Persistence of experimental Rocio virus infection in the golden hamster (Mesocricetus auratus)

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.

Arboviroses da Amazônia: estudo do mecanismo de morte celular e da resposta fenotípica do hospedeiro na febre amarela / Arboviruses of the Amazonia: study of the cell death mechanism of cell death and the fenotipic host response in the yellow fever[

Os eventos histológicos no fígado foram quantificados, usando técnica de imunomarcação para avaliar 53 amostras hepáticas provenientes de viscerotomia de pacientes vitimados por febre amarela silvestre. A análise quantitativa dos eventos demonstrou amplo predomínio do componente apoptótico sobre a necrose. O infiltrado inflamatório é desproporcional em intensidade à morte dos hepatócitos. Houve predomínio de linfócitos TCD4+, ocorrendo em menor proporção linfócitos TCD8+, linfócitos B, células NK e apresentadoras de antígenos (S100). A expressão citocínica foi de perfil Th1, com expressão de TNF-a, IFN-g e acompanhada de intensa imunomarcação para TGF-b. Frente aos achados acreditamos que a predileção pela localização médio zonal das lesões do fígado poderia decorrer de fenômenos de hipóxia por hipofluxo secundária à vasculopatia sistêmica e associada ao efeito citopático viral.In this work, the histological events in the liver were quantified, using a immunomarking technique to evaluate 53 hepatic samples from the viscerotomy of patients with the sylvatic form of yellow fever. Quantitative analysis of the events demonstrated an ample prevalence of an apoptotic component in the necrosis. The intensity of the inflammatory infiltration is disproportionate to the death of the hepatocytes. There is a prevalence of TCD4+ lymphocytes, with a smaller proportion of TCD8+ lymphocytes, B lymphocytes, NK cells and antigen-presenting cells (S100). The cytokine expression presented a profile of Th1, with expression of TNF-a, IFN-g and accompanied by intense immunomarking by TGF-b. Faced with these findings, we consider that the predilection for the midzonal location of the lesions in the liver could arise from the phenomena of hypoxia secondary to systemic vasculopathy associated to the viral cytopathic effect...