Journal Article

Human Complement Bactericidal Responses to a Group A Meningococcal Conjugate Vaccine in Africans and Comparison to Responses Measured by 2 Other Group A Immunoassays

Gregory A. Price, Aimee M. Hollander, Brian D. Plikaytis, Brian T. Mocca, George Carlone, Helen Findlow, Ray Borrow, Samba O. Sow, Aldiouma Diallo, Olubukola T. Idoko, Godwin C. Enwere, Cheryl Elie, Marie-Pierre Preziosi, Prasad S. Kulkarni and Margaret C. Bash

in Clinical Infectious Diseases

Volume 61, issue suppl_5, pages S554-S562
Published in print November 2015 | ISSN: 1058-4838
Published online November 2015 | e-ISSN: 1537-6591 | DOI: https://dx.doi.org/10.1093/cid/civ504
Human Complement Bactericidal Responses to a Group A Meningococcal Conjugate Vaccine in Africans and Comparison to Responses Measured by 2 Other Group A Immunoassays

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Background. PsA-TT (MenAfriVac) is a conjugated polysaccharide vaccine developed to eliminate group A meningococcal disease in Africa. Vaccination of African study participants with 1 dose of PsA-TT led to the production of anti-A polysaccharide antibodies and increased serum bactericidal activity measured using rabbit complement (rSBA). Bactericidal responses measured with human complement (hSBA) are presented here.

Methods. Sera collected before and at 28 days and 1 year after vaccination with either PsA-TT or quadrivalent polysaccharide vaccine (PsACWY) from a random, age-distributed 360-subject subset of the Meningitis Vaccine Project study of PsA-TT in Africans aged 2–29 years were tested for hSBA. Geometric mean titer, fold-rise, and threshold analyses were compared between vaccine groups and age groups. hSBA, rSBA, and immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) results were compared and assay correlation and agreement determined.

Results. hSBA responses to PsA-TT were substantially higher than those to PsACWY at 28 days and 1 year following immunization, similar to previously reported rSBA and IgG results. The hSBA and IgG ELISA results identified differences between age groups that were not evident by rSBA. The rSBA data indicated sustained high titers 1 year after immunization, whereas hSBA GMTs at 1 year approached 4 in young children.

Conclusions. The high level of protection following PsA-TT immunization campaigns is consistent with the strong hSBA immune responses observed here. Future implementation decisions will likely depend on immunologic data and their long-term correlation with disease and carriage prevention. Expanded immunologic and epidemiologic surveillance may improve the interpretation of differences between these immunoassays.

Keywords: MenAfriVac; bactericidal activity; assay development; Neisseria meningitidis; clinical trials

Journal Article.  5841 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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