Ostrich produce cross-reactive neutralization antibodies against pandemic influenza virus A/H1N1 following immunization with a seasonal influenza vaccine

Abstract

An outbreak of influenza in 2009 was found to be caused by a novel strain of influenza virus designated as pandemic influenza A/H1N1 2009. Vaccination with recent seasonal influenza vaccines induced little or no cross-reactive antibody response to the pandemic influenza virus A/H1N1 2009 in any age group in human populations. Accordingly, most people had low immunity against this pathogen, thus resulting in the worldwide spread of the infection to produce a so-called 'pandemic'. This report presents the important finding that ostrich eggs generate cross-reactive antibodies to the pandemic influenza virus A/H1N1 following immunization of female ostrich with a seasonal influenza vaccine. This simple method produced a large amount of antibodies against influenza viruses by one female ostrich. An enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry indicated that the ostrich antibodies possessed strong cross-reactivity to the pandemic A/H1N1 as well as to the seasonal A/H1N1, A/H3N2 and B viruses. The hemaggregation activities of erythrocytes induced by this pandemic strain were also inhibited by the ostrich antibodies. In addition, the cytopathological effects of infection with a pandemic virus on MDCK cells were clearly inhibited in co-cultures with the ostrich antibodies, thereby indicating the neutralization of viral infectivity in the cells. In conclusion, cross-reactive neutralization antibodies against pandemic influenza virus A/H1N1 2009 were successfully generated in ostrich eggs produced by females immunized with seasonal influenza viral vaccine.

Figure 1.

Immunocytochemistry of influenza virus-infected MDCK cells. MDCK cells were infected with seasonal influenza viruses [A/Osaka/309/2007 (H1N1), A/Osaka/2587/2005 (H3N2), B/Osaka/21/2005] and pandemic A/H1N1 [A/Osaka/2040/2009 (H1N1)pdm)]. The cells were fixed 5 days after infection, reacted with ostrich IgY, and then visualized with an FITC-conjugated secondary antibody. None of the cells infected with each virus were stained by preimmune IgY. In contrast, the cells infected with each seasonal influenza virus were strongly stained with the IgY produced by ostrich immunized with the seasonal influenza vaccine. Notably, the IgY cross-reacted with the cells infected with the pandemic A/H1N1 virus. Bars, 100 μm.