CD4+ T cell mediated HLA class II cross-restriction in HIV controllers

Abstract Rare individuals, termed HIV controllers, spontaneously control HIV infection by mounting efficient T cell responses against the virus. Protective CD4+ T cell responses from HIV controllers involve high affinity public T cell receptors (TCRs) recognizing an immunodominant capsid epitope (Gag293) presented by a remarkably broad array of HLA class II molecules. Here we determine the structures of a prototypical public TCR bound to HLAD-R1, –DR11, and –DR15 molecules presenting the Gag293 epitope. TCR recognition was driven by contacts with the Gag293 epitope, a feature that underpinned the extensive HLA cross-restriction. These high affinity TCRs promoted mature immunological synapse formation and cytotoxic capacity in both CD4+ and CD8+ T cells. The public TCRs suppressed HIV replication in multiple genetic backgrounds ex vivo, emphasizing the functional advantage conferred by broad HLA class II cross-restriction.