HIV-1-induced impairment of dendritic cell cross talk with γδ T lymphocytes.

ABSTRACT

UNLABELLED The interplay between dendritic cells (DC) and γδ T lymphocytes represents a network of paracrine and cell contact interactions important for an integrated immune response to pathogens. HIV-1 infection dramatically affects the number and functions of both cell populations, and DC/γδ T cell cross talk may represent a target of virus-induced immune escape. We investigated whether HIV-exposed DC could deliver aberrant signals to interacting γδ T cells. Here we report that the interaction of human γδ T lymphocytes with HIV-1-exposed autologous monocyte-derived DC, but not direct exposure to the virus, impairs lymphocyte expansion and gamma interferon (IFN-γ) production in response to phosphoantigens. This effect is independent of virus strain and occurred in 55% of the donors analyzed. The donor-dependent variation observed relies on the responsiveness of DC to HIV-1 and is strictly related to the capacity of the virus to suppress the maturation-induced expression of interleukin 12 (IL-12). In fact, γδ T cell response to phosphoantigens is almost completely recovered when this cytokine is exogenously added to the DC/lymphocyte cocultures. Interestingly, we show that γδ T lymphocytes are recruited by HIV-1-exposed DC through a CCR5-mediated mechanism and exert a CCL4-mediated control on virus dissemination within DC and susceptible CD4(+) T lymphocytes. These results demonstrate an association between HIV-induced DC dysfunction and alterations of γδ T cell responses. The aberrant cross talk between these two cell populations may contribute to the pathogenesis of HIV infection by further reducing the strength of antiviral immune response. IMPORTANCE This study provides new evidence on the mechanisms exploited by HIV-1 to evade the host immune response. We report that HIV-1 impairs the cross talk between DC and γδ T lymphocytes, by reducing the capacity of DC to promote functional γδ T cell activation. Interestingly, the virus does not per se interfere with γδ T cell activation, thus highlighting the key role of early DC-HIV-1 interaction in this phenomenon. Furthermore, the results obtained unravel the novel role of γδ T cells in controlling HIV-1 dissemination within the DC population as well as virus transfer to susceptible CD4(+) T lymphocytes. The interactions of DC with innate lymphocytes represent a major control mechanism for an integrated immune response to infection. Understanding how HIV-1 harnesses these pathways may provide important insights on the pathogenesis of disease and offer new opportunities for therapeutic interventions.