In a pilot study of six patients,
scientists detected specific antibodies linked to latent
Epstein-Barr virus reactivation in blood samples from people
who had experienced classic CFS symptoms and responded to
antiviral treatment. Control blood samples from 20 healthy
people showed no such antibodies.
The research team, led by scientists from
Ohio State University and Oakland University William
Beaumont School of Medicine, acknowledges that the number of
patients is small. But the researchers say the study's power
rests in their access to 16 months of blood samples for each
patient -- a collection allowing for an unprecedented
longitudinal look at CFS.
The researchers plan to move forward
with development of a clinical laboratory test that can
detect these antibodies in blood samples.
The study is published in the Nov. 14
issue of the journal PLOS ONE.
The Epstein-Barr virus is a human
herpes virus that causes infectious mononucleosis and
several different types of tumors. An estimated 95 percent
of Americans have been infected with the virus by adulthood,
according to the Centers for Disease Control and Prevention
(CDC), but fewer than half have experienced an active
illness. Once a person is infected, the virus remains
dormant in the body, and can be reactivated without causing
symptoms of illness.
In these six patients, the study
suggests that a latent Epstein-Barr virus had begun to
reactivate, but that the newly awakened virus never reached
its full potential to take over its host cells. That partial
reactivation advanced enough to generate at least two viral
proteins, DNA polymerase and dUTPase, and these patients
produced antibodies specifically designed to identify and
neutralize those proteins for more than a year.
The scientists theorize that even in
the absence of a complete active infection, these viral
proteins' ability to induce inflammatory chemical signals
causes enough immune system chaos to lead to CFS. The
disorder's main symptom is profound fatigue for at least six
months that does not improve with rest, and is accompanied
by problems that can include weakness, muscle pain, impaired
memory and depression. Because the illness mimics many other
disorders, diagnosis is difficult. An estimated 1 million
Americans have CFS, but experts believe only 20 percent are
diagnosed.
The study's senior researchers agree
that the work should be repeated in more patients "to
confirm that these observations are real," said virologist
Ron Glaser, director of the Institute for Behavioral
Medicine Research at Ohio State and a co-author of the
study. "But finally, after more than 20 years, this is at
least something to go on."
Glaser's primary collaborators on this
work are Marshall Williams, professor of molecular virology,
immunology and medical genetics at Ohio State, and A. Martin
Lerner, a professor of internal medicine at Oakland
University William Beaumont School of Medicine.
Ohio State and Lerner's private
practice, CFS LLC, have applied for a patent for the
diagnostic method.
Glaser and Williams first published a
paper in 1988 suggesting that these two viral proteins
associated with partially reactivated Epstein-Barr virus
could function as biomarkers for certain illnesses,
including CFS. Meanwhile, Lerner became severely ill in 1986
and struggled for 10 years with CFS symptoms before
treatment with antivirals dramatically improved his health.
Lerner, an infectious diseases
specialist, runs his private CFS practice in Michigan, and
his long-term tracking of patients' characteristics and
response to treatment made this longitudinal research
possible.
The fact that CFS patients experience
different symptoms and multiple types of viral and bacterial
infections has led researchers to believe CFS potentially
has numerous causes. That lack of uniformity also
complicates the diagnostic process and development of
treatments.
"Part of the problem in trying to
identify an agent or biomarkers for chronic fatigue syndrome
is the extreme variability among people who say they have
CFS. How to sort that out has held the field back a lot of
years," said Glaser, who has studied the Epstein-Barr virus
(EBV) for decades.
Lerner had long ago separated 142 of
his patients into two groups: those who had tested positive
for various antibodies against three types of herpes viruses
and responded to months-long treatment with one of two types
of antivirals, and a smaller group that had viral infections
and a variety of co-infections who showed minimal response
to antiviral treatment. As part of this tracking, he
collected multiple blood serum samples for more than a year
from each patient.
From those patients, he selected blood
samples from six for this study. Five had been identified as
an Epstein-Barr virus subset, and the sixth had Epstein-Barr
virus and a bacterial co-infection. For comparison,
researchers collected samples from 20 healthy people matched
to the six CFS patients for age and sex.
Lerner, too, had independently
hypothesized that CFS patients might be experiencing partial
virus reactivation. Patients might test negative for the
most active antibodies required to fight a virus, but could
still recover from CFS after long-term antiviral treatment.
One antiviral he uses is known to inhibit DNA polymerase,
which would halt Epstein-Barr virus reactivation in its
tracks.
With the CFS patients' and control
blood samples in hand, Williams used a highly sensitive
laboratory method to detect whether they contained
antibodies to the two target Epstein-Barr viral proteins,
DNA polymerase and dUTPase, that are produced early in the
process of viral reactivation.
Overall, 78.8 percent of the serum
samples from the six CFS patients were positive for
antibodies against DNA polymerase and 44.2 percent were
positive for antibodies against dUTPase. No antibodies to
these two proteins were detected in the 20 control samples.
"Every one of the six had antibodies
to DNA polymerase or EBV dUTPase and those antibodies
persisted over some 408 days," Lerner said. "And the
antibody levels were extraordinarily high." High levels of
antibodies circulating in the blood suggest long-term immune
activation against those proteins.
Williams noted that the levels might
be less significant than the antibodies being present in the
first place.
"If you look at most healthy
individuals, they wouldn't have any reason to have an
antibody against either of these proteins," he said. "The
antibodies alone are a good differentiator."
This work was partially supported by
the National Institutes of Health.
How Herpesvirus Invades
Nervous System
Mar. 28, 2013 —
Northwestern Medicine scientists have
identified a component of the herpesvirus
that "hijacks" machinery inside human cells,
allowing the virus to rapidly and
successfully invade the nervous system upon
initial exposure.
Led by Gregory Smith,
associate professor in immunology and
microbiology at Northwestern University
Feinberg School of Medicine, researchers
found that viral protein 1-2, or VP1/2,
allows the herpesvirus to interact with
cellular motors, known as dynein. Once
the protein has overtaken this motor,
the virus can speed along intercellular
highways, or microtubules, to move
unobstructed from the tips of nerves in
skin to the nuclei of neurons within the
nervous system.
This is the first
time researchers have shown a viral
protein directly engaging and subverting
the cellular motor; most other viruses
passively hitch a ride into the nervous
system.
"This protein not
only grabs the wheel, it steps on the
gas," says Smith. "Overtaking the
cellular motor to invade the nervous
system is a complicated accomplishment
that most viruses are incapable of
achieving. Yet the herpesvirus uses one
protein, no others required, to
transport its genetic information over
long distances without stopping."
Herpesvirus is
widespread in humans and affects more
than 90 percent of adults in the United
States. It is associated with several
types of recurring diseases, including
cold sores, genital herpes, chicken pox,
and shingles. The virus can live dormant
in humans for a lifetime, and most
infected people do not know they are
disease carriers. The virus can
occasionally turn deadly, resulting in
encephalitis in some.
Until now,
scientists knew that herpesviruses
travel quickly to reach neurons located
deep inside the body, but the mechanism
by which they advance remained a
mystery.
Smith's team
conducted a variety of experiments with
VP1/2 to demonstrate its important role
in transporting the virus, including
artificial activation and genetic
mutation of the protein. The team
studied the herpesvirus in animals, and
also in human and animal cells in
culture under high-resolution
microscopy. In one experiment,
scientists mutated the virus with a
slower form of the protein dyed red, and
raced it against a healthy virus dyed
green. They observed that the healthy
virus outran the mutated version down
nerves to the neuron body to insert DNA
and establish infection.
"Remarkably, this
viral protein can be artificially
activated, and in these conditions it
zips around within cells in the absence
of any virus. It is striking to watch,"
Smith says.
He says that
understanding how the viruses move
within people, especially from the skin
to the nervous system, can help better
prevent the virus from spreading.
Additionally,
Smith says, "By learning how the virus
infects our nervous system, we can mimic
this process to treat unrelated
neurologic diseases. Even now,
laboratories are working on how to use
herpesviruses to deliver genes into the
nervous system and kill cancer cells."
Smith's team will
next work to better understand how the
protein functions. He notes that many
researchers use viruses to learn how
neurons are connected to the brain.
"Some of our
mutants will advance brain mapping
studies by resolving these connections
more clearly than was previously
possible," he says.