T Regulatory Cell Responses to Immunization with a Soluble Egg Antigen in Schistosoma mansoni-Infected Mice

The aim of the study is to characterize the phenotypes of CD4+ CD25+ T regulatory cells within the liver granulomas and association with both Foxp-3 gene expression and splenic cytokines. Naive C57BL/6 mice were intravenously injected with multiple doses of the soluble egg antigen (SEA) 7 days before cercarial infection. The immunized and infected control groups were sacrificed 8 and 16 weeks post-infection (PI). Histopathology, parasitological parameters, splenic phenotypes for T regulatory cells, the FOXP-3 expression in hepatic granuloma using real-time PCR, and the associated splenic cytokines were studied. Histopathological examination of the liver revealed remarkable increase in degenerated ova within hepatic granuloma which decreased in diameter at weeks 8 and 16 PI (P<0.01). The percentage of T regulatory cells (CD4+ CD25+) increased significantly (P<0.01) in the immunized group compared to the infected control at weeks 8 and 16 PI. The FOXP-3 expression in hepatic granulomas increased from 10 at week 8 to 30 fold at week 16 PI in the infected control group. However, its expression in the immunized group showed an increase from 30 at week 8 to 70 fold at week 16 PI. The splenic cytokine levels of pro-inflammatory cytokines, IFN-gamma, IL-4, and TNF-alpha, showed significant decreases (P<0.05) compared to the infected control group. In conclusion, the magnitude and phenotype of the egg-induced effects on T helper responses were found to be controlled by a parallel response within the T regulatory population which provides protection in worm parasite-induced immunopathology.

Protective Role of Purified Cysteine Proteinases against Fasciola gigantica Infection in Experimental Animals

Fascioliasis is one of the public health problems in the world. Cysteine proteinases (CP) released by Fasciola gigantica play a key role in parasite feeding, migration through host tissues, and in immune evasion. There has been some evidence from several parasite systems that proteinases might have potential as protective antigens against parasitic infections. Cysteine proteinases were purified and tested in vaccine trials of sheep infected with the liver fluke. Multiple doses (2 mg of CP in Freund's adjuvant followed by 3 booster doses 1 mg each at 4 week intervals) were injected intramuscularly into sheep 1 week prior to infect orally with 300 F. gigantica metacercariae. All the sheep were humanely slaughtered 12 weeks after the first immunization. Changes in the worm burden, ova count, and humoral and cellular responses were evaluated. Significant reduction was observed in the worm burden (56.9%), bile egg count (70.7%), and fecel egg count (75.2%). Immunization with CP was also found to be associated with increases of total IgG, IgG1, and IgG2 (P<0.05). Data showed that the serum cytokine levels of pro-inflammatory cytokines, IL-12, IFN-gamma, and TNF-alpha, revealed significant decreases (P<0.05). However, the anti-inflammatory cytokine levels, IL-10, TGF-beta, and IL-6, showed significant increases (P<0.05). In conclusion, it has been found that CP released by F. gigantica are highly important candidates for a vaccine antigen because of their role in the fluke biology and host-parasite relationships.

Immunolocalization of B7-z and CD28 costimulatory molecules in schistosomal soluble egg antigra -induced granulomatous hyporesponsiveness

In this work, the changes in expression of the costimulatory molecules [B7-2/CD28] were studied at 6, 8 and 16 weeks p.i. on immuno-inflammatory cells of livers in S. mansoni-infected and SEA-sensitized mice model by immunohistochemistry. Both B7-2 and CD28 were only expressed positively at 6 weeks p.i. in both groups with significantly lower cell counts in SEA group compared to infected control group. The distribution of B7-2 was concentrated towards the periphery of the granulomas, while that of CD28 was homogeneously distributed all through the granulomas. The present data showed that repeated i.v. injection of SEA before infection resulted in the drop of B7-2/CD28 to lower levels than its expected natural course. This drop may explain the decrease of host immunopathological reaction to S. mansoni eggs in the SEA group than infected control group