The P-selectin ligand PSGL-1 (CD162) is efficiently incorporated by primary HIV-1 isolates and can facilitate trans-infection

ABSTRACT While P-selectin glycoprotein ligand-1 (PSGL-1/CD162) has been studied extensively for its role in mediating leukocyte rolling through interactions with its receptor, P-selectin, recently, it was identified as a novel HIV-1 host restriction factor. One key mechanism of HIV-1 restriction is the ability of PSGL-1 to be physically incorporated into the external viral envelope, which effectively reduces infectivity by blocking virus attachment through the steric hindrance caused by its large ectodomain. Importantly, a large portion of the literature demonstrating the antiviral activity of PSGL-1 has utilized viruses produced in transfected cells which express high levels of PSGL-1. However, herein we show that virion-incorporated PSGL-1 is far less abundant on the surface of viruses produced via infection of physiologically relevant models (T cell lines and primary cells) compared to transfection (overexpression) models. Unique to this study, we show that PSGL-1 is incorporated in a broad range of HIV-1 and SIV isolates, supporting the physiological relevance of this incorporation. We also report that high levels of virion-incorporated PSGL-1 are detectable in plasma from viremic HIV-1 infected individuals, further corroborating the clinical relevance of PSGL-1 in natural infection. Additionally, we show that PSGL-1 on viruses is functionally active and can bind its cognate receptor, P-selectin, and that virions captured via P-selectin can subsequently be transferred to HIV-permissive bystander cells in a model of trans-infection. Taken together, our data suggest that PSGL-1 may have diverse roles in the physiology of HIV-1 infection, not restricted to the current antiviral paradigm. IMPORTANCE PSGL-1 is an HIV-1 host restriction factor which reduces viral infectivity by physically incorporating into the envelope of virions. While the antiviral effects of PSGL-1 in viruses produced by transfection models is profound, HIV-1 continues to remain infectious when produced through natural infection, even when PSGL-1 is incorporated. To study this discordance, we compared the differences in infectivity and PSGL-1 abundance in viruses produced by transfection or infection. Viruses produced via transfection contained unnaturally high levels of incorporated PSGL-1 compared to viruses from primary cells, and were much less infectious. We also found PSGL-1 to be present on a broad range of HIV-1 isolates, including those found in plasma from HIV-infected patients. Remarkably, we show that virion-incorporated PSGL-1 facilitates virus capture and transfer to HIV-permissive host cells via binding to P-selectin. These findings suggest that PSGL-1 may also work to enhance infection in vivo.