Hepatic damage associated with dengue-2 virus replication in liver cells of BALB/c mice

We thank Dr Rita Nogueira (Laboratory of Flaviviruses, Instituto Oswaldo Cruz, Fiocruz) for supplying the dengue 2 isolate and Dr Ricardo Galler (BioManguinhos, Fiocruz) for the anti-DENV-2 serum raised in monkey. We are also grateful for the technical assistance of Aline Vilas Boas Vianna.One difficulty in studying dengue virus (DENV) is the lack of an experimental model that reproduces the human disease. In a previous work, we have shown that BALB/c mice intraperitoneally inoculated with a DENV-2 isolate presented viremia and mild focal areas of liver injuries. In this study, mice were inoculated by the intravenous route and presented extensive damage areas in the liver tissue, which were evaluated by histopathological and ultrastructural analysis. Hepatic injury was noted mainly around the central vein and portal tracts. Damages consist of hepatocyte injury, including steatosis, swelling and necrosis. Further, erythrophagocytosis, intercellular edema and vascular damages were evident, including hemorrhage, which is characteristic of the dengue-induced hepatitis in human liver. Hepatic lesions were already noted 2 days post infection (p.i.), although effects were more extensive after the seventh day p.i. An increase in alanine aminotransferase and aspartate aminotransferase serum levels was detected 7 and 14 days p.i., respectively, and had correlation to hepatic lesions. Alterations caused by the DENV infection were self-limiting, with a remarkable reduction of all liver damages 49 days p.i. Virus antigens were detected in hepatocytes, Kupffer cells and vascular endothelium, suggesting virus replication in these cells. In situ hybridization, using a probe that anneals in the virus negative RNA strand, showed positive reaction in hepatocytes and vascular endothelium cells of infected mice, thus confirming virus replication in such cells. In general, results revealed that this mouse model reproduces some histopathological effects observed in humans and supports previous findings indicating virus replication in the hepatic tissue