CD28 COSTIMULATION AND T-LYMPHOCYTE PROLIFERATIVE RESPONSES IN HIV-1 INFECTION

To investigate whether defective costimulatory signals could be involv ed in the loss of T lymphocyte functions during HIV-1 infection, we te sted the effect of CD28 costimulation on both T cell receptor/CD3 and HIV-1 antigen-induced proliferative responses. Although CD3-mediated r esponses significantly decreased with more advanced stages of HIV-1 in fection, the ability of potentiating the responses through CD28 costim ulation was maintained at all stages and did not differ from that of H IV-1(-) subjects. When CD28 costimulation was studied in lymphocyte cu ltures stimulated with HIV-1 gp160 or p24, potentiation was seen only when a significant response was present without additional CD28 trigge ring, namely in subjects receiving active immunization with recombinan t gp160. These results confirm the integrity of the CD28 pathway of co stimulation during HIV-1 infection, and suggest that lymphocytes respo nding to soluble HIV-1 antigen are not deleted in HIV-l-infected patie nts, but do not receive significant priming during the natural course of the infection.