Colonization |
PilC | Pilus-associated adhesin; phase variable expression, variable and conserved regions | 4 |
PilQ | Outer membrane channel through which pili are extruded; stable expression and antibodies against meningococcal PilQ are bactericidal | 5 |
PorB | Major porin, two serogroups (PorB1A and PorB1B), stable expression; involved in gonococcal invasion of cervical cells through the C3R integrin; PorB1A molecules directly mediate uptake through the SREC-1 receptor | 6 7 |
Opa proteins | Phase variable; 8–10 antigenically distinct Opa proteins per strain; peptide antigens may be used to avoid immunosuppressive domains; a cyclic peptide corresponding to the semivariable (SV) loop recognises Opa proteins with as many as 6–8 amino acid differences in this loop | 26 |
OmpA | Surface-exposed, stably expressed, highly conserved. Mediates invasion of cervical and endometrial cells | 27 |
Nutrient acquisition |
TbpA, TbpB | Transferrin receptor; TbpA and TbpB are highly and semiconserved, respectively. Purified TbpA or TbpB induce bactericidal antibodies in mice that block growth in the presence of Tf as a sole iron source | 28 |
LbpA, LpbB | Lactoferrin receptor; antibodies against N meningitidis homologues are bactericidal | 13 |
TdfJ | Iron-induced zinc transporter; antibodies against the meningococcal homologue (ZnuD) are bactericidal | 29 30 |
Evasion of innate defenses |
MtrE | Surface-exposed channel of the MtrC-MtrD-MtrE and FarA-FarB-MtrE active efflux pumps; stable expression and highly conserved; antibodies to recombinant MtrE are bactericidal | (AJ DeRocco and AE Jerse, unpublished data) |
Lst | α2,3 sialyltransferase; catalyses the addition of host-derived sialic acid to the LNT species of LOS; protects gonococci from complement, non-opsonic uptake by neutrophils and antimicrobial peptides. Antibodies to purified Lst reduce sialylation | 16 17 |
PorB | In serum resistant strains, PorB binds soluble negative regulators of the complement cascade (C4b-binding protein, factor H) to down-regulate complement activation at the gonococcal surface | 31 |
Other |
2C7 epitope | Bactericidal LOS epitope; phase variable but expressed by >95% of isolates. Antibodies to a 2C7 peptide mimetic are bactericidal and opsonophagocytic and active and passive protection was demonstrated in mice | 20 32 |
AniA | Nitrite reductase; surface-exposed, conserved; induced by low O2 tension and the presence of nitrite. Required for anaerobic growth and biofilm formation; plays a role in serum resistance. A truncated AniA protein that lacked the glycosylated C-terminus induced antibodies that inhibited nitrite reductase activity | 8–10 |
OpcA | Stably expressed in N gonorrhoeae. OMV from N meningitidis with a phase-locked ‘on’ opcA gene is a candidate meningococcal vaccine | 33 34 |
NspA | Stably expressed, highly conserved. Meningococcal NspA is protective in mouse model of meningococcal infection | 35 |
Outer membranes | Can be engineered to stabilise the expression of phase variable or regulated antigens and increase the diversity of antigenic variants present. An outer membrane preparation was protective against N gonorrhoeae in a mouse model | 3 |