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NEW YORK- The discovery of a possible new herpes virus may help explain why some AIDS patients develop a rare form of cancer called Kaposi's sarcoma.

Kaposi's sarcoma (KS) is a rare form of cancer that causes purple blotchy marks on the skin. and can eventually spread to lymph glands and the digestive tract. Before the 1980's it was rarely seen except in older patients of Mediterranean extraction with impaired immune systems. Then with the advent of the AIDS epidemic, physicians suddenly began to see hundreds of cases of Kaposi's sarcoma. Moreover, the form now seen in up to a third of AIDS patients is more aggressive than the previous form.

Clinicians soon observed that the cancer was much more prevalent in homosexual male AIDS patients, up to 20 times more frequent than in heterosexual patients with AIDS. This led to the hypothesis that a sexually transmitted infectious organism could be associated with KS transmission. A number of potential causes were proposed including cytomegalovirus, hepatitis B virus and HIV itself. Nitrite inhalers, poppers, were also considered. None of these were proven to cause KS.

A team of researchers at Columbia University obtained KS specimens from 27 patients who had died of AIDS. Using a new technique for purifying selected DNA sequences from within the genome called "representational difference analysis", the researchers found that 25 of the 27 specimens had DNA sequences associated with herpes viruses. The new method makes simplified "representations" of genomes from diseased and normal tissue, using PCR to amplify short DNA sequences. A representation from diseased tissue is attached to a priming sequence and hybridized to a normal tissue representation. Subsequent rounds of PCR reveal unique DNA sequences in the diseased tissue.

Using this technique, the researchers also evaluated other tissues. They found the herpes DNA sequences in only six of 39 non-KS tissues from AIDS patients, and in none of the tissues of people who did not have AIDS or KS. Two of six positive specimens from AIDS patients were from patients with KS in other sites. Another three positive specimens were from patients who may have been in early stages of KS.

The researchers identified DNA sequences containing fragments of genes common to several herpes viruses in the Kaposi's sarcoma tissues. The sequences are homologous to those seen in other herpes viruses, saimiri and Epstein Barr virus. However, the sequences were different enough to suggest a new human herpes virus may have been discovered.

The current research remains preliminary. The existence of the new herpes virus remains to be confirmed and visualized. Moreover, more research will be needed to determine if the virus does indeed cause or promote KS, or if it is merely a passenger in the KS lesions. Researchers will also want to look at KS in non AIDS patients for signs of the virus.

If indeed future research confirms a causal link between a new herpes virus and KS, it might be possible to develop improved diagnostic and treatment approaches for this form of cancer which is currently difficult to treat and impossible to cure..

Recent research has shown that viruses can cause cancers, notably, papilloma virus and cervical cancer; Epstein-Barr virus and lymphoma; and HTLV, a relative of HIV, and a form of leukemia.

For more information see: Chang et al., Science, v.266, 12/16/94, pp. 1865-1869.

Transmitted: 94-12-29 14:58:31 EST