Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China.
Key Laboratory of Zoonosis of Ministry of Agriculture & National Animal Protozoa Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, China.
Parasit Vectors. 2019 Jul 12;12(1):347. doi: 10.1186/s13071-019-3605-6.
Live anticoccidial vaccines have been a tremendous success for disease prevention. The establishment of the reverse genetic manipulation platform has enabled the development of Eimeria parasites, the live anticoccidial vaccine strains, as vaccine vectors. In our previous study, recombinant E. tenella expressing a single immunodominant antigen of E. maxima (Et-EmIMP1) was able to protect chickens against challenge infection with E. maxima. This promising result encouraged us to further explore strategies to improve the protection efficacy of recombinant Eimeria and develop it as a vaccine vector.
We constructed a novel recombinant Eimeria line expressing apical membrane antigen 1 of E. maxima (Et-EmAMA1) and then immunized chickens with Et-EmAMA1 and/or Et-EmIMP1. We found that the E. maxima soluble antigen-specific cell-mediated immunity was much stronger in the birds that were co-immunized with Et-EmAMA1 and Et-EmIMP1 than in those that were immunized with Et-EmAMA1 or Et-EmIMP1 alone. The oocyst production after E. maxima infection was significantly reduced in the recombinant Eimeria-immunized birds compared with the wild-type-immunized and naïve birds. The oocyst production in the birds co-immunized with Et-EmAMA1 and Et-EmIMP1 was consistently the lowest among the treatment groups after E. maxima infection.
These results demonstrated that Eimeria is an effective vaccine vector that can carry and deliver heterologous Eimeria antigens to the host immune system and trigger specific immune responses. Our results also suggested that increasing the number of recombinant Eimeria lines is an effective approach to enhance protective immunity against infections with heterologous pathogens.
活抗球虫疫苗在疾病预防方面取得了巨大成功。反向遗传操作平台的建立使活抗球虫疫苗株——柔嫩艾美耳球虫成为疫苗载体得以发展。在我们之前的研究中，表达柔嫩艾美耳球虫（E.tenella）单一免疫优势抗原（Et-EmIMP1）的重组柔嫩艾美耳球虫能够保护鸡免受强毒感染。这一有希望的结果鼓励我们进一步探索提高重组艾美耳球虫保护效力的策略，并将其开发为疫苗载体。
我们构建了一种表达柔嫩艾美耳球虫顶膜抗原 1（Et-EmAMA1）的新型重组艾美耳球虫系，然后用 Et-EmAMA1 和/或 Et-EmIMP1 免疫鸡。我们发现，与单独用 Et-EmAMA1 或 Et-EmIMP1 免疫的鸡相比，用 Et-EmAMA1 和 Et-EmIMP1 共同免疫的鸡中，E. maxima 可溶性抗原特异性细胞介导免疫更强。与野生型免疫和未免疫的鸡相比，重组艾美耳球虫免疫的鸡在感染 E. maxima 后卵囊产量显著降低。在用 Et-EmAMA1 和 Et-EmIMP1 共同免疫的鸡中，在感染 E. maxima 后，卵囊产量始终是各组中最低的。
这些结果表明，艾美耳球虫是一种有效的疫苗载体，能够将异源艾美耳球虫抗原携带并递送到宿主免疫系统中，并触发特异性免疫反应。我们的结果还表明，增加重组艾美耳球虫系的数量是提高对异源病原体感染的保护性免疫的有效方法。
