Functional Characterization of Antibodies against Neisseria gonorrhoeae Opacity Protein Loops

Abstract

BackgroundThe development of a gonorrhea vaccine is challenged by the lack of correlates of protection. The antigenically variable neisserial opacity (Opa) proteins are expressed during infection and have a semivariable (SV) and highly conserved (4L) loop that could be targeted in a vaccine. Here we compared antibodies to linear (Ablinear) and cyclic (Abcyclic) peptides that correspond to the SV and 4L loops and selected hypervariable (HV2) loops for surface-binding and protective activity in vitro and in vivo.Methods/FindingsAbSV cyclic bound a greater number of different Opa variants than AbSV linear, including variants that differed by seven amino acids. Antibodies to the 4L peptide did not bind Opa-expressing bacteria. AbSV cyclic and AbHV2 cyclic, but not AbSV linear or AbHV2 linear agglutinated homologous Opa variants, and AbHV2BD cyclic but not AbHV2BD linear blocked the association of OpaB variants with human endocervical cells. Only AbHV2BD linear were bactericidal against the serum resistant parent strain. Consistent with host restrictions in the complement cascade, the bactericidal activity of AbHV2BD linear was increased 8-fold when rabbit complement was used. None of the antibodies was protective when administered vaginally to mice. Antibody duration in the vagina was short-lived, however, with <50% of the antibodies recovered 3 hrs post-administration.ConclusionsWe conclude that an SV loop-specific cyclic peptide can be used to induce antibodies that recognize a broad spectrum of antigenically distinct Opa variants and have agglutination abilities. HV2 loop-specific cyclic peptides elicited antibodies with agglutination and adherence blocking abilities. The use of human complement when testing the bactericidal activity of vaccine-induced antibodies against serum resistant gonococci is also important.

Quantitative Proteomics of the 2016 WHO Neisseria gonorrhoeae Reference Strains Surveys Vaccine Candidates and Antimicrobial Resistance Determinants

“…Expression and Homologs of Gonorrhea Vaccine Candidates-We first evaluated expression profiles of extensively studied gonorrhea vaccine candidates including MtrE (91-93), PorB (94,95), PilQ (96), TbpA (97,98), Opa (99,100), and AniA (19,(101)(102)(103). MtrE was upregulated in 8 isolates (Table II).…”

Quantitative proteomics of the 2016 WHONeisseria gonorrhoeaereference strains surveys vaccine candidates and antimicrobial resistance determinants

“…We first evaluated expression profiles of extensively studied gonorrhea vaccine candidates including MtrE (93–95), PorB (96, 97), PilQ (98), TbpA (99, 100), Opa (101, 102), and AniA (19, 103–105). MtrE and PorB were up-and down-regulated, respectively, in 12 isolates (Table 2).…”

Oral Immunization of Rabbits with S. enterica Typhimurium Expressing Neisseria gonorrhoeae Filamentous Phage Φ6 Induces Bactericidal Antibodies Against N. gonorrhoeae

“…Determination the level of anti- N gonorrhoeae specific IgG and IgA antibodies in the rabbit sera was based on the method by Afonina et al 55 and Cole and Jerse 56 . N. gonorrhoeae cells (2 μl of 10 8 cells/ml diluted in PBS) were spotted in triplicate onto 10 × 50 mm strips of nitrocellulose and allowed to air dry.…”