|
|
||||||||
1 From the Departments of Ophthalmology, 2 Molecular Virology and Microbiology, and 3 Pathology, Baylor College of Medicine, Houston, Texas.
| Abstract |
|---|
|
|
|---|
METHODS. In a randomized masked study, 64 temporal artery biopsy specimens were analyzed by PCR for VZV DNA. The samples included 35 specimens histologically positive and 29 specimens histologically negative for GCA. Immunohistochemical staining for VZV viral antigen IE-63 was performed on seven of the specimens positive for GCA and five negative specimens. Transmission electron microscopy (TEM) was performed on five of the specimens positive for GCA.
RESULTS. PCR was positive for VZV DNA in 9 (26%) temporal arteries tested that showed histologic evidence of GCA. The remaining 26 histologically positive temporal arteries and all 29 histologically negative arteries tested gave negative PCR results for VZV DNA. Statistical analysis (z-test) comparing the association of VZV DNA between the specimens that were positive and negative for GCA showed a significant difference (P = 0.010). Immunohistochemical studies were positive in several biopsy specimens within adventitial histiocytes-macrophages, but these results did not correlate with either the presence or absence of VZV DNA or with the histologic evidence of GCA. No viral particles were observed by TEM.
CONCLUSIONS. This study showed a significant association of VZV DNA to temporal artery biopsy samples positive for GCA compared with the negative specimens. The results support the hypothesis that VZV may play a role in the pathogenesis of some cases of GCA. However, PCR, immunohistochemical, and electron microscopic findings suggest the virus is present at extremely low quantities, is abortively replicating, or is latent.
| Introduction |
|---|
|
|
|---|
Varicella zoster virus (VZV), a member of the Herpesviridae family of viruses, is a potential candidate. It is a ubiquitous human pathogen, establishes a life-long latent infection from which it can reactivate, can be associated with arteries, and is capable of producing a granulomatous reaction with multinucleated cells.1 2 Similar to the incidence of GCA, the risk of VZV reactivation causing herpes zoster is age-associated. Approximately 75% of herpes zoster occurs in patients more than 45 years old,3 and the incidence increases to more than 10 cases per 1000 persons by the age of 75.4
A previous histopathologic study of 21 eyes enucleated for complications of herpes zoster ophthalmicus (HZO) revealed that two of the eyes had a granulomatous vasculitis involving the posterior ciliary arteries just behind the sclera.5 The histopathologic findings observed in these arteries showed a striking resemblance to those observed in cases of GCA. Additionally, another eye enucleated because of severe HZO disclosed diffuse granulomatous vasculitis involving the choroidal vessels. VZV has also been linked to generalized granulomatous angiitis of the central nervous system in immunocompromised patients,6 7 and detection of viruslike particles has been reported in granulomatous angiitis.8 9 10 These observations provide evidence that VZV may be associated with GCA.
The purpose of the present study was to further investigate whether VZV is associated with the pathogenesis of GCA. We histopathologically studied 71 temporal artery biopsy specimens, of which 37 were histologically positive and 34 were histologically negative for GCA. Nested PCR for VZV DNA (IE-63) was performed in a randomized masked study on DNA extracted from 64 specimens that were PCR positive for human ß-actin and the findings compared with the results of the histopathology. Selected temporal artery biopsy specimens were also analyzed for viral antigen, by using immunohistochemistry and for viral capsids by using transmission electron microscopy (TEM). VZV-infected placental tissue and an eye enucleated because of HZO were evaluated as positive control specimens for the PCR and immunohistochemical studies.
| Materials and Methods |
|---|
|
|
|---|
Polymerase Chain Reaction
Primers used for the nested amplification of the VZV immediate
early-63 (IE-63) gene and the amplification of the human
ß-actin gene have been previously described.15
16
17
For
the first round of PCR amplification, 20% of the extracted DNA from
each sample analyzed was incubated in a 50-µl reaction using
conditions previously detailed,13
14
except 2.5 mM
MgCl2 and 50 pmol of each primer was used, and no
[32P]dATP was added. The first cycle consisted
of 3 minutes each at 95°C, 58°C, and 72°C followed by 35 cycles
at the same temperatures for 1 minute each. For the second round of PCR
amplification of the nested VZV PCR, 20% of the first amplification
reaction was used as template in similar reaction conditions using 50
pmol of each internal primer. The first cycle of the nested
amplification consisted of 3 minutes each at 95°C and 72°C followed
by 35 cycles at the same temperatures for 1 minute each. The ß-actin
PCR used similar reaction conditions, except 20 pmol of each primer and
only 2% of the extracted DNA was used. The cycle parameters of the
ß-actin PCR were 3 minutes each at 95°C, 61°C, and 72°C,
followed by 35 cycles at the same temperatures for 45 seconds each.
Control DNA templates are described in the text and included plasmids
pVZV-EcoE and pVZV-EcoB; and viral DNA isolated
from cell cultures infected with herpes simplex virus (HSV) type 1
(strains KOS and 17+syn), HSV type 2 (strain HG52), or murine
cytomegalovirus (MCMV). Control PCR reactions included approximately 1
ng viral DNA. Analysis of all PCR reactions included electrophoresis of
20% of the reaction on 1.8% agarose/0.5x Tris-borate-EDTA (TBE)
electrophoresis gels containing 0.5 µg/ml ethidium bromide.
Immunohistochemistry
An indirect immunohistochemical method was used to detect and
localize VZV viral antigen within temporal artery biopsy specimens. The
immunohistochemical staining was optimized using infected placental
tissue from a neonate who died of culture-proven disseminated
congenital VZV. Specimens were sectioned and prepared for
immunostaining, as previously described,18
with the
following modifications: The deparaffinized sections were blocked with
a 5% solution of normal goat serum followed by a 1:100 dilution of
rabbit antiserum directed against the VZV IE-63
protein.19
20
The tissue sections were incubated with the
primary antibody at 4°C overnight. All other incubations were
performed at room temperature. A biotinylated secondary antibody (goat
anti-rabbit) was used as recommended by the manufacturer (Vector).
Secondary antibody binding was visualized by addition of
avidin-biotin-peroxidase complexes (Vectastain Elite ABC kit; Vector)
and 3-amino-9-ethylcarbazole (AEC) as a chromogen.21
Sections were counterstained with aqueous hematoxylin.
Transmission Electron Microscopy
Formalin-fixed tissue from five temporal artery biopsy specimens
that were PCR positive for VZV DNA was submitted for conventional TEM.
Thick sections (±1 µm) were stained with toluidine blue or paragon.
Thin sections were stained with uranyl acetate and lead citrate and
mounted on copper grids for examination.
| Results |
|---|
|
|
|---|
|
|
DNA was extracted from 71 masked samples of temporal artery biopsy specimens and tested in control ß-actin PCR assays. Sixty-four samples were confirmed to be acceptable for PCR analysis, of which 35 were histologically positive for GCA and 29 were negative. The ß-actinpositive samples were analyzed using the nested VZV PCR assay (Table 1) . PCR was positive for VZV DNA in 9 (26%) temporal artery specimens that showed histologic evidence of GCA. The remaining 26 histologically positive temporal arteries and all 29 histologically negative arteries gave negative PCR results for VZV DNA. The positive results were confirmed by repeated PCR analysis. Statistical analysis (z-test) comparing the association of VZV DNA between the specimens positive and negative for GCA showed a significant difference (P = 0.010). The samples were unmasked. Representative PCR results are shown in Figure 3 .
|
|
|
|
| Discussion |
|---|
|
|
|---|
Application of the highly sensitive and specific PCR-based technique described herein to temporal artery biopsy specimens demonstrated an association of VZV DNA and GCA. Viral DNA was present in 26% of the specimens histologically positive for GCA. Although this association was statistically significant, VZV DNA was not detected in 74% of the specimens from this group. A possible explanation for this finding is that VZV may be associated with only a subset of cases of GCA. Another reason may be that viral DNA was present at amounts below the level of detection. The primers used for PCR amplification target a conserved region of the VZV genome and have been shown previously to amplify a wide variety of clinical VZV isolates.15 Therefore, a negative result is not likely to be a false negative, because of viral strain genetic variability. Regardless, VZV DNA was amplified from approximately one quarter of the temporal artery biopsy specimens that were histologically positive for GCA.
Whether the association of VZV DNA and GCA is causal or casual cannot be determined from our findings. It is plausible that GCA and its associated granulomatous inflammation are related to the VZV DNAs becoming detectable. Another possibility is that the VZV DNA is only incidentally associated with GCA.
Because VZV DNA was present in a significant portion of the temporal artery biopsy specimens tested, it was of interest to determine whether viral antigen or viral particles could be detected, regardless of the type of association that might exist. Our immunohistochemical findings of positive immunoreactivity of histiocytes-macrophages was consistent with a report that used antiserum obtained from patients who had herpes zoster, one of whom had a basilar artery aneurysm at the site of granulomatous angiitis.10 Of interest, the positive immunoreactivity we observed was not unique to temporal arteries positive for GCA but was also present in some arteries that were histologically negative for GCA or were negative by PCR analysis.
Possible reasons for the discordance between our PCR and immunohistochemical results may include issues of sensitivity or sampling problems within the biopsy; however, we do not believe that these adequately explain our findings. It is unlikely that the immunohistochemical staining would be more sensitive than PCR, especially at the lower limit of detection that we have demonstrated for the PCR assay. Also, because the sections used for immunohistochemical staining were serial sections to those used for PCR analysis, we believe sampling problems within the biopsy specimens were not likely, especially when considering that multiple specimens gave similar results. A more likely explanation is that the primary antibody used in the immunohistochemical staining cross-reacted with some antigen on the adventitial histiocytes. A similarity between the study by Fukumoto et al.10 and ours is that they both showed positive staining with granular cytoplasmic deposits within the adventitial histiocytes. The report by Fukumoto et al. did not include control tissue, and the specificity of the immunoreactivity they reported is therefore unclear.
One difference between our findings and those of Fukumoto et al.10 is the presence of viral particles. Whereas they demonstrated enveloped viral particles in the cytoplasm of the histiocytes in the walls of the aneurysm by using electron microscopy, we did not detect any viral particles, even after extensive evaluation of several different specimens. This could have been due to a difference in the prevalence of virus in temporal arteries compared with the basilar artery lesion evaluated and even suggests that viral particles may be absent during the clinical manifestations of GCA. The absence of viral particles would not necessarily exclude the potential presence of viral DNA or antigens. For instance, viral DNA and some viral antigens, including the protein IE-63, are present during latent infections, but viral replication and the production of virus particles are limited.19
Contrary to our findings of VZVs association with GCA are the results
of Nordborg et al.25
who reported the inability to detect
either VZV antigen or DNA in arteries from 10 histopathologically
verified cases of GCA. Final conclusions about these negative findings
should be made with caution because of the potential limitation in the
sensitivity of the PCR assay used and the small sample size studied.
The PCR assay used by Nordborg et al. involved a single PCR reaction
and detected 103 copies of a plasmid containing
VZV DNA. This lower limit of detection was similar to our experience
using a single-PCRreaction approach (data not shown); however, we
were able to increase our lower limit of detection by approximately two
logs by using the double-PCR assay described. Secondly, at an expected
prevalence of 26%, twice the number of specimens tested by Nordborg et
al. would be needed to assure at least one positive result at a
confidence level of 0.8 (
= 0.05). Therefore, either the lower
limits of detection or the number of specimens evaluated in the two
studies could account for the ultimate differences in the results
obtained.
The granulomatous vasculitis typically associated with multinucleated giant cells, which is histologically characteristic of GCA, is consistent with an infectious cause. The fact that GCA is an arterial disease and that it is associated with the elderly are both consistent with VZV as the responsible agent. Findings in our study further support the hypothesis that VZV may play a role in the pathogenesis of some cases of GCA. These results provide some of the first direct data that VZV may be a causative agent for GCA. However, our immunohistochemical and electron microscopic findings suggest the virus was present at extremely low quantities, abortively replicating, or latent.
| Acknowledgements |
|---|
| Footnotes |
|---|
Submitted for publication January 29, 2001; revised June 5, 2001; accepted June 15, 2001.
Commercial relationships policy: N.
The publication costs of this article were defrayed in part by page
charge payment. This article must therefore be marked
"advertisement" in accordance with 18 U.S.C.
1734
solely to indicate this fact.
Corresponding author: Bradley M. Mitchell, Department of Ophthalmology, NC205, Baylor College of Medicine, 6565 Fannin St., Houston, TX 77030. bmm{at}bcm.tmc.edu
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
R Alvarez-Lafuente, B Fernandez-Gutierrez, J A Jover, E Judez, E Loza, D Clemente, J A Garcia-Asenjo, and J R Lamas Human parvovirus B19, varicella zoster virus, and human herpes virus 6 in temporal artery biopsy specimens of patients with giant cell arteritis: analysis with quantitative real time polymerase chain reaction Ann Rheum Dis, May 1, 2005; 64(5): 780 - 782. [Abstract] [Full Text] [PDF] |
||||
![]() |
W. Ma-Krupa, M.-S. Jeon, S. Spoerl, T. F. Tedder, J. J. Goronzy, and C. M. Weyand Activation of Arterial Wall Dendritic Cells and Breakdown of Self-tolerance in Giant Cell Arteritis J. Exp. Med., January 20, 2004; 199(2): 173 - 183. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. M. Weyand and J. J. Goronzy Giant-Cell Arteritis and Polymyalgia Rheumatica Ann Intern Med, September 16, 2003; 139(6): 505 - 515. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. M. Weyand and J. J. Goronzy Medium- and Large-Vessel Vasculitis N. Engl. J. Med., July 10, 2003; 349(2): 160 - 169. [Full Text] [PDF] |
||||
![]() |
D Le Thi Huong, M R Andreu, P Duhaut, P Godeau, and J C Piette Intra-alveolar haemorrhage in temporal arteritis Ann Rheum Dis, February 1, 2003; 62(2): 189 - 190. [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |