T cell immunity to dengue virus infection in transgenic mice expressing human HLA molecules

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Based on the recent identification of the non-structural proteins NS3, NS4B and NS5 of dengue virus (DENV) as the main targets for T cell responses in humans, we have designed a minimal DENV antigen, called PolyDV-NS, enriched in conserved and highly antigenic epitopes (patent WO2015/197565, initially filed on June 23, 2014). This PolyDV-NS vaccine can induce a strong CD8 T-cell response and a protection against DENV1 infection in transgenic mice that express different human HLA class I molecules (Roth et al., manuscript in preparation). To optimize immunogenicity as much as possible against the 4 DENV serotypes, we will measure the magnitude of T-cell responses (mediated by CD4 and/or CD8 T cells) by quantifying ex vivo IFN-g responses against peptides from DENV1 and from their serotype variants covering the whole PolyDV-NS sequence by enzyme linked immunosorbent spot assay (ELISPOT assay). The contribution of DENV-specific CD8+ T cells elicited by the PolyDV-NS vaccination will also be determined by analyzing the phenotype and frequency of peptide-specific CD8⁺ T cells that are CD44^hi CD62L^lo (i.e. effector memory cells) and express IFN-g alone, both IFN-g and TNF-a, or Granzyme B. Altogether, these analyses should allow us to better predict and enhance the efficiency of the DV-NS vaccine against the different DENV serotypes.