# Interlaboratory study to assess precision and reproducibility of the meningococcal antigen surface expression (MEASURE) assay to quantify factor H binding protein expression at the surface of meningococcal serogroup B strains

## TL;DR

This study shows that a new test for measuring a protein on meningococcal bacteria gives consistent results across different labs.

## Contribution

The MEASURE assay's interlaboratory precision and reproducibility were validated for meningococcal fHbp surface expression.

## Key findings

- The MEASURE assay showed >97% agreement across three labs for fHbp expression levels in 42 MenB strains.
- Each lab met precision criteria with ≤30% total relative standard deviation.
- Previously established cutoffs for antibody susceptibility can be reliably applied across labs using MEASURE data.

## Abstract

The serum bactericidal antibody using human complement (hSBA) assay, the accepted surrogate measure of meningococcal vaccine efficacy, is limited by human sera and complement requirements. Pfizer developed and validated the flow-cytometry–based Meningococcal Antigen Surface Expression (MEASURE) assay to quantify surface-expressed factor H binding protein (fHbp) levels on intact meningococci. Surface expression of fHbp is correlated with hSBA assay killing by MenB-fHbp (Trumenba®)–induced antibody, meaning the MEASURE assay can be used to predict meningococcal serogroup B (MenB) strain susceptibility to antibodies elicited by MenB-fHbp. This study aimed to evaluate interlaboratory precision and reproducibility of the MEASURE assay.

The MEASURE assay was transferred to UK Health Security Agency (UKHSA) and US Centers for Disease Control and Prevention (CDC) laboratories. MEASURE assay results from 42 MenB strains encoding sequence-diverse fHbp variants that express fHbp at different levels were compared between the UKHSA, CDC, and Pfizer laboratories. Intermediate precision within each laboratory was determined.

Pairwise comparisons of fHbp expression levels for all 42 MenB test strains showed >97 % agreement across the 3 laboratories when strains were grouped above or below a mean fluorescence intensity level of 1000, the threshold previously established as indicative of susceptibility to MenB-fHbp–induced antibodies in the hSBA assay. Each laboratory met assay precision criteria of ≤30 % total relative standard deviation.

Quantification of fHbp surface expression using the MEASURE assay is robust and reproducible across different laboratories. Previously determined cutoffs corresponding to predicted susceptibility to vaccine-induced antibodies can be applied to MEASURE data generated across laboratories.