Abstract
Rocio virus (ROCV) is an encephalitic flavivirus endemic to Brazil. Experimental flavivirus infections have previously demonstrated a persistent infection and, in this study, we investigated the persistence of ROCV infection in golden hamsters (Mesocricetus auratus). The hamsters were infected intraperitoneally with 9.8 LD50/0.02 mL of ROCV and later anaesthetised and sacrificed at various time points over a 120-day period to collect of blood, urine and organ samples. The viral titres were quantified by real-time-polymerase chain reaction (qRT-PCR). The specimens were used to infect Vero cells and ROCV antigens in the cells were detected by immunefluorescence assay. The levels of antibodies were determined by the haemagglutination inhibition technique. A histopathological examination was performed on the tissues by staining with haematoxylin-eosin and detecting viral antigens by immunohistochemistry (IHC). ROCV induced a strong immune response and was pathogenic in hamsters through neuroinvasion. ROCV was recovered from Vero cells exposed to samples from the viscera, brain, blood, serum and urine and was detected by qRT-PCR in the brain, liver and blood for three months after infection. ROCV induced histopathological changes and the expression of viral antigens, which were detected by IHC in the liver, kidney, lung and brain up to four months after infection. These findings show that ROCV is pathogenic to golden hamsters and has the capacity to cause persistent infection in animals after intraperitoneal infection.
Highlights
Rocio virus (ROCV) was first described in 1975 as the causative agent of an encephalitis epidemic in humans that occurred in the Ribeira Valley area of the southern coast of the state of São Paulo (SP), Brazil (Tiriba 1975, Tiriba et al 1976, Lopes et al 1978, Pinheiro et al 1997)
Clinical findings - The 30 hamsters inoculated with the ROCV suspension and the 15 hamsters used as negative controls remained active and showed no signs of disease during the experiment
Infected hamsters developed viraemia, which was detected by an indirect fluorescent assay (IFA) of the supernatants of cell cultures inoculated with blood, for a maximum period of four days p.i
Summary
Rocio virus (ROCV) was first described in 1975 as the causative agent of an encephalitis epidemic in humans that occurred in the Ribeira Valley area of the southern coast of the state of São Paulo (SP), Brazil (Tiriba 1975, Tiriba et al 1976, Lopes et al 1978, Pinheiro et al 1997). The presence of neutralising antibodies to ROCV was confirmed in two of these cases. To cause a persistent infection, the virus must actively reduce the antiviral immune response of the host. As an important part of persistent viral replication, the virus disrupts the homeostasis of the host by causing disease without destroying the infected cell (Oldstone 2005). In an experimental study, Siirin et al (2007) demonstrated that adult hamsters infected with online | memorias.ioc.fiocruz.br
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