Min Xiangyang, Feng Meng, Guan Yue, Man Suqin, Fu Yongfeng, Cheng Xunjia, Tachibana Hiroshi
Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Fudan University, Shanghai, China.
Department of Infectious Diseases, Tokai University School of Medicine, Isehara, Kanagawa, Japan.
PLoS Negl Trop Dis. 2016 Jan 29;10(1):e0004419. doi: 10.1371/journal.pntd.0004419. eCollection 2016 Jan.
Entamoeba histolytica is an intestinal protozoan parasite that causes amoebiasis, including amebic dysentery and liver abscesses. E. histolytica invades host tissues by adhering onto cells and phagocytosing them depending on the adaptation and expression of pathogenic factors, including Gal/GalNAc lectin. We have previously reported that E. histolytica possesses multiple CXXC sequence motifs, with the intermediate subunit of Gal/GalNAc lectin (i.e., Igl) as a key factor affecting the amoeba's pathogenicity. The present work showed the effect of immunization with recombinant Igl on amebic liver abscess formation and the corresponding immunological properties.
METHODOLOGY/PRINCIPAL FINDINGS: A prokaryotic expression system was used to prepare the full-length Igl and the N-terminal, middle, and C-terminal fragments (C-Igl) of Igl. Vaccine efficacy was assessed by challenging hamsters with an intrahepatic injection of E. histolytica trophozoites. Hamsters intramuscularly immunized with full-length Igl and C-Igl were found to be 92% and 96% immune to liver abscess formation, respectively. Immune-response evaluation revealed that C-Igl can generate significant humoral immune responses, with high levels of antibodies in sera from immunized hamsters inhibiting 80% of trophozoites adherence to mammalian cells and inducing 80% more complement-mediated lysis of trophozoites compared with the control. C-Igl was further assessed for its cellular response by cytokine-gene qPCR analysis. The productions of IL-4 (8.4-fold) and IL-10 (2-fold) in the spleen cells of immunized hamsters were enhanced after in vitro stimulation. IL-4 expression was also supported by increased programmed cell death 1 ligand 1 gene.
CONCLUSIONS/SIGNIFICANCE: Immunobiochemical characterization strongly suggests the potential of recombinant Igl, especially the C-terminal fragment, as a vaccine candidate against amoebiasis. Moreover, protection through Th2-cell participation enabled effective humoral immunity against amebic liver abscesses.
溶组织内阿米巴是一种肠道原生动物寄生虫，可引起阿米巴病，包括阿米巴痢疾和肝脓肿。溶组织内阿米巴通过黏附并吞噬细胞来侵袭宿主组织，这依赖于致病因子（包括半乳糖/ N - 乙酰半乳糖胺凝集素）的适应性和表达。我们之前报道过，溶组织内阿米巴具有多个CXXC序列基序，其中半乳糖/ N - 乙酰半乳糖胺凝集素的中间亚基（即Igl）是影响阿米巴致病性的关键因素。本研究展示了用重组Igl免疫对阿米巴肝脓肿形成的影响及其相应的免疫学特性。
方法/主要发现：使用原核表达系统制备全长Igl以及Igl的N端、中间和C端片段（C - Igl）。通过向仓鼠肝内注射溶组织内阿米巴滋养体来评估疫苗效力。发现经全长Igl和C - Igl肌肉注射免疫的仓鼠分别有92%和96%对肝脓肿形成具有免疫力。免疫反应评估显示，C - Igl可产生显著的体液免疫反应，免疫仓鼠血清中的高水平抗体可抑制80%的滋养体黏附哺乳动物细胞，与对照组相比，诱导的补体介导的滋养体裂解增加80%。通过细胞因子基因qPCR分析进一步评估C - Igl的细胞反应。体外刺激后，免疫仓鼠脾细胞中IL - 4（8.4倍）和IL - 10（2倍）的产生增加。程序性细胞死亡1配体1基因的增加也支持了IL - 4的表达。
结论/意义：免疫生化特性强烈表明重组Igl，尤其是C端片段，作为抗阿米巴病疫苗候选物的潜力。此外，通过Th2细胞参与的保护作用实现了对阿米巴肝脓肿的有效体液免疫。
