Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom.
Meningococcal Reference Unit, Public Health England, Manchester Royal Infirmary, Manchester, United Kingdom.
J Clin Microbiol. 2018 Aug 27;56(9). doi: 10.1128/JCM.00204-18. Print 2018 Sep.
A recombinant NadA protein is one of the four major protective antigens of 4C-MenB (Bexsero), a vaccine developed for serogroup B (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 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 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.
一种重组 NadA 蛋白是 4C-MenB（Bexsero）疫苗的四种主要保护性抗原之一，该疫苗用于预防 B 群（MenB）流脑。脑膜炎球菌抗原分型系统（MATS）被用作高通量检测 4C-MenB 对侵袭性 MenB 菌株的覆盖度的方法。该基因存在时，由于位于调控区的 5’TAAA 重复序列，其转录会发生相变异构变化。对 906 株携带 基因的侵袭性脑膜炎球菌病分离株进行了基因内区（IGR）序列和 5’TAAA 重复数目的测定。排除 5’TAAA 重复序列后，IGR 等位基因数从 82 减少到 23。Western blot 和酶联免疫吸附试验（ELISA）检测发现，重复数与 NadA 表达水平的高低有关。NadA-2/3 或 NadA-1 肽变异体的 179 株 MenB 分离株和 NadA-2/3 肽变异体的 480 株 MenW ST-11 复合群分离株中，低表达重复数的出现频率分别为 83%和 68%。对于具有疫苗相容 NadA 变异体的分离株，93%的 MATS 阴性分离株与低表达重复数相关，而在 MATS 相对效价（RP）评分高于阳性杀菌阈值 95%置信区间的分离株中，有 63%的分离株具有高表达重复数。5’TAAA 重复数分析具有作为评估 4C-MenB 中 NadA 成分菌株覆盖度的快速、高通量方法的潜力。其主要应用将是评估仅通过 PCR 确认且无法应用 MATS 的脑膜炎球菌病病例中的覆盖度。
