IgA-dependent cell phagocytosis of HIV-infected cells elicits cross-presentation to CD8+T cells and immune memory in effector monocytes.

Mucosal IgA antibodies are the first defence against mucosal infections. Besides targeting specific antigens by their Fab-region, IgA also mediates antiviral functions via their Fc-domain, allowing infected cells destruction by antibody-dependent cellular phagocytosis (ADCP). Passive immunisation with anti-HIV-1 IgG protected Non-Human Primates in a CD8⁺ T cell-dependent manner, a process likely involving ADCP. Here, we unravel the consequences of ADCP of HIV-1-infected cells mediated by anti-HIV envelope IgA compared to IgG. We found that IgA-mediated ADCP, not IgG, drives viral antigen cross-presentation to HIV-1-specific cytotoxic CD8⁺ T cells. IgA effector function reprogrammed ADCP effector monocytes into activated macrophages exhibiting a mixed pro- and anti-inflammatory profile combined with increased pro-inflammatory chemokines. IgA-mediated ADCP sensitizes monocytes to respond to a novel bacterial challenge by secreting IL-6 and TNFα, indicative of acquired trained immunity. Altogether, these data establish a bridge between humoral and cellular immunity that could be exploited in HIV preventive strategies.