According to a study, investigators at the National Institute of Allergy and Infectious Diseases discovered that activation of the immune system by other stimuli boosts HIV replication in HIV-infected people. Dr. Sharilyn Stanley and colleagues inoculated 13 asymptomatic HIV-infected people and 10 uninfected volunteers with tetanus booster shots to stimulate their immune system. Blood samples were drawn on the day of the injection and 3, 7, 14, 21, 28, and 42 days later. Findings showed that the amount of HIV in the blood streams of HIV-infected subjects increased 2- to 36-fold following immunization. Notably, the virus was much more readily grown from the blood cells of 9 of the HIV-infected patients after immunization. In addition, examinations of the immune system cells of the uninfected volunteers found that cells from 7 of these 10 people were more easily infected with HIV in the test tube after immunization than before immunization. Overall, data suggest that ongoing immune activation may play a part in HIV pathogenesis and may also enhance susceptibility of uninfected people to HIV. However, it was noted that the increases in HIV following immunization were transient and that the protection afforded by immunization most likely outweighs the potential risks resulting from the transient increase in HIV. Development of therapies against microbes that contribute to a state of chronic and persistent immune activation in HIV-infected people is recommended.