Background and the purpose of the study: Selenium enriched Lactobacillus has been reported as an immunostimulatory agent which can be used to increase the life span of cancer bearing animals. Lactic acid bacteria can reduce selenium ions to elemental selenium nanoparticles (SeNPs) and deposit them in intracellular spaces. In this strategy two known immunostimulators, lactic acid bacteria (LAB) and SeNPs, are concomitantly administered for enhancing of immune responses in cancer bearing mice. Methods: Forty five female inbred BALB/c mice were divided into three groups of tests and control, each containing 15 mice. Test mice were orally administered with SeNP-enriched Lactobacillus brevis or Lactobacillus brevis alone for 3 weeks before tumor induction. After that the administration was followed in three cycles of seven days on/three days off. Control group received phosphate buffer saline (PBS) at same condition. During the study the tumor growth was monitored using caliper method. At the end of study the spleen cell culture was carried out for both NK cytotoxicity assay and cytokines measurement. Delayed type hypersensitivity (DTH) responses were also assayed after 72h of tumor antigen recall. Serum lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) levels were measured, the livers of mice were removed and prepared for histopathological analysis. Results: High level of IFN-γ and IL-17 besides the significant raised in NK cytotoxicity and DTH responses were observed in SeNP-enriched L. brevis administered mice and the extended life span and decrease in the tumor metastasis to liver were also recorded in this group compared to the control mice or L.brevis alone administered mice. Conclusion: Our results suggested that the better prognosis could be achieved by oral administration of SeNP-enriched L. brevis in highly metastatic breast cancer mice model.

Background: Lactic acid bacteria are considered important probiotics for prevention of some infections. The aim of this work was to investigate the effect of selenium dioxide on the antifungal activity of Lactobacillus plantarum and L. johnsonii against Candida albicans. Methods: Lactobacillus plantarum and L. johnsonii cells, grown in the presence and absence of selenium dioxide, and their cell-free spent culture media were tested for antifungal activity against C. albicans ATCC 14053 by a hole-plate diffusion method and a time-kill assay. Results: Both L. plantarum and L. johnsonii reduced selenium dioxide to cell-associated elemental selenium nanoparticles. The cell-free spent culture media, from both Lactobacillus species that had been grown with selenium dioxide for 48 h, showed enhanced antifungal activity against C. albicans. Enhanced antifungal activity of cell biomass against C. albicans was also observed in cultures grown with selenium dioxide. Conclusions: Selenium dioxide-treated Lactobacillus spp. or their cell-free spent broth inhibited the growth of C. albicans and should be investigated for possible use in anti-Candida probiotic formulations in future.

The immunomodulatory effects of lactic acid bacteria have been demonstrated previously. In this study, a Lactobacillus plantarum strain was selected and enriched with selenium nanoparticles for use as a new immunomodulating agent in a breast cancer murine model. 30 female inbred BALB/c mice were equally divided into a test group and a control group. For 2 weeks prior to tumor induction, each mouse received a daily oral administration of 2.5×10⁸ CFU/ml of L. plantarum enriched with selenium nanoparticles (SeNPs), and then 1×10⁶ 4T1 cells were injected subcutaneously. After tumor induction, daily SeNP administration was repeated for 3 cycles of 7 days on/3 days off. Immunological parameters such as levels of cytokines, NK cell activity, tumor growth, and mouse survival were evaluated. The production of the pro-inflammatory cytokines IFN-γ, TNF-α, and IL-2 in spleen cell cultures was increased in test mice administered SeNP-enriched L. plantarum. The test mice also showed significant increases in NK cell activity. The tumor volumes of treated mice were decreased and their survival rate notably increased when compared to mice that received L. plantarum alone or control mice. Administration of SeNP-enriched L. plantarum can induce an efficient immune response through the elevation of the pro-inflammatory cytokines IFN-γ, TNF-α and IL-2 levels and increased NK cell activity. Therefore, this treatment may result in better cancer prognosis.

Lactic acid bacteria can affect the maturation of immune cells and their products not only in the gut but also on the systemic immune organs such as lymph nodes and spleen. In the present work, we studied the effects of oral administration ofLactobacillus acidophiluson the immune responses of BALB/c mice bearing transplanted breast tumour. Two groups of female inbred BALB/c mice, each containing nine mice as test and control, were used. TheL. acidophilusATCC4356 strain was inoculated in DeMan–Rogosa–Sharpe broth and cultivated for 24 h at 37°C. Then, it was collected by centrifugation, and was washed and suspended in PBS. Afterwards, 0·5 ml/d of this suspension, which contained 2·7 × 10⁸ colony forming units/ml of bacteria, was orally administered to the mice by gavage, 14 d before tumour transplantation and 30 d after that with 3-d intervals. Similar to the test mice, the control mice received an equal volume of PBS. The results showed that oral administration ofL. acidophilusincreased the production of IL-12 (P < 0·05) and decreased the level of transforming growth factor β (P = 0·05) in the splenocyte culture. Moreover, the growth rate of tumour in the test mice decreased (P < 0·01), and the results of delayed-type hypersensitivity assay after 48 h were risen (P < 0·05) in comparison with the controls. Results suggest that daily consumption ofL. acidophiluscan improve the production of immunomodulatory cytokine IL-12 in the splenocyte culture, which was stimulated by tumour antigen in BALB/c mice bearing transplanted breast tumour. But further studies are needed to find out some other possible mechanisms of this effect.