Therapeutic effects of recombinant SPLUNC1 on Mycoplasma ovipneumoniae-infected Argali hybrid sheep

Abstract

Clinical therapeutic and immunoregulatory effects of recombinant SPLUNC1 protein (rSPLUNC1) were evaluated in Mycoplasma ovipneumoniae (Mo)-infected Argali hybrid sheep (AHS). Group A contained six Bashibai sheep (BS) and groups B–D contained six AHS each. All sheep were manually infected with Mo. Five days post-infection, rSPLUNC1 from BS and AHS was injected intratracheally into group C and D animals; physiological saline was administered to groups A and B. Serum IL-5, IL-6, and IL-9 were quantified by ELISA. After sacrificing the sheep, lung tissues were extracted for pathological examination. The qPCR was used to quantify Mo load in the lungs and evaluate therapeutic efficacy. Serum IL-5, IL-6, and IL-9 concentrations increased during early infection stages in all groups but were significantly lower in groups A, C, and D than in group B on days 14 and 21. On day 21, IL-5 concentrations were lower in group A than in groups C and D. IL-6 concentration in groups A, C, and D was significantly lower than that in group B, and that in groups C and D was significantly lower than that in group A. Mean mycoplasma pneumonia histopathology scores were significantly lower in groups C and D than in group B, and Mo load in group C and D lung tissue decreased significantly compared to that in group B. Intratracheal injection of rSPLUNC1 into Mo-infected sheep decreased the cytokine levels and alleviated clinical symptoms with no mortality. rSPLUNC1 had significant therapeutic effects on Mo-infected AHS and can regulate pro-inflammatory cytokines.