Characterization of murine Caraparu Bunyavirus liver infection and immunomodulator-mediated antiviral protection

Imaging Bunyavirus Infections by Transmission Electron Microscopy: Conventional Sample Preparation vs High-Pressure Freezing and Freeze-Substitution

Transmission electron microscopy significantly contributed to unveil the course of virus entry, replication, morphogenesis, and egress. For these studies, the most widely used approach is imaging ultrathin sections of virus-infected cells embedded in a plastic resin that is transparent to electrons. Before infiltration in a resin, cells must be processed to stabilize their components under the observation conditions in an electron microscope, such as high vacuum and irradiation with electrons. For conventional sample preparation, chemical fixation and dehydration are followed by infiltration in the resin and polymerization to produce a hard block that can be sectioned with an ultramicrotome. Another method that provides a superior preservation of cell components is high-pressure freezing (HPF) followed by freeze substitution (FS) before resin infiltration and polymerization. This chapter describes both procedures with cells infected with Bunyamwera virus (BUNV), a well characterized member of the Bunyavirales, and compares the morphological details of different viral structures imaged in the two types of samples. Advantages, disadvantages, and applications of conventional processing and HPF/FS are also presented and discussed.

In vitro and in vivo studies of the Interferon-alpha action on distinct Orthobunyavirus

Oropouche, Caraparu, Guama, Guaroa and Tacaiuma viruses (Orthobunyavirus genus) cause human febrile illnesses and/or encephalitis. To achieve a therapeutical agent to prevent and/or treat these diseases we evaluated the antiviral action of Interferon-alpha (IFN-α) on these orthobunyaviruses. In vitro results showed that all the studied orthobunyaviruses are susceptible to antiviral action of IFN-α, but this susceptibility is limited and dependent on both concentration of drug and treatment period. In vivo results demonstrated that IFN-α present antiviral action on Oropouche and Guaroa viruses when used as a prophylactic treatment. Moreover, a treatment initiated 3 h after infection prevented the death of Guaroa virus infected-mice. Additionally, mortality of mice was related to the migration and replication of viruses in their brains. Our results suggest that IFN-α could be potentially useful in the prevention of diseases caused by Oropouche virus and in the prevention and/or treatment of diseases caused by Guaroa virus.

In vitro study of antiviral activity of mycophenolic acid on Brazilian orthobunyaviruses

OBJECTIVE

Oropouche, Caraparu, Guama, Guaroa and Tacaiuma are ssRNA viruses that belong to the genus Orthobunyavirus and have been associated with human febrile illnesses and/or encephalitis. In this study, we evaluated the antiviral action of mycophenolic acid (MPA) on theseorthobunyaviruses to achieve a therapeutic agent to treat the diseases caused by these viruses.

METHODS

The in vitro antiviral evaluation to MPA was done by using plaque assay at different periods of treatment.

RESULTS

Results showed that MPA at a concentration of 10 microg/ml has significant antiviral activity on Tacaiuma virus when treatment was initiated either 24 h before or 2 h after viral infection. Moreover, MPA has an inhibitory effect on Guama virus replication, but only when treatment was initiated before cell infection. Addition of guanosine in the culture reverted the inhibitory effect of MPA on Tacaiuma and Guama viruses, suggesting that the antiviral activity of this substance was via depletion of the intracellular guanosine pool.

CONCLUSION

Our results suggest that MPA would not be a good therapeutic agent to treat the diseases caused by Oropouche, Caraparu, Guama, Guaroa, and Tacaiuma viruses.