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Inter-Clade Protection Offered by Mw-Adjuvanted Recombinant HA, NP Proteins, and M2e Peptide Combination Vaccine in Mice Correlates with Cellular Immune Response.

ABSTRACT: We documented earlier that Mw (heat-killed suspension of Mycobacterium indicus pranii) adjuvant when used with conserved antigens, nucleoprotein (NP), and ectodomain of matrix (M2) protein (M2e) provided complete protection against homologous (clade 2.2) virus challenge in mice. The present study extends these observations to inter-clade challenge (clade 2.3.2.1) H5N1 virus and attempts to understand preliminary immunologic basis for the observed protection. Female BALB/c mice immunized with a single or two doses of vaccine formulations (clade 2.2 antigens) were challenged with 100LD50 homologous or heterologous (clade 2.3.2.1) virus. To understand the preliminary immunologic mechanism, we studied proportions of selected immune cell types, immune response gene expression, and Th1/Th2 cytokines induced by antigen-stimulated splenocytes from immunized mice, at different time points. Complete protection was conferred by Mw-HA, Mw-HA + NP, and Mw-HA + NP + M2e against homologous challenge. The protection correlated with IgG2a antibody titers indicating important role of Th1 response. Despite high inter-cladal antigenic differences, complete protection against the heterologous strain was achieved with Mw-HA + NP + M2e. Of note, a single dose with higher antigen concentrations (50 µg HA + 50 μg NP + 50 μg M2e) led to 80% protection against clade 2.3.2.1 strain. The protection conferred by Mw-HNM correlated with induction of IFN-γ, CD8⁺ T cytotoxic cells, and CD4⁺ T helper cells. Mw-adjuvanted HA + NP + M2e combination represents a promising vaccine candidate deserving further evaluation.

SUBMITTER: Ingle NB

PROVIDER: S-EPMC5220098 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundInfluenza infection could be more effectively controlled if a multi-purpose vaccine with the ability to induce responses against most, or all, influenza A subtypes could be generated. Conserved viral proteins are a promising basis for the creation of a broadly protective vaccine. In the present study, the immunogenicity and protective properties of three recombinant proteins (vaccine candidates), comprising conserved viral proteins fused with bacterial flagellin, were compared.MethodsBalb/c mice were immunized intranasally with recombinant proteins comprising either one viral protein (the ectodomain of the M2 protein, 'M2e') or two viral proteins (M2e and the hemagglutinin second subunit 'HA2' epitope) genetically fused with flagellin. Further, two different consensus variants of HA2 were used. Therefore, three experimental positives were used in addition to the negative control (Flg-his). The mucosal, humoral, and T-cell immune responses to these constructs were evaluated.ResultWe have demonstrated that insertion of the HA2 consensus polypeptide (aa 76-130), derived from either the first (HA2-1) or second (HA2-2) virus phylogenetic group, into the recombinant Flg4M2e protein significantly enhanced its immunogenicity and protective properties. Intranasal administration of the vaccine candidates (Flg-HA2-2-4M2e or Flg-HA2-1-4M2e) induced considerable mucosal and systemic responses directed at both the M2e-protein and, in general, the influenza A virus. However, the immune response elicited by the Flg-HA2-1-4M2e protein was weaker than the one generated by Flg-HA2-2-4M2e. These recombinant proteins containing both viral peptides provide complete protection from lethal challenge with various influenza viruses: A/H3N2; A/H2N2; and A/H5N1.ConclusionThis study demonstrates that the intranasal administration of Flg-HA2-2-4M2e recombinant protein induces a strong immune response which provides broad protection against various influenza viruses. This construct is therefore a strong candidate for development as a universal vaccine.

Project description:The H5N8 highly pathogenic avian influenza (HPAI) clade 2.3.4.4 virus spread to North America by wild birds and reassorted to generate the H5N2 HPAI virus that caused the poultry outbreak in the United States in 2015. In previous studies, we showed that H5N2 viruses isolated from poultry in the later stages of the outbreak had higher infectivity and transmissibility in chickens than the wild bird index H5N2 virus. Here, we determined the genetic changes that contributed to the difference in host virus fitness by analyzing sequence data from all of the viruses detected during the H5N2 outbreak, and studying the pathogenicity of reassortant viruses generated with the index wild bird virus and a chicken virus from later in the outbreak. Viruses with the wild bird virus backbone and either PB1, NP, or the entire polymerase complex of the chicken isolate, caused higher and earlier mortality in chickens, with three mutations (PB1 E180D, M317V, and NP I109T) identified to increase polymerase activity in chicken cells. The reassortant virus with the HA and NA from the chicken virus, where mutations in functionally known gene regions were acquired as the virus circulated in turkeys (HA S141P and NA S416G) and later in chickens (HA M66I, L322Q), showed faster virus growth, bigger plaque size and enhanced heat persistence in vitro, and increased pathogenicity and transmissibility in chickens. Collectively, these findings demonstrate an evolutionary pathway in which a HPAI virus from wild birds can accumulate genetic changes to increase fitness in poultry.IMPORTANCE H5Nx highly pathogenic avian influenza (HPAI) viruses of the A/goose/Guangdong/1/96 lineage continue to circulate widely affecting both poultry and wild birds. These viruses continue to change and reassort, which affects their fitness to different avian hosts. In this study, we defined mutations associated with increased virus fitness in chickens as the clade 2.3.4.4. H5N2 HPAI virus circulated in different avian species. We identified mutations in the PB1, NP, HA, and NA virus proteins that were highly conserved in the poultry isolates and contributed to the adaptation of this virus in chickens. This knowledge is important for understanding the epidemiology of H5Nx HPAI viruses and specifically the changes related to adaptation of these viruses in poultry.

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Inter-Clade Protection Offered by Mw-Adjuvanted Recombinant HA, NP Proteins, and M2e Peptide Combination Vaccine in Mice Correlates with Cellular Immune Response.

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