Recombinant Trichinella pseudospiralis Serine Protease Inhibitors Alter Macrophage Polarization In Vitro

Abstract

During parasite infection, serine protease inhibitors secreted by parasites play important roles in suppressing host defenses. However, the mechanism of immune regulation is unclear. In this study, a serpin gene from Trichinella pseudospiralis, named Tp-Serpin, was cloned and expressed, in order to reveal its role in the regulation of the host immune response in T. pseudospiralis infection. The results showed that Tp-Serpin encodes a 43 kDa protein that was recognized by serum from T. pseudospiralis infected mice at 60 days post-infection (dpi). Tp-Serpin was found to be expressed at all developmental stages of T. pseudospiralis. Inhibitory activity analysis showed that recombinant Tp-Serpin (rTp-Serpin) effectively inhibited the hydrolytic activity of porcine pancreatic elastase (elastase P), human neutrophil elastase (elastase H), and mouse mast cell protease-1, but showed little inhibitory for human neutrophil cathepsin G (cathepsin G). Furthermore, rTp-Serpin induced polarization of macrophages toward the alternatively activated phenotype (M2) alone by activation of the signal transducer and activator of transcription 3 signaling pathway, and inhibited lipopolysaccharide-induced classically activation (M1) in vitro. These data preliminarily demonstrate that Tp-Serpin may play an important role in the immunoregulation of T. pseudospiralis infection by activating the M2-polarized signaling pathway.

Fasciola hepatica serine protease inhibitor family (serpins): Purposely crafted for regulating host proteases

“…It is noteworthy that rFhSrp2 efficiently inhibits lysosomal serine proteases such cathepsin G and elastase, which are expressed predominantly in neutrophils and monocytes/macrophages [48] and play a central role during inflammatory responses by attracting monocytes [49]. Interestingly, a recombinant Trichinella pseudospiralis serpin with similar activity to rFhSrp2, Tp-Serpin, was demonstrated to induce alternative activated macrophages (M2 phenotype) in vitro [50]. It is possible that F. hepatica serpins are involved in the task of influencing host innate immune cells and contributing to the induction of Th2-polarised responses as the parasite crosses the intestine and makes its way to the liver.…”

The Immunological Properties of Recombinant Multi-Cystatin-Like Domain Protein From Trichinella Britovi Produced in Yeast

“…It obtained good results, suggesting that yeast-derived antigen is superior to bacteria-derived antigens, as the milder immunization conditions yielded a similar immunoprotective effect. It is important to mention that, as far as we are aware, all recombinant Trichinella antigens tested so far have been produced in a bacterial expression system and may not have been fully active (52–56). To better characterize the functions of the proteins of interest, a eukaryotic expression system, such as the yeast expression chosen in this study, should be used.…”

The Immune Protection Induced by a Serine Protease Inhibitor From the Foodborne Parasite Trichinella spiralis

“…A serpin from T. pseudospiralis (GenBank accession no. JF764789.1) have an important function for immunoregulating Trichinella infection through activating the M2-polarized signaling pathway ( Xu et al, 2017c ). Compared with the other Trichinella antigens, the TsSPI as a vaccine molecule might have the following advantages: the TsSPI is highly expressed in intestinal stage worms and widely distributed on the cuticle of the nematode, TsSPI could protect intestinal worms from host’s serine proteolysis; whereas high levels of anti-TsSPI antibody produced by rTsSPI immunization could neutralize the anti-proteolytic activity of the TsSPI and inhibit the parasite immune evasion ( Yan et al, 2005 ).…”