Genetic instability and fragmentation of a stealth viral genome.

Partial sequencing was performed on cloned DNA obtained from cultures of a stealth virus isolated from a patient with the chronic fatigue syndrome. The results extend earlier findings showing regions of homology to cytomegalovirus (CMV). Although the virus is much more closely related to simian CMV than to human CMV, many of the cloned viral segments could be aligned with the human CMV genome. The aggregate size of the aligned segments exceeds 100 kilobase pairs (kbp). Undigested viral DNA has a mobility in agarose gel electrophoresis corresponding to approximately 20 kbp. The virus, therefore, apparently exists in multiple fragments. Considerable sequence variation exists between individual clones which overlap to similar regions of the human CMV genome. The fragmented genome and sequence microheterogeneity suggest that both the processivity and the fidelity of replication of the viral genome are defective. An unstable viral genome may provide a potential mechanism of recovery from stealth viral illness.