Abstract

SIV vaccines made of inactivated whole virus, modified live virus and native and recombinant envelope antigens have protected macaques against experimental infection with low doses of cell-free SIV given systemically. The few vaccinated monkeys that do become infected have tended to live longer than the infected controls. Protection against cell-associated virus has not as yet been tested. The recombinant envelope vaccines now on test have generally not been as effective as the whole virus vaccines. Post-infectious immunotherapy with SIV vaccines has been ineffective. The same whole virus and modified live virus vaccines that protect against systemic infection fail to protect against genital mucosal challenge with cell-free virus. Since sexual transmission is the major route of HIV spread on a global scale, a major effort is now required to develop vaccines in this animal model that induce genital mucosal as well as systemic immunity against infection with both cell-free and cell-associated SIV.