Intranasal immunization with live attenuated influenza vaccine plus chitosan as an adjuvant protects mice against homologous and heterologous virus challenge
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Our previous studies have proven the adjuvanticity of chitosan in mice when administered with inactivated and subunit influenza vaccine. In this study, we investigated the adjuvant effect of chitosan on the immunogenicity and protective efficacy of a live attenuated influenza vaccine. Mice were inoculated intranasally with live attenuated influenza vaccine plus chitosan and then challenged with a high, lethal dose of homologous or heterologous virus. Antibody responses, secretion of IFN-γ by spleen cells, body weight loss, survival rates, and residual lung virus titers were tested. The results demonstrated that live attenuated influenza vaccine with chitosan adjuvant not only protected mice completely against challenge with the homologous virus but also provided good cross-protection against a heterologous virus. In addition, chitosan as adjuvant could significantly increase the levels of antigen-specific antibodies and the population of IFN-γ-secreting T cells. These results reveal the potential of chitosan as a candidate adjuvant for use in a live attenuated influenza vaccine.
This study was supported by the following research funds: National High Technology Research and Development Program of China (863 Program 2010AA022905 and 2010AA022908); National 973 Project (2010CB530301); National Natural Science Foundation of China (No. 81071346 and No. 81172738). We thank R. G. Webster (from St. Jude Children’s Research Hospital, Memphis, TN) for the pHW2000 plasmid.
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