Allelic Diversity of the Two Transferrin Binding Protein B Gene Isotypes among a Collection of Neisseria meningitidis Strains Representative of Serogroup B Disease: Implication for the Composition of a Recombinant TbpB-Based Vaccine

Abstract

The distribution of the two isotypes of tbpB in a collection of 108 serogroup B meningococcal strains belonging to the four major clonal groups associated with epidemic and hyperendemic disease (the ET-37 complex, the ET-5 complex, lineage III, and cluster A4) was determined. Isotype I strains (with a 1.8-kb tbpB gene) was less represented than isotype II strains (19.4 versus 80.6%). Isotype I was restricted to the ET-37 complex strains, while isotype II was found in all four clonal complexes. The extent of the allelic diversity of tbpB in these two groups was studied by PCR restriction analysis and sequencing of 10 new tbpB genes. Four major tbpB gene variants were characterized: B16B6 (representative of isotype I) and M982, BZ83, and 8680 (representative of isotype II). The relevance of these variants was assessed at the antigenic level by the determination of crossbactericidal activity of purified immunoglobulin G preparations raised to the corresponding recombinant TbpB (rTbpB) protein against a panel of 27 strains (5 of isotype I and 22 of isotype II). The results indicated that rTbpB corresponding to each variant was able to induce cross-bactericidal antibodies. However, the number of strains killed with an anti-rTbpB serum was slightly lower than that obtained with an anti-TbpA ؉ B complex. None of the sera tested raised against an isotype I strain was able to kill an isotype II strain and vice versa. None of the specific antisera tested (anti-rTbpB or anti-TbpA ؉ B complex) was able to kill all of the 22 isotype II strains tested. Moreover, using sera raised against the C-terminus domain of TbpB M982 (amino acids 352 to 691) or BZ83 (amino acids 329 to 669) fused to the maltose-binding protein, cross-bactericidal activity was detected against 12 and 7 isotype II strains, respectively, of the 22 tested. These results suggest surface accessibility of the C-terminal end of TbpB. Altogether, these results show that although more than one rTbpB will be required in the composition of a TbpB-based vaccine to achieve a fully cross-bactericidal activity, rTbpB and its C terminus were able by themselves to induce cross-bactericidal antibodies.

Specific Ligand Binding Attributable to Individual Epitopes of Gonococcal Transferrin Binding Protein A

“…Thus, the more conserved of the Tbp proteins was capable of eliciting a cross-reactive, protective immune response. Antigenically variable epitopes have been recognized as immunodominant in neisserial porins (35,37), in neisserial FrpB (38) (now called FetA; [9]), and in meningococcal TbpB (30); however, these immunodominant epitopes have also been shown to elicit strain-specific antibody responses that did not confer broadly cross-reactive biological activities (30,35,37,38). Thus, in the search for a cross-reactive response, we may be more successful identifying immunorecessive epitopes that could be "unmasked" by removal of the immunodominant, antigenically variable residues.…”

Oral administration of recombinantNeisseria meningitidisPorA genetically fused toH. pyloriHpaA antigen increases antibody levels in mouse serum, suggesting that PorA behaves as a putative adjuvant

“…This strain belongs to the clonal complex group ET-5. 47 The PCR product, as expected, was approximately 1.2 kb. This dA tailed fragment was cloned in pGEM-T/ DH5a cells and subcloned in the expression system pET21a/BL21 (DE3) (Fig.…”

Transferrin-Binding Protein B of Neisseria meningitidis : Sequence-Based Identification of the Transferrin-Binding Site Confirmed by Site-Directed Mutagenesis

“…The bactericidal activities of purified rabbit IgGs specific for the various MBP-TbpB fusions have been determined, as reported earlier (5,24). The bactericidal titers were expressed as the last dilution of purified IgG in which at least 50% killing compared to the complement control was achieved.…”

“…There is no universal vaccine to control and stop this disease. Immunization with TbpB has been shown to elicit a protective immune response in laboratory animals, which has been related to the production of bactericidal antibodies (17,24). Based on genomic and antigenic features of TbpB, meningococcal strains have been classified into two major families: isotype I, containing TbpB with a mass of ϳ68 kDa, and isotype II, harboring TbpB with a mass between 80 and 90 kDa (26).…”