Interlaboratory Standardization of the Sandwich Enzyme-Linked Immunosorbent Assay Designed for MATS, a Rapid, Reproducible Method for Estimating the Strain Coverage of Investigational Vaccines

Abstract

The meningococcal antigen typing system (MATS) sandwich enzyme-linked immunosorbent assay (ELISA) was designed to measure the immunologic cross-reactivity and quantity of antigens in target strains of a pathogen. It was first used to measure the factor H-binding protein (fHbp), neisserial adhesin A (NadA), and neisserial heparin-binding antigen (NHBA) content of serogroup B meningococcal (MenB) isolates relative to a reference strain, or "relative potency" (RP). With the PorA genotype, the RPs were then used to assess strain coverage by 4CMenB, a multicomponent MenB vaccine. In preliminary studies, MATS accurately predicted killing in the serum bactericidal assay using human complement, an accepted correlate of protection for meningococcal vaccines. A study across seven laboratories assessed the reproducibility of RPs for fHbp, NadA, and NHBA and established qualification parameters for new laboratories. RPs were determined in replicate for 17 MenB reference strains at laboratories A to G. The reproducibility of RPs among laboratories and against consensus values across laboratories was evaluated using a mixed-model analysis of variance. Interlaboratory agreement was very good; the Pearson correlation coefficients, coefficients of accuracy, and concordance correlation coefficients exceeded 99%. The summary measures of reproducibility, expressed as between-laboratory coefficients of variation, were 7.85% (fHbp), 16.51% (NadA), and 12.60% (NHBA). The overall withinlaboratory measures of variation adjusted for strain and laboratory were 19.8% (fHbp), 28.8% (NHBA), and 38.3% (NadA). The MATS ELISA was successfully transferred to six laboratories, and a further laboratory was successfully qualified.

Molecular and Serological Diversity of Neisseria meningitidis Carrier Strains Isolated from Italian Students Aged 14 to 22 Years

“…fHbp variant 2 clearly prevailed over fHbp-1, as expected from other carriage studies (53,54). fHbp-1 has indeed been described to be predominant in invasive isolates (16,31,(55)(56)(57). Thirteen of the 15 fHbp subvariants were also detected in invasive isolates, and only two were new.…”

A Large Portion of Meningococcal Antigen Typing System-Negative Meningococcal Strains from Spain Is Killed by Sera from Adolescents and Infants Immunized with 4CMenB

“…The number of strains killed in the hSBA assay was higher than the number of strains predicted to be killed by MATS (9). The reasons for that might be the use of very conservative algorithms in the MATS analysis (3,4,9) but also some level of synergy of the different antibodies raised against the different antigens (particularly between those raised against fHbp, NHBA, or OMV non-PorA antigens), augmenting the SBA response.…”

“…The marker used is the serum bactericidal antibody (SBA; or the human SBA [hSBA] when human complement is used in the assay), and SBA assays can be used to measure the ability of serum antibodies to kill a specific meningococcal strain (2). However, due to the diversity of the sequences of the antigens included in this novel vaccine and their different levels of expression, the use of hSBA requires the testing of many serum samples with large panels of isolates to evaluate the bactericidal killing of many different meningococcal strains, making this approach not feasible (3,4). Therefore, the development of alternative methods that can give information about immunologic recognition, the level of expression of the antigens, and the association of those parameters with killing in the hSBA assay has been critical in this history.…”

“…Therefore, the development of alternative methods that can give information about immunologic recognition, the level of expression of the antigens, and the association of those parameters with killing in the hSBA assay has been critical in this history. As a result, a meningococcal antigen typing system (MATS; which combines conventional PorA genotyping [porA variable region 2 {VR2}] with an enzyme-linked immunosorbent assay [ELISA] that quantifies both the expression and the cross-reactivity of antigenic variants for each antigen) was developed (3)(4)(5). MATS quantifies the relative expression and cross-reactivity of antigenic variants by assigning a relative potency (RP) against fHbp, NHBA, and NadA in each strain.…”

“…The assay has been introduced in several European, American, and Australian reference laboratories through a strict interlaboratory standardization study (4) to ensure the comparability of strain coverage data collected worldwide. The potential coverage of the 4CMenB vaccine against meningococcal group B (MenB) strains collected in one or two epidemiological years in different countries has been estimated to range from 66% to Ͼ90% (6-8).…”