A single immunization with HA DNA vaccine by electroporation induces early protection against H5N1 avian influenza virus challenge in mice

Liyun Zheng,Zhongdong Yang,Ze Chen,Jianjun Chen,Haiyan Chang,Fuyan Wang

doi:10.1186/1471-2334-9-17

Abstract

BackgroundDeveloping vaccines for the prevention of human infection by H5N1 influenza viruses is an urgent task. DNA vaccines are a novel alternative to conventional vaccines and should contribute to the prophylaxis of emerging H5N1 virus. In this study, we assessed whether a single immunization with plasmid DNA expressing H5N1 hemagglutinin (HA) could provide early protection against lethal challenge in a mouse model.MethodsMice were immunized once with HA DNA at 3, 5, 7 days before a lethal challenge. The survival rate, virus titer in the lungs and change of body weight were assayed to evaluate the protective abilities of the vaccine. To test the humoral immune response induced by HA DNA, serum samples were collected through the eye canthus of mice on various days after immunization and examined for specific antibodies by ELISA and an HI assay. Splenocytes were isolated after the immunization to determine the antigen-specific T-cell response by the ELISPOT assay.ResultsChallenge experiments revealed that a single immunization of H5N1 virus HA DNA is effective in early protection against lethal homologous virus. Immunological analysis showed that an antigen-specific antibody and T-cell response could be elicited in mice shortly after the immunization. The protective abilities were correlated with the amount of injected DNA and the length of time after vaccination.ConclusionA single immunization of 100 μg H5 HA DNA vaccine combined with electroporation was able to provide early protection in mice against homologous virus infection.

Highlights

Developing vaccines for the prevention of human infection by H5N1 influenza viruses is an urgent task
All H5N1 viruses isolated from humans retain characteristic features of avian influenza viruses and are not currently transmissible among humans, the potential for a pandemic caused by H5N1-HPAIV is increasing [8,12]
We showed that a single immunization of H5N1 DNA vaccine was able to provide early protection in mice against homologous virus infection

Summary

Introduction

Developing vaccines for the prevention of human infection by H5N1 influenza viruses is an urgent task. The outbreak of human infections of H5N1 influenza in 1997 in Hong Kong and in 2003–2004 in most Asian countries demonstrated that purely avian viruses could be transmitted to humans and cause severe disease [1]. Prior to the Hong Kong outbreak, H5 influenza viruses had been isolated only from avian species [2]. They exist in a non-pathogenic form in wild aquatic birds in different (page number not for citation purposes). All H5N1 viruses isolated from humans retain characteristic features of avian influenza viruses and are not currently transmissible among humans, the potential for a pandemic caused by H5N1-HPAIV is increasing [8,12]

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Conclusion