**Genetically Modified Mouse Mesenchymal Stem Cells Expressing Non-Structural Proteins of Hepatitis C Virus Induce E**ff**ective Immune Response**

**Olga V. Masalova 1,\*, Ekaterina I. Lesnova 1, Regina R. Klimova 1, Ekaterina D. Momotyuk 1, Vyacheslav V. Kozlov 1, Alla M. Ivanova 1, Olga V. Payushina 2, Nina N. Butorina 3, Natalia F. Zakirova 4, Alexander N. Narovlyansky 1, Alexander V. Pronin 1, Alexander V. Ivanov 4,\* and Alla A. Kushch <sup>1</sup>**


Received: 5 December 2019; Accepted: 31 January 2020; Published: 2 February 2020

**Abstract:** Hepatitis C virus (HCV) is one of the major causes of chronic liver disease and leads to cirrhosis and hepatocarcinoma. Despite extensive research, there is still no vaccine against HCV. In order to induce an immune response in DBA/2J mice against HCV, we obtained modified mouse mesenchymal stem cells (mMSCs) simultaneously expressing five nonstructural HCV proteins (NS3-NS5B). The innate immune response to mMSCs was higher than to DNA immunization, with plasmid encoding the same proteins, and to naïve unmodified MSCs. mMSCs triggered strong phagocytic activity, enhanced lymphocyte proliferation, and production of type I and II interferons. The adaptive immune response to mMSCs was also more pronounced than in the case of DNA immunization, as exemplified by a fourfold stronger stimulation of lymphocyte proliferation in response to HCV, a 2.6-fold higher rate of biosynthesis, and a 30-fold higher rate of secretion of IFN-γ, as well as by a 40-fold stronger production of IgG2a antibodies to viral proteins. The immunostimulatory effect of mMSCs was associated with pronounced IL-6 secretion and reduction in the population of myeloid derived suppressor cells (MDSCs). Thus, this is the first example that suggests the feasibility of using mMSCs for the development of an effective anti-HCV vaccine.

**Keywords:** hepatitis C virus (HCV); mesenchymal stem cells (MSC); modified MSC; DNA immunization; nonstructural HCV proteins; immune response; HCV vaccine; myeloid derived suppressor cells (MDSCs)
