Neisseria meningitidis factor H-binding protein bound to monoclonal antibody JAR5: implications for antibody synergy

Abstract

Factor H-binding protein (fHbp) is an important antigen of Neisseria meningitidis that is capable of eliciting a robust protective immune response in humans. Previous studies on the interactions of fHbp with antibodies revealed that some anti-fHbp monoclonal antibodies that are unable to trigger complement-mediated bacterial killing in vitro are highly co-operative and become bactericidal if used in combination. Several factors have been shown to influence such co-operativity, including IgG subclass and antigen density. To investigate the structural basis of the anti-fHbp antibody synergy, we determined the crystal structure of the complex between fHbp and the Fab (fragment antigen-binding) fragment of JAR5, a specific anti-fHbp murine monoclonal antibody known to be highly co-operative with other monoclonal antibodies. We show that JAR5 is highly synergic with monoclonal antibody (mAb) 12C1, whose structure in complex with fHbp has been previously solved. Structural analyses of the epitopes recognized by JAR5 and 12C1, and computational modeling of full-length IgG mAbs of JAR5 and 12C1 bound to the same fHbp molecule, provide insights into the spatial orientation of Fc (fragment crystallizable) regions and into the possible implications for the susceptibility of meningococci to complement-mediated killing.

Variant Signal Peptides of Vaccine Antigen, FHbp, Impair Processing Affecting Surface Localization and Antibody-Mediated Killing in Most Meningococcal Isolates

“…The susceptibility of the isolates to complement-mediated killing with antibodies JAR4 and JAR5 was assessed using approaches adapted from previous studies (Beernink et al, 2008(Beernink et al, , 2011Vu et al, 2012). JAR4 and JAR5 were used in combination, in place of serum antibodies, to generate bactericidal activity (Beernink et al, 2008;Welsch et al, 2008;Malito et al, 2016). Eight µg of each antibody were used to ensure maximum killing (Beernink et al, 2008).…”

“…The SBA assay was performed using the FHbp-specific monoclonal antibody JAR5 along with JAR4. Cooperativity between these two antibodies is necessary to elicit bactericidal activity in the presence of human complement (Beernink et al, 2008;Welsch et al, 2008;Malito et al, 2016). JAR5 is known to bind the FHbp epitope comprising AA residues 84-91 and 115-123 (Malito et al, 2016) ( Supplementary Table S1).…”

Vaccine antigen, Factor H binding protein, is typically a non-lipidated precursor that localises to the meningococcal surface by Slam

“…The SBA assay was performed using the FHbp-specific monoclonal antibody JAR5 along with JAR4. Cooperativity between these 2 antibodies is necessary to elicit bactericidal activity in the presence of human complement [41][42][43]. JAR5 is known to bind the FHbp epitope comprising AA residues 84-91 and 115-123 [41] (Table S1).…”

“…Cooperativity between these 2 antibodies is necessary to elicit bactericidal activity in the presence of human complement [41][42][43]. JAR5 is known to bind the FHbp epitope comprising AA residues 84-91 and 115-123 [41] (Table S1). Strains MC58 and L91543 were previously shown to contrast starkly in their FHbp exposure and susceptibility to killing by FHbp-immunised sera in SBA assays [27] and were used as positive and negative control strains respectively to benchmark all other isolates.…”

“…The susceptibility of the isolates to complement-mediated killing with antibodies JAR4 and JAR5 was assessed using approaches adapted from previous studies [42,59,60]. JAR4 and JAR5 were used in combination, in place of serum antibodies, to generate bactericidal activity [41][42][43]. Eight μg of each antibody were used to ensure maximum killing [42].…”