Аннотация:Trichinella nativa (Britov & Boev, 1972) is widely distributed among wildlife in the Holarctic region of the globe and is characterised by low reproductive potential, severe clinical manifestations of trichinosis disease and high resistance to prolonged freezing. More than 700 isolates originating from terrestrial and marine carnivores inhabiting arctic and subarctic areas have been identified as T. nativa (Pozio, 2016). Trichinella excretory-secretory (E-S) proteins are the determining factor of virulence because they interact directly with the host immune system during invasion and have pronounced strain specificity. A wide variety of adaptive reactions of Trichinella genus during the development of parasite-host relationships is ensured by proteolytic enzymes and other protein molecules contained in the E-S products of Trichinella. However, fundamental data on composition of E-S proteins of the species T. nativa widespread in natural biocenosis are practically absent so far. Larvae of T. nativa strain ISS 7635 isolated from muscles of Ursus arctos L., 1758 were passaged on white mice. Invasive larvae were isolated from mouse muscles by proteolysis in artificial gastric juice, and then cultured in DMEM medium for 24, 48 and 72 h. The resulting E-S products were analysed by tandem mass spectrometry coupled to high-performance liquid chromatography (LC-MS/MS). Common proteins reliably determined by four or more unique peptides and present at all three culturing stages were selected from the E-S products. A total of 86 proteins, both with known and unidentified functions were revealed, apparently reflecting the bulk of the spectrum of proteins involved in parasite-host interactions. All of these proteins have posttranslational modifications. Judging by the ratio of the number of peptides detected for one of the transmembrane serine proteinases (75) and actin (37), and considering the unique peptides determined for these two proteins (74 and 9, respectively), their presence in E-S products was not caused by larval death and lysis but rather by secretion by the living larvae, probably as part of transport vesicles. The possible role of a number of identified proteins in the interaction of muscle larvae with host cells is discussed (Support: Program of Fundamental Scientific Research of the State Academies of Sciences FNSE-2019-0009; 121032300088-6 without attracting additional sources of funding).