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

• Main Authors: Fengsai Li, Xiaona Wang, Rumeng Ma, Wei Wu, Fei Teng, Xi Cheng, Yanping Jiang, Han Zhou, Li Wang, Lijie Tang, Xinyuan Qiao, Yijing Li
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Viruses
• Subjects: <i>Lactobacillus casei</i>; PCV2; Cap; LTB; oral administration
• Online Access: https://www.mdpi.com/1999-4915/13/7/1302
• ISSN: 1999-4915

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 <i>Lactobacillus casei ATCC393</i> (<i>L. casei 393</i>) expressing PCV2 capsid protein (Cap) fusion with the <i>Escherichia</i> <i>coli</i> heat-labile toxin B subunit (LTB) in mice. Recombinant <i>L. casei</i> 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)/<i>L. casei 393</i> and pPG612.1-Cap-LTB (pPG-2-Cap-LTB)/<i>L. casei 393</i> 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/<i>L. casei 393</i> were higher than those in mice administered pPG-1-Cap-LTB/<i>L. casei 393</i> 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 <i>L. casei</i> could aid in vaccine development for PCV2.