Divergent Patterns of Colonization and Immune Response Elicited from Two IntestinalLactobacillusStrains That Display Similar Properties In Vitro

Abstract

Lactobacilli derived from the endogenous flora of normal donors are being increasingly used as probiotics in functional foods and as vaccine carriers. However, a variety of studies done with distinct strains of lactobacilli has suggested heterogeneous and strain-specific effects. To dissect this heterogeneity at the immunological level, we selected two strains of lactobacilli that displayed similar properties in vitro and studied their impact on mucosal and systemic B-cell responses in monoxenic mice. Germfree mice were colonized withLactobacillus johnsonii(NCC 533) orLactobacillus paracasei(NCC 2461). Bacterial loads were monitored for 30 days in intestinal tissues, and mucosal and systemic B-cell responses were measured. Although bothLactobacillusstrains displayed similar growth, survival, and adherence properties in vitro, they colonized the intestinal lumen and translocated into mucosal lymphoid organs at different densities.L. johnsoniicolonized the intestine very efficiently at high levels, whereas the number ofL. paracaseidecreased rapidly and it colonized at low levels. We determined whether this difference in colonization correlated with an induction of different types of immune responses. We observed that colonization with either strain induced similar germinal center formation and immunoglobulin A-bearing lymphocytes in the mucosa, suggesting that both strains were able to activate mucosal B-cell responses. However, clear differences in patterns of immunoglobulins were observed between the two strains in the mucosa and in the periphery. Therefore, despite similar in vitro probiotic properties, distinctLactobacillusstrains may colonize the gut differently and generate divergent immune responses.