Human neutrophils are not activated by Zika virus but reduce the infection of susceptible cells

Zika virus (ZIKV) emergence highlighted the need for a deeper understanding on virus-host interaction to pave the development of antiviral therapies. The present work aimed to address the response of neutrophils during ZIKV infection. Neutrophils are an important effector cell in innate immunity involved in the host response to neurotropic arboviruses. Our results indicate that human neutrophils were not permissive to Asian or African ZIKV strains replication. Indeed, after stimulation with ZIKV, neutrophils were not primed against the virus as evaluated by the absence of CD11b modulation, secretion of inflammatory cytokines and granule content, production of reactive oxygen species and neutrophil extracellular traps formation. Overall, neutrophils did not affect ZIKV infectivity. Moreover, ZIKV infection of primary innate immune cells in vitro did not trigger neutrophil migration. However, neutrophil co-cultured with ZIKV susceptible cells (A549) resulted in lower frequencies of infection on A549 cells by cell-to-cell contact. In vivo, neutrophil depletion from immunocompetent mice did not affect ZIKV spreading to the draining lymph nodes. The data suggest human neutrophils do not play a per se antiviral role against ZIKV, but these cells might participate in an infected environment shaping the ZIKV infection in other target cells.