title: Assessment of Lactobacillus gasseri as a candidate oral vaccine vector.
abstract: Lactobacillus species are commensal bacteria that have long been recognized as probiotic microbes and are generally regarded as safe (GRAS) for human consumption. We have investigated the use of L. gasseri as a vaccine vector for oral immunization against mucosal pathogens. Recent research has shown that the immune response to different lactobacilli can vary widely depending on the species or subspecies of Lactobacillus being studied. While some lactobacilli seem to induce oral tolerance, others induce an adaptive immune response. This study characterized the systemic and mucosal immune response to wild-type and genetically modified L. gasseri. L. gasseri primarily activates TLR2/6, with additional activation through the TLR2 homodimer. To expand the Toll-like receptor (TLR) activation profile of L. gasseri and the immunogenicity of the vector, a plasmid containing fliC, the gene encoding bacterial flagellin, was introduced which resulted in the strong activation of TLR5. The treatment of human myeloid dendritic cells with recombinant lactobacilli expressing flagellin triggered phenotypic maturation and the release of proinflammatory cytokines. In contrast, bacterial treatment also resulted in a statistically significant increase in IL-10 production. In vivo studies established that treatment with L. gasseri led to a diversification of B-cell populations in the lamina propria of the murine colon. Furthermore, treatment with genetically modified L. gasseri led to a significant decrease in the percentage of FoxP3(+) colonic lymphocytes. Taken together, these data clarify the interaction of L. gasseri with the host immune system and support further investigation of the in vivo immunogenicity of L. gasseri expressing both flagellin and candidate vaccine antigens.
authors: Center for Comparative Medicine and Translational Research, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
authors: Laura
authors: L
authors: Stoeker
authors: Shila
authors: S
authors: Nordone
authors: Sara
authors: S
authors: Gunderson
authors: Lin
authors: L
authors: Zhang
authors: Akinobu
authors: A
authors: Kajikawa
authors: Alora
authors: A
authors: LaVoy
authors: Michael
authors: M
authors: Miller
authors: Todd R
authors: TR
authors: Klaenhammer
authors: Gregg A
authors: GA
authors: Dean
mesh_terms: D000276:Adjuvants, Immunologic / Q000235:genetics; D000284:Administration, Oral; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D001428:Bacterial Vaccines / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology*; D001769:Blood / Q000276:immunology; D003106:Colon / Q000276:immunology; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology / Q000382:microbiology; D004337:Drug Carriers / Q000008:administration & dosage*; D005260:Female; D005408:Flagellin / Q000235:genetics; D005822:Genetic Vectors; D006801:Humans; D007413:Intestinal Mucosa / Q000276:immunology; D007778:Lactobacillus / Q000235:genetics* / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids; D051198:Toll-Like Receptor 5 / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D001428:Bacterial Vaccines; D016207:Cytokines; D004337:Drug Carriers; D051198:Toll-Like Receptor 5; D005408:Flagellin