Monoclonal antibody targeting complement C9 binding domain of Trichinella spiralis paramyosin impairs the viability of Trichinella infective larvae in the presence of complement

BACKGROUND: Trichinella spiralis expresses paramyosin (Ts-Pmy) not only as a structural protein but also as an immunomodulator that inhibits host complement as a survival strategy. Previous studies demonstrated that Ts-Pmy bound to complement components C8 and C9 and inhibited the polymerization of C9 during the formation of the membrane attack complex (MAC). The C9 binding domain of Ts-Pmy was identified within 14 amino acid residues at the C-terminus of Ts-Pmy. The production of a monoclonal antibody that specifically targets the C9 binding site is necessary for further studies of Ts-Pmy function and may be used as a therapeutic agent for T. spiralis infection. METHODS: In this study, a monoclonal antibody against the complement C9 binding domain of Ts-Pmy (mAb 9G3) was produced using hybridoma technology. The binding activity of the mAb produced for recombinant or native Ts-Pmy and the blockade of Ts-Pmy binding to C9 by the mAb were assessed by Western blot analysis. The effect of the mAb on the viability of T. spiralis was observed by co-incubation of T. spiralis with mAb 9G3 in the presence of complement in vitro and by passive transfer of the mAb into naive mice following T. spiralis larval challenge. RESULTS: mAb 9G3 was successfully produced against the C9 binding domain of Ts-Pmy and bound specifically not only to recombinant Ts-Pmy but also to native Ts-Pmy expressed in different stages of T. spiralis, including adult worms, newborn larvae and muscle larvae. The binding of mAb 9G3 to Ts-Pmy efficiently blocked the binding of Ts-Pmy to human complement C9, resulting in a significant increase in the complement-mediated killing of newborn larvae in vitro and reduced infectivity of T. spiralis larvae in mice passively transferred with the mAb. CONCLUSIONS: mAb 9G3 is a specific antibody that binds to the C9 binding domain of Ts-Pmy and interferes with Ts-Pmy’s complement-binding activity. Therefore, this mAb is a protective antibody that has potential as a preventive and therapeutic agent for T. spiralis infection.