Lactococcus lactis-expressing listeriolysin O (LLO) provides protection and specific CD8+ T cells against Listeria monocytogenes in the murine infection model

Abstract

Lactococcus lactis has previously been proposed as a vaccine platform for the safe delivery of heterologous antigens. Here we utilized L. lactis as a live vector for expression of listeriolysin O (LLO), a major Listeria monocytogenes antigen and virulence factor. A variety of plasmid constructs were designed to permit either constitutive or nisin-inducible expression of secreted or non-secreted LLO in L. lactis. Recombinant strains were subsequently tested in a murine model for vaccination efficacy against L. monocytogenes infection. CD8(+) T lymphocytes specific for the LLO(91-99) epitope were detected when strains were administered via the intraperitoneal (IP) but not the oral route. Challenge with live L. monocytogenes revealed different levels of protection among the three vaccine strains tested with the nisin-inducible LLO-secreting L. lactis strain providing the greatest protection against secondary infection. This work highlights the usefulness of the GRAS (Generally Regarded As Safe) organism L. lactis as the basis of a live vaccine vector against L. monocytogenes. The work suggests that LLO-expressing L. lactis strains may also have the potential to act as a platform for directing other co-expressed antigens towards the cytosolic MHC class I pathway for enhanced stimulation of the CD8(+) T-cell response.

Genome Organization and Characterization of the Virulent Lactococcal Phage 1358 and Its Similarities to Listeria Phages

“…Moreover, it was previously shown that Listeria genes can be expressed and proteins can be produced in Lactococcus (6,31,61). It is not the first time that a phage infecting a generallyrecognized-as-safe (GRAS) bacterium (L. lactis) shared structural similarities with phages infecting pathogenic bacteria (20,62).…”

Listeria monocytogenesmutants defective in gallbladder replication represent safety-enhanced vaccine delivery platforms

“…The assay was carried out as described previously. 8,23,24 The data indicated that both Tnlmo0598 and Tnlmo2566 strains were capable of eliciting a potent Listeria-specific T cell response that was comparable to that elicited by the wild-type bacterium and significantly higher than that seen in na€ ıve (sham inoculated) mice (Fig. 4A, B).…”

“…5,6 The ability to proliferate within the cytoplasm significantly influences the magnitude of the resultant immune response as bacteria incapable of replication in this environment demonstrate markedly lower immunogenicity. 7,8 In addition, the ability to spread from cell to cell is likely to influence the efficacy of nucleic acid delivery to solid tumors and other tissues. 4,9 The pathogen is genetically tractable and it is possible to target specific genes in order to create mutants which are attenuated but retain vaccine potential.…”

A mutant in the Listeria monocytogenes Fur-regulated virulence locus (frvA) induces cellular immunity and confers protection against listeriosis in mice

“…It has been demonstrated that protective immunity against L. monocytogenes is dependent on induction of specific CD8 + T cells to the listerial epitopes LLO and P60 (Pamer, 2004). It is noteworthy that several studies have used live bacterial vectors, such as Salmonella Typhimurium (S. Typhimurium) and Lactococcus lactis, expressing LLO and/or P60 for vaccination against listeriosis (Bahey-El-Din et al, 2008Hess et al, 1996). Here we show that mice immunized with L. monocytogenes DfrvA via the i.p.…”