DataSheet_1_LigA formulated in AS04 or Montanide ISA720VG induced superior immune response compared to alum, which correlated to protective efficacy in a hamster model of leptospirosis.pdf

Leptospirosis is a zoonotic disease of global importance. The current vaccine provides serovar-specific and short-term immunity and does not prevent bacterial shedding in infected animals. Subunit vaccines based on surface proteins have shown to induce protection in an animal model. However, these proteins were tested with non-clinical adjuvants and induced low to moderate protective efficacy. We formulated a variable region of Leptospira immunoglobulin-like protein A (LAV) in clinical adjuvants, AS04 and Montanide ISA720VG, and then evaluated the immune response in mice and protective efficacy in a hamster model. Our results show that animals immunized with LAV-AS04 and LAV-Montanide ISA720VG (LAV-M) induced significantly higher levels of LAV-specific antibodies than LAV-Alum. While LAV-Alum induced Th2 response with the induction of IgG1 and IL-4, AS04 and LAV-M induced a mixed Th1/Th2 response with significant levels of both IgG1/IL-4 and IgG2c/IFN-γ. Both LAV-AS04 and LAV-M induced the generation of a significantly higher number of cytotoxic T cells (CTLs). The immune response in LAV-AS04- and LAV-M-immunized animals was maintained for a long period (>180 days) with the generation of a significant level of B- and T-cell memory. The strong immune response by both vaccines correlated to enhanced recruitment and activation of innate immune cells particularly DCs at draining lymph nodes and the formation of germinal centers (GCs). Furthermore, the immune response generated in mice correlated to protective efficacy in the hamster model of leptospirosis. These results indicate that LAV-AS04 and LAV-M are promising vaccines and can be further evaluated in clinical trials.

钩端螺旋体病（Leptospirosis）是一种具有全球重要性的人畜共患病。现有疫苗仅能提供血清型特异性的短期免疫，且无法阻止感染动物的细菌排菌。基于表面蛋白的亚单位疫苗已在动物模型中展现出保护效力，但这类蛋白曾使用非临床佐剂进行测试，仅能诱导低至中等水平的保护效果。本研究将钩端螺旋体免疫球蛋白样蛋白A（Leptospira immunoglobulin-like protein A, LAV）的可变区与临床佐剂AS04及Montanide ISA720VG进行配伍，随后在小鼠体内评估其免疫原性，并在仓鼠模型中检测其保护效力。实验结果显示，经LAV-AS04和LAV-Montanide ISA720VG（简称LAV-M）免疫的动物，其LAV特异性抗体水平显著高于LAV-Alum免疫组。其中，LAV-Alum仅诱导以IgG1和白细胞介素4（IL-4）为特征的Th2型免疫应答，而AS04与LAV-M则可诱导混合的Th1/Th2型免疫应答，同时产生高水平的IgG1/IL-4与IgG2c/干扰素γ（IFN-γ）。LAV-AS04与LAV-M均可显著诱导更多的细胞毒性T淋巴细胞（cytotoxic T cells, CTLs）生成。两类疫苗免疫动物后的免疫应答可长期维持（超过180天），并产生显著水平的B细胞与T细胞记忆。两种疫苗诱导的强免疫应答，与引流淋巴结内先天免疫细胞（尤其是树突状细胞，DCs）的招募激活增强以及生发中心（germinal centers, GCs）的形成密切相关。此外，小鼠体内诱导的免疫应答与钩端螺旋体病仓鼠模型中的保护效力呈正相关。上述结果表明，LAV-AS04与LAV-M是极具潜力的候选疫苗，可进一步开展临床试验。