EFFECT OF IMMUNIZATION WITH A COMMON RECALL ANTIGEN ON VIRAL EXPRESSION IN PATIENTS INFECTED WITH HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1

Background. Activation of the immune system is a normal response to an tigenic stimulation, and such activation enhances the replication of h uman immunodeficiency virus type 1 (HIV-1). We studied the effect of i mmunization with a common recall antigen on viral expression in HIV-1- infected patients, on the ability to isolate virus, and on the suscept ibility to HIV-1 infection of peripheral-blood mononuclear cells (PBMC s) from control subjects not infected with HIV-1. Methods. Thirteen HI V-1-infected patients and 10 uninfected adults were given a 0.5-ml boo ster dose of tetanus toroid. Studies were performed to evaluate change s in the degree of plasma viremia, proviral burden, the ability to iso late HIV-1, and the susceptibility of PBMCs to acute infection in vitr o. Two patients underwent sequential lymph-node biopsies for the asses sment of viral burden in these tissues. Results. All 13 HIV-1-infected patients had transient increases in plasma viremia after immunization , and the proviral burden increased in 11. These changes did not corre late with the base-line CD4+ T-cell counts. The lymph-node tissue also had increases in the proviral burden and viral RNA after immunization . The virus was more easily isolated from PBMCs from nine of the patie nts after immunization than before immunization. Despite considerable variability in the results, PBMCs from 7 of the 10 normal subjects wer e more easily infected in vitro with HIV-1 after immunization than bef ore immunization. Conclusions. Activation of the immune system by an o ngoing antigen-specific immune response to an exogenous stimulus trans iently increases the expression of HIV-1 and may enhance the susceptib ility of uninfected subjects to HIV-1. (C) 1996, Massachusetts Medical Society.