Combining immunogenic peptides and Nef blockade to enhance CD8 T-cell-mediated clearance of HIV-infected cells

University Of Sydney, Sydney

Investigators

Abstract

Project Summary The expression of the HIV protein Nef during therapy contributes to the persistence of HIV in cells by downregulating cell-surface major histocompatibility complex type I (MHC-I) and antigen presentation which allows the virus to evade immune response. Therefore, inhibiting the expression of Nef would allow for MHC-I expression of HIV antigens on the surface of HIV-infected cells and their clearance by HIV-specific CD8 T cells. In addition to MHC-I downregulation, there are challenges in developing an effective CD8 cytotoxic T cell (CTL) response against replication-competent proviruses. The intracellular HIV reservoir becomes dominated by viral variants containing CTL escape mutations that are resistant to immune response and defective HIV proviruses can produce viral proteins that act as decoys for CTL response. However, recent studies show polyfunctional response of CD8 T cells and/or the targeting of T cell epitopes from structurally important (i.e., highly networked) and genetically-conserved regions of viral proteins are essential for HIV control. In addition, cells harboring T cell epitope escape mutations can be eliminated by redirecting CD8 T cell response to unmutated viral epitopes By employing an innovative technique-- an ex vivo HIV eradication assay --using cells from participants on effective therapy, we expect this exploratory study will reveal that Nef blockade significantly enhances CD8 T cell–mediated elimination of HIV-infected cells containing inducible proviruses. In combination with Nef blockade, we will augment the clearance of these HIV reservoir cells by expanding HIV-specific CD8 T cells with a pool of immunogenic peptides that induce polyfunctional/effector CD8 T cell response. These peptides are selected from topologically important and genetically-conserved regions of six HIV proteins by applying an immunoinformatics analysis pipeline. Due to the fact these peptides are highly networked within their protein of origin, they are expected to represent T cell epitopes which lack escape mutations. Therefore, in conducting this study we will determine the best combination of Nef blockers and immunogenic peptide pools for eliciting CD8 T cell-mediated clearance of HIV-infected cells. This study will accelerate the development of a new HIV treatment strategy that combines Nef blockade for MHC-I restoration and immunotherapies that elicit effective CTL response and provide the evidentiary basis for progressing to an in vivo model before this approach can be applied in a clinical setting.