Abstract
BackgroundParamyosin is a thick myofibrillar protein found exclusively in invertebrates. Evidence suggested that paramyosin from helminths serves not only as a structural protein but also as an immunomodulatory agent. We previously reported that recombinant Trichinella spiralis paramyosin (Ts-Pmy) elicited a partial protective immunity in mice. In this study, the ability of Ts-Pmy to bind host complement components and protect against host complement attack was investigated.Methods and FindingsIn this study, the transcriptional and protein expression levels of Ts-Pmy were determined in T. spiralis newborn larva (NBL), muscle larva (ML) and adult worm developmental stages by RT-PCR and western blot analysis. Expression of Ts-Pmy at the outer membrane was observed in NBL and adult worms using immunogold electron microscopy and immunofluorescence staining. Functional analysis revealed that recombinant Ts-Pmy(rTs-Pmy) strongly bound to complement components C8 and C9 and inhibited the polymerization of C9 during the formation of the membrane attack complex (MAC). rTs-Pmy also inhibited the lysis of rabbit erythrocytes (ER) elicited by an alternative pathway-activated complement from guinea pig serum. Inhibition of native Ts-Pmy on the surface of NBL with a specific antiserum reduced larvae viability when under the attack of complement in vitro. In vivo passive transfer of anti-Ts-Pmy antiserum and complement-treated larvae into mice also significantly reduced the number of larvae that developed to ML.ConclusionThese studies suggest that the outer membrane form of T. spiralis paramyosin plays an important role in the evasion of the host complement attack.
Highlights
Trichinellosis is one of the common parasitic zoonoses and is a serious public threat in both developing and developed countries [1,2,3,4,5,6]
These studies suggest that the outer membrane form of T. spiralis paramyosin plays an important role in the evasion of the host complement attack
The results show that Trichinella spiralis paramyosin (Ts-Pmy) is expressed in all three developmental stages (ML, adult worm and newborn larvae (NBL)) of T. spiralis at the level of both mRNA transcription and protein expression
Summary
Trichinellosis is one of the common parasitic zoonoses and is a serious public threat in both developing and developed countries [1,2,3,4,5,6]. Trichinella spiralis (T. spiralis) infection is initiated by the consumption of meat contaminated with infective muscle larvae (ML). Five days post-infection, gravid females begin to produce newborn larvae (NBL), which penetrate the intestinal mucosa and enter the lymphatic vessels and bloodstream [7]. NBL travel through capillaries to various organs and invade the muscles, where they form cysts. During the life cycle of T. spiralis in the host, all developmental stages are exposed to host complement, which is the first line of defense against pathogenic organisms and is a functional bridge between the innate and adaptive immune responses [8]. Paramyosin is a thick myofibrillar protein found exclusively in invertebrates. We previously reported that recombinant Trichinella spiralis paramyosin (Ts-Pmy) elicited a partial protective immunity in mice. The ability of Ts-Pmy to bind host complement components and protect against host complement attack was investigated
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