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Research
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Conclusion
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Modification on Salmonella typhimurium-derived exosomes.
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Expi293F cells were transfected with plasmids containing genes encoding SpyTag and receptor-binding domain (RBD) fusion proteins to obtain and purify the fusion proteins of SpyTag and RBD. SpyCatcher-positive bacterium-derived exosome-like vesicles were isolated from attenuated Salmonella typhimurium containing the expression plasmid encoding the gene for SpyCatcher. Recombinant RBD-coupled exosomes were produced by incubating recombinant RBD fusion proteins with Salmonella typhimurium-derived exosomes based on SpyTag/SpyCatcher conjugation.
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Evaluation of the effectiveness of modified Salmonella typhimurium-derived exosomes.
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After three intranasal vaccinations immunized hamster model, temperature and body weight monitoring results demonstrated no effect of the Salmonella typhimurium-derived exosome vaccine. After the viral attack, weight loss was rescued in the Salmonella typhimurium-derived exosome-vaccinated group compared to the pathogenic group.
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Immunization with Salmonella typhimurium-derived exosomes induced the production of specific neutralizing antibodies in the hamster model's plasma.
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The ELISA results for determining the antibody levels against Spike-RBD in immunized hamsters showed that the plasma of Salmonella typhimurium-derived exosome vaccine-treated hamsters contained high titers of IgG. After the second vaccination, the antibody level was higher compared to the first and reached the maximum. Moreover, the titers of plasma IgG did not differ significantly between male and female hamsters. The neutralization assay results showed that these plasma antibodies were neutralizing against the respective viruses.
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Immunization with exosomes produced from Salmonella typhimurium resulted in the development of mucosal antibodies.
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IgG, IgM, and IgA were detected in bronchoalveolar lavage samples from hamsters vaccinated with Salmonella typhimurium-derived exosome vaccine after the fourth day of viral attack, whereas those in the exosome-treated and unimmunized groups without RBD modification were not detected.
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Vaccination with Salmonella typhimurium-derived exosome vaccine reduced the titer of infectious virus in hamsters and attenuated focal area pathology.
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Assays of lung tissue and alveolar lavage fluid from Salmonella typhimurium-derived exosome vaccine-immunized hamsters after viral attack showed a significant reduction in infectious viral load in the lungs. Moreover, lung inflammatory and hemorrhagic lesion areas were also significantly reduced compared to the unimmunized group. This suggests that the Salmonella typhimurium-derived exosome vaccine exerted a protective effect on the hamster model.
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Fig. 1 Modified Salmonella typhimurium-derived exosome vaccine significantly alleviated lung lesions in virus-attacked hamsters.1
