Novel Complement Blocking Antibodies Against Serogroup B <em>N. meningitidis</em>: A Dissertation
Authors
Dutta Ray, TathagatFaculty Advisor
Peter A. Rice, M.D.; Sanjay Ram, M.D.Academic Program
Immunology and MicrobiologyUMass Chan Affiliations
MedicineDocument Type
Doctoral DissertationPublication Date
2010-07-23Keywords
Neisseria meningitidisSerogroup B
Meningococcal Vaccines
Amino Acids, Peptides, and Proteins
Bacteria
Bacterial Infections and Mycoses
Environmental Public Health
Immunology and Infectious Disease
Investigative Techniques
Nervous System Diseases
Pathological Conditions, Signs and Symptoms
Therapeutics
Metadata
Show full item recordAbstract
N. meningitidis is a common commensal of the human upper respiratory tract and a leading cause of bacterial meningitis and septicemia worldwide. The classical pathway of complement (C) is essential for both naturally acquired and vaccine induced immunity against N. meningitidis. Qualitative and/or quantitative differences in anti-meningococcal antibodies (Abs) in serum is one reason for variations in C-dependent bactericidal Ab activity among individuals. I showed that IgG isolated from select individuals could block killing of group B meningococci by Abs that were otherwise bactericidal. Ligand overlay immunoblots revealed that these blocking IgG Abs were directed against a meningococcal antigen called H.8, Killing of meningococci in reactions containing bactericidal mAbs and human blocking Abs was restored when blocking Ab binding to meningococci was inhibited (or competed for) using either synthetic peptides corresponding to H.8 or a non-blocking mAb against H.8. Further, genetic deletion of H.8 from target organisms abrogated blocking. The Fc region of the blocking IgG was required for blocking because F(ab)2 fragments alone generated by pepsin treatment were ineffective. Blocking required IgG glycosylation; deglycosylation of blocking IgG with peptide:N-glycanase (PNGase) eliminated blocking. C4 deposition mediated by a bactericidal mAb directed against a meningococcal vaccine candidate, called factor H-binding protein (fHbp), was reduced by blocking Ab. Anti-fHbp-mediated C4 deposition was unaffected, however, by deglycosylated blocking IgG. Although preliminary, our data suggests blocking of serum bactericidal activity by human anti-H.8 blocking antibody may require mannan-binding lectin (MBL), which itself is a complement activator. Also, whether MBL recruits a complement inhibitor(s) that facilitates blocking remains to be determined. In conclusion, we have identified H.8 as a meningococcal target for novel blocking antibodies that are commonly found in human serum. Blocking Ab may reduce the efficacy of meningococcal vaccines. We propose that outer membrane vesicle-containing meningococcal vaccines may be more efficacious if purged of subversive immunogens such as H.8.DOI
10.13028/kwp1-3r83Permanent Link to this Item
http://hdl.handle.net/20.500.14038/31829Rights
Copyright is held by the author, with all rights reserved.ae974a485f413a2113503eed53cd6c53
10.13028/kwp1-3r83