Cloning and characterization of thioredoxin peroxidases from Trichinella spiralis

The intracellular parasitic nematode, Trichinella spiralis, can initiate a high level of oxidative stress, especially during rapid growth and generative propagation phases. Thioredoxin peroxidases (TPXs) protect helminths against oxidative stress, but none has been identified in T. spiralis. Here, 3 members of the TPX family were cloned from T. spiralis muscle larvae (ML). The lengths of TsTPX ORFs were 747bp, 588bp and 594bp, respectively, and the deduced proteins predicted to contain AhpC-TSA and 1-cys Prx_C domains. Interestingly, qRT-PCR data showed that TsTPX genes were expressed in all three developmental stages of T. spiralis. The TsTPX2 and TsTPX3 genes were up-regulated in day 3 adults (Ad3) compared with newborn larvae (NBL) and ML (P<0.05); expression levels of the TsTPX1 gene in ML were higher compared with Ad3 and NBL amounts (P<0.05). After prokaryotic expression, the reactivity of rTsTPX proteins was assessed by Western-blotting: only rTsTPX1 was specifically recognized by T. spiralis infection sera from pigs. Enzyme catalytic experiments showed that rTsTPX proteins could deoxidize H₂O₂ in the presence of DTT, with the catalytic ability increasing with protein concentration and time.