Profile of natural killer cells after a previous natural Vaccinia virus infection in an in vitro viral re-exposure

•The present study compares the profile of NK cells in an in vitro re-exposure by VACV.•Previous vaccination leads to a milder form of the disease.•VACV triggers an increase of NCRs: NKp30, NKp44, and NKp46.•VACV downregulates Perforin, Granzyme A, and CD107a, but upregulate CD94.•VACV upregulates IFN-γ+ and TNF-α+ NK cells.

The present study compares the profile of NK cells in an in vitro re-exposure by Vaccinia virus (VACV), in groups that have had a previous vaccination or natural infection. Our data suggests that stimulation with VACV triggers a cytotoxic response by NK cells marked by an increase of NCRs: NKp30, NKp44, and NKp46 in infected (vaccinated and unvaccinated) subjects and in non-infected vaccinated patients, when compared with non-infected unvaccinated individuals. However, the degranulation and secretion processes are inhibited in infected (vaccinated and unvaccinated) subjects and in the non-infected vaccinated patients, when compared with non-infected unvaccinated individuals. We demonstrated that stimulation with VACV downregulates the percentage of expression of Perforin, Granzyme A, and CD107a, but upregulate CD94 in infected (vaccinated and unvaccinated) subjects and in non-infected vaccinated patients, when compared with non-infected unvaccinated individuals. Furthermore, the percentage of IFN-γ+ NK cells was significantly lower in non-infected unvaccinated subjects, when compared with infected (vaccinated and unvaccinated) and non-infected vaccinated individuals. Our results also show that the percentage of TNF-α+ NK cells was significantly higher in infected (vaccinated and unvaccinated) subjects and in non-infected vaccinated patients, when compared with non-infected unvaccinated individuals, after in vitro stimulation with UV-inactivated VACV. Our data suggest that the expression of NCRs NKp30, NKp44, NKp46 and cytokines by NK cells are important in the innate response against VACV.