During early
infection with Trichinella spiralis, host neutrophils destroy newborn larvae migrating in the bloodstream, preventing
infection. However, parasites secrete various immunomodulatory molecules to escape the host's defense mechanisms, allowing them to infect the host and live for long periods. T. spiralis secretes
serine protease inhibitors (TsSERPs), which are key inhibitory molecules that regulate
serine proteases involved in digestion and
inflammation. However, the modulatory roles of TsSERP in the inhibition of neutrophil
serine proteases (NSPs) and neutrophil functions are unknown. Therefore, the immunomodulatory properties of recombinant TsSERP1 (rTsSERP1) on NSPs and neutrophil functions were investigated in this study. rTsSERP1 preferentially inhibited human
neutrophil elastase (hNE). In addition, incubation of rTsSERP1 with fMLP-induced neutrophils impaired their phagocytic ability. The formation of neutrophil extracellular traps (NETs) was activated with
phorbol myristate acetate (PMA), and NETs were dramatically reduced when treated with rTsSERP1. Furthermore, rTsSERP1 suppressed the production of proinflammatory
cytokines and
chemokines during neutrophil activation, which are essential for neutrophil-mediated local or systemic
inflammation regulation. In conclusion, T. spiralis immune evasion mechanisms are promoted by the inhibitory properties of TsSERP1 against
neutrophil elastase and neutrophil defense functions, and these might be promising alternative treatment targets for inflammatory disorders.