Efficacy of a potential DNA vaccine encoding Cryptosporidium baileyi rhomboid protein against homologous challenge in chickens

- Rhomboid gene from Cryptosporidium baileyi is evaluated as a vaccine candidate against cryptosporidiosis.
- This nucleic acid based vaccine can induce antibody responses and peripheral blood T lymphocytes proliferation.
- Immune reactions caused by vaccination exert no obvious effect on the body weight of experimental chickens.
- High dose (100 μg) CbROM gene recombinant DNA in vaccinated chickens conferred certain protective immunity against Cryptosporidium infection.

The parasite Cryptosporidium baileyi can infect the larynx, trachea, bursa and cloaca of poultry, causing high mortality during severe infection and leading to substantial economic losses of the poultry industry. The rhomboid protein is very important in Cryptosporidium infection. In this study, a nucleic acid based vaccine candidate pEGFP-CbROM was constructed. After orally challenging with C. baileyi oocysts, the corresponding immune responses induced were analyzed and the immunoprotective effect evaluated in chickens. Obtained results revealed that this nucleic acid based vaccine could induce antibody responses and peripheral blood T lymphocytes proliferation significantly (P < 0.05), while the peripheral blood B lymphocyte proliferation increased significantly (P < 0.05) only at a high dose of 100 μg of pEGFP-CbROM, compared with the PBS control group. After C. baileyi infection, the duration of oocysts shedding was shortened by 2 days in the 100 μg pEGFP-CbROM group, and the rate of reduction could reach to around 71.3%. While no significant difference in body weight gain was observed among the immunized groups (P > 0.05), the differences between the immunized and the non-immunized groups were found to be significant (P < 0.05). Our data provides a useful basis for further work in cryptosporidiosis prevention and treatment.