Higher‐temperature‐adapted dengue virus serotype 2 strain exhibits enhanced virulence in AG129 mouse model

Abstract

The factors that drive dengue virus (DENV) evolution, and selection of virulent variants are yet not clear. Higher environmental temperature shortens DENV extrinsic incubation period in mosquitoes, increases human transmission, and plays a critical role in outbreak dynamics. In the present study, we looked at the effect of temperature in altering the virus virulence. We found that DENV cultured at a higher temperature in C6/36 mosquito cells was significantly more virulent than the virus grown at a lower temperature. In a mouse model, the virulent strain induced enhanced viremia and aggressive disease with a short course, hemorrhage, severe vascular permeability, and death. Higher inflammatory cytokine response, thrombocytopenia, and severe histopathological changes in vital organs such as heart, liver, and kidney were hallmarks of the disease. Importantly, it required only a few passages for the virus to acquire a quasi‐species population harboring virulence‐imparting mutations. Whole genome comparison with a lower temperature passaged strain identified key genomic changes in the structural protein‐coding regions as well as in the 3′UTR of the viral genome. Our results point out that virulence‐enhancing genetic changes could occur in the dengue virus genome under enhanced growth temperature conditions in mosquito cells.

Fingolimod (FTY720), an FDA‐approved sphingosine 1‐phosphate (S1P) receptor agonist, restores endothelial hyperpermeability in cellular and animal models of dengue virus serotype 2 infection

“…41,63 We used an animal model based on AG129 mice for in vivo experiments, wherein the DENV2 strain induced the clinical symptoms and around 80% mortality within 7 days postinfection. 32 Similar mice models were also reported by other authors with different strains of DENV. 33,34,64 As depicted in Figure 6, the FTY720 treatment significantly improved the body weight and also improved the survival in the DENV-infected animals.…”

“…In our laboratory, we have developed a lethal dengue animal model using the RGCB880/KL/2010 DENV2 35P strain infection in the interferon receptor (α/β/γ) deficient AG129 mice 32 . As depicted in the experimental schematic (Figure 6A), 3–4 weeks old AG129 mice, when infected with the DENV2 (10 4 PFU/mice; sub‐cutaneous route), develop ruffled fur, hunched back, loss of appetite, reduction in body weight; and show a significant (~80%) mortality within 7th day post‐infection.…”

“…AG129 mice [deficient in interferon‐α/β and γ receptors], obtained from B&K Universal (UK), were bred, maintained, and experimented under specific‐pathogen‐free conditions in individually ventilated cages. AG129 mice of 3–4 weeks old, weighing 9–10 g were infected with DENV2 RGCB880 35P strain (10 4 pfu per mice) through subcutaneous (s/c) route, as described previously 32 . Animals injected with the same volume of heat‐inactivated virus (Mock) were used as controls in the experiments.…”

“…AG129 mice of 3-4 weeks old, weighing 9-10 g were infected with DENV2 RGCB880 35P strain (10 4 pfu per mice) through subcutaneous (s/c) route, as described previously. 32 Animals injected with the same volume of heat-inactivated virus (Mock) were used as controls in the experiments. For heat-inactivation, virus was incubated at 56 C for 30 min; and inactivation was confirmed by plaque assay.…”

“…In our laboratory, we have developed a lethal dengue animal model using the RGCB880/KL/2010 DENV2 35P strain infection in the interferon receptor (α/β/γ) deficient AG129 mice. 32 As depicted in the experimental schematic (Figure 6A), 3-4 weeks old AG129 mice, when infected with the DENV2 (10 4 PFU/mice; sub-cutaneous route), develop ruffled fur, hunched back, loss of appetite, reduction in body weight; and show a significant (80%) mortality within 7th day post-infection. Treatment with FTY720 was significantly beneficial in maintaining the body weight of the infected mice, approximately 20% more than untreated animals on 8th-10th day postinfection, by which time all the DENV-infected, untreated animals died (Figure 6B).…”