Immunogenicity of Oral Vaccine Candidate in Recombinant Lactococcus lactis Expressing HBcAg and IFNα-2b for Hepatitis B Prevention

Abstract Background: Hepatitis B is a liver inflammation caused by virus infection leading to acute and chronic conditions. Antigenic compound of HBcAg could induce specific T and B cell that generating high immunity response rather than HBsAg. Therapeutic agent for hepatitis and cancer treatment which has been approved by USFDA is Interferon α-2b (IFNα-2b). This type of class I cytokine plays a role in inhibiting viral replication and modulating adaptive immune system. Objectives: In this study, we analyzed immunogenicity of recombinant HBcAg and IFNα-2b expressed in L. lactis NZ3900. Methods: In vivo test was carried out using female Balb/c mice. Antibody responses for oral immunization were quantified as total IgG using ELISA on days 21, 35 and 51. Safety compound of this oral vaccine candidate was also described by liver and spleen condition after immunization. The differential leukocyte counting was performed to confirm the inflammatory process. Results: Post immunization with L. lactis recombinant strains could induce optimum total humoral immune responses on day 35, with IgG concentration at 4.96±1.03 mg/mL. Single treatment with HBcAg was more potent in inducing immune response (IgG) rather than HBcAg-IFNa-2b combination. Immunization for 51 days could not alleviate animal body weight in each group. The maintaining IgG production until 51 days was just because lymphocytes activities persisted above 70%. The lymphocytes number which achieved 76.3% (P2) and 78.3% (P3) compared to Control group with 62%. Conclusion: Single treatment with recombinant HBcAg expressed in L. lactis NZ3900 was better inducing IgG production and maintaining for 51 days. This result suggested, L. lactis recombinant strain can be as potential vaccine candidate to induce immune response protecting from hepatitis B virus. Moreover, no organ damage was found in liver and spleen of Balb/c mice.