Fasciola gigantica Recombinant Abelson Tyrosine Protein Kinase (rFgAbl) Regulates Various Functions of Buffalo Peripheral Blood Mononuclear Cells

<i>Fasciola gigantica</i> can modulate host immune mechanisms through excretory-secretory products (ESP). As one of the components of ESP, it is unknown whether Abelson tyrosine protein kinase (Abl) is involved in parasite-host immune interaction. To investigate the immunoregulatory function of Abl in <i>Fasciola gigantica</i>, we cloned and expressed the <i>Fasciola</i> gigantica Abl protein and assessed its effect on specific immune functions of buffalo peripheral blood mononuclear cells (PBMCs). Recombinant <i>F. gigantica</i> Abelson tyrosine protein kinase (r<i>Fg</i>Abl) was expressed in <i>Escherichia coli</i>. Western blot analysis was performed to assess the reactivity of anti-r<i>Fg</i>Abl antibodies with r<i>Fg</i>Abl, serum from <i>F. gigantica</i>-infected buffalo, and excretion and secretion products of <i>F. gigantica</i>. Immunohistochemical analysis was conducted to determine the localization of <i>Fg</i>Abl in tissues from larval stages and adult worms of <i>F. gigantica</i>. Furthermore, immunofluorescence analysis was utilized to evaluate the binding ability of the r<i>Fg</i>Abl protein to buffalo peripheral blood mononuclear cells (PBMCs), as well as to investigate the effects of varying concentrations of r<i>Fg</i>Abl protein (5, 10, 20, 40, and 80 μg/mL) on the functional responses of PBMCs. Anti-r<i>Fg</i>Abl antibodies specifically recognize r<i>Fg</i>Abl, serum from buffalo infected with <i>F. gigantica</i>, and <i>Fg</i>ESP. r<i>Fg</i>Abl is localized in the cecum and capsule of juvenile worms, as well as in the testis and viellaria of adult worms. Additionally, r<i>Fg</i>Abl enhances cell proliferation, migration, nitric oxide (NO) production, and phagocytosis, while also increasing the transcription levels of cytokines (IFN-γ, IL-12, TNF-α, IL-4, IL-10, and TGF-β). The results indicate that r<i>Fg</i>Abl can influence the immune function of PBMCs. Further investigation into the immunomodulatory properties of the r<i>Fg</i>Abl protein will enhance our understanding of the immune interaction mechanisms between trematodes and their hosts.