Qualitative and quantitative assessment of meningococcal antigens to evaluate the potential strain coverage of protein-based vaccines.
A unique multicomponent vaccine against serogroup B meningococci incorporates the novel genome-derived proteins fHbp, NHBA, and NadA that may vary in sequence and level of expression. Measuring the effectiveness of such vaccines, using the accepted correlate of protection against invasive meningococcal disease, could require performing the serum bactericidal assay (SBA) against many diverse strains for each geographic region. This approach is impractical, especially for infants, where serum volumes are very limited. To address this, we developed the meningococcal antigen typing system (MATS) by combining a unique vaccine antigen-specific ELISA, which detects qualitative and quantitative differences in antigens, with PorA genotyping information. The ELISA correlates with killing of strains by SBA and measures both immunologic cross-reactivity and quantity of the antigens NHBA, NadA, and fHbp. We found that strains exceeding a threshold value in the ELISA for any of the three vaccine antigens had ≥80% probability of being killed by immune serum in the SBA. Strains positive for two or more antigens had a 96% probability of being killed. Inclusion of multiple different antigens in the vaccine improves breadth of coverage and prevents loss of coverage if one antigen mutates or is lost. The finding that a simple and high-throughput assay correlates with bactericidal activity is a milestone in meningococcal vaccine development. This assay allows typing of large panels of strains and prediction of coverage of protein-based meningococcal vaccines. Similar assays may be used for protein-based vaccines against other bacteria.
Donnelly
John
J
Novartis Vaccines and Diagnostics, 53100 Siena, Italy. john.donnelly_iii@novartis.com
Medini
Duccio
D
Boccadifuoco
Giuseppe
G
Biolchi
Alessia
A
Ward
Joel
J
Frasch
Carl
C
Moxon
E Richard
ER
Stella
Maria
M
Comanducci
Maurizio
M
Bambini
Stefania
S
Muzzi
Alessandro
A
Andrews
William
W
Chen
Jie
J
Santos
George
G
Santini
Laura
L
Boucher
Philip
P
Serruto
Davide
D
Pizza
Mariagrazia
M
Rappuoli
Rino
R
Giuliani
Marzia Monica
MM
D000942:Antigens, Bacterial / Q000032:analysis*; D001426:Bacterial Proteins / Q000276:immunology / Q000627:therapeutic use; D015373:Bacterial Typing Techniques / Q000379:methods*; D003429:Cross Reactions / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005838:Genotype; D006801:Humans; D022401:Meningococcal Vaccines / Q000276:immunology / Q000494:pharmacology*; D038541:Neisseria meningitidis, Serogroup B / Q000276:immunology*; D013045:Species Specificity
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D022401:Meningococcal Vaccines