ABSTRACT Understanding the earliest events of HIV sexual transmission is critical to develop and optimize HIV prevention strategies. To gain insights into the earliest steps of HIV rectal transmission, including cellular targets, rhesus macaques were intra-rectally challenged with a single-round SIV-based dual reporter that expresses luciferase and iRFP670 upon productive transduction. The vector was pseudotyped with the HIV-1 envelope JRFL. Regions of tissue containing foci of luminescent, transduced cells were identified macroscopically using an in vivo imaging system, and individual transduced cells expressing fluorescent protein were identified and phenotyped microscopically. This system revealed that anal and rectal tissues are both susceptible to transduction 48 hours after the rectal challenge. Detailed phenotypic analysis revealed that on average, 62% of transduced cells are CCR6 + T cells—the vast majority of which express RORγT, a Th17 lineage-specific transcription factor. The second most common target cells were immature dendritic cells at 20%. These two cell types were transduced at the rates that are four to five times higher than their relative abundances indicate. Our work demonstrates that Th17 T and immature dendritic cells are preferential initial targets of HIV/SIV rectal transmission. IMPORTANCE Men and women who participate in unprotected receptive anal intercourse are at high risk for acquiring HIV. While in vitro data have developed a framework for understanding HIV cell tropism, the initial target cells in the rectal mucosa have not been identified. In this study, we identify these early host cells by using an innovative rhesus macaque rectal challenge model and methodology, which we previously developed. Thus, by shedding light on these early HIV/SIV transmission events, this study provides a specific cellular target for future prevention strategies.

Th17 T cells and immature dendritic cells are the preferential initial targets after rectal challenge with an SIV-based replication-defective dual-reporter vector