April 19, 1996
Media Contact: Michael Purdy
Phone: (410) 955-8725
Johns Hopkins researchers have found tentative evidence that yearly flu shots are safe for HIV-positive patients.
Clinicians treating these patients have been torn by concern that annual influenza vaccinations might increase HIV levels by stimulating the production of the immune cells in which the virus reproduces.
Marshall Glesby, M.D., a postdoctoral fellow at Johns Hopkins, treated HIV-positive patients with a flu-vaccine or a placebo, then measured HIV levels in the bloodstream for a month.
"We found that the influenza vaccinations had no significant impact on average patient HIV levels," Glesby says. "We should conduct further studies to determine if influenza is a common problem for HIV patients, and whether vaccinations are an effective way of reducing that problem."
Vaccines, which are weakened or inactivated forms of disease-causing agents, stimulate production of memory cells, a type of immune cell. Exposure to weakened germ creates memory cells that are primed to quickly recognize the germ if it returns. The memory cells can then summon the immune system's heavy weaponry to attack the infection before it spreads.
However, HIV infects and reproduces in a type of memory cell, the memory T-cell.
"Scientists have been worried about giving a vaccine that causes memory T-cells to multiply," says Glesby. "That's because these cells act like virus factories when they are infected by HIV."
Memory T-cells for any given germ are relatively rare, Glesby notes, and the number of those T-cells that are infected with HIV may be even rarer. This could explain the results of the study.
Glesby says, "The vaccine may have increased production of a small group of memory T-cells, and because only a few of these memory T-cells were infected with HIV, HIV levels did not go up significantly."
Patient response to the vaccine also could account for the results, he notes. HIV-positive patients respond less frequently to vaccines than the general population.
"It's becoming clearer that the answer to this question--does immune system stimulation aid HIV?-- may depend on what type of germ or vaccine is involved," he says. "Tuberculosis, for example, has been shown to increase HIV levels and accelerate progression to AIDS."
Glesby was selected to receive the annual Helen B. Taussig Award for his work with influenza vaccination and HIV patients. His mentor is Alfred Saah, M.D., Ph.D., an associate Hopkins professor of epidemiology and medicine. Glesby's study was funded by the National Institutes of Health.