Immunomodulatory effect of Lactobacillus johnsonii La1 in a murine model of infection with Giardia intestinalis.

HUMEN, M. A. AND PÉREZ, P. F.

Córdoba

Congreso; VI Congreso Argentino de Microbiología General (SAMIGE); 2009

SAMIGE

Immunomodulatory effect of Lactobacillus johnsonii La1 in a murine model of infection with Giardia intestinalis.   Humen1* MA; Pérez1, 2  PF. 1Centro de Investigación y Desarrollo en Criotecnología de Alimentos y  2Cátedra de Microbiología. Facultad de Ciencias Exactas, UNLP. 47 y 116 La Plata 1900. Argentina. *e-mail: mhumen@cidca.org.ar   The ability of probiotic microorganisms to antagonize intestinal bacterial pathogens has been widely documented. However, little is known on the effect of probiotics on intestinal protozoa such as Giardia intestinalis. We have demonstrated, in vivo, the ability of Lactobacillus johnsonii La1 to antagonize Giardia infection. In the present work we sought to gain insight on the effect of the administration of lactobacilli on the balance of relevant cellular populations in a murine model of giardiasis. Lactobacillus johnsonii La1 was administered (5.108 CFU/day) to C57 BL/6 mice for 7 days prior the infection with 107 trophozoites/mice with  Giardia intestinalis (strain GS, clone H7). After 7 and 14 days, samples of mesenteric lymph nodes (MLN), Peyer´s patches (PP), and spleen were collected. Ratio of CD4+/CD8+, mast cells, B cells and the expression of MHC-II were evaluated by flow cytometry. As compared with untreated controls, administration of Lactobacillus johnsonii La1 for 7 days prior the infection with Giardia, leads to a decrease in CD4+/CD8+ ratio in PP (P=0.02). This results seems to be related to a diminution of the ratio of CD4+ cells. In PP, an increase in the expression of MHC-II was observed in both B220+ (B cells) and B220- cells. In contrast, in MLN, there was a decrease in the expression of MHC-II in B220+ cells due to the probiotic treatment. Seven days after infection with the parasite, ratios of CD4+ and CD8+ cells showed no changes as compared with the infected group without probiotic treatment. In the same time-point, a decrease in the ratio of CD4+ cells in MLN was observed. Concerning the expression of MHC-II and ratio of mast cells, no differences were detected between the probiotic and placebo groups. Our results show that probiotic administration modifies the ratio of relevant immune cells in a murine model of giardiasis. Higher differences were found at day 7 of probiotic treatment and prior the infection with the parasite. Probiotic treatment increases expression of MHC-II in PP thus indicating a modification of antigen presentation that could improve immune response against the parasite. Since no changes were found in MLN, it can be hypothesize that there is no antigen translocation from the intestinal mucosa. Presented results could explain, at least partially, the decrease in the infection rates observed in a murine model of giardiasis treated with Lactobacillus johnsonii La1. Thus, we showed the capacity of Lactobacillus johnsonii La1 to modify the distribution of different cellular populations preparing the host in a better manner to deal with this parasitic infection.