Vaccination with Live Attenuated Simian Immunodeficiency Virus (SIV) Protects from Mucosal, but Not Necessarily Intravenous, Challenge with a Minimally Heterologous SIV

Few studies have evaluated the impact of the viral challenge route on protection against a heterologous simian immunodeficiency virus (SIV) challenge. We vaccinated seven macaques with a live attenuated SIV that differed from SIVmac239 Delta nef by 24 amino acids, called m3KO Delta nef. All animals were protected from an intrarectal SIVmac239 challenge, whereas only four animals were protected from subsequent intravenous SIVmac239 challenge. These data suggest that immune responses elicited by vaccination with live attenuated SIV in an individual animal can confer protection from intrarectal challenge while remaining insufficient for protection from intravenous challenge. IMPORTANCE Our study is important because we show that vaccinated animals can be protected from a mucosal challenge with a heterologous SIV, but the same animals are not necessarily protected from intravenous challenge with the same virus. This is unique because in most studies, either vaccinated animals are challenged multiple times by the same route or only a single challenge is performed. An individually vaccinated animal is rarely challenged multiple times by different routes, so protection from different challenge routes cannot be measured in the same animal. Our data imply that vaccine-elicited responses in an individual animal may be insufficient for protection from intravenous challenge but may be suitable for protection from a mucosal challenge that better approximates human immunodeficiency virus (HIV) exposure.