Monoclonal Antibody Targeting Neutralizing Epitope on H5N1 Influenza Virus of Clade 1 and 0 for Specific H5 Quantification

H5N1 influenza viruses cause high mortality in avian and mammalian species, including humans. Antigenic drift in H5 sequence poses challenges in the development of vaccine and therapeutic antibody. In this study, a monoclonal antibody 11G12 was produced from inactivated H5N1 immunized mice. Results from IFA, ELISA, HI, and virus neutralization indicated that Mab 11G12 can specifically recognize and neutralize H5 type hemagglutinin from clade 1 and 0 without any cross-reaction to any other clades of H5N1 viruses. Mab 11G12 was used to differentiate and quantify the expression of H5N1 strain A/VietNam/1203/04 from a trivalent vaccine mix in ELISA. Sequencing of escape mutants identified that Mab 11G12 targets a major neutralizing epitope of influenza H5 hemagglutinin. The study indicated that some major neutralizing epitopes in H5s of early strains were mutated due to antigenic drift.