CYTOKINE GENE-EXPRESSION IN SKIN OF SUSCEPTIBLE GUINEA-PIG INFECTED WITH TREPONEMA-PALLIDUM

Using a semi-quantitative multiplex reverse transcription-polymerase c hain reaction assay, we examined cytokine mRNA expression for interleu kin-1 alpha (IL-1 alpha), IL-2, IL-10, IL-12p40, tumour necrosis facto r-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) in skin samples obtained from C4-deficient (C4D) guinea-pigs inoculated i ntradermally with virulent Treponema pallidum (VTP). Controls included unmanipulated animals, guinea-pigs injected with T. pallidum-free rab bit inflammatory testicular fluid (TTF) alone, or mixed with heat-kill ed organisms (HKTP). The expression of IL-1 alpha, IL-12p40, and TNF-a lpha mRNA [T helper type 1 (Th1)] remained within the normal range in both infected and control animals throughout the experimental period. However, a significant increase (P<0.05) in IL-10 mRNA (Th2) was found exclusively in the VTP-inoculated animals from 3 to 30 days post-infe ction. Another unique characteristic of the inflammatory response in i nfected guinea-pigs was the appearance, between 11 and 30 days postino culation, of a substantial number of eosinophils in addition to infilt rating mononuclear cells. The results showed a local Th2 response whic h is consistent with an inadequate immune response. This is reflected by the lengthy and incomplete clearance of the pathogen from the local site of entry and the chronic infection of distant organs.