**5. Conclusions**

Our data serves as evidence that mast cells are permissive to ZIKV infection, since a non-structural protein, NS1, was detected 24 h post infection. ZIKV can induce degranulation on its first contact and can produce cytokines and VEGF both short term and over a few hours of infection. This response of mast cells can facilitate the installation of a pro-inflammatory environment in the sites where these cells are found, such as in mucous membranes like the placenta. In addition, the fact that they can support the replication of the virus in the human placenta suggests that this type of cell may contribute to vertical transmission. Further studies are needed to fully elucidate the role of mast cells in ZIKV infection.

**Author Contributions:** Conceptualization, K.R., M.P.O.D., A.J.D.S.G. and M.V.P.; material, L.J.D.S., S.M.B.d.L., G.F.T., M.P.d.O.D., A.J.D.S.G., A.P.S., B.L.D. and M.V.P, methodology, K.R., M.P.d.O.D., B.T.C., N.R.A.T., B.L.D. and A.J.D.S.G.; formal analysis, K.R., M.P.O.D. and A.J.D.S.G.; writing—original draft preparation, K.R.; writing—review and editing, all authors; supervision, M.P.O.D., J.J.C., M.V.P.; project administration, M.P.O.D., J.J.d.C., M.V.P.; funding acquisition, M.P.d.O.D., J.J.d.C., M.V.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by CNPq and the FAPERJ, gran<sup>t</sup> number (E-26/010.001.498/2016 and E-26/110.511/2014).

**Acknowledgments:** We thank the Platform of Confocal and Electron Microscopy at the State University of Rio de Janeiro and the Platform of Electron Microscopy in Fiocruz. We are grateful to D. Willian Provance for the manuscript review. This work was supported by the *CNPq* (308780/2015-9) and the *FAPERJ* (E-26/110.511/2014, E-26/010.001.498/2016 and E26/202.003/2016).

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