Departamento de Bioquímica e Imunologia do Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
Instituto Nacional de Ciência e Tecnologia em Doenças Tropicais (INCT-DT), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Ministério da Ciência e Tecnologia (MCT), Salvador, Brazil.
Front Immunol. 2018 Jul 30;9:1762. doi: 10.3389/fimmu.2018.01762. eCollection 2018.
Current schistosomiasis control strategies are mainly based on chemotherapy, but the development of a vaccine against this parasitic disease would contribute to a long-lasting decrease in disease spectrum and transmission. When it comes to vaccine candidates, several genes encoding proteins expressed at the mammalian host-parasite interface have been tested. Among the most promising molecules are the proteins present on the tegument and digestive tract of the parasite. In this study, we evaluate the potential of KI-1, the first Kunitz-type protease inhibitor functionally characterized in , as a vaccine candidate. Bioinformatic analysis points to the C-terminal fragment as the main region of the molecule responsible for the development of a potential protective immune response induced by KI-1. Therefore, for the vaccine formulations, we produced the recombinant (r) KI-1 and two different fragments, its Kunitz (KI) domain and its C-terminal tail. First, we demonstrate that mice immunized with recombinant SmKI-1 (rKI-1) or its fragments, formulated with Freund's adjuvant, induced the production of IgG-specific antibodies. Further, all vaccine formulations tested here also induced a Th1-type of immune response, as suggested by the production of IFN-γ and TNF-α by protein-stimulated cultured splenocytes. However, the protective effect conferred by vaccination was only observed in groups which received rSmKI-1 or C-terminal domain vaccines. Mice administered with rSmKI-1 demonstrated reduction of 47% in worm burden, 36% in egg number in mouse livers, and 33% in area of liver granulomas. Additionally, mice injected with C-terminal domain showed reduction of 28% in worm burden, 38% in egg number in liver, and 25% in area of liver granulomas. In contrast, KI domain immunization was unable to reduce worm burden and ameliorate liver pathology after challenge infection. Taken together, our data demonstrated that KI-1 is a potential candidate for use in a vaccine to control schistosomiasis, and its C-terminal tail seems to be the main region of the molecule responsible for protection conferred by this antigen.
当前的血吸虫病控制策略主要基于化学疗法，但针对这种寄生虫病的疫苗的开发将有助于长期降低疾病谱和传播。在疫苗候选物方面，已经测试了几种编码在哺乳动物宿主-寄生虫界面表达的蛋白质的基因。在最有前途的分子中，有寄生虫体被膜和消化道上存在的蛋白质。在这项研究中，我们评估了 KI-1 作为疫苗候选物的潜力，KI-1 是功能上在 中首次被鉴定的 Kunitz 型蛋白酶抑制剂。生物信息学分析表明，分子的 C 末端片段是负责由 KI-1 诱导产生潜在保护性免疫应答的主要区域。因此，对于疫苗制剂，我们生产了重组 (r) KI-1 及其两个不同片段，即其 Kunitz (KI) 结构域和 C 末端尾部。首先，我们证明用重组 SmKI-1 (rKI-1) 或其片段免疫的小鼠，用 Freund 佐剂配制，可诱导 IgG 特异性抗体的产生。此外，本文测试的所有疫苗制剂还诱导了 Th1 型免疫应答，这是由蛋白刺激培养的脾细胞产生 IFN-γ和 TNF-α所提示的。然而，仅在接受 rSmKI-1 或 C 末端域疫苗接种的组中观察到了疫苗接种赋予的保护作用。用 rSmKI-1 处理的小鼠显示出蠕虫负担减少 47%，肝脏中虫卵数量减少 36%，肝脏肉芽肿面积减少 33%。此外，注射 C 末端域的小鼠蠕虫负担减少 28%，肝脏中虫卵数量减少 38%，肝脏肉芽肿面积减少 25%。相比之下，KI 结构域免疫接种不能减少蠕虫负担并改善挑战感染后的肝脏病理学。总之，我们的数据表明 KI-1 是控制血吸虫病疫苗的潜在候选物，其 C 末端尾部似乎是该抗原赋予保护作用的主要区域。
