title: Phase-Variable Heptose I Glycan Extensions Modulate Efficacy of 2C7 Vaccine Antibody Directed against Neisseria gonorrhoeae Lipooligosaccharide.
abstract: Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection, gonorrhea, has developed resistance to most conventional antibiotics. Safe and effective vaccines against gonorrhea are needed urgently. A candidate vaccine that targets a lipooligosaccharide (LOS) epitope recognized mAb 2C7 attenuates gonococcal burden in the mouse vaginal colonization model. Glycan extensions from the LOS core heptoses (HepI and HepII) are controlled by phase-variable LOS glycosyltransferase (lgt) genes; we sought to define how HepI glycan extensions affect mAb 2C7 function. Isogenic gonococcal mutants in which the lgt required for mAb 2C7 reactivity (lgtG) was genetically locked on and the lgt loci required for HepI variation (lgtA, lgtC, and lgtD) were genetically locked on or off in different combinations were created. We observed 100% complement-dependent killing by mAb 2C7 of a mutant that expressed lactose (Gal-Glc) from HepI, whereas a mutant that expressed Gal-Gal-Glc-HepI fully resisted killing (>100% survival). Mutants that elaborated 4- (Gal-GlcNAc-Gal-Glc-HepI) and 5-glycan (GalNAc-Gal-GlcNAc-Gal-Glc-HepI) structures displayed intermediate phenotypes (<50% killing with 2 μg/ml and >95% killing with 4 μg/ml mAb 2C7). The contrasting phenotypes of the lactose-HepI and the Gal-Gal-Glc-HepI LOS structures were recapitulated with phase variants of a recently isolated clinical strain. Despite lack of killing of the Gal-Gal-Glc-HepI mutants, mAb 2C7 deposited sufficient C3 on these bacteria for opsonophagocytic killing by human neutrophils. In conclusion, mAb 2C7 showed functional activity against all gonococcal HepI LOS structures defined by various lgtA/C/D on/off combinations, thereby providing further impetus for use of the 2C7 epitope in a gonococcal vaccine.
authors.affiliation: Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605; and.
authors.forename: Srinjoy
authors.identifier: 0000-0001-9321-5921
authors.initials: S
authors.lastname: Chakraborti
authors.affiliation: Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605; and.
authors.forename: Lisa A
authors.identifier: 0000-0001-9469-9083
authors.initials: LA
authors.lastname: Lewis
authors.affiliation: Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Cox
authors.affiliation: Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada.
authors.forename: Frank
authors.initials: F
authors.lastname: St Michael
authors.affiliation: Human Health Therapeutics Portfolio, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.affiliation: Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605; and.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Rice
authors.affiliation: Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605; and sanjay.ram@umassmed.edu.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Ram
mesh_terms: D000914:Antibodies, Viral / Q000276:immunology*; D006539:Heptoses / Q000276:immunology*; D006801:Humans; D008070:Lipopolysaccharides / Q000276:immunology*; D009344:Neisseria gonorrhoeae / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D006539:Heptoses; D008070:Lipopolysaccharides; D014765:Viral Vaccines; C023023:lipid-linked oligosaccharides