Susceptibilidade diferencial de células trofoblásticas humanas (BeWo) e cervicais uterinas (HeLa) à infecção por Neospora caninum

Abstract

Neospora caninum is an obligate intracellular parasite, closely related to Toxoplasma gondii, and considered a major cause of abortion and congenital neosporosis in cattle worldwide. As trophoblast cells act in mechanisms of innate immune defense at fetal-maternal interface, and no data are available about the interaction of this parasite with human trophoblasts, this study aimed to verify the susceptibility of human trophoblastic (BeWo) compared to uterine cervical (HeLa) cell lines to Neospora caninum infection. BeWo and HeLa cells were infected with different parasite:cell ratios of Neospora caninum tachyzoites and analyzed in different times after infection for cell viability using the colorimetric assay of thiazolyl blue tetrazole (MTT) and cell lysis by measuring the lactate dehydrogenase (LDH) activity. Both cell lines were also evaluated for cytokine production and parasite infection/replication assays when pretreated or not with Neospora lysate antigen (NLA) or human recombinant interferon-gamma (IFN-γ). It was found that Neospora caninum induced increased cell viability in both cell lines, more evidently in BeWo cells, in the first hours of infection, suggesting that parasite infection could to be able to early inhibit cell death and/or to induce cell proliferation. Also, Neospora caninum infection induced upregulation of the macrophage migration inhibitory factor (MIF), mostly in HeLa cells, which was improved with cell pretreatment with NLA or IFN-γ. Conversely, parasite infection induced downregulation of the transforming growth factor (TGF-β), mostly in BeWo cells, which was more decreased with NLA or IFN-γ pretreatment. HeLa cells were more susceptible to Neospora caninum infection than BeWo cells, and IFN-γ pretreatment resulted in significant decrease in the percentage of infected cells in both cell lines, and the control of the parasite growth was mediated by IFN-γ through an indoleamine-2,3- dioxygenase (IDO)-dependent mechanism in HeLa cells only. In conclusion, this study demonstrated for the first time that BeWo and HeLa cells are potential targets as host cells for Neospora caninum, although presenting differences in susceptibility to infection, cytokine production and cell viability, reflecting in strategies used by the parasite for survival inside the host cells.