Stealth adaptation of an African green monkey simian cytomegalovirus

DNA extracted from cultures of a cytopathic virus isolated from a patient with chronic fatigue syndrome was cloned into pBluescript plasmid. The nucleotide sequences of the plasmid inserts were analyzed using the BlastN and BlastX programs of the National Center for Biotechnology Information. In confirmation of earlier studies, many of the sequences show partial homology to various regions within the genome of human cytomegalovirus (HCMV). The matching regions were unevenly distributed throughout the HCMV genome. No matches were seen with either the UL55 or the UL83 genes, which provide the major antigenic targets for anti-HCMV cytotoxic T-cell-mediated immunity. This finding is consistent with the notion that certain viruses can avoid immune elimination by deleting genes required for effective antigenic recognition by the cellular immune system. The term "stealth" has been applied to such viruses. Comparisons were also made between the sequences of the stealth virus and the limited sequence data available on cytomegaloviruses from rhesus monkeys and from African green monkeys. These comparisons unequivocally establish that the virus was derived from an African green monkey simian cytomegalovirus.