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Infection and Immunity, June 2005, p. 3787-3789, Vol. 73, No. 6
0019-9567/05/$08.00+0 doi:10.1128/IAI.73.6.3787-3789.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Microbiology, Immunology and Parasitology, Universidade Federal de São Paulo, Escola Paulista de Medicina, São Paulo, SP,1 Division of Parasitology, Faculdade NOVAFAPI, Teresina, PI,2 Division of Infectious and Parasitic Diseases, Universidade Federal do Piauí, Teresina, PI,3 Department of Clinical Veterinary, Universidade Federal do Piauí, Teresina, Piauí, PI, Brazil4
Received 20 October 2004/ Returned for modification 8 December 2004/ Accepted 20 January 2005
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in asymptomatic subjects or of IFN-
, interleukin 4 (IL-4), and IL-10 in oligosymptomatic subjects. In contrast, responses of symptomatic patients and dogs were lower, with production of IL-4 and IL-10. |
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) (3, 4, 5, 8, 13). Leishmania (L.) infantum cysteine proteinases have been used for the evaluation of humoral and cellular immune responses in human and canine VL (9, 12). A recombinant cysteine proteinase from L. (L.) chagasi, rLdccys1, expressed by the Ldccys1 gene (10) in Escherichia coli, was shown to be a suitable tool for the diagnosis of American VL (6). The present study demonstrates that rLdccys1 elicits cellular immune responses in naturally infected humans and dogs in different stages of VL.
L. (L.) chagasi (MHOM/BR/1972/LD) amastigotes were isolated from spleens of infected hamsters, as previously described (2). The L. (L.) chagasi Ldccys1 was cloned and expressed as described elsewhere (6). The study population included human and canine blood samples obtained from subjects living in Teresina, Piauí State, Brazil, an area where VL is endemic, and were classified as shown in Table 1. The human and dog procedures were approved by the Ethical Committee for Human and Animal Care at the Universidade Federal de São Paulo, Escola Paulista de Medicina. The lymphoproliferative assays were performed with peripheral blood mononuclear cells (PBMC) purified by Ficoll-Hypaque density gradient centrifugation. For in vitro proliferation assays, the cells were cultured into 96-wells plates (1 x 106 cells/ml) in RPMI 1640 medium with 10% pooled human serum (R10) in the presence of rLdccys1 (2.5 µg/ml) or L. (L.) chagasi amastigote extracts (AM) (equivalent to 1 x 107 amastigotes). After 96 h at 37°C in 5% CO2, the cells were pulsed with 1 µCi of [3H]thymidine/well for 18 h, and [3H]thymidine uptake was determined after filtration on glass fiber filters. Lymphoproliferative responses were expressed as stimulation indexes (SI) determined by dividing the mean counts per minute for antigen-stimulated cells, in triplicate, by the mean counts for the control medium. Student's t test was used with SigmaStat software to evaluate the significance of the data (P < 0.05). After stimulation with rLdccys1, PBMC from asymptomatic, oligosymptomatic, symptomatic, and treated patients proliferated with mean stimulation indexes of 8.0, 6.25, 2.45, and 4.1, respectively, whereas healthy individuals showed basal levels of lymphoproliferation. Lower stimulation was obtained for PBMC from the same patients with AM (SI of 2.5, 5.0, 2.1, and 2.0 from asymptomatic, oligosymptomatic, symptomatic, and treated patients, respectively) (Fig. 1A). In PBMC from asymptomatic, oligosymptomatic, and symptomatic dogs, rLdccys1 induced SI means of 11, 3.3, and 1.8, respectively, whereas lower responses were obtained with AM (SI of 2.2, 1.2, and 0.6 from asymptomatic, oligosymptomatic, and symptomatic dogs, respectively). Corroborating our results, the lymphoproliferative responses stimulated by the recombinant L. (L.) infantum cysteine proteinase B (rCPB) in Iranian dogs with active VL were weaker in symptomatic than in asymptomatic animals. However, in contrast to our results, asymptomatic dogs showed higher lymphoproliferative responses to the total L. (L.) infantum lysate than to rCPB. In addition, for asymptomatic dogs, we found that higher lymphoproliferative responses were elicited by rLdccys1 (SI = 11) than by rCPB (SI
4.0) (9, 12). For evaluation of lymphokine production, 1 x 107 PBMC from VL patients and dogs were cultured in 1 ml of R10 and maintained for 72 h in the presence of 2.5 µg/ml rLdccys1. Culture supernatants were tested for IFN-
, IL-4, and IL-10 using a specific enzyme-linked immunosorbent assay. PBMC from asymptomatic patients secreted high levels of IFN-
when stimulated with rLdccys1 (1.722 ng/ml). Lower levels of IFN-
(0.871 ng/ml) were produced by PBMC from oligosymptomatic patients, whereas this lymphokine was not detected in symptomatic individuals. IL-4 and IL-10 were secreted by PBMC from oligosymptomatic patients (0.277 ng/ml and 0.317 ng/ml, respectively), and a significant increase in the secretion of these two lymphokines was detected in symptomatic individuals (0.848 ng/ml and 0.725 ng/ml for IL-4 and IL-10, respectively). No lymphokine secretion was found in the PBMC supernatants from normal and treated patients (Table 2). These results corroborate literature data which show that VL patients with a controlled form of the disease display Th1-type lymphokines, whereas immunosuppression and a Th2 profile predominate in individuals with exacerbated disease (1, 8, 14). Secretion of significant levels of IFN-
, IL-4, and IL-10 by lymphocytes from oligosymptomatic patients is in agreement with data which showed both resistant (IFN-
) and susceptible (IL-10) profiles in this form of VL (7). PBMC from asymptomatic and oligosymptomatic dogs secreted IFN-
, whereas IL-4 and IL-10 were released by PBMC from symptomatic animals (Table 3). Lymphocytes from oligosymptomatic dogs did not secrete IL-4; however, IL-10 values were comparable in the supernatants of PBMC from humans and dogs presenting symptomatic and oligosymptomatic signs of VL. Few studies have reported cytokine dosage in dogs with VL (15), impairing comparison with our results. The production of nitric oxide (NO) was also evaluated for the supernatants from human and dog lymphocytes stimulated by rLdccys1, by use of the Griess reagent. PBMC from asymptomatic and oligosymptomatic patients secreted significant levels of NO (108.42 µM ± 19.22 µM and 58.71 µM ± 7.78 µM, respectively), whereas symptomatic and treated patients secreted lower NO concentrations (19.22 µM ± 0.8 µM and 5.02 µM ± 0.2 µM, respectively) (Fig. 2A). A similar relationship between NO production and the clinical signs of VL was observed with PBMC cultures from dogs stimulated with rLdccys1 (82.16 µM ± 8.33 µM, 25.21 µM ± 7.44 µM, and 7.79 µM ± 0.34 µM from asymptomatic, oligosymptomatic, and symptomatic dogs, respectively) (Fig. 2B). The observed direct correlation between the secretion of IFN-
and NO during the development of VL in humans and dogs has been previously reported (11, 16).
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TABLE 1. Classification of study population according to VL clinical symptoms and isolation of L. (L.) chagasi amastigotes from bone marrow
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FIG. 1. Proliferative responses of PBMC recovered from normal, asymptomatic, oligosymptomatic, symptomatic, and treated humans (A) and dogs (B) in the presence of rLdccys1 and AM. Data are representative of three experiments and are shown as mean SI ± standard deviations. An SI of 2.0 was considered a positive response (P < 0.05).
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TABLE 2. Lymphokine production by PBMC from normal and VL patients stimulated by L. (L.) chagasi rLdccysa
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TABLE 3. Lymphokine production by PBMC from normal and VL dogs stimulated by L. (L.) chagasi rLdccysa
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FIG. 2. NO production. PBMC isolated from human (A) and dog (B) blood were cultured for 72 h in the presence of 2.5 µg/ml rLdccys1, and NO was assayed in the cellular supernatants as described previously. Results are shown as the means ± standard deviations and are representative of three experiments.
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This study was supported by FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo), CAPES (Conselho Nacional de Desenvolvimento Científico e Tecnológico), and FACULDADE NOVAFAPI.
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production and lymphocyte proliferation in visceral leishmaniasis. J. Immunol. 152:5949-5956.[Abstract]
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