ca-074-methyl-ester and Leishmaniasis--Cutaneous

Prior to the activation of CD4 (+) T cells, exogenous proteins must be digested by endo/lysosomal enzymes in antigen-presenting cells (APC) to produce antigenic peptides that are able to be presented on class II molecules of the MHC. Studies described here inspect the functional significance of cathepsin L inhibition for antigen processing and T (h) 1/T (h) 2 differentiation in experimental leishmaniasis. We first demonstrated using in vitro systems that cathepsin L is one of the candidate endo/lysosomal enzymes in processing of soluble Leishmania antigen (SLA) and that its specific inhibitor, CLIK148, modulated the processing of SLA. BALB/c mice are known to be susceptible to infection with Leishmania major. Interestingly, treatment of BALB/c mice with CLIK148 exacerbated the infection by enhancing the development of SLA-specific T (h) 2-type response such as production of IL-4 and generation of T (h) 2-dependent specific IgE/IgG1 antibodies. Moreover, addition of CLIK148 in incubation of a SLA-specific CD4 (+) T cell line with APC up-regulated the production of IL-4. However, CLIK148 did not exert any direct influence on the function of T cells themselves. Taken together, these findings suggest that treatment of host mice with CLIK148 affects the processing of SLA in APC, resulting in the potentiation of T (h) 2-type immune responses and thus leading to exacerbation of the infection. Furthermore, endo/lysosomal cathepsin L was found to be functionally distinct from previously described cathepsins B and D.

Topics: Adjuvants, Immunologic; Animals; Antigen Presentation; Antigens, Protozoan; Cathepsin L; Cathepsins; Cell Differentiation; Cell Line; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors; Dipeptides; Endosomes; Epoxy Compounds; Female; Injections, Intraperitoneal; Leishmania major; Leishmaniasis, Cutaneous; Lysosomes; Mice; Mice, Inbred BALB C; Pyridines; Solubility; Th2 Cells

We previously reported that CA074, a specific inhibitor of cathepsin B, significantly deviated immune responses from the disease-promoting Th2 type to the protective Th1 type in BALB/c mice infected with Leishmania major. Herein, we found that pepstatin A-sensitive aspartic proteases (PSAP) in lysosomes seem to play a different role from that of cathepsin B in antigen-processing and Ii-degradation. That is, cathepsin B appears to digest 16-, 28-, and 31-kDa peptides of soluble leishmania antigen (SLA), whereas PSAP seems to process mainly 28-kDa peptides. Furthermore, the latter protease contributed to the degradation of Ii but cathepsin B did not. Following treatment with pepstatin A, both Th1 and Th2 responses were profoundly suppressed in resistant DBA/2 mice (H-2(d)) and in susceptible BALB/c mice (H-2(d)), and both strains of mice became markedly susceptible compared with the untreated groups, probably owing to failure in degradation of Ii and partly to failure in digestion of 28-kDa peptide.

Topics: Animals; Antibody Formation; Antigen Presentation; Antigen-Presenting Cells; Antigens, Differentiation, B-Lymphocyte; Antigens, Protozoan; Aspartic Acid Endopeptidases; Cathepsin B; CD4-Positive T-Lymphocytes; Cell Division; Cysteine Proteinase Inhibitors; Cytokines; Dipeptides; Disease Models, Animal; Female; Histocompatibility Antigens Class II; Leishmania major; Leishmaniasis, Cutaneous; Lymphocytes; Lysosomes; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Pepstatins; Th1 Cells; Th2 Cells