Abstract
Although a variety of virus species can infect amphibians, diseases caused by ranaviruses ([RVs]; Iridoviridae) have become prominent, and are a major concern for biodiversity, agriculture and international trade. The relatively recent and rapid increase in prevalence of RV infections, the wide range of host species infected by RVs, the variability in host resistance among population of the same species and among different developmental stages, all suggest an important involvement of the amphibian immune system. Nevertheless, the roles of the immune system in the etiology of viral diseases in amphibians are still poorly investigated. We review here the current knowledge of antiviral immunity in amphibians, focusing on model species such as the frog Xenopus and the salamander (Ambystoma tigrinum), and on recent progress in generating tools to better understand how host immune defenses control RV infections, pathogenicity, and transmission.
Highlights
Amphibians have received much attention during the last two decades because of a now-general understanding that more species are at risk of extinction in this class than those of any other classes of vertebrates [1]
In X. laevis, we have shown that frog virus 3 (FV3) localization in immunocompetent adults is mostly limited to kidneys, and that FV3 remains localized to discrete area that are rapidly cleared by the immune response
As discussed extensively in this review, there is compelling evidence for mass deaths among amphibian populations resulting from infectious disease outbreaks
Summary
Amphibians have received much attention during the last two decades because of a now-general understanding that more species are at risk of extinction in this class than those of any other classes of vertebrates [1]. Thanks to the momentum initiated by the symposium, a Global Ranavirus Consortium was created to stimulate interactions among ranavirus researchers, and to provide updated information [11] From these data, it has become clear that RVs have the capability of directly contributing to amphibian population declines. Despite the goodly amount of data supporting the important role played by RVs, it remains unclear why RVs-associated deaths of amphibian have been noted only recently [15] It is currently unclear why some species are susceptible, whereas others are tolerant or even resistant to one or the other RV pathogens. Given the importance of the host immune system in controlling and clearing pathogens, one hypothesis that has been advanced to explain the recent increase in virulence and prevalence resulting in mass die-offs is that at least some amphibian species or populations have.
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