<em>Fasciola gigantica</em> Recombinant Abelson Tyrosine Protein Kinase (r<em>Fg</em>Abl) Regulates Various Functions of Buffalo Peripheral Blood Mononuclear Cells

Abstract

<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.