Comparative analysis of liver involvement caused by two DENV-2 lineages using an immunocompetent murine model

Abstract

Dengue (DEN) is the most prevalent arbovirus among humans, and four billion people live at risk of infection. The clinical manifestations of DEN are variable, and the disease may present subclinically or asymptomatically. A quarter of patients develop classical dengue (CD) or severe dengue (SD), which is potentially lethal and involves vascular permeability changes, severe hemorrhage and organ damage. The involvement of the liver is a fairly common feature in DEN, and alterations range from asymptomatic elevation of transaminases to acute liver failure. Since its introduction in Brazil in 1990, two strains of Dengue virus (DENV) serotype 2 (DENV-2) have been detected: Lineage I, which is responsible for an outbreak in 1991, and Lineage II, which caused an epidemic greater than the previous one and had a different epidemiological profile. To date, studies on different strains of the same serotype/genotype and their association with disease severity are scarce. In addition, one of the greatest challenges regarding the study of DEN pathogenesis and the development of drug and vaccine therapies is the absence of an animal model that reproduces the disease as it occurs in humans. The main goals of this study were to assess BALB/c mouse susceptibility experimentally infected by two distinct DENV-2 strains and characterize possible differences in the clinical signs and alterations induced in the liver resulting from those infections. Mice infected by the two DENV-2 lineages gained less weight than uninfected mice; however, their livers were slightly heavier. Increased AST and AST levels were observed in infected mice, and the number of platelets increased in the first 72 h of infection and subsequently decreased. Mice infected with both lineages presented leukocytosis but at different times of infection. The histopathological changes induced by both lineages were similar and comparable to the changes observed in DEN fatal cases. The viral genome was detected in two liver samples. The results demonstrate the susceptibility of BALB/c mice to both DENV-2 lineages and suggest that the changes induced by those strains are similar, although for some parameters, they are manifested at different times of infection.

Morphological Aspects and Viremia Analysis of BALB/c Murine Model Experimentally Infected with Dengue Virus Serotype 4

“…Focal points of necrosis were detected, characterized by the hepatocyte nucleus undergoing pyknosis. Activated platelets were observed within the capillary, suggesting alterations of blood vessel permeability, as previously described by Paes et al [16], Barth et al [17], Caldas [18] and Jácome et al [19]. The alterations observed here correspond to those described in human fatal cases, with similar profiles of hemorrhage, inflammation and vascular congestion [9,11,12,14].…”

“…Previous studies have shown that the experimental infection of immunocompetent BALB/c mice with a non-neuroadapted DENV-2 strain, by either intraperitoneal or intravenous routes, resulted in histopathological alterations similar to those commonly described in dengue human cases, with no fatalities observed in the mice [16,17,19,23,24].…”

“…Nuclear lipid-like inclusions in hepatocytes were also observed [16][17][18]. In a study of BALB/c mice infected with two distinct Brazilian lineages of DENV-2, Jácome et al [19] showed livers with vascular congestion, presence of inflammatory infiltrate in the proximity of the portal area, hepatocyte ballooning degeneration, nuclear area enlargement, with chromatin pattern alterations and sinusoid capillary dilation around centrolobular veins and nuclear atypia. A singular case presented lipid droplets within the parenchyma, and signs of necrosis were observed in one of the analyzed lineages.…”

Brazilian Dengue Virus Type 2-Associated Renal Involvement in a Murine Model: Outcomes after Infection by Two Lineages of the Asian/American Genotype

“…However, studies have shown that BALB/c mice present thrombocytopenia, increased levels of hepatic enzimes alanine aminotrasferase (ASL) and aspartate aminotransferase (ALT), anorexia, weight loss, anemia and even develop severe disease and paralysis, when infected with neuroadapted strains [54][55][56][57]. Viral replication and dissemination have been observed in this experimental model infected with DENV-1, -2 and -4 and viral genome or antigen have been detected in heart, lungs spleen, brain, liver, kidneys and saliva samples [53][54][55][58][59][60][61][62][63]. In kidney tissue of DENV infected BALB/c mice, increased glomerular volume and mesangial cellularity have been reported [58].…”

“…Since the DENV infection outcome can be affected by the virulence of different strains [ 47 ], and dengue related histopathological data on kidney is still scarce, here we aimed to investigate the renal involvement of BALB/c mice after infection with two distinct DENV-2 Asian/American lineages. Moreover, as this report is a part of a project whose goal is to present BALB/c mice as a suitable non-severe dengue experimental model for studies on the pathogenesis of dengue in different organs, we have recently demonstrated the susceptibility of the aforementioned murine model to both lineages and showed that the changes induced by those strains in the liver were similar to those observed in human cases, but it was observed that some parameters were manifested at different times of infection [ 63 ].…”