Immunological features of LPS from Ochrobactrum intermedium on sheep experimentally infected with Fasciola hepatica

• We analyzed the immunological effects of the LPS from Ochrobactrum intermedium.
• The LPS improved the resistance against Fasciola hepatica on sheep.
• The LPS induced a Th 2 response, characterized by IL-4, IL-10 and TGF-β expression.
• Also, there was an important IgG1 production along the assay.
• There was a synergistic action between IL-10 and TGF-β in order to induce fibrosis.

The effects of the lipopolysaccharide (LPS) from Ochrobactrum intermedium in sheep with fasciolosis was reported previously, resulting in lower fecal egg counts and fluke burden. In the current study, we analyzed its immunological effects in two groups of sheep, treated (T) and controls (C). Fasciolosis induces a T helper (Th) type-2 response, characterized by IL-4 and IL-10 production; however, at the beginning of the infection, the IFN-γ production predominates (Th type-1 response). Although we did not find differences in IL-4 production or in the expression level of this gene in the hepatic lymph nodes, the expression level of IL-10 was higher (P < 0.05) in the T group at 4 wpi. The IFN-γ production was higher (P < 0.01) at 12 wpi as well as its level of expression at 4 wpi (P < 0.05) in the T group. We found a higher expression level of TGF-β at 4 wpi in the T group (P < 0.05), associated with the previous report of thicker fibrous tracks in a treated group. Immunoglobulin G1, related with a Th type-2 response, was higher (P < 0.01) in the T group at 4 and 12 wpi. In conclusion, the effects of LPS from O. intermedium could have resulted from a predominant Th type-2 immune response.