Dengue virus specific dual HLA binding T cell epitopes induce CD8⁺T cell responses in seropositive individuals

Abstract

Dengue virus infects an estimated 300 million people each year and even more are at risk of becoming infected as the virus continues to spread into new areas. Despite the increase in viral prevalence, no anti-viral medications or vaccines are approved for treating or preventing infection. CD8C T cell responses play a major role in viral clearance. Therefore, effective vaccines that induce a broad, multi-functional T cell response with substantial cross-reactivity between all virus serotypes can have major impacts on reducing infection rates and infection related complications. Here, we took an immunoproteomic approach to identify novel MHC class I restricted T cell epitopes presented by dengue virus infected cells, representing the natural and authentic targets of the T cell response. Using this approach we identified 4 novel MHC-I restricted epitopes: 2 with the binding motif for HLA-A24 molecules and 2 with both HLA-A2 and HLA-A24 binding motifs. These peptides were able to activate CD8 C T cell responses in both healthy, seronegative individuals and in seropositive individuals who have previously been infected with dengue virus. Importantly, the dual binding epitopes activated pre-existing T cell precursors in PBMCs obtained from both HLA-A2 C and HLA-A24 C seropositive individuals. Together, the data indicate that these epitopes are immunologically relevant T cell activating peptides presented on infected cells during a natural infection and therefore may serve as candidate antigens for the development of effective multi-serotype specific dengue virus vaccines.

A novel immunization approach for dengue infection based on conserved T cell epitopes formulated in calcium phosphate nanoparticles

“…Our previous studies demonstrated that DV specific free peptides can activate CD8CT cells in vitro. 28,29 Here, we evaluated if the same peptides formulated with nanoparticles could enhance DV specific T cell response. A total of 6 HLA-A2 C , A2 C /A24 C dual binding DV peptides (Table 1) were selected and formulated in 0.3% CaPNP particle suspension either individually or combined as a pool of multiple peptides.…”

“…Dengue virus specific MHC class I associated peptides identified previously by immunoproteomics. 28,29 Peptide…”

“…28 We have also shown that these T cells are able to be activated via selected HLA-A2C and HLA-A24C in both healthy, seronegative, individuals and in seropositive individuals who have been previously infected with DV. 29 These studies suggested that a vaccine that activates a CTL response against DV and another that can be paired with an efficient humoral immune-stimulating vaccine could be used to induce sustained immunity against DV.…”

“…Therefore, there was great interest in investigating the potential of CaPNPs for development of vaccines against DV infection. Building on our prior work of antigenic peptides discovered from DV, 28,29 we aimed to investigate the beneficial properties of CaPNPs in terms of stability, capacity to incorporate peptide antigens, simplicity of formulation protocols, and T cell responses. The HLA-A2C DV peptides selected for this work were previously identified through a comprehensive analysis of naturally presented epitopes on infected cells using an immunoproteomic approach.…”

“…The HLA-A2C DV peptides selected for this work were previously identified through a comprehensive analysis of naturally presented epitopes on infected cells using an immunoproteomic approach. 28,29 These novel HLA-A2C DV-specific peptides are derived from conserved regions of DV proteins. We previously demonstrated that DV peptides derived from conserved regions are capable of inducing cross-reactive T cell responses, 28 a benefit when designing a vaccine to protect against multiple strains.…”