基于白念珠菌细胞表面多糖抗原抗真菌疫苗的合成及免疫活性评价

The rising incidence and mortality rate associated with systemic or disseminated candidiasis, as well as the toxicity and severe resistance to therapeutic drugs, are providing impetus for development of antifungal vaccines as a prophylactic and therapeutic strategy. β-1,2-mannan and β-1,3-glucan oligosaccharides are two types of T cell dependent antigens on Candida albicans cell surface which play an important part in invasion, recognition or adhesion of host cells. Moreover, it was demonstrated that the specific immune response and protective antibodies can be elicited by immunization with vaccines containing β-1,2-mannan or β-1,3-glucan antigens bound to carrier proteins and other immunologic stimulants. However, the immune response induced by such type of vaccines was not strong enough. In our design, we were interested in incorporating B-cell antigens of β-1,2-mannan and β-1,3-glucan oligosaccharides with a helper T cell peptide (TT947-967: FNNFTVSFWLRVPKVSASHLE), which was aimed to serve as the glycan carrier and reduce unnecessary immune activation, to form new glycopeptide vaccine candidates. Finally, further study of mechanism will be carried out based on the results of immunological studies of vaccine candidates.

白念珠菌感染引起的死亡率不断上升，加上病菌针对抗菌药物产生严重的耐药性，临床上需要有效的预防和治疗白念珠菌感染的策略。β-1,2-甘露聚 糖、β-1,3-葡聚糖是存在白念珠菌细胞表面的T-细胞依赖型多糖抗原，通常将它们分别与载体蛋白偶联形成糖蛋白疫苗，研究发现这类单一成分的疫苗能诱导机体产生保护性抗体，但引起的免疫应答有限。本课题我们拟将β-1,2-甘露三糖、β-1,3-葡聚糖两类B-细胞抗原同时与能替代破伤风类毒素（Tetanus Toxoid，TT）发挥作用的辅助T-细胞抗原多肽（TT947-967: FNNFTVSFWLRVP KVSASHLE）偶联形成新型糖肽疫苗，以期两类B细胞抗原能发挥协同作用效应，增强疫苗诱导机体产生免疫应答的能力，引入的小分子抗原多肽能够降低传统载体蛋白引起的无效免疫应答，增加产生血清抗体的有效性和选择性，免疫活性评价结果将为下一步疫苗的深入研究提供指导。

白念珠菌感染引起的死亡率不断上升，加上病菌针对抗菌药物产生严重的耐药性，临床上需要有效的预防和治疗白念珠菌感染的策略和技术，而免疫治疗因为具有毒副作用小、疗效显著且不易产生耐药性等特点被认为是解决这一难题的好方法。研究表明，白念珠菌入侵机体并引起机体产生主动性免疫应答主要是与其表面存在的多糖及蛋白抗原有关，而β-1,2-甘露聚糖、β-1,3-葡聚糖则是存在白念珠菌细胞表面的常见的T-细胞依赖型B细胞多糖抗原。本课题我们将β-1,2-甘露聚糖、β-1,3-葡聚糖两类B-细胞抗原分别与T-细胞抗原多肽（FNNFTVSFWLRVPKVSASHLE）及载体蛋白共价连接形成新型糖肽、糖肽-蛋白化合物，并将合成的化合物作为疫苗免疫小鼠进行进一步的免疫活性评价。初步的免疫结果表明所合成的大部分化合物能够引起机体产生较强的免疫应答并产生高水平的IgG抗体，免疫荧光和流式细胞实验显示部分化合物免疫小鼠所得血清能特异性识别白念珠菌细胞表面β-1,2-甘露聚糖、β-1,3-葡聚糖多糖抗原，从而能够起到抗白念珠菌感染的作用。因此，本课题所设计合成的疫苗具有较强的应用价值。