[Variation of primary structure and conformation of NP protein from influenza A virus, recognized by monoclonal...

The antigenic structure of influenza A NP protein was studied by using a panel of 12 monoclonal antibodies (mAbs). A group of strains of influenza-A virus with the known NP amino acid sequence was analyzed by radioimmunoprecipitation with a subsequent analysis of the immune complexes by electrophoresis in polyacrylamide gel. The examined group of strains comprised pairs of closely related variants like A/USSR/90/77 and A/Brazil/1/78 as well as A/Puerto Rico/8/34 (Mount Sinai variant) and A Puerto Rico/8/34 Cambridge 1 variant). The results made it possible to identify position 353 as a part of antigenic site. The combined results of radioimmunoprecipitation and immunoblotting suggest that the mentioned site is recognized by mAb IVE8 as a linear epitope and by mAb as a confirmation epitope. Amino acids in positions 196 and/or 290 are involved in the formation of another antigenic site. The N-terminal part of NP, removed in the course of protein processing, is not involved in the differentiation of avian and human strains by mAb 315. None of the mAbs used in our study recognized the N-terminal part of NP as a linear epitope.