Early immunologic events in mucosal and systemic lymphoid tissues after intrarectal inoculation with simian immunodeficiency virus

The pathogenesis of human immunodeficiency virus transmission via the recta l route remains poorly understood. By use of the simian immunodeficiency vi rus (SIV)-rhesus macaque model and intrarectal inoculation with pathogenic SIVmac251, a significant increase was found in the percentage of CD11b(+) m onocyte lineage cells expressing HLA-DR and/or B7-2 in local and peripheral immune inductive sites, but not in mucosal effector sites, as early as 7 d ays after inoculation and up to 50 days after inoculation. Moreover, at 21 and 50 days after inoculation, not only the gut but also the lung mucosa we re depleted of CD4(+) T cells, which suggests that early loss of CD4(+) T c ells may be a common feature of mucosal effector sites. These data suggest that, after intrarectal inoculation with SIV, early activation occurs withi n the monocyte lineage cell population at immunologic inductive sites, whic h is followed by a loss of CD4(+) T cells at local and distant mucosal effe ctor sites.