Influenza A virus
infections are the major public health concern and cause significant morbidity and mortality each year worldwide. Vaccination is the main strategy of
influenza epidemic prevention. However, seasonal
vaccines induce strain-specific immunity and must be reformulated annually based on prediction of the strains that will circulate in the next season. Thus, it is essential to develop
vaccines that would induce broad and persistent immunity to influenza viruses.
Hemagglutinin is the major
surface antigen of the influenza virus. Recent studies revealed the importance of HA stalk-specific
antibodies in neutralization of different influenza virus strains. Therefore, it is important to design an immunogen that would focus the immune response on the HA stalk domain in order to elicit
neutralizing antibodies. In the present study, we report characterization of a conserved truncated
protein, potentially a universal influenza virus
antigen from the H5N1 Highly Pathogenic
Avian Influenza A virus strain. Our results indicate that exposure of the HA stalk domain containing conserved
epitopes results in cross reactivity with different
antibodies (against group 1 and 2 HAs). Additionally, we conclude that HA stalk domain contains not only conformational
epitopes recognized by universal FI6 antibody, but also linear
epitopes recognized by other
antibodies.