Characterization of adaptive mutations in dengue virus serotype 2 (DENV2) cultured in different systems using high-throughput sequencing

Abstract

The accumulation of mutations in arboviruses, dengue included, does not occur as fast as in other RNA viruses like HCV and HIV. Probably the strong selection resulting from the alternation of hosts, coupled with a possible higher fidelity of RNA polymerase keep genetic stability observed in arboviruses. To be effectively transmitted between hosts from different classes, the fitness of an arbovirus has to be similar in both hosts, limiting the level of adaptation of the virus to only one type of host. Therefore, the alternation of host generates generalists viruses, where the neutral or favorable substitutions for replication in both hosts would be more easily selected (trade-off hypothesis). In addition to natural selection impacting the gain variability, the virus can still lose variability by genetic drift. Moreover, it has been shown that certain arboviruses were able to infect new host, enhance their replication capacity or increase their virulence in the vertebrate host by changing one amino acid. Still, little is known about the mechanisms that govern the gain / loss of fitness and pathogenicity in natural conditions. For this reason, models that mimic viral replication in different conditions and micro-environments may help in understanding the evolution of these viruses and the elucidation of immunopathogenic mechanisms of infection by these agents. So the aim of this project is o obtain a better understanding of the mechanisms of acquisition of adaptive substitutions in virus grown in insect cells and mammalian cells, and also in the insect vectors Aedes aegipty. The complete genome of the virus present in different mosquito tissues (midgut and salivary glands) and in cell culture will be achieved through high-throughput sequencing, which will allow a detailed analysis of the viral population. Since our group has generated similar data from the vertebrate host, the results obtained in this study can be analyzed in a comprehensive and comparative way. Thus, these results will contribute to the understanding of the impact of selective pressure exerted by each host in the viral fitness, and consequently, the evolution of these viruses in the short and medium term. (AU)