Fasciola gigantica tegumental calcium-binding EF-hand protein 4 exerts immunomodulatory effects on goat monocytes

Abstract

Background The liver fluke Fasciola gigantica secretes excretory-secretory proteins during infection to mediate its interaction with the host. In this study, we investigated the immunomodulatory effects of a recombinant tegumental calcium-binding EF-hand protein 4 of F. gigantica (rFg-CaBP4) on goat monocytes. Methods The rFg-CaBP4 protein was induced and purified by affinity chromatography. The immunogenic reaction of rFg-CaBP4 against specific antibodies was detected through western blot analysis. The binding of rFg-CaBP4 on surface of goat monocytes was visualized by immunofluorescence assay. The localization of CaBP4 within adult fluke structure was detected by immunohistochemical analysis. The cytokine transcription levels in response to rFg-CaBP4 were examined using ABI 7500 real-time PCR system. The expression of the major histocompatibility complex (MHC) class-II molecule (MHC-II) in response to rFg-CaBP4 protein was analyzed using Flow cytometry. Results The isopropyl-ß-D-thiogalactopyranoside-induced rFg-CaBP4 protein reacted with rat sera containing anti-rFg-CaBP4 polyclonal antibodies in a western blot analysis. The adhesion of rFg-CaBP4 to monocytes was visualized by immunofluorescence and laser scanning confocal microscopy. Immunohistochemical analysis localized native CaBP4 to the oral sucker, pharynx, genital pore, acetabulum and tegument of adult F. gigantica. Co-incubation of rFg-CaBP4 with concanavalin A-stimulated monocytes increased the transcription levels of interleukin (IL)-2, IL-4, interferon gamma and transforming growth factor-β. However, a reduction in the expression of IL-10 and no change in the expression of tumor necrosis factor-α were detected. Additionally, rFg-CaBP4-treated monocytes exhibited a marked increase in the expression of the major histocompatibility complex (MHC) class-II molecule (MHC-II) and a decrease in MHC-I expression, in a dose-dependent manner. Conclusions These findings provide additional evidence that calcium-binding EF-hand proteins play roles in host-parasite interaction. Further characterization of the immunomodulatory role of rFg-CaBP4 should expand our understanding of the strategies used by F. gigantica to evade the host immune responses. Graphical abstract

Proteomics coupled with in vitro model to study the early crosstalk occurring between newly excysted juveniles of Fasciola hepatica and host intestinal cells

“…hepatica GST (also found here overexpressed in the somatic extract of FhNEJ) has shown anti-inflammatory properties [ 54 ], and F . gigantica CABP4 stimulated IL-2 and IFN-γ Th1-type cytokines and reduced IL-10 (Th2) expression levels by activated goat monocytes [ 55 ]. As observed in other trematode species (e.g., schistosomes [ 56 ]), these proteins could play a role in the first steps of infection by protecting FhNEJ from inflammatory responses as well as eliciting a transient Th1-type immune response during early infection.…”

Fasciola gigantica vaccine construct: an in silico approach towards identification and design of a multi-epitope subunit vaccine using calcium binding EF-hand proteins

“…These findings substantiated the claims that calcium-binding EF-hand proteins play important roles in host-parasite interaction. To enhance our understanding of the strategies used by F. gigantica in evading host immune responses, characterization of the immunomodulatory role of rFg-CaBP4 should be undertaken [ 53 ].…”