STEALTH VIRUS LINKED TO MONKEY VIRUS
A virus isolated from a patient diagnosed with chronic fatigue syndrome (CFS) has been linked through DNA sequencing to a virus which originated from African green monkeys, according to an article appearing in the July issue of the peer-reviewed Journal of Clinical and Diagnostic Virology, by Dr. W. John Martin and his colleagues at the University of Southern California School of Medicine.
The results could be significant because kidney cells of African green monkeys have been used for years in the production of polio and other live virus vaccines. Although these vaccines are routinely screened under FDA supervision for contaminating viruses, Dr. Martin -- who once worked for the FDA in vaccine evaluation -- says that the novel virus he has isolated probably would not be detected using current screening methods. Both FDA and CDC are reviewing the results with interest, according to Dr. Martin, but he acknowledged that further investigation would be necessary before any definitive conclusions could be drawn.
The virus Dr. Martin is studying belongs to a family of novel viruses which he has called "stealth viruses," because they are not detected by the body's cellular defense mechanisms and appear to lack the antigens which normally evoke an inflammatory response from the immune system.
In earlier work reported in the American Journal of Pathology, Dr. Martin found evidence that stealth viruses had DNA sequences in common with the human cytomegalovirus (HCMV). But the newly published paper reports a much closer DNA match to the simian cytomegalovirus (SCMV), which infects the specific type of African green monkey used in vaccine production. As an example, the standard FASTA computer program for DNA sequence comparison scored the match between one region of the stealth virus and HCMV at 348 (where scores over 100 are considered significant). But the corresponding match between the stealth virus and SCMV was scored at 2638.
Dr. Martin also used the polymerase chain reaction (PCR) to assess similarity of the stealth virus and SCMV. Several primer sets, based on known DNA sequences from both viruses, reacted in a comparable fashion with the stealth virus and SCMV in (relatively high stringency) PCR. However, when primer sets based on certain other sequences in the genome were used in PCR, negative results were obtained, indicating that although the viruses contain regions of nearly identical sequences, they are distinct viruses having some significant DNA differences. The viruses also show differences in animal cell culture, in their rates of growth and characteristic cytopathic effects.
Dr. Martin's paper also notes that in 1973, a novel virus known as the "Colburn strain" was isolated from a brain biopsy of a neurologically ill human child. Using the molecular methods available at the time, there appeared to be a 5% homology (match) to HCMV, but more than 90% homology to SCMV. Although it was studied in several papers in the 1970s, it was not linked to other cases of human disease until now. Stealth virus DNA matches to the Colburn strain led Dr. Martin to systematically study the relationship between the stealth virus, HCMV, SCMV, and a rhesus monkey CMV. Reviewing the evidence, Dr. Martin says that the close DNA match "strongly suggests" that the stealth virus he is studying was derived through mutation from the SCMV.
Since stealth viruses grow in cells of the brain and nervous system, Dr. Martin theorizes that milder infections by such viruses could underly at least some cases of CFS, which frequently involves affective and cognitive disorders as well as profound fatigue and depression. He is even more concerned about a number of patients from whom he has isolated stealth viruses, who have more severe neurological disorders, some of these patients have died, had seizures or gone into comas. Dr. Martin has worked with the Los Angeles County Public Health Department on these cases and has reported them to both FDA and CDC.
Although he acknowledges that much more work needs to be done, Dr. Martin feels that stealth viruses are important from a public health standpoint and could account for a number of recent cases of human illness which have puzzled both attending physicians and neurologists -- these cases include some (though not necessarily all) cases of CFS.
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