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- Title
Molecular characterization of a Trichinella spiralis aspartic protease and its facilitation role in larval invasion of host intestinal epithelial cells.
- Authors
Xu, Jia; Liu, Ruo Dan; Bai, Sheng Jie; Hao, Hui Nan; Yue, Wen Wen; Xu, Yang Xiu Yue; Long, Shao Rong; Cui, Jing; Wang, Zhong Quan
- Abstract
Background: T. spiralis aspartic protease has been identified in excretion/secretion (ES) proteins, but its roles in larval invasion are unclear. The aim of this study was to characterize T. spiralis aspartic protease-2 (TsASP2) and assess its roles in T. spiralis invasion into intestinal epithelial cells (IECs) using RNAi. Methodology/Principal findings: Recombinant TsASP2 (rTsASP2) was expressed and purified. The native TsASP2 of 43 kDa was recognized by anti-rTsASP2 serum in all worm stages except newborn larvae (NBL), and qPCR indicated that TsASP2 transcription was highest at the stage of intestinal infective larvae (IIL). IFA results confirmed that TsASP2 was located in the hindgut, midgut and muscle cells of muscle larvae (ML) and IIL and intrauterine embryos of the female adult worm (AW), but not in NBL. rTsASP2 cleaved several host proteins (human hemoglobin (Hb), mouse Hb, collagen and IgM). The proteolytic activity of rTsASP2 was host-specific, as it hydrolyzed mouse Hb more efficiently than human Hb. The enzymatic activity of rTsASP2 was significantly inhibited by pepstatin A. The expression levels of TsASP2 mRNA and protein were significantly suppressed by RNAi with 5 μM TsASP2-specific siRNA. Native aspartic protease activity in ML crude proteins was reduced to 54.82% after transfection with siRNA. Larval invasion of IECs was promoted by rTsASP2 and inhibited by anti-rTsASP2 serum and siRNA. Furthermore, cell monolayer damage due to larval invasion was obviously alleviated when siRNA-treated larvae were used. The adult worm burden, length of adult worms and female fecundity were clearly reduced in mice challenged using siRNA-treated ML relative to the PBS group, Conclusions: rTsASP2 possesses the enzymatic activity of native aspartic protease and facilitates T. spiralis invasion of host IECs. Author summary: Trichinellosis has been regarded as a re-emerging or emerging disease, and it is distributed worldwide. Studies investigating T. spiralis ES protein are beneficial to explore potential molecular targets for anti-T. spiralis vaccines. The functions of aspartic protease have been studied in other parasites and demonstrated to be crucial for their parasitism in the host. However, the functions of T. spiralis aspartic protease have not been reported. Here, we expressed and purified a T. spiralis aspartic protease-2 (TsASP2). Our results showed that TsASP2 was expressed in all T. spiralis developmental stages more than NBL and located in the hindgut, midgut and muscle cells of ML and IIL, as well as in areas surrounding embryos within the female uterus. The rTsASP2 possessed aspartic protease activity and functioned to cleave hemoglobin, collagen and IgM. Silencing of the TsASP2 gene could significantly decrease the aspartic protease activity in muscle larva crude proteins, larval invasion of IECs and worm development in the host. We conclude that TsASP2 plays an important role in T. spiralis penetration into host intestinal epithelial cells and could be a candidate vaccine target molecule against T. spiralis infection.
- Subjects
TRICHINELLA spiralis; EPITHELIAL cells; MUSCLE cells; GENE silencing; TRICHINOSIS
- Publication
PLoS Neglected Tropical Diseases, 2020, Vol 14, Issue 4, p1
- ISSN
1935-2727
- Publication type
Article
- DOI
10.1371/journal.pntd.0008269