University of Leicester
Phase Variation of NadA in Invasive Neisseria meningitidis Isolates Impacts on Coverage Estimates for 4C-MenB, a MenB Vaccine.pdf (2.08 MB)

Phase Variation of NadA in Invasive Neisseria meningitidis Isolates Impacts on Coverage Estimates for 4C-MenB, a MenB Vaccine.

Download (2.08 MB)
journal contribution
posted on 2019-07-05, 13:42 authored by LR Green, J Lucidarme, N Dave, H Chan, S Clark, R Borrow, CD Bayliss
A recombinant NadA protein is one of the four major protective antigens of 4C-MenB (Bexsero), a vaccine developed for serogroup B Neisseria meningitidis (MenB). The meningococcal antigen typing system (MATS) is utilized as a high-throughput assay for assessing the invasive MenB strain coverage of 4C-MenB. Where present, the nadA gene is subject to phase-variable changes in transcription due to a 5'TAAA repeat tract located in a regulatory region. The promoter-containing intergenic region (IGR) sequences and 5'TAAA repeat numbers were determined for 906 invasive meningococcal disease isolates possessing the nadA gene. Exclusion of the 5'TAAA repeats reduced the number of IGR alleles from 82 to 23. Repeat numbers were associated with low and high levels of NadA expression by Western blotting and enzyme-linked immunosorbent assay (ELISA). Low-expression repeat numbers were present in 83% of 179 MenB isolates with NadA-2/3 or NadA-1 peptide variants and 68% of 480 MenW ST-11 complex isolates with NadA-2/3 peptide variants. For isolates with vaccine-compatible NadA variants, 93% of MATS-negative isolates were associated with low-expression repeat numbers, whereas 63% of isolates with MATS relative potency (RP) scores above the 95% confidence interval for the positive bactericidal threshold had high-expression repeat numbers. Analysis of 5'TAAA repeat numbers has potential as a rapid, high-throughput method for assessing strain coverage for the NadA component of 4C-MenB. A key application will be assessing coverage in meningococcal disease cases where confirmation is by PCR only and MATS cannot be applied.


This project was supported by the Medical Research Council (grant MR/M020193/1 to L.R.G.).



Journal of Clinical Microbiology, 2018, 56 (9)

Author affiliation

/Organisation/COLLEGE OF LIFE SCIENCES/Biological Sciences/Genetics and Genome Biology


  • VoR (Version of Record)

Published in

Journal of Clinical Microbiology


American Society for Microbiology Journals



Acceptance date


Copyright date


Available date



Supplemental material for this article may be found at .00204-18. SUPPLEMENTAL FILE 1, PDF file, 0.6 MB. SUPPLEMENTAL FILE 2, PDF file, 0.2 MB.



Usage metrics

    University of Leicester Publications