Influenza virus-like particles presenting Toxoplasma gondii dense granule protein 7 protect mice from lethal ME49 challenge

Toxoplasma gondii dense granule antigen 7 (GRA7) is a membrane-associated protein expressed across parasite life cycle and represents a promising vaccine target. This study aimed to develop a GRA7-based virus-like particle (VLP) vaccine and assess its protective efficacy. GRA7 VLPs were constructed using an influenza M1 scaffold via the baculovirus expression system. Female BALB/c mice were immunized intranasally three times and orally challenged with lethal T. gondii ME49 cysts. Humoral and cellular immune responses, brain inflammation, and parasite burden were evaluated at 40 days post-infection. Body weight reduction and survival rate were monitored after challenge. GRA7 VLPs induced robust T. gondii-specific IgG in serum after immunization. Following challenge with cysts, elevated antibody levels were detected in intestinal, fecal, and brain tissues, accompanied by enhanced activation of IgG-secreting cells, germinal center B cells, memory B cells, as well as CD4+ and CD8+ T cells in antigen-restimulated splenocytes of vaccinated mice. Notably, vaccinated mice exhibited 100% survival and sustained body weight, alongside a marked reduction in cerebral pro-inflammatory cytokines and parasite cyst burden. GRA7 VLPs confer strong systemic and mucosal immunity and significant protection against chronic toxoplasmosis, underscoring their potential as a promising vaccine platform.

刚地弓形虫（Toxoplasma gondii）致密颗粒抗原7（GRA7）是一种在寄生虫整个生活周期中均有表达的膜相关蛋白，是极具潜力的疫苗靶点。本研究旨在开发基于GRA7的病毒样颗粒（virus-like particle, VLP）疫苗，并评估其防护效力。研究人员通过杆状病毒表达系统，以流感病毒M1蛋白作为骨架构建了GRA7病毒样颗粒。对雌性BALB/c小鼠经鼻腔免疫三次，随后以致死性刚地弓形虫ME49包囊经口攻毒。于感染后40天，评估小鼠的体液与细胞免疫应答、脑部炎症情况以及寄生虫负荷；攻毒后监测小鼠的体重下降情况与存活率。免疫后，GRA7病毒样颗粒可诱导小鼠血清中产生高效价的刚地弓形虫特异性IgG抗体。经包囊攻毒后，免疫小鼠的肠道、粪便及脑组织中抗体水平显著升高；同时，在抗原再刺激的脾细胞中，IgG分泌细胞、生发中心B细胞、记忆B细胞以及CD4+和CD8+ T细胞的活化水平均得到增强。值得注意的是，免疫小鼠的存活率达100%，体重保持稳定，同时脑部促炎细胞因子水平与寄生虫包囊负荷均显著降低。GRA7病毒样颗粒可诱导强烈的全身性与黏膜免疫，并对慢性弓形虫病提供显著防护，这凸显了其作为极具潜力的疫苗平台的应用价值。