IMMUNIZATION WITH CLASS-I HUMAN HISTOCOMPATIBILITY LEUKOCYTE ANTIGEN CAN PROTECT MACAQUES AGAINST CHALLENGE INFECTION WITH SIVMAC-32H

Objective: To evaluate the efficacy of immunopurified class I human hi stocompatibility leukocyte antigen (HLA) to protect against SIV infect ion. Methods: HLA class I antigens were immunopurified from a human B- lymphoblastoid cell line. Groups of four macaques were vaccinated subc utaneously with four doses of the immunogen in adjuvant, or with adjuv ant alone and subsequently challenged intravenously with 10 median mon key infectious doses of cell-free SIVmac-32H. Infection was determined by polymerase chain reaction for SIVmac proviral DNA and by virus iso lation. Antigen-specific humoral and cellular immune responses were mo nitored. Results: Macaques immunized with the HLA molecules produced a nti-HLA class I antibodies that inhibited SIV replication in vitro and downregulated autologous T-cell proliferation against irradiated C816 6 cells. They were partially protected (two out of four) from virus in fection for at least 33 weeks when challenged with SIV grown in human cells. All four control animals were infected. Conclusions: This demon stration of partial protection, together with our previous work report ing that vaccination with allogenic cynomolgus lymphocytes can protect against challenge infection with SIV grown in simian cells, suggests that allogenic immune response induced before or during establishment of HIV infection may have important implications for AIDS disease prog ression.