INCREASED INTESTINAL TNF-ALPHA, IL-1-BETA AND IL-6 EXPRESSION IN OVINE PARATUBERCULOSIS

Mycobacterium avium subspecies paratuberculosis is an intracellular pa rasite of intestinal macrophages and causes a chronic granulomatous en teritis in sheep and other ruminants (paratuberculosis or Johne's dise ase). Macrophages can produce a variety of immunoregulatory cytokines that may influence mycobacterial killing and produce disordered inflam mation within the gut. In this study, messenger RNA (mRNA) was extract ed from intestinal tissue from control and multibacillary diseased she ep and profiles for the cytokines tumour necrosis factor-alpha (TNF-al pha), interleukin-1 beta (IL-1 beta), IL-6, transforming growth factor -beta 1 (TGF-beta 1) and granulocyte-macrophage colony stimulating fac tor (GM-CSF) were semi-quantified using reverse transcriptase polymera se chain reactions (RT-PCR). Infected intestinal tissues had significa ntly increased mRNA for TNF-alpha, IL-1 beta and IL-6 but TGF-beta 1 a nd GM-CSF mRNA levels were not significantly different from controls. Supernatants from in vitro intestinal cultures were assayed for TNF-al pha activity using the PK(15)-1512 cytotoxicity bioassay and levels we re significantly raised in diseased samples. TNF-alpha was not detecte d in any serum samples. Further analysis on intestinal tissues from sh eep with the different, paucibacillary, form of disease showed signifi cant elevation of TNF-alpha mRNA but not other cytokines tested. Incre ased pro-inflammatory cytokine expression in the intestine coincident with a failed or misdirected immune response may contribute to the pat hogenesis of paratuberculosis and the persistence of a chronic inflamm atory state.