Production of a Particulate Hepatitis C Vaccine Candidate by an Engineered Lactococcus lactis Strain

Abstract

ABSTRACTVaccine delivery systems based on display of antigens on bioengineered bacterial polyester inclusions can stimulate cellular immune responses. The food-grade Gram-positive bacteriumLactococcus lactiswas engineered to produce spherical polyhydroxybutyrate (PHB) inclusions which abundantly displayed the hepatitis C virus core (HCc) antigen. In mice, the immune response induced by this antigen delivery system was compared to that induced by vaccination with HCc antigen displayed on PHB beads produced inEscherichia coli, to PHB beads without antigen produced inL. lactisorE. coli, or directly to the recombinant HCc protein. Vaccination site lesions were minimal in all mice vaccinated with HCc PHB beads or recombinant protein, all mixed in the oil-in-water adjuvant Emulsigen, while vaccination with the recombinant protein in complete Freund's adjuvant produced a marked inflammatory reaction at the vaccination site. Vaccination with the PHB beads produced inL. lactisand displaying HCc antigen produced antigen-specific cellular immune responses with significant release of gamma interferon (IFN-γ) and interleukin-17A (IL-17A) from splenocyte cultures and no significant antigen-specific serum antibody, while the PHB beads displaying HCc but produced inE. colireleased IFN-γ and IL-17A as well as the proinflammatory cytokines tumor necrosis factor alpha (TNF-α) and IL-6 and low levels of IgG2c antibody. In contrast, recombinant HCc antigen in Emulsigen produced a diverse cytokine response and a strong IgG1 antibody response. Overall it was shown thatL. lactiscan be used to produce immunogenic PHB beads displaying viral antigens, making the beads suitable for vaccination against viral infections.