Universal influenza DNA vaccine encoding conserved CD4+ T cell epitopes protects against lethal viral challenge in HLA-DR transgenic mice

Abstract

The goal of the present study was to design a vaccine that would provide universal protection against infection of humans with diverse influenza A viruses. Accordingly, protein sequences from influenza A virus strains currently in circulation (H1N1, H3N2), agents of past pandemics (H1N1, H2N2, H3N2) and zoonotic infections of man (H1N1, H5N1, H7N2, H7N3, H7N7, H9N2) were evaluated for the presence of amino acid sequences, motifs, that are predicted to mediate peptide epitope binding with high affinity to the most frequent HLA-DR allelic products. Peptides conserved among diverse influenza strains were then synthesized, evaluated for binding to purified HLA-DR molecules and for their capacity to induce influenza-specific immune recall responses using human donor peripheral blood mononuclear cells (PBMC). Accordingly, 20 epitopes were selected for further investigation based on their conservancy among diverse influenza strains, predicted population coverage in diverse ethnic groups and capacity to recall influenza-specific responses. A DNA plasmid encoding the epitopes was constructed using amino acid spacers between epitopes to promote optimum processing and presentation. Immunogenicity of the DNA vaccine was measured using HLA-DR4 transgenic mice and the TriGrid™ in vivo electroporation device. Vaccination resulted in peptide-specific immune responses, augmented HA-specific antibody responses and protection of HLA-DR4 transgenic mice from lethal PR8 influenza virus challenge. These studies demonstrate the utility of this vaccine format and the contribution of CD4 + T cell responses to protection against influenza infection.

Immunodominant CD4+T-Cell Responses to Influenza A Virus in Healthy Individuals Focus on Matrix 1 and Nucleoprotein

“…We also noticed that immunodominant epitopes seemed to have been subjected to greater selective pressure than subdominant ones, if the number of such variants is a direct indication. For three of the PR8-derived immunodominant epitopes, M1 209-221 , NP [404][405][406][407][408][409][410][411][412][413][414][415][416] , and especially NP 463-475 , a perfect sequence match can rarely be found in the IAV strains that have emerged in the last decade in Australia, while the subdominant epitopes, such as M1 [43][44][45][46][47][48][49][50][51][52][53][54][55] and M1 101-113 , showed higher levels of conservation. Although IAV infections are resolved quickly in each infected individual, it is entirely possible that such epitope variants can be generated due to both the immune pressure and the lack of an error-proof nature of the IAV polymerase.…”

“…After that, ex vivo assessments of these epitope-specific memory CD4 ϩ T cell precursor frequencies were conducted to confirm the immunodominance hierarchy (ranking). Using the same approach described above, three subdominant epitopes-M1 [43][44][45][46][47][48][49][50][51][52][53][54][55] , restricted to HLA-DRB1*0701 (Fig. 7A); M1 101-113 , restricted to HLA-DRB1*0404 (Fig.…”

Immunization with cross-conserved H1N1 influenza CD4+T-cell epitopes lowers viral burden in HLA DR3 transgenic mice

“…15,16 This study is consistent with others showing that, in the absence of antibody responses, cellular immune response can provide effective protective immunity in animal models. [17][18][19] With respect to pH1N1 infection, two independent studies demonstrated CTLs and CD4 + T cells raised against the seasonal H1N1 viruses, A/Brisbane/59/2007 and A/New Caledonia/20/99, respectively, were capable of responding against whole protein antigens from the pH1N1 virus. 20,21 In addition, cross-reactive human T helper cell responses were observed for defined HLA-DR4 epitopes.…”

The roles of resident, central and effector memory CD4 T‐cells in protective immunity following infection or vaccination

“…Importantly, Alexander et al . demonstrated that DNA vaccination generated memory CD4 T‐cells that, via their rapid assistance to B‐cells, protected mice from influenza virus infection 70. This rapid assistance to generate high‐affinity class‐switched antibody is particularly relevant to infections such as influenza virus where regions of the virus targeted by antibody alter much more rapidly than epitopes recognized by CD4 T‐cells 71…”