HIV-1 Mediated Cortical Actin Disruption Mirrors ARP2/3 Defects Found in Primary T Cell Immunodeficiencies

Abstract

HIV-1 infection disrupts cortical actin, which balances osmotic and mechanical forces to provide an architectural scaffold that dictates T cell morphology and migration. HIV-1 infected cells have significantly less F-actin, lose their polarization, have reduced velocity and directionality, and lose their ability to traverse endothelial barriers and migrate in more complex dense environments. Although HIV-1 induced morphological changes in primary and oncogenic CD4+ T cells on 2D surfaces are reported to lose their polarization, infected cell migration in vivo show prolonged cell polarization. These discrepancies arise from cell type observed, environmental complexity of the system, and the time scale of observation. Here, we unify these disparate findings with time-lapse and ultrastructural microscopy showing that HIV-1 infection of primary CD4+ T cells causes at least five progressive morphological differences as a result of virally induced cortical cytoskeleton disruption. Although PAK2 and cofilin activity altered by Nef has previously been linked to these structural changes, viral mechanisms outside of Nef likely exist. Infection with a Nef-deleted (ΔNef) virus partially abrogated the dysfunctional phenotype in infected cells. Along with a recently reported lamellipodial blebbing phenotype4, we observe a fifth unreported pathological morphology distinct to HIV-1 infected CD4+ T cells. These two morphologies phenocopy migrating cells which contain genetic determinants of specific T cell primary immunodeficiencies that affect the actin cytoskeleton, particularly diseases affecting the ARP2/3 complex. The branched actin nucleator ARP2/3 is an important component of the lamellipodia during migration as well as the T cell immune synapse during activation and is frequently targeted by intracellular bacteria and enveloped viruses. The mechanically destabilized cellular cortex found in leukocytes from PID and following HIV-1 infection may provide context into cellular and systemic pathologies that drive similar clinical manifestations observed in primary and acquired immunodeficiencies.