Oral Immunization with Lactobacillus casei Expressing the Porcine Circovirus Type 2 Cap and LTB Induces Mucosal and Systemic Antibody Responses in Mice.

Fengsai Li,Han Zhou,Yanping Jiang,Rumeng Ma,Xiaona Wang,Xinyuan Qiao,Lijie Tang,Xi Cheng,Yijing Li,Wei Wu,Li Wang,Fei Teng

doi:10.3390/v13071302

Abstract

Porcine circovirus type 2 (PCV2) causes many diseases in weaned piglets, leading to serious economic losses to the pig industry. This study investigated the immune response following oral administration of Lactobacillus casei ATCC393 (L. casei 393) expressing PCV2 capsid protein (Cap) fusion with the Escherichia coli heat-labile toxin B subunit (LTB) in mice. Recombinant L. casei strains were constructed using plasmids pPG611.1 and pPG612.1. The expression and localization of proteins from recombinant pPG611.1-Cap-LTB (pPG-1-Cap-LTB)/L. casei 393 and pPG612.1-Cap-LTB (pPG-2-Cap-LTB)/L. casei 393 were detected. All recombinant strains were found to be immunogenic by oral administration in mice and developed mucosal and systemic immune responses against PCV2. The titers of specific antibodies in mice administered pPG-2-Cap-LTB/L. casei 393 were higher than those in mice administered pPG-1-Cap-LTB/L. casei 393 in serum and the mucosal samples. The mucosal immune response was not only limited to the gastrointestinal tract but was also generated in other mucosal parts. Thus, the application of recombinant L. casei could aid in vaccine development for PCV2.

Highlights

The results indicated that the oral administration of two recombinant strains, pPG611.1-CapLTB/L. casei 393 and pPG612.1-capsid protein (Cap)-labile toxin B subunit (LTB)/L. casei 393, could induce specific anti-Porcine circovirus type 2 (PCV2) mucosal and systemic immune responses
The sequences of L. casei 393 transformants were confirmed by plasmid DNA sequencing, and the results showed that there were no mutations in the transformants
PPG-1-Cap-LTB/L. casei 393 and pPG-2-Cap-LTB/L. casei 393 were grown overnight in basal MRS medium supplemented with xylose

Summary

Introduction

Porcine circovirus type 2 (PCV2) is etiologically associated with a complex of PCV diseases, including post-weaning multisystemic wasting syndrome (PMWS) [1]. PCV2 is associated with respiratory disease, reproductive failure, hepatitis, and porcine dermatitis and nephropathy syndrome [1,3]. PCV2 is a small, non-enveloped, single-stranded, circular DNA virus with a 1767 or 1768 nt ambisense genome [4] that contains at least two major open reading frames (ORFs). ORF1 encodes the replication proteins (Rep and Rep’) involved in virus replication, and ORF2 encodes the capsid protein (Cap) [5,6]. Cap, associated with the generation of neutralizing antibodies and the protection of antibodies [7,8], is a candidate target for the design of new vaccines against

Methods

Results

Conclusion