threatening, systemic Kaposi's sarcoma can cause widespread problems including severe diarrhea, says Nakamura.

New studies of patients with coinfectionsof both an AIDS virus and a virus thought to cause leukemia suggest that the leukemia virus may advance the progression of AIDS, says Gallo. The virus, called HTLV-I, has been present in the United States for many years and is not considered very contagious. However, unpublished results from NCI say that HTLV-I is spreading through urban populations of intravenous drug abusers, a group considered at risk for AIDS. According to Gallo, the HTLV-I virus may lie dormant in infected cells for perhaps 30 years, but "it should not be forgotten' as a possible cofactor in AIDS. Because of their possible roles in AIDS, Gallo says HTLV-I and -II should be included in planned AIDS vaccines and in screening tests for donated blood.