Abstract

H5N1 highly pathogenic avian influenza (H5N1 HPAI) virus causes elevated mortality compared with seasonal influenza viruses like H1N1 pandemic influenza (H1N1 pdm) virus. We identified a mechanism associated with the severe symptoms seen with H5N1 HPAI virus infection. H5N1 HPAI virus infection induced a decrease of dendritic cell number in the splenic extrafollicular T-cell zone and impaired formation of the outer layers of B-cell follicles, resulting in insufficient levels of antibody production after infection. However, in animals vaccinated with a live recombinant vaccinia virus expressing the H5 hemagglutinin, infection with H5N1 HPAI virus induced parafollicular dendritic cell accumulation and efficient antibody production. These results indicate that a recombinant vaccinia encoding H5 hemagglutinin gene does not impair dendritic cell recruitment and can be a useful vaccine candidate.

Highlights

  • H5N1 highly pathogenic avian influenza (H5N1 HPAI) virus causes elevated mortality compared with seasonal influenza viruses like H1N1 pandemic influenza (H1N1 pdm) virus

  • Pathological analyses demonstrated that the mice infected with H5N1 HPAI virus developed severe pneumonia with diffuse alveolar damage at 7 dpi and that the symptoms were markedly aggravated at 9 dpi (Fig. 1c)

  • To determine whether the differences in responses depended on the species of the host animal, we investigated immune responses in the pathogenesis of H1N1 pdm and H5N1 HPAI viruses in cynomolgus macaques

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Summary

Introduction

H5N1 highly pathogenic avian influenza (H5N1 HPAI) virus causes elevated mortality compared with seasonal influenza viruses like H1N1 pandemic influenza (H1N1 pdm) virus. H5N1 HPAI virus infection induced a decrease of dendritic cell number in the splenic extrafollicular T-cell zone and impaired formation of the outer layers of B-cell follicles, resulting in insufficient levels of antibody production after infection. H5 hemagglutinin, infection with H5N1 HPAI virus induced parafollicular dendritic cell accumulation and efficient antibody production. These results indicate that a recombinant vaccinia encoding H5 hemagglutinin gene does not impair dendritic cell recruitment and can be a useful vaccine candidate. HPAI viruses represent a potential influenza pandemic, as would occur when a new virus emerges globally and infects individuals who have no immunity specific for new subtypes[1]. We hypothesized that the severity of H5N1 HPAI virus infection might reflect attenuation of immune responses necessary for efficient antibody production

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