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Background: Trichinella spiralis is a zoonotic food-borne parasite. A disease caused by infection with T. spiralis is called trichinellosis in humans. It is important to investigate the epidemic situation and the surveillance of herds and then prevent infection in humans. Therefore, this study is to develop a rapid and sensitive diagnostic method for on-site test in domestic and wild animals., Methods: Upconverting phosphor nanoparticles (UCNPs), an excellent optical label, were conjugated with the excretory-secretory (ES) antigens from T. spiralis muscle larvae (ML) or goat anti-rabbit IgG, and a lateral flow (LF) assay based on these probes (UCNPs-ES/goat anti-rabbit IgG) was developed for the rapid and sensitive detection of anti-T. spiralis IgG antibodies in pig serum. The assay is named the UPT-LF-ES assay. In addition, the probes were characterized, and the assay was optimized. A cut-off threshold of the assay was also identified by using 169 known negative pig samples. Performance of the assay to T. spiralis with different infective numbers, cross-reactivity with other parasitic infections, the single-blinded experiment, and coincidence were evaluated with the assay., Results: The UPT-LF-ES assay was successfully constructed and optimized based on the probes of UCNPs-ES/goat anti-rabbit IgG. In the pigs infected with 100, 1000, and 10,000 ML, positive results were first presented at 35 days post-infection (dpi), 30 dpi, and 25 dpi, respectively. The assay had no cross-reaction with other parasitic infections. A single-blinded experiment indicated that the sensitivity and specificity of the UPT-LF-ES assay were 100% and 100%, respectively, the area under the receiver operating characteristic (ROC) curve was 1.000. In addition, the value detected by the UPT-LF-ES assay was significantly different between positive and negative samples. Moreover, compared with the "gold standard" magnetic stirrer method, the coincidence rate of the UPT-LF-ES assay was 87.27%, and the kappa (K) coefficient was 0.7454, showing a substantial agreement., Conclusions: The UPT-LF-ES assay is a useful point-of-care test (POCT) with T. spiralis in the detection of pig, which contributes to preventing human trichinellosis., (© 2021. The Author(s).)

Background: Trichinellosis is a serious food-borne parasitic zoonosis, thus finding high quality antigens is the key to serodiagnosis of trichinosis. This article reports the characterization and sensitivity of four recombinant proteins expressed by four genes (Wn10, Zh68, T668, and Wm5) from different developmental stages of Trichinella spiralis for the diagnosis of trichinellosis in mice. Methods: This study was conducted in Jilin University and National Institute of Parasitic Diseases of Chinese Center for Disease Control and Prevention in 2017-2018. The structures and functions of the proteins encoded by four genes were predicted by bioinformatics analysis. The four genes were cloned and expressed, and the recombinant proteins were purified. Anti-Trichinella IgM and IgG antibodies in the sera of mice infected with T. spiralis from 1-45 d post-infection (dpi) were evaluated by ELISA. Results: The optimal antigen epitopes of four proteins (P1, P2, P3, and P4) encoded by the four genes from T- and B-cells were predicted, and four purified recombinant proteins (r-P1, r-P2, r-P3, and r-P4) were successfully produced. For IgM, the antibody levels detected by the four recombinant antigens were approximately equal to the cut-off value. Anti-Trichinella IgG antibodies were first detected by r-P1 at 8 dpi, followed by r-P2, r-P3, and r-P4 at 10 dpi, 14 dpi, and 16 dpi, respectively, and the antibody levels remained high until 45 dpi. Conclusion: The recombinant antigens r-P1, r-P2, r-P3, and r-P4 could be antigens that react with antibodies, they showed high sensitivity in the detection of anti-Trichinella IgG antibodies in mice. Among these proteins, r-P1 may be a candidate antigen for the detection of anti-Trichinella IgG antibodies in the early infection phase and exhibited the best sensitivity among the antigens. [ABSTRACT FROM AUTHOR]

• Characterized infectivity of muscle larvae during the early stages of infection. • Th2-predominant immune response was induced in Trichinella spiralis infection. • The body weight of infected pigs compared with the control group was increased. • Anti- Trichinella spiralis IgM antibody was detected earlier than IgG antibody. The objective of the present study was to investigate the infectivity and antibody response of four Trichinella species (Trichinella spiralis , Trichinella britovi , Trichinella pseudospiralis and Trichinella murrelli) in experimentally infected pigs. A total of 120 Large White pigs (30 animals per group) were inoculated with 10,000 muscle larvae (ML) of T. spiralis , T. britovi , T. pseudospiralis , and T. murrelli. The pigs were sacrificed at 12–21 days post-infection (dpi) to examine the viability and infectivity of ML. A total of 54 Large White pigs (6 animals per group) were inoculated with 25, 50, 100, 200, 400, 600, 800, 1000 and 10,000 T. spiralis ML. The pigs were sacrificed, and the average numbers of larvae per gram (lpg) from six different muscle tissues were calculated at 120 dpi. The results showed that the larvae first be detectable for T. spiralis , T. britovi , and T. pseudospiralis at 16 dpi, 17 dpi, and 16 dpi, respectively. Viable larvae and average lpg were significantly increased with time from 17 to 21 dpi. The T. spiralis ML burden was dependent of the inoculation dose with an average lpg of 0.003, 0.005, 0.007, 0.17, 0.82, 2.89, 4.90, 28.30 and 226.18, respectively. The IgG antibody response was dose-dependent to generate and increased throughout the experimental period. And the IgG1 isotype was significantly higher than IgG2a, which meant that T. spiralis infection induced the Th2 immune response. The time of detecting IgM antibodies was significantly earlier than IgG antibody detection. These results provide important information in the primary characterization of pigs infected with Trichinella. [ABSTRACT FROM AUTHOR]