Herpesvirus Infection May Slow HIV

New research raises the possibility of harnessing a common type of herpes virus to treat or even prevent HIV infection. In laboratory tests, the human herpesvirus 6 (HHV-6) slowed the reproduction of forms of HIV that are active in the early stages of HIV infection. But it did not have the same effect on more aggressive variants of HIV that appear later in the disease.

"This virus may play a profound role in development of HIV disease," said Dr. Leonid Margolis of the National Institute of Child Health and Human Development in Bethesda, Md. If HHV-6 does prove to be important in the progression of HIV, "it potentially can be used as a tool to manipulate HIV or even to prevent infection," Margolis said.

To see how HHV-6 and HIV interact, Margolis, Jean-Charles Grivel and colleagues took small blocks of human tonsil tissue and infected the tissue with HHV-6 and HIV. They found that HHV-6 blocked the reproduction of the type of HIV that transmits infection and is dominant afterwards, but it did not inhibit the HIV variant that is active later in the disease process, according to the report published in Nature Medicine (November 2001; 7: 1232-1235). Margolis and colleagues found that HHV-6 produces large quantities of a substance called RANTES. The researchers believe that this substance prevents the early-stage variant of HIV from reproducing by keeping it from attaching to the receptor on immune cells. Since HHV-6 and HIV infect the same type of cells, lymphocytes, HHV-6 "induces secretion of this anti-HIV factor exactly where it is most necessary, in lymphoid tissue," Margolis said.

But Margolis and colleagues found that there is a flip side of the coin. Even though HHV-6 seems to keep HIV under control in the early stages of infection, the virus may actually encourage the virus as the infection progresses, one of the co-authors said. To see whether HHV-6 is a conspirator of HIV or is just an innocent bystander, Paolo Lusso, who heads the human virology unit of the San Raffaele Scientific Institute in Milan, Italy, and other researchers have started studying the behavior of the two viruses in monkeys infected with SIV, the monkey form of HIV. Preliminary results show that monkeys infected with both viruses progress to AIDS much more rapidly than monkeys that only have SIV, Lusso explained.

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