Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Infect Immun. 2018 Jul 23;86(8). doi: 10.1128/IAI.00285-18. Print 2018 Aug.
Sialylation of lacto--neotetraose (LNnT) extending from heptose I (HepI) of gonococcal lipooligosaccharide (LOS) contributes to pathogenesis. Previously, gonococcal LOS sialyltransterase (Lst) was shown to sialylate LOS in Triton X-100 extracts of strain 15253, which expresses lactose from both HepI and HepII, the minimal structure required for monoclonal antibody (MAb) 2C7 binding. Ongoing work has shown that growth of 15253 in cytidine monophospho--acetylneuraminic acid (CMP-Neu5Ac)-containing medium enables binding to CD33/Siglec-3, a cell surface receptor that binds sialic acid, suggesting that lactose termini on LOSs of intact gonococci can be sialylated. Neu5Ac was detected on LOSs of strains 15253 and an MS11 mutant with lactose only from HepI and HepII by mass spectrometry; deleting HepII lactose rendered Neu5Ac undetectable. Resistance of HepII lactose Neu5Ac to desialylation by α2-3-specific neuraminidase suggested an α2-6 linkage. Although not associated with increased factor H binding, HepII lactose sialylation inhibited complement C3 deposition on gonococci. Strain 15253 mutants that lacked Lst or HepII lactose were significantly attenuated in mice, confirming the importance of HepII Neu5Ac in virulence. All 75 minimally passaged clinical isolates from Nanjing, China, expressed HepII lactose, evidenced by reactivity with MAb 2C7; MAb 2C7 was bactericidal against the first 62 (of 75) isolates that had been collected sequentially and were sialylated before testing. MAb 2C7 effectively attenuated 15253 vaginal colonization in mice. In conclusion, this novel sialylation site could explain the ubiquity of gonococcal HepII lactose Our findings reinforce the candidacy of the 2C7 epitope as a vaccine antigen and MAb 2C7 as an immunotherapeutic antibody.
脑膜炎奈瑟菌脂寡糖（LOS）中从庚糖 I（HepI）延伸出的乳糖-新四糖（LNnT）的唾液酸化作用有助于发病机制。先前的研究表明，淋球菌 LOS 唾液酸转移酶（Lst）能够使 15253 菌株的 Triton X-100 提取物中的 LOS 发生唾液酸化，而 HepI 和 HepII 则是单克隆抗体（MAb）2C7 结合所必需的最小结构。正在进行的工作表明，在含有胞苷单磷酸-N-乙酰神经氨酸（CMP-Neu5Ac）的培养基中生长可以使 15253 与 CD33/Siglec-3 结合，CD33/Siglec-3 是一种细胞表面受体，可与唾液酸结合，这表明完整淋球菌 LOS 上的乳糖末端可以被唾液酸化。通过质谱法检测到 15253 菌株和仅从 HepI 和 HepII 获得乳糖的 MS11 突变株的 LOS 上存在 Neu5Ac；删除 HepII 乳糖后 Neu5Ac 无法检测到。α2-3 特异性神经氨酸酶对 HepII 乳糖 Neu5Ac 的去唾液酸化的抗性表明存在α2-6 键。尽管与增加因子 H 结合无关，但 HepII 乳糖的唾液酸化抑制了 C3 在淋球菌上的沉积。缺乏 Lst 或 HepII 乳糖的 15253 菌株在小鼠中明显减毒，证实了 HepII Neu5Ac 在毒力中的重要性。中国南京的 75 株经过最小传代的临床分离株均表达 HepII 乳糖，这可通过与 MAb 2C7 的反应得到证实；MAb 2C7 对前 62 株（共 75 株）分离株具有杀菌作用，这些分离株在测试前已经进行了唾液酸化。MAb 2C7 有效地减弱了 15253 在小鼠阴道中的定植。总之，这个新的唾液酸化位点可以解释淋球菌 HepII 乳糖普遍存在的原因。我们的研究结果增强了 2C7 表位作为疫苗抗原和 MAb 2C7 作为免疫治疗性抗体的候选性。
