Mesenchymal stem cells enhance immune response and protect mice against lethal herpes viral infection.

The objective of this study was to evaluate immunoregulatory and protective potential of mesenchymal stem cells (MSC) in a mouse model of lethal HSV1 infection. MSC were isolated from bone marrow of DBA mice and cultured in flasks with DMEM containing 10% FBS, insulin, transferrin, selenite, fibroblast growth factor, glutaminе and gentamicin. Antiviral activity was tested on HSV1-infected Vero cells. In vivo experiments were performed on DBA mice divided into 5 groups (10 animals each): group 1, intact (naive) mice; group 2, intravenous (iv) MSC injection; group 3, intraperitoneal infection with 20 LD50 HSV1 followed by MSC injection; group 4, HSV1 infection followed by acyclovir (ACV) injection; group 5, HSV1 infection and iv injection of saline. Isolated cells were consistent with MSC morphologically, by adhesive ability and surface receptors. Conditioned media from MSC collected after 4-5 passages inhibited HSV1 infection in vitro by 64-70% and contained IL-6 and TNF-α, whose concentrations were 5- and 20-fold higher, respectively, than in the control. MSC and ACV injections protected 70% and 60% of DBA mice, respectively, compared with the control (group 5, 10% survival). High activity of virus neutralizing anti-HSV1 antibodies and activation of T cell proliferation were observed in survived mice from group 3. Serum levels of IL-6 and TNF-α in these mice were lower and that of INF-γ much higher than in agonizing animals of this group (Р<0.05). These findings indicate that MSC therapy is a prospective approach to the development of new effective management of generalized HSV1 infection.