Evaluation of adhesion capacity, cell surface traits and immunomodulatory activity of presumptive probiotic Lactobacillus strains.

Twelve lactobacilli previously isolated from newborn infants' gastrointestinal tract and Feta cheese were further characterized by pulse field gel eletrophoresis (PFGE). All strains exhibited distinct PFGE genotypic patterns with the exception of DC421 and DC423 strains possessing identical patterns. The strains DC421, 2035 and 2012 were found to posses certain cell surface traits such as hydrophobicity, autoaggregation and/or high adhesive capacity suggesting potential immunomodulatory activity. However, application of the dorsal mouse air pouch system revealed that only the DC421, DC429 and 2035 strains exhibited strong immunostimulatory activity such as increased chemotaxis of polymorphonuclear (PMN) cells in association with increased phagocytosis and cytokine production. The same strains also induced immunomodulatory activity in the gut associated lymphoid tissue in mice in the absence of any inflammatory response. All strains induced IgA production while reduced TNFalpha production by small intestine cells. The strains DC421 and DC429 exerted their effect on the intestine through Toll-like receptor TLR2/TLR4/TLR9 mediated signalling events leading to secretion of a certain profile of cytokines in which gamma interferon (IFN-gamma), interleukin (IL)-5, IL-6 and IL-10 are included. The strain 2035 induced similar cytokine profile through the synergy of TLR2/TLR4. This study further supports the eligibility of the air pouch model to discriminate presumptive probiotic Lactobacillus strains exhibiting immunostimulatory activity in the gut. Furthermore, evidence is provided that the cell surface traits examined may not be the only criteria but an alternative and important component of a complex mechanism that enables a microorganism to interact with the host gut to exert its immunoregulatory activity.