Generation of monoclonal antibodies reactive against subtype specific conserved B-cell epitopes on haemagglutinin protein of influenza virus H5N1.

H5-specific monoclonal antibodies may serve as valuable tools for rapid diagnosis of H5N1 avian influenza virus. Therefore, conserved H5-specific sequences of the haemagglutinin (HA) protein were expressed in Pichia pastoris and used for generation of monoclonal antibodies (mAbs). The two mAbs, FD6 and HE4, were strongly reactive against native HA protein and exhibited specificity for subtype H5. By epitope mapping linear epitopes of mAbs were identified that are highly conserved among influenza A virus of subtype H5. Additionally no sequence similarities to homologous regions on HA proteins of other influenza A virus subtypes (i.e. H1, H3, H7, H9) were detected by sequence alignment analysis. Both mAbs did not cross react with native or denatured HA proteins of other influenza A virus subtypes. Furthermore, using ELISA and immunofluorescence test mAb FD6 reacted only to the native H5 protein of recently circulating highly pathogenic H5N1 influenza viruses but not to low pathogenic H5N1 isolates. In conclusion, the use of the two mAbs in non-molecular tests like antigen-capture-ELISA appears promising for detecting influenza A H5N1 virus.