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Abstract
Cloned DNA obtained from the culture of an African green monkey simian cytomegalovirus-derived stealth virus contains multiple discrete regions of significant sequence homology (p values ranging from 4 x 10^sup -3^ to 1 x 10^sup -20^) to portions of known human cellular genes. The stealth virus was cultured from a patient with chronic fatigue syndrome (CFS). Earlier studies had revealed considerable sequence heterogeneity within DNA fragments isolated from virus-infected cells. A set of polymerase chain reaction (PCR) primers generated different PCR products when tested on stealth virus cultures from 4 patients with CFS. Several of the PCR products also contain regions of significant partial homology to distinct cellular sequences, including sequences repetitively expressed throughout the cellular genome. Stealth viruses may play an important role in the origins and in the genetic diversity of both viral and cellular sequences.
Key Words Stealth virus Chronic fatigue syndrome Simian cytomegalovirus Sequencing Genetic recombination
Introduction
The term 'stealth' has been applied to a molecularly heterogeneous grouping of atypically structured, vacuolating cytopathic viruses that cause persistent systemic infection, often with neuropsychiatric manifestations, in the absence of significant antiviral inflammation. The appearance, progression and host range characteristics of the cytopathic effect distinguish stealth viruses from conventional human cytopathic viruses, including herpesviruses, enteroviruses and adenoviruses. Electron microscopy, serology and molecular-based assays can be used to further differentiate stealth viruses from conventional viruses [ 1-4].
DNA sequencing studies on polymerase chain reaction (PCR)-derived products obtained from a prototype stealth virus culture showed a region of partial homology with human cytomegaloviruses [2]. Further sequencing of EcoRI- and SacI-digested DNA obtained from the virus (now designated stealth virus-1) showed several sequences nearly identical to sections of the African green monkey simian cytomegalovirus (SCMV) [3]. While it appeared unequivocal that SCMV had contributed multiple genetic sequences to the stealth virus, other regions of the virus could not be aligned to known herpesviral sequences [4]. The virus DNA appeared to comprise multiple fragments with stretches of herpesviral-derived DNA adjacent to sequences of uncertain origin. The virus also exhibited considerable sequence microheterogeneity. Similar stretches of the viral genome often showed multiple deletions, additions, substitutions and duplications [4]. Sequence heterogeneity was confirmed in stretches of the genome in which genetic recombination had clearly occurred [4].
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