Abstract: 【Objective】 The purpose of this experiment was to prepare microcapsules coated with inactivated Transmissible gastroenteritis virus (TGEV),and evaluate its oral mucosal immune effect on newborn piglets,so as to prevent TGEV from causing severe diarrhea and economic losses.【Method】 Sodium alginate and chitosan were used as the microcapsule wall materials,and inactivated TGEV was used as the antigen to prepare TGEV microcapsules by a one-step method.The quality evaluation indicators of microcapsules included encapsulation rate,protein loading,and in vitro release rate.The effects of the composition of the encapsulation materials and different saline solutions on the properties of the microcapsules were investigated to screen the optimal process conditions for TGEV microcapsule preparation.The release rate of TGEV microcapsules under different environmental conditions and their tolerance to room temperature storage were also evaluated.Finally,immunological analysis was conducted,oral immunity was administered to piglets,various immune indicators were measured,antibody titer testing and virus neutralization tests were conducted.【Result】 The optimal process conditions for preparing microcapsules were determined to be 1.5% sodium alginate,1.2% chitosan,3.5% calcium chloride,and 1-2 mL of inactivated virus antigen addition.Microcapsule prepared under these conditions had a release rate of over 50% on the third day in PBS and saline solutions.On the 18th day,the release rate reached 97% and 88%,respectively.The lowest release rate after 5 months of storage at room temperature was still above 80%.After oral immunization of piglets,the D_{490 nm} value of IgA antibody in the fecal sample of microcapsule high and low dose groups were 0.97 and 1.49,respectively,and the D_{490 nm} value of IgG antibody were 1.03 and 1.75,respectively.In virus neutralization experiments,the virus 50% neutralization titers of IgG antibody in microcapsule high and low dose groups were 1∶512 and 1∶256,respectively.The virus 50% neutralization titers of IgA antibody in microcapsule high and low dose groups with were 1∶128 and 1∶64,respectively.【Conclusion】 The sodium alginate-chitosan microcapsules not only had a sustained-release effect on the inactivated TGEV antigen in the intestine but also had an adjuvant effect on vaccine immunization,which could effectively stimulate mucosal and systemic immune responses in the adaptive mucosal immune response.

Key words: Transmissible gastroenteritis virus (TGEV); microcapsules; sodium alginate; chitosan; mucosal immunization