Monoassociation with Lactobacillus acidophilus UFV-H2b20 stimulates the immune defense mechanisms of germfree mice

Abstract

Probiotics are formulations containing live microorganisms or microbial stimulants that have some beneficial influence on the maintenance of a balanced intestinal microbiota and on the resistance to infections. The search for probiotics to be used in prevention or treatment of enteric infections, as an alternative to antibiotic therapy, has gained significant impulse in the last few years. Several studies have demonstrated the beneficial effects of lactic acid bacteria in controlling infection by intestinal pathogens and in boosting the hosts nonspecific immune response. Here, we studied the use of Lactobacillus acidophilus UFV-H2b20, a lactic acid bacterium isolated from a human newborn from Viçosa, Minas Gerais, Brazil, as a probiotic. A suspension containing 10 8 cells of Lactobacillus acidophilus UFV-H2b20 was inoculated into groups of at least five conventional and germfree Swiss mice to determine its capacity to stimulate the host mononuclear phagocytic activity. We demonstrate that this strain can survive the stressing conditions of the intestinal tract in vivo. Moreover, the monoassociation of germfree mice with this strain for seven days improved the hosts macrophage phagocytic capacity, as demonstrated by the clearance of a Gram-negative bacterium inoculated intravenously. Monoassociated mice showed an undetectable number of circulating E. coli, while 0.1% of the original inoculum was still present in germfree animals. Mice treated with viable or heat-killed Lactobacillus acidophilus UFV-H2b20 presented similarly improved clearance capacity when compared with germfree controls. In addition, monoassociated mice had twice the amount of Kupffer cells, which are responsible for the clearance of circulating bacteria, compared to germfree controls. These results suggest that the L. acidophilus strain used here stimulates a nonspecific immune response and is a strong candidate to be used as a probiotic.

Lactobacillus delbrueckii UFV-H2b20 induces type 1 cytokine production by mouse cells in vitro and in vivo

“…After 7 days of monoassociation, mice were challenged with a Gram-negative bacterium injected systemically. The capacity to clear this bacterium from the circulation was previously shown to be improved in monoassociated mice when compared with germ-free and conventional mice (13). Here, we tested the production of cytokines in response to infection with E. coli.…”

“…The success of monoassociation was checked by investigating the number of microorganisms per gram feces. Monoassociated mice were used 7 days after the original inoculum since L. delbrueckii numbers in the gut were stable starting 2 days after the inoculum (13 …”

“…Intravenous challenge with E. coli was performed as described previously (13). Briefly, germ-free or monoassociated mice were challenged with 2 x 10 7 E. coli in the tail vein.…”

“…This strain was isolated from feces of a newborn child at Universidade Federal de Viçosa (Viçosa, MG, Brazil). This strain resists the stressing conditions of the gastrointestinal tract both in vitro (12) and in vivo (13). Further PCR analysis followed by sequencing classified this strain as L. delbrueckii var.…”

“…We have shown that this strain of L. delbrueckii var. bulgaricus stimulates the phagocytic capacity of macrophages in monoassociated Swiss mice, as demonstrated by clearance of a Gram-negative bacterium inoculated intravenously (13). However, the effect that L. delbrueckii might have on cytokine production in response to a systemic infection was not determined.…”