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Open Access 01-12-2016 | Research

Construction of a molecular clone of ovine enzootic nasal tumor virus

Authors: Scott R. Walsh, María Carla Rosales Gerpe, Sarah K. Wootton

Published in: Virology Journal | Issue 1/2016

Abstract

Background

Enzootic nasal tumor virus (ENTV-1) is an ovine betaretrovirus that has been linked to enzootic nasal adenocarcinoma (ENA), a contagious tumor of the ethmoid turbinates of sheep. Transmission experiments performed using virus isolated from cell free nasal tumor homogenates suggest that ENTV-1 is the causative agent of ENA; however, this etiological relationship has not been conclusively proven due to the fact that the virus cannot be propagated in vitro nor is there an infectious molecular clone of the virus.

Methods

Here we report construction of a molecular clone of ENTV-1 and demonstrate that transfection of this molecular clone into HEK 293T cells produces mature virus particles.

Results

Analysis of recombinant virus particles derived from the initial molecular clone revealed a defect in the proteolytic processing of Gag; however, this defect could be corrected by co-expression of the Gag-Pro-Pol polyprotein from the highly related Jaagsiekte sheep retrovirus (JSRV) suggesting that the polyprotein cleavage sites in the ENTV-1 molecular clone were functional. Mutagenesis of the molecular clone to correct amino acid variants identified within the pro gene did not restore proteolytic processing; whereas deletion of one proline residue from a polyproline tract located in variable region 1 (VR1) of the matrix resulted in production of CA protein of the mature (cleaved) size strongly suggesting that normal virion morphogenesis and polyprotein cleavage took place. Finally, electron microscopy revealed the presence of spherical virus particles with an eccentric capsid and an average diameter of about 100 nm.

Conclusion

In summary, we have constructed the first molecular clone of ENTV-1 from which mature virus particles can be produced. Future experiments using virus produced from this molecular clone can now be conducted to fulfill Koch’s postulates and demonstrate that ENTV-1 is necessary and sufficient to induce ENA in sheep.

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Title: Construction of a molecular clone of ovine enzootic nasal tumor virus
Authors: Scott R. Walsh
María Carla Rosales Gerpe
Sarah K. Wootton
Publication date: 01-12-2016
Publisher: BioMed Central
Published in: Virology Journal / Issue 1/2016
Electronic ISSN: 1743-422X
DOI: https://doi.org/10.1186/s12985-016-0660-x

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Construction of a molecular clone of ovine enzootic nasal tumor virus

Abstract

Background

Methods

Results

Conclusion

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Abstract

Background

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Results

Conclusion

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