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Infect. Immun., 04 1997, 1273-1285, Vol 65, No. 4
RK Straubinger, AF Straubinger, L Harter, RH Jacobson, YF Chang, BA Summers, HN Erb and MJ Appel
Twenty 6-week-old specific-pathogen-free beagles were infected with
Borrelia burgdorferi by tick challenge, and five uninfected dogs served as
controls. During the study, all dogs were monitored for infection, clinical
signs, and antibody response against B. burgdorferi. During episodes of
lameness or postmortem, synovial fluids from each dog were examined for
volume, cell number, polymorphonuclear leukocyte (PMN) content, cell
viability, and chemotactic activity. Twenty-five tissues collected
postmortem from each dog were tested for interleukin-8 (IL-8) mRNA, tumor
necrosis factor alpha (TNF-alpha) mRNA, presence of live spirochetes, and
histopathological changes. Thirteen infected dogs (group A), which
seroconverted rapidly (maximum titers within 50 to 90 days), developed
acute and severe mono- or oligoarthritis almost exclusively in the limb
closest to the tick bite (median incubation period, 66 days). Synovial
fluids of the arthritic joints collected during episodes of lameness had
significantly elevated volume, cell count, PMN proportion, cell viability,
and chemotactic activity for PMNs. The remaining joints of the same animals
contained synovial fluids with elevated chemotactic activity and cell
viability. Twelve dogs tested positive for IL-8 mRNA in multiple tissues
(synovia, pericardium, and peritoneum), and 10 dogs expressed TNF-alpha
mRNA, but only in the tributary lymph nodes of the inflamed joints.
Histological examinations revealed severe poly- or oligoarthritis and
moderate to severe cortical hyperplasia in draining lymph nodes of the
inflamed joints in all 13 dogs. Seven infected dogs with mild or no
clinical signs (group B) seroconverted slowly (peak titers after 90 days),
and only some joint fluids showed chemotactic activity, which on average
was lower than that in inflamed and noninflamed joints from dogs in group
A. Four dogs expressed IL-8 mRNA (in the synovia and pericardium), and
three dogs had TNF-alpha mRNA in tributary lymph nodes. Histologically,
nonsuppurative arthritis was found in multiple joints, and mild to moderate
cortical hyperplasia was found in draining lymph nodes. Five uninfected
dogs without lameness (group C) had normal synovial fluids and tissues. In
all infected dogs, live spirochetes were demonstrated more frequently in
tissues of the somatic quadrant closest to the tick bite than in tissues
further from the site of infection, suggesting that dissemination of B.
burgdorferi occurs more by migration than by blood-borne spread. From these
studies employing a canine model of B. burgdorferi infection, we conclude
that IL-8 is involved in the pathogenesis of acute Lyme arthritis.
Copyright © 1997, American Society for Microbiology
Borrelia burgdorferi migrates into joint capsules and causes an up- regulation of interleukin-8 in synovial membranes of dogs experimentally infected with ticks
James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA. rks4@cornell.edu
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