Active Human Herpesvirus Six and Multiple Sclerosis: Clinical Treatment
and Relationships
K.K. Knox¹, L.J. Lobeck², E.F. Maas², and D.R. Carrigan¹.
Institute for Viral Pathogenesis¹, 10437 Innovation Drive, Milwaukee,
WI 53226
Wisconsin and Department of Neurology, Medical College of Wisconsin², 9200
W Wisconsin Ave, Milwaukee, WI 53226
Presented at the 54th
American Academy of Neurology Annual Meeting; April 2002
Abstract
Several laboratories,
including our own, have presented data linking the pathogenesis of MS to
active HHV-6 infections. Blood
samples were obtained at the time of new clinical relapse in patients
with relapsing-remitting MS and assessed for active HHV-6 infection by
plasma PCR. Then, several weeks later (mean interval:68 days), a second
blood sample was obtained from the same patients and assessed for active
HHV-6 infection. Patients'
changes of Expanded Disability Status Scale (EDSS) from the relapse and
treatments at the time samples were obtained were noted.
Five of 39 (13%) patients had at least one sample positive for
active HHV-6 infection. Variant typing of the positive samples was
possible with 3 of the 5 positives, and 2 were HHV-6 variant A.
Four of the five (80%) positive samples were obtained at the time
of relapse whereas only one (20%) positive was observed in a patient
after relapse. The HHV-6
positive patients suffered a larger change in their EDSS (mean EDSS
change of 1.4) than the HHV-6 negative patients (mean EDSS change of
0.7). It was also found that the patients receiving either beta
interferon or glatirimar acetate (copaxone) were less likely to be HHV-6
positive (2/30; 7%) than the patients receiving no treatment 3/9; 33%).
Since the majority (>75%) of the patients on therapy were
receiving beta interferon,
the decreased positivity for active HHV-6 may reflect the known
antiviral properties of beta interferon.
Introduction
-
In a recently published study, Knox et al.
(Clin Infect Dis 2000;
31:894-903) identified, by means of a rapid culture assay, active HHV-6
viremia in 54% (22/41) of patients with MS.
HHV-6 viremia was not detected in 61 healthy controls.
-
Additional studies [Lobeck et al.; American Academy of
Neurology, 2000] demonstrated a significant relationship between active
HHV-6 viremia, as detected by a rapid culture assay, and disease relapse
in patients with relapsing/remitting MS.MS patients.
-
Based on these findings and the tropism of HHV-6 for blood
leukocytes, the possibility was raised that the CNS lesions of MS are
the result of invasion of the CNS by HHV-6 from the peripheral blood.
Patients And Methods
Patients and Controls
-
Thirty-nine patients, with relapsing remitting MS had blood
samples drawn at the time of a clinical relapse.
-
No patients were receiving corticosteroids when the specimens
were drawn. Most patients
received corticosteroid treatment after onset of their disease relapse.
-
A second blood specimen was drawn from 36 of the same patients six to ten weeks later after the relapse
had resolved.
-
Any treatment that the patients were receiving at the time of the
first blood specimen was noted. Also,
the changes in the patients' Expanded Disability Status Scale (EDSS)
score due to the disease relapse were determined.
-
46 control plasma specimens were obtained from six healthy donors
over a mean period of 140 days (range 62 days to 183 days).
Detection of Active HHV-6
Infections by Plasma PCR
-
DNA was purified from plasma samples by means of a commercially
obtained kit [QIAmp DNA Blood Mini Kit; QIAGEN Inc.; Valencia,
California].
-
DNA PCR was performed using a hotstart taq DNA polymerase system
[TaqBead Hot Start Polymerase; Promega Corp.; Madison, Wisconsin]. The
HHV-6 specific primer pair used has been described in detail previously
(Drobyski et al; NEJM 1994; 330:1356-1360).
This PCR system can detect approximately 200 viral genomes per ml
of plasma (5 genomes per PCR reaction).
Quantitation of the PCR reaction was accomplished by
amplification of a quantitative DNA target control.
The HHV-6 variant involved in the positive samples was determined
by means of variant specific restriction enzymes.
Results
-
Incidence of Active HHV-6
Infections in MS Patients at Time of Relapse Compared with Healthy
Control Individuals.
-
Results are summarized in figure
below.
-
Significantly increased incidence of active HHV-6 infection was
observed with both rapid HHV-6 culture and plasma PCR.
-
Rapid culture was significantly (p < 0.004) more sensitive
than plasma PCR at detected the active HHV-6 infections.
Click
thumbnail to view larger version of figure.
Characteristics of the MS patients who were positive for active HHV-6
Infection by plasma PCR (Table Below).
-
Patients 1 through 4 were positive for active HHV-6 infection at
the time of disease relapse.
-
HHV-6 positive patients did not significantly differ from HHV-6
negative patients with respect to age, gender, disease duration or
disease type.
-
Viral loads varied from 9000 genomes per ml to 500,000 genomes
per ml.
-
Two of the three viruses typed as to variant were HHV-6 variant A.
Click
thumbnail to view larger version of figure.
Relationship Between
Positivity for Active HHV-6 Infection by Plasma PCR and Treatment
Regimens
Click
thumbnail to view larger version of figure.
Relationship Between
Positivity for Active HHV-6 Infection by Plasma PCR and Change in EDSS
score by Disease Relapse
Click thumbnail to view larger version
of figure.
Relationship Between
Tumor Necrosis Alpha (TNFa) And Active
HHV-6 Infection in MS Patients
-
Patients with MS have significantly elevated levels of TNFa mRNA
in their peripheral blood leukocytes (p < 0.0001) and TNFa protein in
their plasma (p < 0.005) compared to healthy controls.
-
No relationship was observed between TNFa mRNA or protein and
active HHV-6 infection.
Conclusions
The major findings of
these studies can be summarized as follows:
-
Cross sectionally, at least 13% of patients with definite MS have
active systemic infections with HHV-6 as detected by plasma PCR.
-
The proportion of MS patients with active systemic infection with
HHV-6 is disproportionately high at the time of clinical relapse.
-
The majority of the active HHV-6 infections in MS patients
involve the A variant of the virus.
-
The viral loads in the sera of the HHV-6 positive patients range
from 10,000 to 500,000 viral genomes per milliliter.
-
Patients with active HHV-6 infections at the time of relapse show
a greater degree of residual disability than HHV-6 negative patients.
-
Patients who are receiving beta interferon or copaxone therapies
are at reduced risk for active HHV-6 infections.
TOP
© 2001-2005 Institute for Viral Pathogenesis. All rights reserved.
