Chitradevi Sekar Tamil Selvi, Kaur Gurpreet, Uppalapati Sivaramakrishna, Yadav Anandprakash, Singh Dependrapratap, Bansal Anju
Division of Experimental Biology, Defence Institute of Physiology and Allied Sciences, Delhi, India.
Division of Microbiology, Defence Food Research Laboratory, Mysore, India.
Cell Mol Immunol. 2015 Nov;12(6):757-67. doi: 10.1038/cmi.2014.86. Epub 2015 Feb 2.
Shigella species cause severe bacillary dysentery in humans and are associated with high morbidity and mortality. The Invasion plasmid antigen (IpaB) protein, which is conserved across all Shigella spp., induces macrophage cell death and is required to invade host cells. The present study evaluates the immunogenicity and protective efficacy of the recombinant (r) domain region of IpaB (rIpaB) of S. flexneri. rIpaB was administered either alone or was co-administered with the rGroEL (heat shock protein 60) protein from S. Typhi as an adjuvant in a mouse model of intranasal immunization. The IpaB domain region (37 kDa) of S. flexneri was amplified from an invasion plasmid, cloned, expressed in BL21 Escherichia coli cells and purified. Immunization with the rIpaB domain alone stimulated both humoral and cell-mediated immune responses. Furthermore, robust antibody (IgG, IgA) and T-cell responses were induced when the rIpaB domain was co-administered with rGroEL. Antibody isotyping revealed higher IgG1 and IgG2a antibody titers and increased interferon-gamma (IFN-γ) secretion in the co-administered group. Immunization of mice with the rIpaB domain alone protected 60%-70% of the mice from lethal infection by S. flexneri, S. boydii and S. sonnei, whereas co-administration with rGroEL increased the protective efficacy to 80%-85%. Organ burden and histopathological studies also revealed a significant reduction in lung infection in the co-immunized mice compared with mice immunized with the rIpaB domain alone. This study emphasizes that the co-administration of the rIpaB domain and rGroEL protein improves immune responses in mice and increases protective efficacy against Shigella infection. This is also the first report to evaluate the potential of the GroEL (Hsp 60) protein of S. Typhi as an adjuvant molecule, thereby overcoming the need for commercial adjuvants.
志贺氏菌属可导致人类严重的细菌性痢疾，并与高发病率和死亡率相关。侵袭质粒抗原（IpaB）蛋白在所有志贺氏菌属中都保守，可诱导巨噬细胞死亡，是侵袭宿主细胞所必需的。本研究评估了福氏志贺氏菌IpaB的重组（r）结构域区域（rIpaB）的免疫原性和保护效力。在鼻内免疫小鼠模型中，单独给予rIpaB或与伤寒沙门氏菌的rGroEL（热休克蛋白60）蛋白作为佐剂共同给予。从侵袭质粒中扩增、克隆福氏志贺氏菌的IpaB结构域区域（37 kDa），在BL21大肠杆菌细胞中表达并纯化。单独用rIpaB结构域免疫可刺激体液免疫和细胞介导的免疫反应。此外，当rIpaB结构域与rGroEL共同给予时，可诱导强烈的抗体（IgG、IgA）和T细胞反应。抗体分型显示，共同给药组中IgG1和IgG2a抗体滴度更高，干扰素-γ（IFN-γ）分泌增加。单独用rIpaB结构域免疫小鼠可使60%-70%的小鼠免受福氏志贺氏菌、鲍氏志贺氏菌和宋内氏志贺氏菌的致死性感染，而与rGroEL共同给药可将保护效力提高到80%-85%。器官负荷和组织病理学研究还显示，与单独用rIpaB结构域免疫的小鼠相比，共同免疫的小鼠肺部感染显著减少。本研究强调，rIpaB结构域和rGroEL蛋白共同给药可改善小鼠的免疫反应，并提高对志贺氏菌感染的保护效力。这也是评估伤寒沙门氏菌的GroEL（Hsp 60）蛋白作为佐剂分子潜力的首份报告，从而无需使用商业佐剂。
