AIDS: a role for CMV?

AIDS: A role for CMV?

Over the next five years, 20 to 30 percent of people infected with the human immunodeficiency virus (HIV) are expected to develop AIDS with its associated infections and tumors. Researchers have long sought a cofactor to explain why only some infected people get the syndrome, and the widespread cytomegalovirus (CMV) is a popular candidate.

W. Lawrence Drew of Mt. Zion Hospital in San Francisco now links CMV to a particular manifestation of AIDS, a skin cancer called Kaposi's sarcoma. And Paul Skolnik of Massachusetts General Hospital in Boston reports that infection of a cell culture with either HIV or CMV promotes infection by the other.

Based on epidemiologic evidence, Drew had previously suggested that CMV promotes the progression from HIV infection to AIDS (SN:8/3/85,p.77). In the current study he reports that a decrease of Kaposi's sarcoma among homosexuals with AIDS has been paralleled by a decrease of CMV in the homosexual community. While in 1981, 70 percent of a group of homosexuals who were CMV-negative became CMV-positive within eight months, in a similar uninfected group in 1985 only about 5 percent have become infected. Meanwhile, the incidence of Kaposi's sarcoma among homosexual men with AIDS has dropped from 63 percent of new AIDS cases in 1981 to 24 percent in 1985.

The association alone is clearly not an indication that CMV causes Kaposi's sarcoma -- other venereally spread diseases have also gone down. "But through many threads of evidence CMV keeps popping up," Drew says. Among the threads: Some laboratories have found CMV genes in Kaposi's sarcoma cells; the virus itself can cause cells in culture to become cancerous; cultured cells infected with CMV and implanted into mice will cause tumors; and Kaposi's sarcoma, like CMV, is less common among intravenous drug abusers with AIDS.

Skolnik approached the CMV-AIDS connection in the laboratory, via two experiments. To look at CMV's effect on HIV, he infected a flask of human cells in culture with HIV alone, and infected cells in a second flask with both HIV and CMV. The amount of HIV was one-hundred-fold greater when CMV was present. In a second experiment he infected some cells with HIV followed by CMV and infected some cells with CMV followed by HIV. He found that CMV was able to establish a productive infection only in cultures that had previously been infected with HIV.

The studies may supply a mechanism for CMV as a cofactor, Skolnik says. CMV could allow HIV to establish itself, or could promote HIV. If it comes before HIV infection, treatment or vaccination against CMV may prove helpful against AIDS; if it comes after HIV infection, learning how the two interact would shed light on the virus, Skolnik says.