STEALTH VIRUS LINKED TO MONKEY VIRUS
Daniel Fylstra
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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