has role protective antigen role protective antigen Haemophilus influenzae protein OmpP1 Allen Xiang protein Protegen ID: 864; NCBI Protein GI: 9716645; NCBITaxon: 727 Oliver He When chinchillas were immunized with recombinant P1 (rP1) obtained from one of these isolates (BCH-3), all animals developed antibodies specific for rP1. Immunized animals were protected against disease when challenged with BCH-3, but not with an ompP1 mutant of BCH-3 or a strain (BCH-2) possessing a heterologous P1 (91% identity). We conclude that (i) while P1 induces protection against NTHI-mediated otitis media, development of a polyvalent vaccine reflecting the variability of P1 would be necessary to construct an efficacious vaccine [PubMed: 10899849].