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Recent clinical observations indicate that bacterial vaccines induce cross-protection against infections produced by different microorganisms. MV130, a polyvalent bacterial sublingual preparation designed to prevent recurrent respiratory infectious diseases, reduces the infection rate in patients with recurrent respiratory tract infections.

On the other hand, mesenchymal stem cells (MSCs) are key cell components that contribute to the maintenance of tissue homeostasis and exert both immunostimulatory and immunosuppressive functions. Herein, we study the effects of MV130 in human MSC functionality as a potential mechanism that contributes to its clinical benefits. We provide evidence that during MV130 sublingual immunization of mice, resident oral mucosa MSCs can take up MV130 components and their numbers remain unchanged after vaccination, in contrast to granulocytes that are recruited from extramucosal tissues.

MSCs treated in vitro with MV130 show an increased viability without affecting their differentiation potential. In the short-term, MSC treatment with MV130 induces higher leukocyte recruitment and T cell expansion. In contrast, once T-cell activation is initiated, MV130 stimulation induces an up-regulated expression of immunosuppressor factors in MSCs. Accordingly, MV130-primed MSCs reduce T lymphocyte proliferation, induce the differentiation of dendritic cells with immunosuppressive features and favor M2-like macrophage polarization, thus counterbalancing the immune response. In addition, MSCs trained with MV130 undergo functional changes, enhancing their immunomodulatory response to a secondary stimulus.

Finally, we show that MSCs are able to uptake, process and retain a reservoir of the TLR ligands derived from MV130 digestion which can be subsequently transferred to dendritic cells, an additional feature that also may be associated to trained immunity.

Keywords
  • Mesenchymal stem cells (MSC)
  • Sublingual mucosal immunotherapy
  • Polybacterial preparation
  • Vaccine
  • Immunomodulation
  • Pattern recognition receptors (PPRs)
  • Short-term memory

Received: 29 May 2020; Accepted: 19 Oct 2020.

Copyright: © 2020 Vázquez, Fernández-Sevilla, Jiménez, Pérez-Cabrera, Yañez, Subiza, Varas, Valencia and Vicente. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Mx. Jaris Valencia, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid., Madrid, Catalonia, Spain, jarisval@ucm.es
Mx. Angeles Vicente, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid., Madrid, Catalonia, Spain, avicente@ucm.es

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