Preclinical evidence for the potential of a bivalent fHBP vaccine to prevent Neisseria meningitidis serogroup C disease

A bivalent factor H binding protein (fHBP) vaccine for the prevention of disease caused by Neisseria meningitidis serogroup B is currently in clinical development. Since fHBP is also expressed by other meningococcal serogroups, anti-fHBP antibodies may have bactericidal activity against meningococci independent of serogroup. To begin examining the susceptibility of other meningococcal serogroups to anti-fHBP antibodies, meningococcal serogroup C invasive isolates (n = 116) were collected from the Centers for Disease Control and Prevention's Active Bacterial Core surveillance (ABCs) sites during 2000-2001. These isolates were analyzed for the presence of the fhbp gene. All serogroup C isolates contained the gene, and sequence analysis grouped the proteins into two subfamilies, A and B. Flow cytometry analysis demonstrated that fHBP was expressed on the surface of similar to 70% of isolates in vitro with varying levels of expression. fHBP was accessible to antibodies on the cell surface even in the presence of the polysaccharide capsule. Nine isolates from different geographic regions were identified which harboured an identical single nucleotide deletion that could result in a truncated subfamily B fHBP. Analysis by flow cytometry using a polyclonal fHBP antibody preparation revealed that a subpopulation of each of these isolates expressed fHBP. Rabbit and non-human primate immune sera generated with bivalent fHBP vaccine were tested for bactericidal activity against a panel of diverse serogroup C clinical isolates using human complement. Sera from both species demonstrated serum bactericidal antibody activity against the serogroup C isolates tested. These promising findings suggest that a bivalent fHBP vaccine may be capable of providing protection against meningococcal disease caused by both serogroup C and B.