Presently, attenuated pathogens such as Salmonella, Shigella, Listeria, Yersinia, PLX4032 as well as, non-pathogenic Escherichia coli have been used as experimental live delivery systems [17, 18]. An advantage of using attenuated pathogens as DNA vaccine vehicles is that they possess mechanisms to adhere or invade host cells with a negligible risk of reversion to a virulent strain via gene transfer or mutation. However, a potential concern is the risk of increased virulence in young or immunocompromised individuals. The use of food-grade lactic acid bacteria
(LAB) as DNA delivery vehicle represents an alternative and attractive strategy to deliver DNA vaccines at the mucosal surfaces Daporinad ic50 (ref review by 19 and 20). The dietary group of LAB, including Lactococcus lactis
and many species of Lactobacillus, is generally regarded as safe (GRAS) organisms of which some are intestinal commensals of humans. Indeed, it has been extensively demonstrated that these bacteria are able to deliver a range of vaccine and therapeutic molecules for applications in allergic, infectious or gastrointestinal diseases [19, 21, 22]. A relatively new development, however, is their use as a vehicle for genetic immunization [23]. Previous experiments performed by our group showed that either native L. lactis (LL) or recombinant invasive LL expressing Fibronectin Binding Protein A (LL-FnBPA+) of Staphylococcus aureus or Internalin A (InlA) of Listeria monocytogenes (LL-InlA+) [24, 25], were able to deliver DNA in epithelial cells both in vitro and in vivo, demonstrating potential as gene transfer Parvulin vehicles [24–27]. However InlA does not bind to its murine receptor, E-cadherin, thus limiting the use of LL-InlA+ in in vivo murine model. On the other hand, FnBPA requires an adequate local concentration of fibronectin to bind to its receptors, integrins [28, 29]. In order to avoid the limitations of InlA and FnBPA and improve our knowledge on the key steps
by which the DNA is transferred to mammalian cells using L. lactis, LL was engineered to express a mutated form of Internalin A (mInlA; Ser192Asn and Tyr369Ser) that increased binding affinity to murine and human E-cadherin [30, 31] thus allowing for in vivo experiments in conventional mice. Herein, we describe the construction and characterization of this novel L. lactis strain as a DNA delivery vector, using cow’s milk β-lactoglobulin (BLG) allergen, to measure DNA transfer to intestinal epithelial cells (IECs) in vitro and in vivo. Overall, the production of mInLA+at the surface of Lactococcus lactis increased the invasisity of bacterium and amount of plasmid transfer by 1000 and 10 fold, respectively.
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