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Molecular adjuvant Ag85A enhances protection against influenza A virus in mice following DNA vaccination.

ABSTRACT: A novel DNA vaccine vector encoding the Mycobacterium tuberculosis secreted antigen Ag85A fused with the influenza A virus (IAV) HA2 protein epitopes, pEGFP/Ag85A-sHA2 (pAg85A-sHA2), was designed to provide protection against influenza. The antigen encoded by the DNA vaccine vector was efficiently expressed in mammalian cells, as determined by reverse transcription polymerase chain reaction (RT-PCR) and fluorescence analyses. Mice were immunized with the vaccine vector by intramuscular injection before challenge with A/Puerto Rico/8/34 virus (PR8 virus). Sera and the splenocyte culture IFN-? levels were significantly higher in immunized mice compared with the control mice. The novel vaccine group showed a high neutralization antibody titer in vitro. The novel vaccine vector also reduced the viral loads, increased the survival rates in mice after the PR8 virus challenge and reduced the alveolar inflammatory cell numbers. Sera IL-4 concentrations were significantly increased in mice immunized with the novel vaccine vector on Day 12 after challenge with the PR8 virus. These results demonstrated that short HA2 (sHA2) protein epitopes may provide protection against the PR8 virus and that Ag85A could strengthen the immune response to HA2 epitopes, thus, Ag85A may be developed as a new adjuvant for influenza vaccines.

SUBMITTER: Dai J

PROVIDER: S-EPMC3528282 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Molecular adjuvant Ag85A enhances protection against influenza A virus in mice following DNA vaccination.

Dai Jun J Pei Decui D Wang Baoning B Kuang Yu Y Ren Laifeng L Cao Kang K Wang Huan H Zuo Bin B Shao Jingjing J Li Sha S Li Hong H Li Mingyuan M

Viruses 20121210 12

A novel DNA vaccine vector encoding the Mycobacterium tuberculosis secreted antigen Ag85A fused with the influenza A virus (IAV) HA2 protein epitopes, pEGFP/Ag85A-sHA2 (pAg85A-sHA2), was designed to provide protection against influenza. The antigen encoded by the DNA vaccine vector was efficiently expressed in mammalian cells, as determined by reverse transcription polymerase chain reaction (RT-PCR) and fluorescence analyses. Mice were immunized with the vaccine vector by intramuscular injectio ...[more]

PMID: 23223215

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Project description:Seasonal influenza virus infections cause significant morbidity and mortality every year. Annual influenza virus vaccines are effective but only when well matched with circulating strains. Therefore, there is an urgent need for better vaccines that induce broad protection against drifted seasonal and emerging pandemic influenza viruses. One approach to design such vaccines is based on targeting conserved regions of the influenza virus hemagglutinin. Sequential vaccination with chimeric hemagglutinin constructs can refocus antibody responses towards the conserved immunosubdominant stalk domain of the hemagglutinin, rather than the variable immunodominant head. A complementary approach for a universal influenza A virus vaccine is to induce T-cell responses to conserved internal influenza virus antigens. For this purpose, replication deficient recombinant viral vectors based on Chimpanzee Adenovirus Oxford 1 and Modified Vaccinia Ankara virus are used to express the viral nucleoprotein and the matrix protein 1. In this study, we combined these two strategies and evaluated the efficacy of viral vectors expressing both chimeric hemagglutinin and nucleoprotein plus matrix protein 1 in a mouse model against challenge with group 2 influenza viruses including H3N2, H7N9 and H10N8. We found that vectored vaccines expressing both sets of antigens provided enhanced protection against H3N2 virus challenge when compared to vaccination with viral vectors expressing only one set of antigens. Vaccine induced antibody responses against divergent group 2 hemagglutinins, nucleoprotein and matrix protein 1 as well as robust T-cell responses to the nucleoprotein and matrix protein 1 were detected. Of note, it was observed that while antibodies to the H3 stalk were already boosted to high levels after two vaccinations with chimeric hemagglutinins (cHAs), three exposures were required to induce strong reactivity across subtypes. Overall, these results show that a combinations of different universal influenza virus vaccine strategies can induce broad antibody and T-cell responses and can provide increased protection against influenza.

Project description:UnlabelledIn an attempt to assess the cross-protective potential of the influenza virus neuraminidase (NA) as a vaccine antigen, different subtypes of recombinant NA were expressed in a baculovirus system and used to vaccinate mice prior to lethal challenge with homologous, heterologous, or heterosubtypic viruses. Mice immunized with NA of subtype N2 were completely protected from morbidity and mortality in a homologous challenge and displayed significantly reduced viral lung titers. Heterologous challenge with a drifted strain resulted in morbidity but no mortality. Similar results were obtained for challenge experiments with N1 NA. Mice immunized with influenza B virus NA (from B/Yamagata/16/88) displayed no morbidity when sublethally infected with the homologous strain and, importantly, were completely protected from morbidity and mortality when lethally challenged with the prototype Victoria lineage strain or a more recent Victoria lineage isolate. Upon analyzing the NA content in 4 different inactivated-virus vaccine formulations from the 2013-2014 season via Western blot assay and enzyme-linked immunosorbent assay quantification, we found that the amount of NA does indeed vary across vaccine brands. We also measured hemagglutinin (HA) and NA endpoint titers in pre- and postvaccination human serum samples from individuals who received a trivalent inactivated seasonal influenza vaccine from the 2004-2005 season; the induction of NA titers was statistically less pronounced than the induction of HA titers. The demonstrated homologous and heterologous protective capacity of recombinant NA suggests that supplementing vaccine formulations with a standard amount of NA may offer increased protection against influenza virus infection.ImportanceDespite the existence of vaccine prophylaxis and antiviral therapeutics, the influenza virus continues to cause morbidity and mortality in the human population, emphasizing the continued need for research in the field. While the majority of influenza vaccine strategies target the viral hemagglutinin, the immunodominant antigen on the surface of the influenza virion, antibodies against the viral neuraminidase (NA) have been correlated with less severe disease and decreased viral shedding in humans. Nevertheless, the amount of NA is not standardized in current seasonal vaccines, and the exact breadth of NA-based protection is unknown. Greater insight into the cross-protective potential of influenza virus NA as a vaccine antigen may pave the way for the development of influenza vaccines of greater breadth and efficacy.

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Molecular adjuvant Ag85A enhances protection against influenza A virus in mice following DNA vaccination.

Publications

Molecular adjuvant Ag85A enhances protection against influenza A virus in mice following DNA vaccination.

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