**5. Conclusions**

Thus, for the first time, we demonstrated the feasibility of using modified MSCs expressing non-structural HCV proteins as a platform for creating an effective vaccine against hepatitis C. The mMSC induced a higher innate and adaptive immune response than DNA immunization with the same plasmid. The immunostimulating phenotype of these cells is associated with a high level of IL-6 secretion and a reduction in the proportion of myeloid-derived suppressor cells.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2076-393X/8/1/62/s1, Figure S1: Immunohistochemical staining of HCV proteins in MSC transfected with pcNS3-NS5B, Figure S2: Immunoblot analysis of HCV protein expression in MSC transfected with pcNS3-NS5B.

**Author Contributions:** Conceptualization, O.V.M. and A.A.K.; methodology, O.V.M., R.R.K., A.N.N., A.V.P., and A.A.K.; investigation, O.V.M., E.I.L., R.R.K., E.D.M., V.V.K., A.M.I., N.F.Z., O.V.P., N.N.B.; resources, A.N.N., A.V.P., and A.V.I.; data curation, O.V.M. and A.A.K.; writing—original draft preparation, O.V.M., R.R.K., O.V.P., A.N.N., A.V.I., and A.A.K.; writing—review and editing, O.V.M., A.N.N., A.V.I., and A.A.K.; visualization, O.V.M. and A.A.K.; project administration, O.V.M.; funding acquisition, O.V.M. and A.V.I. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Russian Foundation for Basic Research (grants 17-04-01238 and 17-00-00085). Genetic engineering and production of recombinant proteins were supported by Ministry of Science and Higher Education of the Russian Federation [Agreement No. 075-15-2019-1660].

**Conflicts of Interest:** The authors declare no conflict of interest.
