INTRARECTAL TRANSMISSION OF SIMIAN IMMUNODEFICIENCY VIRUS IN RHESUS MACAQUES - SELECTIVE AMPLIFICATION AND HOST RESPONSES TO TRANSIENT OR PERSISTENT VIREMIA

Intrarectal simian immunodeficiency virus (SIV) infection in rhesus ma caques is a model for sexual transmission of primate retroviruses. Phy logenetic studies on envelope gene sequences that were present in bloo d following intrarectal SIV inoculation provided evidence for selectiv e amplification of a subset of viruses present in the inoculum and def ined one amino acid sequence uniquely associated with intrarectal infe ction. Both persistent and transient viremia states were observed afte r intrarectal infection. Immune responses in persistently infected ani mals accounted for slower rates of disease progression despite the pre sence of highly pathogenic viruses that were documented by transfusion studies, Transient viremia elicited protective immunity against subse quent intrarectal virus challenge but did not protect against intraven ous virus challenge. Transient viremia usually but not always led to s elf-limiting infection, In one animal, we documented a relapse to acti ve viremia long after the initial transient viremia. SIV transmission across mucosal barriers affects pathogenesis In the short term by limi ting the types of viruses established in the host and in the longer te rm by establishing host responses that slow disease progression despit e the presence of highly pathogenic viruses in blood.