This is a multidisciplinary preclinical program designed to study the role of TNFalpha in experimental tuberculosis and other mycobacterial infections and to explore how TNFalpha production and the ensuing toxicity are inhibited by thalidomide. Our preliminary results are derived from clinical studies and in vitro studies. In patients with leprosy we have found that lepromatous patients suffering from Erythema Nodosum Leprosum (ENL) produce greater quantities of TNFalpha than do patients without ENL. Thalidomide treatment reduces TNFalpha production both in vivo and in vitro. Similar results have been obtained in vitro with cells from patients with active tuberculosis, thus prompting the recent initiation of a thalidomide trial in patient with tuberculosis and HIV-1 infection. To enable a more extensive analysis of the effect of thalidomide on M. tuberculosis infection than is possible in humans, we are using the M. tuberculosis infection of guinea pigs as a model that is known to most closely resemble human tuberculosis infection. As well, we are performing experiments to evaluate the effect of thalidomide on TNFalpha production in mice in response to the well studied TNFalpha agonist LPS. The effect of thalidomide on TNFalpha production is monitored in the blood and tissue spaces as well as TNFalpha-induced cellular extravasation, shock, and death. Using molecular biological techniques, including Northern blot analysis, PCR and nuclear runoff assays, we will define the mechanisms whereby thalidomide inhibits TNFalpha production by monocytes and other cell types which are known to produce TNFalpha and are likely to participate in TNFalpha-induced inflammatory responses. The selectivity of the effect of thalidomide on TNFalpha production versus other cytokines will also be examined to establish whether thalidomide can inhibit TNFalpha induced inflammation and toxicity without interfering with the generation of T cell mediated immunity during tuberculosis and other mycobacterial infections. The relative selectivity and efficiency of thalidomide will be compared with other known TNFalpha inhibitors, such as Dexamethasone and Pentoxifylline, both in vivo and in vitro. In addition, thalidomide-related compounds with absent or reduced teratogenicity will be compared with the parent compound for their capacity to inhibit TNFalpha production. These studies will enable us to design rational clinical trials in humans aimed at selectively reducing TNFalpha-induced inflammatory toxicity in the context of immunodulation and cytokine therapy of tuberculosis and other infections.
