Abstract
BackgroundThe use of lactic acid bacteria as vehicles to delivery antigens to immunize animals is a promising issue. When genetically modified, these bacteria can induce a specific local and systemic immune response against selected pathogens. Gastric acid and bile salts tolerance, production of antagonistic substances against pathogenic microorganisms, and adhesive ability to gut epithelium are other important characteristics that make these bacteria useful for oral immunization.ResultsBacteria isolated on de Man, Rogosa and Sharpe medium (MRS) from different gastrointestinal portions of broiler chicks were evaluated for their resistance to artificial gastric acid and bile salts, production of hydrogen peroxide, and cell surface hydrophobicity. Thirty-eight isolates were first typed at species level by PCR amplification of 16S-23S rRNA intergenic spacers using universal primers that anneal within 16S and 23S genes, followed by restriction digestion analyses of PCR amplicons (PCR-ARDRA). An expression cassette was assembled onto the pCR2.1-Topo vector by cloning the promoter, leader peptide, cell wall anchor and terminator sequences derived from the laminin binding S-layer protein gene of L. crispatus strain F5.7 (lbs gene). A sequence encoding the green fluorescent protein (GFP) was inserted as reporter gene, and an erythromycin resistance gene was added as selective marker. All constructs were able to express GFP in the cloning host E. coli XL1-Blue and different Lactobacillus strains as verified by FACS and laser scanning confocal microscopy.ConclusionLactobacillus isolated from gastrointestinal tract of broiler chickens and selected for probiotic characteristics can be genetically modified by introducing an expression cassette into the lbs locus. The transformed bacteria expressed on its cell wall surface different fluorescent proteins used as reporters of promoter function. It is possible then that similar bacterial model expressing pathogen antigens can be used as live oral vaccines to immunize broilers against infectious diseases.
Highlights
In Probiotics 2: Applications and Practical Aspects Edited by: Fuller R
Thirty-eight isolates of bacteria were obtained from different gastrointestinal portions of five broiler chickens and selected as Gram-positive non-sporing, catalase negative, and presenting rods with diverse sizes
Species identification by 16S-23S rRNA ARDRA showed that 7 different species were recovered in the following order: 12 L. reuteri (31,6%), 11 L. acidophilus (29,0%), 4 L. johnsonii (10,5%), 4 L. salivarius (10,5%), 4 L. vaginalis (10,5%), 2 L. crispatus (5,3%), and 1 Lactobacillus spp (2,6%)
Summary
In Probiotics 2: Applications and Practical Aspects Edited by: Fuller R. The use of lactic acid bacteria as vehicles to delivery antigens to immunize animals is a promising issue. When genetically modified, these bacteria can induce a specific local and systemic immune response against selected pathogens. When ingested in sufficient numbers, probiotics are believed to play an important role in the control of host intestinal microbiota and modulation of host immune responses [7]. Both local and systemic immune responses can be modulated by probiotics, with production of a set of cytokines such as IFN-γ, TNF-α, IL-6 and IL12, and nitric oxide (NO) [8,26]. Most of the probiotic preparations studied or commercialised contains lactic acid bacteria (LAB)
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