Expression of major capsid protein VP-1 in the absence of viral particles in thymomas induced by murine polyomavirus.
Thymomas induced by polyomavirus strain PTA in mice are known to express the major capsid protein VP-1. Since the expression of a late structural protein such as VP-1 is considered a sign of virus replication, the present work attempted to clarify the implication of the presence of this protein in tumor cells. Electron microscopy of tumors showed a striking absence of viral particles in the vast majority of the cells. However, immunoelectron microscopy of the same samples demonstrated intranuclear VP-1 in most cells despite the absence of viral particles. Very little infectious virus was recovered from tumors. A change in the electrophoretic mobility of VP-1 from thymomas was detected compared with VP-1 from productively infected cells. The data presented in this work prove that the expression of VP-1 in polyomavirus-induced tumors is not synonymous with the presence of infectious virus, suggesting a possible defect in viral encapsidation.
Laboratory of Experimental Pathology, Department of Microbiology, University of Buenos Aires School of Medicine, Buenos Aires, Argentina. patoexpe@fmed.uba.ar
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Sanjuan
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Porrás
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Otero
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Perazzo
D000818:Animals; D002213:Capsid / Q000032:analysis* / Q000378:metabolism; D036022:Capsid Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D007668:Kidney / Q000821:virology; D051379:Mice; D008806:Mice, Inbred AKR; D011120:Polyomavirus / Q000302:isolation & purification* / Q000502:physiology; D027601:Polyomavirus Infections / Q000378:metabolism / Q000821:virology*; D013945:Thymoma / Q000378:metabolism / Q000821:virology*; D013953:Thymus Neoplasms / Q000378:metabolism / Q000821:virology*; D014412:Tumor Virus Infections / Q000378:metabolism / Q000821:virology; D014771:Virion / Q000378:metabolism*; D014779:Virus Replication
D036022:Capsid Proteins; C062481:VP1 protein, polyomavirus