Arboviruses belonging to the genus Flavivirus (Flaviviridae family) are responsible for considerable morbidity and mortality, may cause severe cases of encephalitis, hemorrhagic fever, hepatitis and febrile disease in vertebrates, including humans. Rocio flavivirus (ROCV) is very important for public health in Brazil, as it represents a serious threat of occurrence of sudden encephalitis outbreaks. The immunopathology of encephalitis caused by flavivirus is not yet fully understood and many aspects involved in modulation of immune responses in the CNS need to be unraveled. Thus, the aim of this study was to analyze the pattern of gene expression of cytokines in primary culture of neural cells when exposed to infection with Rocio. Mixed primary cultures (neuron/glia), obtained from the brains of BALB/C lineage isogenic newborns mice were inoculated with ROCV (MOI equal to 2) on the seventh day of culture and confirmation of infection was made by immunocytochemistry (anti-VROC). Viral replication was quantified in infected primary cultures, depending on the infectious period, by viral titer method. Total cellular RNA was extracted and used for detection of cytokines by real time RT-qPCR techniques. The study showed that primary cultures of neural cells is a good experimental model for the study of CNS infections by Rocio flavivirus. ROCV efficiently infected the primary cultured neural cells leading to cytopathic changes from the 2nd day a.i., when it detected the higher viral titer. The ROCV-infected primary culture survived up to 7 days a.i. and quantification of viral load showed a viral replication kinetics compatible with cell death kinetics of culture infected by ROCV. During the first five days a.i. of the primary culture, there was reduction of IFN-α gene expression, IFN-β, IFN-γ and IL-1β, there was no change in TNF-α expression and there was an increase in TGF-β expression in the 1st, 3rd and 5th day a.i.. The findings of this study suggest that ROCV has the ability to downregulate modulators cytokines of antiviral and inflammatory immune responses and, in this experimental model, immunoregulation exerted by TGF-β predominates over the modulation of inflammatory and antiviral immune responses, larger studies are needed to elucidate immunopathology of CNS infection by ROCV.
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