When grown under
iron restriction, Neisseria meningitidis expresses new outer-
membrane proteins, some of which are antigenic and potentially useful as
vaccine components. This is particularly relevant to N. meningitidis serogroup B, against which neither
polysaccharide nor
conjugate vaccines are effective. We investigated recognition of N. meningitidis serogroup B outer-membrane
antigens by three sera from patients recovered from
meningitis. Recognition of
antigens from the homologous strain provided information on in vivo expression during
infection and immunogenicity, while cross-reactivity with outer
membrane proteins from the other two strains and from another five strains in our collection allowed evaluation of antigenic heterogeneity. Our results demonstrate that
transferrin-binding protein 2 (TBP2) is immunogenic in humans, to varying degrees depending on the strain, and that TBP2s (like the equivalent
proteins of Haemophilus influenzae type b) are among the most important
iron-regulated outer membrane
antigens expressed during
infection. Other immunogenic outer
membrane proteins (some
iron-regulated) are also expressed during
infection; in a previous study in mouse, three of these
proteins (with M(r) of 50, 70 and 77 kDa) did not induce an immune response. Our cross-reactivity data provide some support for Robki et al.'s two-group classification of N. meningitidis strains, and provide evidence against the possibility that the antigenic domains shared by the TBP2s of all N. meningitidis strains induce immune responses in vivo.