Contribution of factor H-Binding protein sequence to the cross-reactivity of meningococcal native outer membrane vesicle vaccines with over-expressed fHbp variant group 1

Abstract

Factor H-binding protein (fHbp) is an important meningococcal vaccine antigen. Native outer membrane vesicles with over-expressed fHbp (NOMV OE fHbp) have been shown to induce antibodies with broader functional activity than recombinant fHbp (rfHbp). Improved understanding of this broad coverage would facilitate rational vaccine design. We performed a pair-wise analysis of 48 surface-exposed amino acids involved in interacting with factor H, among 383 fHbp variant group 1 sequences. We generated isogenic NOMV-producing meningococcal strains from an African serogroup W isolate, each over-expressing one of four fHbp variant group 1 sequences (ID 1, 5, 9, or 74), including those most common among invasive African meningococcal isolates. Mice were immunised with each NOMV, and sera tested for IgG levels against each of the rfHbp ID and for ability to kill a panel of heterologous meningococcal isolates. At the fH-binding site, ID pairs differed by a maximum of 13 (27%) amino acids. ID 9 shared an amino acid sequence common to 83 ID types. The selected ID types differed by up to 6 amino acids, in the fH-binding site. All NOMV and rfHbp induced high IgG levels against each rfHbp. Serum killing from mice immunised with rfHbp was generally less efficient and more restricted compared to NOMV, which induced antibodies that killed most meningococci tested, with decreased stringency for ID type differences. Breadth of killing was mostly due to anti-fHbp antibodies, with some restriction according to ID type sequence differences. Nevertheless, under our experimental conditions, no relationship between antibody cross-reactivity and variation fH-binding site sequence was identified. NOMV over-expressing different fHbp IDs belonging to variant group 1 induce antibodies with fine specificities against fHbp, and ability to kill broadly meningococci expressing heterologous fHbp IDs. The work reinforces that meningococcal NOMV with OE fHbp is a promising vaccine strategy, and provides a basis for rational selection of antigen sequence types for over-expression on NOMV.

Investigating the Role of Antigen Orientation on the Immune Response Elicited by Neisseria meningitidis Factor H Binding Protein on GMMA

“…The reason for this could be linked to multiple factors not yet fully elucidated, including that GMMA present key antigens in their native conformation and orientation. As with many previous studies, in this study we have confirmed that N. meningitidis fHbp, when presented on the GMMA surface, is much more immunogenic than fHbp alone or simply physically mixed with GMMA [ 27 , 29 , 34 , 36 ]. Indeed, fHbp on GMMA elicited a higher antibody response than the controls despite a lower fHbp amount and, importantly, induced bactericidal titers post I, differently from the controls, and titers much higher than the controls after re-injection.…”

Neisseria meningitidis Factor H Binding Protein Surface Exposure on Salmonella Typhimurium GMMA Is Critical to Induce an Effective Immune Response against Both Diseases

“…The polymerase incomplete primer extension (PIPE) cloning method [40] was used to insert fHbp (variant 1-ID5 from Neisseria meningitidis serogroup A strain) [41] into a pGEX-derived plasmid, carrying the sequence encoding the leader peptide for secretion of E. coli OmpA. The Escherichia coli HK-100 strain was used for cloning and plasmid generation and was grown in Luria-Bertani (LB) broth at 37 • C. Ampicillin was used at the final concentration of 100 µg/mL.…”

OMV Vaccines and the Role of TLR Agonists in Immune Response

“…For instance, when N. meningitidis OMVs displaying the antigenic porin protein PorA were examined in comparison to purified PorA protein, a humoral immune response was elicited in response to both candidate vaccines, but only the PorA-containing OMVs induced bactericidal antibodies [ 141 ]. The functional immune response induced by OMVs over-expressing fHbp is similar to that induced by > 10-fold higher fHbp administered in recombinant form, suggesting that the native conformation and self-adjuvant properties of OMV have a great impact in the immune response induced [ 142 ]. OMVs naturally released from a recombinant African N. meningitidis W strain with deleted capsule locus, attenuated LPS toxicity ( lpxL1 mutant), improved OMV yield ( gna33 mutant) and with overexpressed fHbp v.1 have been proposed as an affordable vaccine with broad coverage against strains from all main serogroups currently causing meningococcal meningitis in sub-Saharan Africa [ 38 ].…”