IgG antibody subclass responses determined by immunoblot in infants' sera following vaccination with a meningococcal recombinant hexavalent PorA OMV vaccine

The introduction of meningococcal serogroup C conjugate vaccines into the U K immunisation schedule has led to the decline of serogroup C disease in th ose vaccinated but there is no imminent vaccine solution for serogroup B di sease. The PorA outer membrane protein (OMP) is a potential serogroup B vac cine candidate and an outer membrane vesicle (OMV) vaccine containing six d ifferent PorA OMPs (each representing a different serosubtype) has been eva luated in phase II trials with encouraging results. Little is known about t he IgG subclass response to the various antigens contained within this vacc ine. These responses are important due to the different half-lives and comp lement fixing abilities of these antibodies. In this study, immunoblotting was undertaken with infants' sera following either three or four doses of v accine, and OMVs from six isogenic meningococcal strains differing only in their PorA serosubtype. Following either three or four doses of the vaccine , IgG(3) and IgG(1) subclass antibodies were induced to all six of the isog enic strains, although sera collected after four doses of vaccine showed st ronger antibody levels. IgG(3) was found in more sera than IgG(1). For both sets of sera, the two isogenic strains expressing P1.5,2 and P1.5(c),10 in duced stronger IgG subclass antibody responses than the other four meningoc occal strains. The recombinant hexavalent PorA OMV vaccine stimulates both IgG(1) and IgG(3) subclass antibodies, the subclasses that are most effecti ve in activating the complement system. (C) 2001 Elsevier Science Ltd. All rights reserved.