De Benedetto G, Alfini R, Cescutti P, Caboni M, Lanzilao L, Necchi F, Saul A, MacLennan C A, Rondini S, Micoli F
GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy; Dipartimento di Scienze della Vita, Ed. C11, Università degli Studi di Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy.
Vaccine. 2017 Jan 11;35(3):419-426. doi: 10.1016/j.vaccine.2016.11.089. Epub 2016 Dec 18.
Invasive nontyphoidal Salmonella disease (iNTS) is a leading cause of death and morbidity in Africa. The most common pathogens are Salmonella enterica serovars Typhimurium and Enteritidis. The O-antigen portion of their lipopolysaccharide is a target of protective immunity and vaccines targeting O-antigen are currently in development. Here we investigate the use of Generalized Modules for Membrane Antigens (GMMA) as delivery system for S. Typhimurium and S. Enteritidis O-antigen. Gram-negative bacteria naturally shed outer membrane in a blebbing process. By deletion of the tolR gene, the level of shedding was greatly enhanced. Further genetic modifications were introduced into the GMMA-producing strains in order to reduce reactogenicity, by detoxifying the lipid A moiety of lipopolysaccharide. We found that genetic mutations can impact on expression of O-antigen chains. All S. Enteritidis GMMA characterized had an O-antigen to protein w/w ratio higher than 0.6, while the ratio was 0.7 for S. Typhimurium ΔtolR GMMA, but decreased to less than 0.1 when further mutations for lipid A detoxification were introduced. Changes were also observed in O-antigen chain length and level and/or position of O-acetylation. When tested in mice, the GMMA induced high levels of anti-O-antigen-specific IgG functional antibodies, despite variation in density and O-antigen structural modifications. In conclusion, simplicity of manufacturing process and low costs of production, coupled with encouraging immunogenicity data, make GMMA an attractive strategy to further investigate for the development of a vaccine against iNTS.
侵袭性非伤寒沙门氏菌病（iNTS）是非洲死亡和发病的主要原因。最常见的病原体是肠炎沙门氏菌血清型鼠伤寒沙门氏菌和肠炎沙门氏菌。其脂多糖的O抗原部分是保护性免疫的靶点，目前正在研发针对O抗原的疫苗。在此，我们研究了膜抗原通用模块（GMMA）作为鼠伤寒沙门氏菌和肠炎沙门氏菌O抗原递送系统的用途。革兰氏阴性菌在起泡过程中自然脱落外膜。通过缺失tolR基因，脱落水平大大提高。为了降低反应原性，通过使脂多糖的脂质A部分解毒，对产生GMMA的菌株进行了进一步的基因改造。我们发现基因突变会影响O抗原链的表达。所有表征的肠炎沙门氏菌GMMA的O抗原与蛋白质的重量比高于0.6，而鼠伤寒沙门氏菌ΔtolR GMMA的该比例为0.7，但在引入脂质A解毒的进一步突变后降至小于0.1。在O抗原链长度以及O-乙酰化水平和/或位置上也观察到了变化。在小鼠中进行测试时，尽管密度和O抗原结构存在差异，GMMA仍诱导产生了高水平的抗O抗原特异性IgG功能性抗体。总之，生产过程简单、成本低，再加上令人鼓舞的免疫原性数据，使得GMMA成为进一步研究开发抗iNTS疫苗的有吸引力的策略。
