Phase-Variable Heptose I Glycan Extensions Modulate Efficacy of 2C7 Vaccine Antibody Directed against Neisseria gonorrhoeae Lipooligosaccharide

Student Author(s)

Srinjoy Chakraborti

UMMS Affiliation

Division of Infectious Diseases and Immunology, Department of Medicine

Publication Date


Document Type



Bacteriology | Immunity | Immunology and Infectious Disease | Immunology of Infectious Disease | Immunopathology | Immunoprophylaxis and Therapy | Medicine and Health Sciences | Other Immunology and Infectious Disease


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 (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.


monoclonal antibody (mAb), complement dependent cytotoxicity (CDC), complement, phagocytosis, vaccine, Neisseria gonorrhoeae, gonorrhea, lipooligosaccharide (LOS), lipopolysaccharide (LPS), immunotherapy, neutrophil phagocytosis

DOI of Published Version



Phase-Variable Heptose I Glycan Extensions Modulate Efficacy of 2C7 Vaccine Antibody Directed against Neisseria gonorrhoeae Lipooligosaccharide. Srinjoy Chakraborti, Lisa A. Lewis, Andrew D. Cox, Frank St. Michael, Jianjun Li, Peter A. Rice, Sanjay Ram. The Journal of Immunology June 1, 2016, 196 (11) 4576-4586; DOI: 10.4049/jimmunol.1600374. Link to article on publisher's website

Journal/Book/Conference Title

Journal of Immunology

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Link to article in PubMed

PubMed ID