Marini Arianna, Rossi Omar, Aruta Maria Grazia, Micoli Francesca, Rondini Simona, Guadagnuolo Serafina, Delany Isabel, Henderson Ian R, Cunningham Adam F, Saul Allan, MacLennan Calman A, Koeberling Oliver
Institute of Immunology and Immunotherapy, College of Medicine and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.
GSK Vaccines Institute for Global Health (GVGH), Siena, Italy.
PLoS One. 2017 Jul 25;12(7):e0181508. doi: 10.1371/journal.pone.0181508. eCollection 2017.
Factor H-binding protein (fHbp) is an important meningococcal vaccine antigen. Native outer membrane vesicles with over-expressed fHbp (NOMV OE fHbp) have been shown to induce antibodies with broader functional activity than recombinant fHbp (rfHbp). Improved understanding of this broad coverage would facilitate rational vaccine design. We performed a pair-wise analysis of 48 surface-exposed amino acids involved in interacting with factor H, among 383 fHbp variant group 1 sequences. We generated isogenic NOMV-producing meningococcal strains from an African serogroup W isolate, each over-expressing one of four fHbp variant group 1 sequences (ID 1, 5, 9, or 74), including those most common among invasive African meningococcal isolates. Mice were immunised with each NOMV, and sera tested for IgG levels against each of the rfHbp ID and for ability to kill a panel of heterologous meningococcal isolates. At the fH-binding site, ID pairs differed by a maximum of 13 (27%) amino acids. ID 9 shared an amino acid sequence common to 83 ID types. The selected ID types differed by up to 6 amino acids, in the fH-binding site. All NOMV and rfHbp induced high IgG levels against each rfHbp. Serum killing from mice immunised with rfHbp was generally less efficient and more restricted compared to NOMV, which induced antibodies that killed most meningococci tested, with decreased stringency for ID type differences. Breadth of killing was mostly due to anti-fHbp antibodies, with some restriction according to ID type sequence differences. Nevertheless, under our experimental conditions, no relationship between antibody cross-reactivity and variation fH-binding site sequence was identified. NOMV over-expressing different fHbp IDs belonging to variant group 1 induce antibodies with fine specificities against fHbp, and ability to kill broadly meningococci expressing heterologous fHbp IDs. The work reinforces that meningococcal NOMV with OE fHbp is a promising vaccine strategy, and provides a basis for rational selection of antigen sequence types for over-expression on NOMV.
补体因子H结合蛋白（fHbp）是一种重要的脑膜炎球菌疫苗抗原。已证明过表达fHbp的天然外膜囊泡（NOMV OE fHbp）比重组fHbp（rfHbp）诱导的抗体具有更广泛的功能活性。对这种广泛覆盖范围的深入了解将有助于合理的疫苗设计。我们对383个fHbp 1型变体序列中与补体因子H相互作用的48个表面暴露氨基酸进行了成对分析。我们从一株非洲W群分离株中构建了产生等基因NOMV的脑膜炎球菌菌株，每个菌株过表达四个fHbp 1型变体序列（ID 1、5、9或74）中的一个，包括在侵袭性非洲脑膜炎球菌分离株中最常见的那些序列。用每种NOMV免疫小鼠，并检测血清中针对每种rfHbp ID的IgG水平以及杀死一组异源脑膜炎球菌分离株的能力。在fH结合位点，ID对之间最多相差13个（27%）氨基酸。ID 9具有83种ID类型共有的氨基酸序列。所选的ID类型在fH结合位点最多相差6个氨基酸。所有NOMV和rfHbp均诱导针对每种rfHbp的高IgG水平。与NOMV相比，用rfHbp免疫的小鼠血清杀菌效率通常较低且更具局限性，NOMV诱导的抗体能杀死大多数测试的脑膜炎球菌，对ID类型差异的严格性降低。杀菌的广度主要归因于抗fHbp抗体，根据ID类型序列差异有一定的局限性。然而，在我们的实验条件下，未发现抗体交叉反应性与fH结合位点序列变异之间的关系。过表达属于1型变体的不同fHbp ID的NOMV诱导针对fHbp具有精细特异性的抗体，并具有广泛杀死表达异源fHbp ID的脑膜炎球菌的能力。这项工作强化了OE fHbp的脑膜炎球菌NOMV是一种有前景的疫苗策略，并为合理选择在NOMV上过表达的抗原序列类型提供了基础。
