has role protective antigen role protective antigen Influenza virus protein HA from Influenza A virus (A/Hong Kong/1/68(H3N2)) Protegen ID: 525; NCBI Protein GI: 16960108; NCBITaxon: 10090 Oliver He Vaccination with HA-VRP derived from Influenza A virus (A/Hong Kong/1/68(H3N2)) did not strongly stimulate either neutralizing or IgG1 antibodies but did induce IgG2a antibodies. Expression of IgG2a antibodies in this context correlated with clearance of virus and increased protection against lethal influenza challenge [PubMed: 16960108]. protein Allen Xiang