Abstract
BackgroundCaseous lymphadenitis (CLA) is a disease of small ruminants caused by Corynebacterium pseudotuberculosis. The pathogenesis of CLA is a slow process, and produces a chronic rather than an acute disease state. Acute phase proteins (APP) such as haptoglobin (Hp) serum amyloid A (SAA) and α1 acid glycoprotein (AGP) are produced by the liver and released into the circulation in response to pro-inflammatory cytokines. The concentration of Hp in serum increases in experimental CLA but it is not known if SAA and AGP respond in parallel or have differing response profiles.ResultsThe concentration in serum of Hp, SAA and AGP in 6 sheep challenged with 2 × 105 cells of C. pseudotuberculosis showed significant increases (P < 0.05) compared to 3 unchallenged control sheep. By day 7 post infection. (p.i.) the Hp and SAA concentrations reached mean (± SEM) values of 1.65 ± 0.21 g/L and 18.1 ± 5.2 mg/L respectively. Thereafter, their concentrations fell with no significant difference to those of the control sheep by day 18 p.i.. In contrast, the serum AGP concentration in infected sheep continued to rise to a peak of 0.38 ± 0.05 g/L on day 13 p.i., after which a slow decline occurred, although the mean concentration remained significantly higher (P < 0.05) than the control group up to 29 days p.i.. Specific IgG to phospholidase D of C. pseudotuberculosis became detectable at 11 days p.i. and continued to rise throughout the experiment.ConclusionThe serum concentrations of Hp, SAA and AGP were raised in sheep in an experimental model of CLA. An extended response was found for AGP which occurred at a point when the infection was likely to have been transforming from an acute to a chronic phase. The results suggest that AGP could have a role as a marker for chronic conditions in sheep.
Highlights
Caseous lymphadenitis (CLA) is a disease of small ruminants caused by Corynebacterium pseudotuberculosis
Caseous Lymphadenitis (CLA) is a chronic disease of sheep and goats caused by Corynebacterium pseudotuberculosis and is characterised by the formation of pyogranulomas within the superficial lymph nodes draining the site of infection
In the previous study it was demonstrated that subcutaneous inoculation of sheep with 104 colony-forming units of a virulent, UK C. pseudotuberculosis isolate was sufficient to reproduce the symptoms observed in naturally-occurring CLA
Summary
Caseous lymphadenitis (CLA) is a disease of small ruminants caused by Corynebacterium pseudotuberculosis. Caseous Lymphadenitis (CLA) is a chronic disease of sheep and goats caused by Corynebacterium pseudotuberculosis and is characterised by the formation of pyogranulomas within the superficial lymph nodes draining the site of infection. Measurement of the production of IFN-γ by peripheral blood lymphocytes in response to C. pseudoturberculosis antigen has been reported as a marker of cell-mediated immunity in CLA [2] Inflammatory cytokines such as TNF-α, IL-1β and IL6 are known to stimulate the systemic acute phase response [6] and this pathophysiological reaction has been identified in experimental CLA. An increase in concentrations of serum haptoglobin (Hp), a major acute phase protein in sheep and other ruminants [8], has been reported in response to C. pseudotuberculosis infection [9]
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