Diethylcarbamazine (DEC) is an anthelmintic piperazine derivative drug with putative immunomodulating properties, including increased platelet and granulocyte adhesion to parasites and enhanced production of cytokines. To further analyse these properties in a well-established animal model, we evaluated the effect of DEC on antibody, cellular cytokine response and respiratory burst in BALB/c mice. Animals were challenged with a thymus-dependent (tetanus toxoid, (TT)) and with a thymus-independent (lipopolysaccharide, (LPS)) antigen and treated with DEC for seven days with two different doses (50 mg/day and 500 mg/day). Serum was assessed for antibody production at 0, 4, 7, 14, 21 and 28 days after stimulation and at 0, 24 and 48 h for IL-2, IFN-γ, IL-10 and IL-12 release. Respiratory burst of neutrophils and monocytes from peripheral blood was measured by flow cytometry. We found low-dose treatment with DEC enhanced cytokine production vs. TT and antibody production vs. LPS, whereas a higher dose enhanced significantly the respiratory burst of both polymorphonuclear leukocytes and monocytes, with a significant higher effect on the former. Our results suggest a stimulating, dose-dependent immunomodulatory effect of DEC with a higher effect on the phagocytic cells.

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We isolated and purified to homogeneity a caseinolytic protease from a Nocardia brasiliensis cell extract. Preparative polyacrylamide gel electrophoresis and electroelution were employed for purification. This purified protease was injected in BALB/c mice and induced IgM and IgG anti-protease antibodies. Active immunization of mice with this protease prevented mycetoma development in experimentally infected animals. Passive immunization with hyperimmune sera containing a high anti-protease antibody titer conferred partial but transient protection when collected 30 days after donor's immunization. The protective effect of hyperimmune sera was lost when obtained from donors after 60 days from their immunization despite its higher anti-protease antibody concentration. Cytokines are good candidates to explain these findings.

We prepared a Nocardia brasiliensis cell extract and purified two immunodominant antigens with molecular weights of 61,000 and 24,000. The isolated proteins were shown to be reasonably pure when analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (8 to 18% polyacrylamide gradient) and stained with Coomassie blue and silver nitrate. By using an immunoelectrotransfer blot method (Western blotting), we demonstrated that these two purified proteins reacted strongly with serum from N. brasiliensis-infected mycetoma patients. To obtain anti-P61 and anti-P24 monoclonal antibodies (MAbs), we used an N. brasiliensis cell extract as the antigen for the first immunization; 2 weeks later female mice were reimmunized with a semipurified antigen containing the P24 or P61 fraction. A booster injection was given 3 days before the fusion was carried out. Two hybrids that reacted strongly with P24 were cloned by limiting dilution, the generated MAbs were analyzed for isotyping, and their specificity was tested in a Western blot assay with cell extracts from Nocardia asteroides and Mycobacterium tuberculosis cultures. Anti-P24 MAbs were shown to be specific for N. brasiliensis HUJEG-1 and did not cross-react with either the N. asteroides or M. tuberculosis strains used. However, additional studies with several N. asteroides and N. brasiliensis strains are needed to investigate whether there are cross-reactions between strains or species when these MAbs are used. The anti-P61 and anti-P24 MAbs were used to locate the antigen in N. brasiliensis cells by immunofluorescence. The lack of reaction with intact cells suggests that the P24 and P61 antigens are not exposed in the complete bacterial cell surface or that the recognized epitopes are different. Only one anti-P61 MAb that reacted specifically with the N. brasiliensis cell extract was obtained.