Characterization and functional analysis of Trichinella spiralis Nudix hydrolase

Trichinella spiralis Nudix hydrolase (TsNd) was identified by screening a T7 phage display cDNA library from T. spiralis intestinal infective larvae (IIL), and vaccination of mice with recombinant TsNd protein (rTsNd) or TsNd DNA vaccine produced a partial protective immunity. The aim of this study was to identify the characteristics and biological functions of TsNd in the process of invasion and development of T. spiralis larvae. Transcription and expression of TsNd gene at all developmental stages of T. spiralis were observed by qPCR and immunofluorescent test (IFT). The rTsNd had the Nd enzymatic activity to dGTP, NAD, NADP and CoA. Its kinetic properties on the preferred substrate dGTP were calculated, and the Vmax, Km, and kcat/Km values at pH 8.0 were 3.19 μM min(-1) μg(-1), 370 μM, and 144 s(-1) M(-1), respectively, in reaction matrix containing 5 mM Zn(2+) and 2 mM DTT. The rTsNd was active from 25 °C to 50 °C, with optimal activity at 37 °C. rTsNd was able to bind specifically to mouse intestinal epithelial cells (IECs) and promoted the larval invasion of IECs, whereas anti-rTsNd antibodies inhibited the larval invasion of IECs in a dose-dependent manner. Anti-rTsNd antibodies could kill T. spiralis infective larvae by an ADCC-mediated mechanism. Our results showed that the rTsNd protein was able to interact with host IECs, had the Nudix hydrolasing activity and the enzymatic activity appeared to be essential indispensable for the T. spiralis larval invasion, development and survival in host.