Immunogenicity and protective efficacy of a recombinant filamentous haemagglutinin from Bordetella pertussis

Bordetella pertussis is the causative agent of whooping cough, a major childhood pathogen; acellular vaccines consisting of purified B. pertussis antigens such as filamentous haemagglutinin (FHA) are commonly used to prevent pertussis. Despite the importance of FHA in B. pertussis pathogenesis and its inclusion in most acellular vaccines, the functional importance of individual domains in the induction of protective immunity is largely unknown. In this study, we have purified a recombinant FHA protein from Escherichia coli consisting of a 42 kDa maltose binding domain of E. coli and the 43 kDa type I immunodominant domain of FHA. The fusion protein (Mal85) was purified from E. coli cell lysates via affinity chromatography with an amylose column. Mal85 was then delivered to BALB/c mice intranasally encapsulated in liposomes, formulated with Protollin(TM) or in conjunction with an immunostimulatory CpG oligonucleotide. Mice were also vaccinated intraperitoneally with alum-adsorbed Mal85. Sera from all treatment groups showed strong IgG responses to Mal85 and recognized native FHA. Specific salivary IgA was induced in mice vaccinated with Mal85 in liposomes, Protollin(TM) and delivered with CpG. Vaccination with Mal85 encapsulated in liposomes or formulated with Protollin(TM) provided protection against aerosol challenge with B. pertussis in BALB/c mice. These data indicate that the type I domain of FHA is a protective antigen in mice and may serve as a candidate for inclusion in new acellular pertussis vaccines.