Microneme-located VP2 in elicits effective protective immunity against infectious bursal disease virus.

Using transgenic spp. to deliver exogenous antigens is a viable option for developing multivalent live vaccines. Previous research revealed that the location of antigen expression in recombinant dictates the magnitude and type of immune responses. In this study, we constructed genetically modified that expressed VP2 protein, a protective antigen from infectious bursal disease virus (IBDV), on the surface or in the microneme of sporozoites. After vaccination, VP2-specific antibody was readily detected in specific pathogen-free chickens receiving transgenic parasites expressing VP2 in microneme, but animals vaccinated with which expressing VP2 on surface failed to produce detectable antibody after two times immunizations. Moreover, the bursal lesion of microneme-located VP2 transgenic immunized chickens was less severe compared with un-immunized animals after IBDV challenge infection. Therefore, genetically modified that express IBDV-derived VP2 in micronemes are effective in inducing specific antibody responses against VP2, while parasites that have VP2 expression on cell surface are not suitable. Thus, the use of parasites as vaccine vectors needs to consider the proper targeting of exogenous immunogens. Our results have implications for the design of other vector vaccines.