ag-213 and Trypanosomiasis--African

Bidirectional signalling between Trypanosoma brucei brucei and CD8+ T cells involves reciprocal action of the parasite-derived trypanosome derived lymphocyte triggering factor (TLTF) and lymphocyte-derived IFN-gamma. Herein we further characterize this relationship and report quantitation of TLTF secretion into culture supernatants using a newly developed ELISA. Secretion is induced by IFN-gamma in a dose-response manner, with 100 U/ml giving maximal yields of bioactive TLTF as assessed by ELISA and ELISPOT. This is a constitutive and active secretion. Furthermore, IFN-gamma-induced secretion was dependent on tyrosine protein kinase activity. Specific blockers of this signalling system resulted in lower yields of TLTF in the culture supernatants.

Topics: Animals; Antibodies, Monoclonal; Blotting, Western; Dose-Response Relationship, Drug; Electrophoresis, Polyacrylamide Gel; Enzyme Inhibitors; Enzyme-Linked Immunosorbent Assay; Fluorescent Antibody Technique; Interferon-gamma; Leukocytes, Mononuclear; Protein-Tyrosine Kinases; Protozoan Proteins; Rats; Rats, Inbred Lew; Rats, Sprague-Dawley; Signal Transduction; Trypanosoma brucei brucei; Trypanosomiasis, African; Tyrphostins

The tyrosine kinase activity of Trypanosoma brucei brucei upon stimulation with interferon-gamma (IFN-gamma) was investigated. IFN-gamma induced a rapid and strong increase of tyrosine phosphorylation of several cellular proteins that reached maximum after 5 min and was followed by a decrease to control levels after 120 min. The tyrosine kinase-specific inhibitor tyrphostin A47 at a concentration of 10(-6) M reduced IFN-gamma-induced protein phosphorylation. In vitro application of 10(-6) M tyrphostin A47 to the trypanosome cultures caused a significant reduction of [3H]thymidine uptake by IFN-gamma-stimulated trypanosomes. In animals, 2 x 0.5 mg of tyrphostin A47 (injected intraperitoneally) caused a significant reduction of parasite growth compared with the vehicle dimethyl sulfoxide or the inactive compound tyrphostin A1. In conclusion, tyrosine kinases are strongly up-regulated in IFN-gamma-stimulated T. b. brucei, and specific tyrosine kinase inhibitors can prevent trypanosome growth in vitro and in vivo.

Topics: Animals; Caffeic Acids; Enzyme Inhibitors; Interferon-gamma; Male; Mice; Phosphoproteins; Phosphorylation; Protein-Tyrosine Kinases; Rats; Recombinant Proteins; Trypanosoma brucei brucei; Trypanosomiasis, African; Tyrphostins