Adjuvant effect of LPS and killed Propionibacterium acnes on the development of experimental gastrointestinal nematode infestation in sheep.

Gastrointestinal helminthic infection is an important worldwide sheep disease. The emergence of anthelminthic resistance has led to drives to seek new means of therapeutic control of helminthiasis in sheep. Several data demonstrated the adjuvant effect of Propionibacterium acnes on resistance to infection. Herein, we evaluate the adjuvant effect of the commercial suspension containing LPS and P. acnes on experimental helminthiasis. Sheep received three doses of LPS and P. acnes commercial suspension or saline 0.9% (control group). Both groups received orally Haemonchus contortus infective larvae on day 0. Parasitological, haematological, lymphoproliferation analysis, IL-5 and IgE determination were made once a week until 35th day after infection. Our results revealed increase on packed cell volumes on day 14, in LPS + P. acnes treated group. On 21st and 35th days after infection in the same group occurred increase on circulating eosinophils and lymphocytes, and also in the lymphoproliferative response to mitogen. On 35th day, the faecal eggs peak in LPS + P. acnes treated group was significantly lower than control. A negative correlation between faecal eggs counts and circulating eosinophils in the immunostimulant treated group was also observed. Our findings suggest that LPS + P. acnes suspension can be used as a strategy to control helminthiasis in sheep.

Modulatory effect of killed Propionibacterium acnes and its purified soluble polysaccharide on peritoneal exudate cells from C57Bl/6 mice: major NKT cell recruitment and increased cytotoxicity.

Propionibacterium acnes has been described as a potent adjuvant to immune responses in vitro and in vivo. Presently, we analysed the modulation of peritoneal exudate cells (PEC) by heat-killed P. acnes or its purified soluble polysaccharide (PS), both injected intraperitoneally in C57Bl/6 mice, aiming at their recruitment and cytotoxicity. Both treatments induced an increase in macrophages, immature dendritic cells, B1a lymphocytes and NK1.1(+) CD3(+) cells. The bacterium caused a remarkable increase in a NK1.1(+) CD3(+) CD4(-) CD8(-) cells subpopulation, whereas the PS component seemed responsible for the recruitment of mainly macrophage cells. To assess P. acnes and PS adjuvant effect on PEC cytotoxicity we evaluated their in vitro effect on murine B16F10 melanoma cells. The effector cells from the heat-killed bacteria and PS-treated groups lysed melanoma cells in co-cultures with PEC. Mice genetically deficient in IFN-gamma, when stimulated with P. acnes or PS, had reduced PEC cytotoxicity, and the cytotoxic effect was completely abrogated in PEC from iNOS(-/-) mice. The tumoricidal activity of PEC from P. acnes-treated mice was mediated by macrophages and NKT cells stimulated with IL-12. In PS-treated mice the cytotoxicity was mediated mainly by macrophages. Moreover, both treatments increased IL-4 and IFN-gamma production by NKT cells. In conclusion, we show that P. acnes act mainly by recruiting and activating NKT double-negative cells in PEC, which were shown to be tumoricidal in vitro when induced by IL-12. Macrophages induced by both P. acnes and PS have their antitumour effect dependent on NO production.