Fasciola hepatica induces Foxp3 T cell, proinflammatory and regulatory cytokine overexpression in liver from infected sheep during early stages of infection

Abstract

The expression of T regulatory cells (Foxp3), regulatory (interleukin [IL]-10 and transforming growth factor beta [TGF-β]) and proinflammatory (tumor necrosis factor alpha [TNF-α] and interleukin [IL]-1β) cytokines was quantified using real time polymerase chain reaction (qRT-PCR) in the liver of sheep during early stages of infection with Fasciola hepatica (1, 3, 9, and 18 days post-infection [dpi]). Portal fibrosis was also evaluated by Masson’s trichrome stain as well as the number of Foxp3+ cells by immunohistochemistry. Animals were divided into three groups: (a) group 1 was immunized with recombinant cathepsin L1 from F. hepatica (FhCL1) in Montanide adjuvant and infected; (b) group 2 was uniquely infected with F. hepatica; and (c) group 3 was the control group, unimmunized and uninfected. An overexpression of regulatory cytokines of groups 1 and 2 was found in all time points tested in comparison with group 3, particularly at 18 dpi. A significant increase of the number of Foxp3+ lymphocytes in groups 1 and 2 was found at 9 and 18 dpi relative to group 3. A progressive increase in portal fibrosis was found in groups 1 and 2 in comparison with group 3. In this regard, group 1 showed smaller areas of fibrosis than group 2. There was a significant positive correlation between Foxp3 and IL-10 expression (by immunohistochemistry and qRT-PCR) just as between portal fibrosis and TGF-β gene expression. The expression of proinflammatory cytokines increased gradually during the experience. These findings suggest the induction of a regulatory phenotype by the parasite that would allow its survival at early stages of the disease when it is more vulnerable.

Identification of reference genes for real-time PCR cytokine gene expression studies in sheep experimentally infected with Fasciola hepatica

“…Increased expression of regulatory cytokines supports a role for Tregs in the generation of a suppressive environment which is favourable to parasite persistence. Furthermore, TGF-β is an essential cytokine in the development of fibrosis, as demonstrated in our previous study 33 .…”

“…33 R 5′-AACGTGGGCTACCGGCTTGTTATTTGAGGC-3′73.6(99.56) IL-1β NM_001009465.2F 5′-GAAGCTGAGGAGCCGTGCCTACGAACA-3′68.81851.001Pacheco et al . 33 R 5′-CCAGCACCAGGGATTTTTGCTCTCTGTCC-3′69.0(99.85) FoxP3 NM_001144947.1F 5′-GCCCATCTGGCTGGGAAGATGGCCCAAACC-3′76.51660.991Pacheco et al . 33 R 5′- AGAGGTGCCTCCGCACGGCAAACAGG-3′76.2(99.16) IL-10 NM_001009327.1F 5′-TCAGCCGTGCTCTGTTGCCTGGTCTTCC-3′73.81240.999Pacheco et al .…”

“…5). An increase in IL-10 expression has been seen to be associated with the expansion of FoxP3 + Tregs 31,33 . The expression of TGF-β showed a gradual increase throughout the time course of the experiment.…”

Histochemical and Immunohistochemical Characterizations of Hepatic Trematodiasis in Odontocetes

“…In the three species analyzed, while Foxp3-positive cells were found in the lesion sites of all individuals, the numbers were generally small. Experimental infection of F. hepatica in sheep Ovis aries have demonstrated that the number of regulatory T cells is significantly higher in the early stages of infection and decrease as the infection progresses, which has been speculated to be due to the parasite inducing a modulation in the host response to evade its immune system ( 48 ). The results of immunohistochemistry for Foxp3 in the analyzed cetaceans also suggested a chronic stage of the disease, which may be indicating a similar evading system in the trematodes of cetaceans to that of F. hepatica .…”

A Vaccine Based on Kunitz-Type Molecule Confers Protection Against Fasciola hepatica Challenge by Inducing IFN-γ and Antibody Immune Responses Through IL-17A Production

“…These complex parasite-derived molecules can interact with the immune system and inhibit the Th1-driven protective pro-inflammatory responses through the induction of M2 macrophages (9), mast cells (10), and Th2-type responses (11,12), and promote regulatory T (Treg) cell development (6,13). Thus, the induction of an ineffective immune response against this parasite allows the development of a chronic infection.…”