HIV Infection Stabilizes Macrophage-T Cell Interactions To Promote Cell-Cell HIV Spread

Abstract

Macrophages are susceptible to HIV infection and play an important role in viral dissemination through cell-cell contacts with T cells. However, our current understanding of macrophage-to-T cell HIV transmission is derived from studies that do not consider the robust migration and cell-cell interaction dynamics between these cells. Here, we performed live-cell imaging studies in 3-dimensional (3D) collagen that allowed CD4+ T cells to migrate and to locate and engage HIV-infected macrophages, modeling the dynamic aspects of the in situ environment in which these contacts frequently occur. We show that HIV+ macrophages form stable contacts with CD4+ T cells that are facilitated by both gp120-CD4 and LFA-1–ICAM-1 interactions and that prolonged contacts are a prerequisite for efficient viral spread. LFA-1–ICAM-1 adhesive contacts function to restrain highly motile T cells, since their blockade substantially destabilized macrophage-T cell contacts, resulting in abnormal tethering events that reduced cell-cell viral spread. HIV-infected macrophages displayed strikingly elongated podosomal extensions that were dependent on Nef expression but were dispensable for stable cell-cell contact formation. Finally, we observed persistent T cell infection in dynamic monocyte-derived macrophage (MDM)-T cell cocultures in the presence of single high antiretroviral drug concentrations but achieved complete inhibition with combination therapy. Together, our data implicate macrophages as drivers of T cell infection by altering physiological MDM-T cell contact dynamics to access and restrain large numbers of susceptible, motile T cells within lymphoid tissues. IMPORTANCE Once HIV enters the lymphoid organs, exponential viral replication in T cells ensues. Given the densely packed nature of these tissues, where infected and uninfected cells are in nearly constant contact with one another, efficient HIV spread is thought to occur through cell-cell contacts in vivo. However, this has not been formally demonstrated. In this study, we performed live-cell imaging studies within a 3-dimensional space to recapitulate the dynamic aspects of the lymphoid microenvironment and asked whether HIV can alter the morphology, migration capacity, and cell-cell contact behaviors between macrophages and T cells. We show that HIV-infected macrophages can engage T cells in stable contacts through binding of virus- and host-derived adhesive molecules and that stable macrophage-T cell contacts were required for high viral spread. Thus, HIV alters physiological macrophage-T cell interactions in order to access and restrain large numbers of susceptible, motile T cells, thereby playing an important role in HIV progression.

M-Sec facilitates intercellular transmission of HIV-1 through multiple mechanisms

“…The length and thickness of TNTs and the signal of Env were quantified using ImageJ 1.52n software (NIH). The cell surface area and circularity were also quantified using the same software, according to a recent report [ 34 ].…”

Human TRIM5α: Autophagy Connects Cell-Intrinsic HIV-1 Restriction and Innate Immune Sensor Functioning

“…As macrophages express the HIV-1 entry receptor CD4 and co-receptors CCR5 and CXCR4, they are themselves susceptible to HIV-1 infection [ 13 ]. In addition, HIV-1 infected macrophages can transmit virus to CD4 + T cells via a viral synapse, i.e., cell-to-cell contact, in a manner similar to that of DCs ( Figure 2 D) [ 173 , 174 , 175 ].…”

HIV-Captured DCs Regulate T Cell Migration and Cell-Cell Contact Dynamics to Enhance Viral Spread

“…To preserve the migratory DC morphology in collagen, chambers were fixed with 4% paraformaldehyde/5% sucrose overnight at 37°C / 5% CO2, as described previously (Lopez et al, 2019). Glycine buffer (0.15M) was used to quench residual PFA.…”

“…Another outstanding question is how DCs, in the absence of productive infection, restrain motile T cells to promote stable DC:T cell conjugates to facilitate viral transfer. We and others have utilized 3D collagen model systems to better characterize the dynamic on-off kinetics between infected and uninfected cells and have described key aspects of cell-cell contact behaviors that impact viral dissemination kinetics and pathogenesis ( Lopez et al., 2019 ; Symeonides et al., 2015 ; Usmani et al, 2019 ). Herein, we addressed whether HIV-captured DCs retain their ability to exit the genital mucosae, enter the lymphatic vessels, and migrate toward LN-homing chemo-attractants and whether they can restrain motile T cells for long enough to permit viral transfer in the absence of cognate antigen recognition.…”