Researchers have isolated a new strain of herpesvirus from cells of Kaposi's sarcoma, the most common cancer in AIDS patients. The achievement, reported in tomorrow's issue of the New England Journal of Medicine, may help researchers explore how the new virus is spread. Preliminary work with the virus already suggests it plays a role in the cancer's development.
Kaposi's lesions consist of spindle-shaped tumor cells in the lining of tiny blood vessels. A team led by virologist Gary Nabel of the University of Michigan Medical Center in Ann Arbor and pathologist Brian Nickoloff of Loyola University Medical Center isolated the new virus from cells in skin lesions taken from five HIV-positive people. Other groups had isolated unique herpes DNA fragments from Kaposi's lesions, but this is the first study to grow live virus from tumor cells. When the group added the virus to embryonic kidney cells, the cells became infected with viral DNA for 20 cell generations.
The finding is an important step in understanding the transmission of Kaposi's sarcoma, says Parkash Gill, a professor of pathology and medicine who studies these tumors at the University of Southern California. It's still unclear whether the virus causes the lesions, says Nabel, but the replication of virus seems to implicate it in the origin of the tumors.
That kidney epithelial cells are infected, Nabel says, may also help explain why Kaposi's sarcoma is common among gay men with AIDS. That's because epithelial cells line the rectum--a port of entry for the virus during anal sex--and embryonic kidney cells are closely related to those of the urogenital tract and bladder, which along with genital secretions could harbor the virus, he says.
Getting the herpesvirus to replicate in the test tube is a big step toward developing animal models of the new virus and antiviral drugs. Says Nabel, "All of these now become possibilities."