A monoclonal antibody directed against the influenza A virus is described, which is capable of binding human and animal isolates of influenza A viruses expressing the H1-subtype hemagglutinin. A preferred embodiment is the antibody designated as Fab49, which shows a neutralizing activity against a plurality of influenza A virus isolates expressing the H1-subtype hemagglutinin, including animal-derived isolates. Anti-idiotype antibodies directed against the monoclonal antibody of the invention, immunogenic or vaccine compositions comprising the monoclonal antibody of the invention are also described, as well as therapeutic, prophylactic and diagnostic applications for the monoclonal antibody of the invention. The monoclonal antibody of the invention can also be employed for testing antibody preparations to be used as vaccines.
