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xenopus laevis: a possible vector of ranavirus infection?frog virus 3 (fv3) or fv3-like viruses (iridoviridae) infect a wide range of amphibian species, and they are becoming increasingly and causally associated with amphibian disease outbreaks worldwide. we have established the frog xenopus laevis as an experimental model to study host defense and pathogenesis of fv3 infection. although x. laevis adults usually clear fv3 infection within a few weeks, viral dna has been detected in the kidneys several months after they had been experimentally infected ...200717984259
effect of imidacloprid on the survival of xenopus tadpoles challenged with wild type frog virus 3.the sensitivity of amphibians to ranavirus may be increased by exposure to other environmental stressors, including chemical contaminants. neonicotinoid insecticides comprise 27% of the global insecticide market and have been detected in wetlands and other aquatic habitats. the present study focused on the effects of exposure of pre-metamorphic xenopus laevis to the neonicotinoid, imidacloprid (imi) on sensitivity to frog virus 3 (fv3) infection. it was hypothesized that exposure of tadpoles to ...029179150
immune evasion strategies of ranaviruses and innate immune responses to these emerging pathogens.ranaviruses (rv, iridoviridae) are large double-stranded dna viruses that infect fish, amphibians and reptiles. for ecological and commercial reasons, considerable attention has been drawn to the increasing prevalence of ranaviral infections of wild populations and in aquacultural settings. importantly, rvs appear to be capable of crossing species barriers of numerous poikilotherms, suggesting that these pathogens possess a broad host range and potent immune evasion mechanisms. indeed, while som ...201222852041
the amphibian (xenopus laevis) type i interferon response to frog virus 3: new insight into ranavirus pathogenicity.the increasing prevalence of ranavirus (rv; iridoviridae) infections of wild and commercially maintained aquatic species is raising considerable concerns. while xenopus laevis is the leading model for studies of immunity to rv, amphibian antiviral interferon (ifn) responses remain largely uncharacterized. accordingly, an x. laevis type i interferon was identified, the expression of the gene for this ifn was examined in rv (frog virus 3 [fv3])-infected tadpoles and adult frogs by quantitative pcr ...201424623410
negative effects of low dose atrazine exposure on the development of effective immunity to fv3 in xenopus laevis.the recent dramatic increase of the prevalence and range of amphibian host species and populations infected by ranaviruses such as frog virus 3 (fv3) raises concerns about the efficacies of amphibian antiviral immunity. in this context, the potential negative effects of water contaminants such as the herbicide atrazine, at environmentally relevant levels, on host antiviral immunity remains unclear. here we describe the use of the amphibian xenopus laevis as an ecotoxicology platform to elucidate ...201424984115
inflammation-induced reactivation of the ranavirus frog virus 3 in asymptomatic xenopus laevis.natural infections of ectothermic vertebrates by ranaviruses (rv, family iridoviridae) are rapidly increasing, with an alarming expansion of rv tropism and resulting die-offs of numerous animal populations. notably, infection studies of the amphibian xenopus laevis with the ranavirus frog virus 3 (fv3) have revealed that although the adult frog immune system is efficient at controlling rv infections, residual quiescent virus can be detected in mononuclear phagocytes of otherwise asymptomatic ani ...201425390636
prominent amphibian (xenopus laevis) tadpole type iii interferon response to the frog virus 3 ranavirus.ranaviruses (iridoviridae) are posing an increasing threat to amphibian populations, with anuran tadpoles being particularly susceptible to these viral infections. moreover, amphibians are the most basal phylogenetic class of vertebrates known to possess both type i and type iii interferon (ifn)-mediated immunity. moreover, little is known regarding the respective roles of the ifn mediators in amphibian antiviral defenses. accordingly, we transcriptionally and functionally compared the amphibian ...201525717104
nonclassical mhc-restricted invariant vα6 t cells are critical for efficient early innate antiviral immunity in the amphibian xenopus laevis.nonclassical mhc class ib-restricted invariant t (it) cell subsets are attracting interest because of their potential to regulate immune responses against various pathogens. the biological relevance and evolutionary conservation of it cells have recently been strengthened by the identification of it cells (invariant vα6 [ivα6]) restricted by the nonclassical mhc class ib molecule xnc10 in the amphibian xenopus laevis. these ivα6 t cells are functionally similar to mammalian cd1d-restricted invar ...201526062996
frog virus 3 dissemination in the brain of tadpoles, but not in adult xenopus, involves blood brain barrier dysfunction.while increasing evidence points to a key role of monocytes in amphibian host defenses, monocytes are also thought to be important in the dissemination and persistent infection caused by ranavirus. however, little is known about the fate of infected macrophages or if ranavirus exploits immune privileged organs, such as the brain, in order to establish a reservoir. the amphibian xenopus laevis and frog virus 3 (fv3) were established as an experimental platform for investigating in vivo whether ra ...201626931458
long term effects of carbaryl exposure on antiviral immune responses in xenopus laevis.water pollutants associated with agriculture may contribute to the increased prevalence of infectious diseases caused by ranaviruses. we have established the amphibian xenopus laevis and the ranavirus frog virus 3 (fv3) as a reliable experimental platform for evaluating the effects of common waterborne pollutants, such as the insecticide carbaryl. following 3 weeks of exposure to 10 ppb carbaryl, x. laevis tadpoles exhibited a marked increase in mortality and accelerated development. exposure at ...201727988452
amphibian (xenopus laevis) tadpoles and adult frogs mount distinct interferon responses to the frog virus 3 ranavirus.infections of amphibians by frog virus 3 (fv3) and other ranavirus genus members are significantly contributing to the amphibian declines, yet much remains unknown regarding amphibian antiviral immunity. notably, amphibians represent an important step in the evolution of antiviral interferon (ifn) cytokines as they are amongst the first vertebrates to possess both type i and type iii ifns. accordingly, we examined the roles of type i and iii ifns in the skin of fv3-challenged amphibian xenopus l ...201728081430
immune roles of amphibian (xenopus laevis) tadpole granulocytes during frog virus 3 ranavirus infections.infections by frog virus 3 (fv3) and other ranaviruses (rvs) are contributing to the amphibian declines, while the mechanisms controlling anuran tadpole susceptibility and adult frog resistance to rvs, including the roles of polymorphonuclear granulocytes (pmns) during anti-fv3 responses, remain largely unknown. since amphibian kidneys represent an important fv3 target, the inability of amphibian (xenopus laevis) tadpoles to mount effective kidney inflammatory responses to fv3 is thought to cont ...201728238879
mechanisms of amphibian macrophage development: characterization of the xenopus laevis colony-stimulating factor-1 receptor.macrophage-lineage cells are indispensable to vertebrate homeostasis and immunity. in turn, macrophage development is largely regulated through colony-stimulating factor-1 (csf1) binding to its cognate receptor (csf1r). to study amphibian monopoiesis, we identified and characterized the x. laevis csf1r cdna transcript. quantitative analysis revealed that csf1r tissue gene expression increased with x. laevis development, with greatest transcript levels detected in the adult lung, spleen and liver ...201426154317
characterization of primary and memory cd8 t-cell responses against ranavirus (fv3) in xenopus laevis.in mammals, resistance to primary and secondary viral infections critically involves major histocompatibility complex class i-restricted cytotoxic cd8+ t lymphocytes (ctls). although many gene homologues involved in ctl function have been identified in all vertebrate classes, antiviral ctl responses have been poorly characterized for ectothermic vertebrates. because of the threat of emerging wildlife viral diseases to global biodiversity, fundamental research on comparative viral immunity has be ...200717182687
susceptibility of xenopus laevis tadpoles to infection by the ranavirus frog-virus 3 correlates with a reduced and delayed innate immune response in comparison with adult frogs.xenopus laevis adults mount effective immune responses to ranavirus frog virus 3 (fv3) infections and clear the pathogen within 2-3 weeks. in contrast, most tadpoles cannot clear fv3 and succumb to infections within a month. while larval susceptibility has been attributed to ineffective adaptive immunity, the contribution of innate immune components has not been addressed. accordingly, we performed a comprehensive gene expression analysis on fv3-infected tadpoles and adults. in comparison to adu ...201222819836
xenopus laevis and emerging amphibian pathogens in chile.amphibians face an extinction crisis with no precedence. two emerging infectious diseases, ranaviral disease caused by viruses within the genus ranavirus and chytridiomycosis due to batrachochytrium dendrobatidis (bd), have been linked with amphibian mass mortalities and population declines in many regions of the globe. the african clawed frog (xenopus laevis) has been indicated as a vector for the spread of these pathogens. since the 1970s, this species has been invasive in central chile. we co ...201627682604
improved knockout methodology reveals that frog virus 3 mutants lacking either the 18k immediate-early gene or the truncated vif-2alpha gene are defective for replication and growth in vivo.to better assess the roles of frog virus 3 (fv3; genus ranavirus, family iridoviridae) genes in virulence and immune evasion, we have developed a reliable and efficient method to systematically knock out (ko) putative virulence genes by site-specific integration into the fv3 genome. our approach utilizes a dual selection marker consisting of the puromycin resistance gene fused in frame with the enhanced green fluorescent protein (egfp) reporter (puro-egfp cassette) under the control of the fv3 i ...201121865381
waterborne infectivity of the ranavirus frog virus 3 in xenopus laevis.ranaviruses like frog virus 3 (fv3) are responsible for emerging infectious diseases spreading worldwide to fish, amphibian and reptilian species. we have developed, in xenopus laevis, an experimental model to investigate viral transmission. we show that fv3 released in water by immunocompromised infected adults can infect adult and larval stages of xenopus within 3h of exposure. time course of virus load and viral transcription in different tissues suggests that early waterborne fv3 infection t ...201121783222
innate immune responses and permissiveness to ranavirus infection of peritoneal leukocytes in the frog xenopus laevis.ranaviruses such as frog virus 3 ([fv3] family iridoviridae) are increasingly prevalent pathogens that infect reptiles, amphibians, and fish worldwide. whereas studies in the frog xenopus laevis have revealed the critical involvement of cd8 t-cell and antibody responses in host resistance to fv3, little is known about the role played by innate immunity to infection with this virus. we have investigated the occurrence, composition, activation status, and permissiveness to infection of peritoneal ...201020200236
in vivo and in vitro techniques for comparative study of antiviral t-cell responses in the amphibian xenopus.activation of lymphocytes in mammals is often quantified by measuring the amount of proliferation during the expansion phase of an immune response. bromodeoxyuridine (brdu) incorporation and carboxyfluorescein diacetate succinimidyl ester (cfse) dilution assays are some of the techniques widely used in mammalian studies of pathogen-induced proliferation and provide a convenient way of quantifying the cellular response. we have extended the use of these proliferation assays to the amphibian xenop ...200818385804
differentiation-dependent antiviral capacities of amphibian (xenopus laevis) macrophages.infections by ranaviruses such as frog virus 3 (fv3) are significantly contributing to the worldwide amphibian population declines. notably, amphibian macrophages (mφs) are important to both the fv3 infection strategies and the immune defense against this pathogen. however, the mechanisms underlying amphibian mφ fv3 susceptibility and resistance remain unknown. mφ differentiation is mediated by signaling through the colony-stimulating factor-1 receptor (csf-1r), which is now known to be bound by ...201729259133
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