Human immunodeficiency virus vaccines

Coupling of HIV-1 Antigen to the Selective Autophagy Receptor SQSTM1/p62 Promotes T-Cell-Mediated Immunity

Vaccines aiming to promote T-cell-mediated immune responses have so far showed limited efficacy, and there is a need for novel strategies. Studies indicate that autophagy plays an inherent role in antigen processing and presentation for CD4⁺ and CD8⁺ T cells. Here, we report a novel vaccine strategy based on fusion of antigen to the selective autophagy receptor sequestosome 1 (SQSTM1)/p62. We hypothesized that redirection of vaccine antigen from proteasomal degradation into the autophagy pathway would increase the generation of antigen-specific T cells. A hybrid vaccine construct was designed in which the antigen is fused to the C-terminus of p62, a signaling hub, and a receptor that naturally delivers ubiquitinated cargo for autophagic degradation. Fusion of the human immunodeficiency virus-1 antigen Gagp24 to p62 resulted in efficient antigen delivery into the autophagy pathway. Intradermal immunization of mice revealed that, in comparison to Gagp24 delivered alone, fusion to p62 enhanced the number of Gagp24-specific interferon-γ-producing T cells, including CD8⁺ T cells. The strategy may also have the potential to modulate the antigenic peptide repertoire. Because p62 and autophagy are highly conserved between species, we anticipate this strategy to be a candidate for the development of T-cell-based vaccines in humans.

Combinatorial hematopoietic stem cell transplantation and vaccination reduces viral pathogenesis following SHIV89.6P-challenge

Development of curative approaches for HIV-1 infected patients requires novel approaches aimed at eliminating viral reservoirs and replacing potential target cells with infection-resistant immune cell populations. We have previously shown that autologous transplantation of genetically modified hematopoietic stem cells (HSCs) with lentiviral vectors encoding the mC46-fusion inhibitor results in a significant reduction in viral pathogenesis following challenge with the highly pathogenic dual tropic, SHIV89.6P strain. In this study, we used a combinatorial approach in which following engraftment of genetically modified HSCs, pigtailed macaques were vaccinated with a previously developed vaccinia-based vaccine expressing SIV-Gag, Pol. Using this dual therapy approach, lower viremia was detected in both the acute and chronic phase of disease with levels reaching near the lower limits of detection. In comparison with macaques receiving HSCT only, the combination approach resulted in a further log decrease in plasma viremia. Similar to our previous studies, positive selection of all CD4(+) T-cell subsets was observed; however, higher gene-modified CD4(+) T-cell levels were observed during the chronic phase when vaccination was included suggesting that combining vaccination with HSCT may lower the necessary threshold for achieving viremic control.