Neisserial Heparin Binding Antigen (NHBA) Contributes to the Adhesion of Neisseria meningitidis to Human Epithelial Cells

Abstract

Neisserial Heparin Binding Antigen (NHBA) is a surface-exposed lipoprotein ubiquitously expressed by Neisseria meningitidis strains and an antigen of the Bexsero® vaccine. NHBA binds heparin through a conserved Arg-rich region that is the target of two proteases, the meningococcal NalP and human lactoferrin (hLf). In this work, in vitro studies showed that recombinant NHBA protein was able to bind epithelial cells and mutations of the Arg-rich tract abrogated this binding. All N-terminal and C-terminal fragments generated by NalP or hLf cleavage, regardless of the presence or absence of the Arg-rich region, did not bind to cells, indicating that a correct positioning of the Arg-rich region within the full length protein is crucial. Moreover, binding was abolished when cells were treated with heparinase III, suggesting that this interaction is mediated by heparan sulfate proteoglycans (HSPGs). N. meningitidis nhba knockout strains showed a significant reduction in adhesion to epithelial cells with respect to isogenic wild-type strains and adhesion of the wild-type strain was inhibited by anti-NHBA antibodies in a dose-dependent manner. Overall, the results demonstrate that NHBA contributes to meningococcal adhesion to epithelial cells through binding to HSPGs and suggest a possible role of anti-Bexsero® antibodies in the prevention of colonization.

The meningococcal vaccine antigen GNA2091 is an analogue of YraP and plays key roles in outer membrane stability and virulence

“…The immunogenicity and stability of the recombinant antigens was optimized by generating protein-protein fusions of fHbp-GNA2091 and NHBA-GNA1030, which induce higher serum bactericidal activity titers than those induced by the individual antigens alone (2). fHbp, Neisserial adhesin A, and NHBA have been extensively characterized and shown to be involved in meningococcal virulence (6)(7)(8)(9)(10)(11). The accessory protein GNA1030 has recently been characterized as a Neisseria ubiquinone binding protein (NUbp) (12).…”

NHBA is processed by kallikrein from human saliva

“…The important role of the NHBA Arg-rich region for host colonization and invasion was demonstrated previously for Heparin binding [7] and Neisseria meningitidis adhesion to Human Ephitelial Cells [16].…”

“…The role of NHBA in Neisseria meningiditis pathogenesis is still unclear. Previous studies have shown that NHBA is able to bind Heparin and GAGs on epithelial cells through the Arg-rich region [16] , supporting the hypothesis that NHBA can not only enhance bacterial survival in human serum, but can also play a crucial role during the adhesion step in Neisseria meninigitidis host colonization [15]. NHBA is cleaved by two specific proteases, NalP, a surface-exposed Neisseria serine protease, and human lactoferrin (hLf), present in several human biological fluids like serum, milk and saliva [7] .…”

“…lactamica , N. polysaccharea and N. Flavescens [7]. Recent studies on NHBA have shown that this protein is implicated in different steps of meningococcal pathogenesis, including bacterial adhesion to epithelial cells [16] , biofilm formation [25] , bacterial survival in the blood, and vascular leakage [15] . It is also able to bind heparin in vitro through an Arginine-rich region [7] and this ability may point to a role of NHBA in the protection of unencapsulated meningococci against complement [15] .…”

Potential benefits of using a multicomponent vaccine for prevention of serogroup B meningococcal disease

“…NHBA is a surface-exposed lipoprotein expressed by most meningococcal strains (Lucidarme et al, 2010;Tsang et al, 2015;Wang et al, 2011) and by other Neisseria species (Muzzi et al, 2013). Binding to heparin has been shown to improve the pathogen's survival in blood and to mediate adhesion to epithelial cells Vacca et al, 2016). NHBA peptide sequence can vary considerably, but cross-protection has been demonstrated across a variety of NHBA variants (Giuliani et al, 2010).…”