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Reassortment between two serologically unrelated bluetongue virus strains is flexible and can involve any genome segment.

ABSTRACT: Coinfection of a cell by two different strains of a segmented virus can give rise to a "reassortant" with phenotypic characteristics that might differ from those of the parental strains. Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) segmented virus and the cause of bluetongue, a major infectious disease of livestock. BTV exists as at least 26 different serotypes (BTV-1 to BTV-26). Prompted by the isolation of a field reassortant between BTV-1 and BTV-8, we systematically characterized the process of BTV reassortment. Using a reverse genetics approach, our study clearly indicates that any BTV-1 or BTV-8 genome segment can be rescued in the heterologous "backbone." To assess phenotypic variation as a result of reassortment, we examined viral growth kinetics and plaque sizes in in vitro experiments and virulence in an experimental mouse model of bluetongue disease. The monoreassortants generated had phenotypes that were very similar to those of the parental wild-type strains both in vitro and in vivo. Using a forward genetics approach in cells coinfected with BTV-1 and BTV-8, we have shown that reassortants between BTV-1 and BTV-8 are generated very readily. After only four passages in cell culture, we could not detect wild-type BTV-1 or BTV-8 in any of 140 isolated viral plaques. In addition, most of the isolated reassortants contained heterologous VP2 and VP5 structural proteins, while only 17% had homologous VP2 and VP5 proteins. Our study has shown that reassortment in BTV is very flexible, and there is no fundamental barrier to the reassortment of any genome segment. Given the propensity of BTV to reassort, it is increasingly important to have an alternative classification system for orbiviruses.

SUBMITTER: Shaw AE

PROVIDER: S-EPMC3536370 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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Reassortment between two serologically unrelated bluetongue virus strains is flexible and can involve any genome segment.

Shaw Andrew E AE Ratinier Maxime M Nunes Sandro Filipe SF Nomikou Kyriaki K Caporale Marco M Golder Matthew M Allan Kathryn K Hamers Claude C Hudelet Pascal P Zientara Stéphan S Breard Emmanuel E Mertens Peter P Palmarini Massimo M

Journal of virology 20121024 1

Coinfection of a cell by two different strains of a segmented virus can give rise to a "reassortant" with phenotypic characteristics that might differ from those of the parental strains. Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) segmented virus and the cause of bluetongue, a major infectious disease of livestock. BTV exists as at least 26 different serotypes (BTV-1 to BTV-26). Prompted by the isolation of a field reassortant between BTV-1 and BTV-8, we systematically characterized ...[more]

PMID: 23097432

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Project description:Reassortment is fundamental to the evolution of influenza viruses and plays a key role in the generation of epidemiologically significant strains. Previous studies indicate that reassortment is restricted by segment mismatch, arising from functional incompatibilities among components of two viruses. Additional factors that dictate the efficiency of reassortment remain poorly characterized. Thus, it is unclear what conditions are favorable for reassortment and therefore under what circumstances novel influenza A viruses might arise in nature. Herein, we describe a system for studying reassortment in the absence of segment mismatch and exploit this system to determine the baseline efficiency of reassortment and the effects of infection dose and timing. Silent mutations were introduced into A/Panama/2007/99 virus such that high-resolution melt analysis could be used to differentiate all eight segments of the wild-type and the silently mutated variant virus. The use of phenotypically identical parent viruses ensured that all progeny were equally fit, allowing reassortment to be measured without selection bias. Using this system, we found that reassortment occurred efficiently (88.4%) following high multiplicity infection, suggesting the process is not appreciably limited by intracellular compartmentalization. That co-infection is the major determinant of reassortment efficiency in the absence of segment mismatch was confirmed with the observation that the proportion of viruses with reassortant genotypes increased exponentially with the proportion of cells co-infected. The number of reassortants shed from co-infected guinea pigs was likewise dependent on dose. With 10? PFU inocula, 46%-86% of viruses isolated from guinea pigs were reassortants. The introduction of a delay between infections also had a strong impact on reassortment and allowed definition of time windows during which super-infection led to reassortment in culture and in vivo. Overall, our results indicate that reassortment between two like influenza viruses is efficient but also strongly dependent on dose and timing of the infections.

Dataset Information

Reassortment between two serologically unrelated bluetongue virus strains is flexible and can involve any genome segment.

Publications

Reassortment between two serologically unrelated bluetongue virus strains is flexible and can involve any genome segment.

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