Effect of TNF-α production inhibitors on the production of pro-inflammatory cytokines by peripheral blood mononuclear cells from HTLV-1-infected individuals

Human T lymphotropic virus type 1 (HTLV-1) is the causal agent of myelopathy/tropical spastic paraparesis (HAM/TSP), a disease mediated by the immune response. HTLV-1 induces a spontaneous proliferation and production of pro-inflammatory cytokines by T cells, and increasing interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) levels are potentially involved in tissue damage in diseases related to HTLV-1. This exaggerated immune response is also due to an inability of the natural regulatory mechanisms to down-modulate the immune response in this group of patients. TNF-α inhibitors reduce inflammation and have been shown to improve chronic inflammatory diseases in clinical trials. The aim of this study was to evaluate the ability of pentoxifylline, forskolin, rolipram, and thalidomide to decrease in vitro production of TNF-α and IFN-γ in cells of HTLV-1-infected subjects. Participants of the study included 19 patients with HAM/TSP (mean age, 53 ± 11; male:female ratio, 1:1) and 18 HTLV-1 carriers (mean age, 47 ± 11; male:female ratio, 1:2.6). Cytokines were determined by ELISA in supernatants of mononuclear cell cultures. Pentoxifylline inhibited TNF-α and IFN-γ synthesis with the minimum dose used (50 µM). The results with forskolin were similar to those observed with pentoxifylline. The doses of rolipram used were 0.01-1 µM and the best inhibition of TNF-α production was achieved with 1 µM and for IFN-γ production it was 0.01 µM. The minimum dose of thalidomide used (1 µM) inhibited TNF-α production but thalidomide did not inhibit IFN-γ production even when the maximum dose (50 µM) was used. All drugs had an in vitro inhibitory effect on TNF-α production and, with the exception of thalidomide, all of them also decreased IFN-γ production.

Clinical and immunological features of patients with atopy and concomitant HTLV-1 infection

Human T-cell lymphotropic virus type 1 (HTLV-1) induces an exacerbated type 1 immune response characterized by high spontaneous IFN-γ and TNF-α production. Allergic rhinitis and asthma are associated with the type 2 immune response, with elevated secretion of IL-4 and IL-5. The aim of this study was to characterize the immune response in atopic HTLV-1 carriers. The cytokine profile of atopic HTLV-1 carriers (N = 10; all females) was compared with that of non-atopic HTLV-1 carriers (N = 14; 9 females and 5 males). Mean patient age of atopic and non-atopic groups was 45 ± 8 and 38 ± 11 years, respectively. All atopic HTLV-1 carriers had rhinitis with or without asthma and a skin prick test positive for Dermatophagoides pteronyssinus antigen 1 (Derp-1). There was no difference in cytokine levels between the two groups in unstimulated peripheral blood mononuclear cell cultures. In cultures stimulated with Derp-1, IFN-γ levels tended to be higher (P = 0.06) and IL-5 levels were higher (P = 0.02) in atopic HTLV-1 patients than in non-atopic subjects. In contrast, IL-10 was lower (P = 0.004) in atopic than in non-atopic HTLV-1-infected subjects. This study shows that HTLV-1 infection with an exaggerated type 1 immune response does not prevent atopy. In this case, the exacerbated type 1 and type 2 immune responses were due to a lack of IL-10 production, a cytokine that plays an important role in down-modulating type 1 and type 2 immune responses and in preventing the development of chronic inflammatory diseases.

High HTLV-1 proviral load, a marker for HTLV-1 associated myelopathy/tropical spastic paraparesis, is also detected in patients with infective dermatitis associated with HTLV-1

Salvador (BA, Brazil) is an endemic area for human T-cell lymphotrophic virus type 1 (HTLV-1). The overall prevalence of HTLV-1 infection in the general population has been estimated to be 1.76%. HTLV-1 carriers may develop a variety of diseases such as adult T-cell leukemia/lymphoma, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and infective dermatitis associated with HTLV-1 (IDH). IDH is a chronic and severe form of childhood exudative and infective dermatitis involving mainly the scalp, neck and ears. It has recently been observed that 30% of patients with IDH develop juvenile HAM/TSP. The replication of HTLV-1 has been reported to be greater in adult HAM/TSP patients than in asymptomatic HTLV-1 carriers. In the current study, the proviral load of 28 children and adolescents with IDH not associated with HAM/TSP was determined and the results were compared to those obtained in 28 HTLV-1 adult carriers and 28 adult patients with HAM/TSP. The proviral load in IDH patients was similar to that of patients with HAM/TSP and much higher than that found in HTLV-1 carriers. The high levels of proviral load in IDH patients were not associated with age, duration of illness, duration of breast-feeding, or activity status of the skin disease. Since proviral load is associated with neurological disability, these data support the view that IDH patients are at high risk of developing HAM/TSP.

Força muscular e mortalidade na lista de espera de transplante de fígado / Muscle strength and mortality while on a liver transplant waiting list

OBJETIVO: Avaliar a força de músculos respiratórios e de mão em pacientes na lista de espera para o transplante de fígado e associá-los a mortalidade. MATERIAIS E MÉTODOS: Foram estudados retrospectivamente 132 pacientes submetidos à avaliação fisioterapêutica de rotina e que esperavam o transplante de fígado. A força dos músculos ventilatórios foi avaliada por meio das pressões inspiratória e expiratória máximas e a força do membro superior por meio de dinamometria. Os pacientes foram divididos em dois grupos: grupo A, com 51 pacientes (14 mulheres, 50,1±12,3 anos) que morreram enquanto estavam na lista de espera e grupo B, com 81 pacientes (31 mulheres, 45,0±3,8 anos) que sobreviveram até o transplante de fígado. Foi utilizado o teste de t de Student com nível de significância de 5 por cento. RESULTADOS: Os valores médios da pressão inspiratória máxima (PImax) dos grupos A e B foram 65,7±28,0 e 77,5±33,8mmHg (p=0,04), respectivamente, e as pressões expiratórias máximas foram 72,9±32,9 e 84,4±33,1mmHg (p=0,07), respectivamente. Os valores médios da força da mão esquerda dos grupos A e B foram 18,5±8,1 e 21,5±10,5kgf (p=0,08), respectivamente, e da força da mão direita foram 20,2±9,7 e 23,5±12,5kgf (p=0,10), respectivamente. CONCLUSÕES: A PImax é menor nos pacientes que morreram enquanto aguardavam o transplante. No mesmo grupo, foi observado que a pressão expiratória máxima e a força da mão direita e esquerda foram menores, apesar de não apresentarem diferenças estatisticamente significante.

OBJECTIVE: To evaluate respiratory muscle strength and hand strength in patients on a liver transplant waiting list and to associate these with mortality. METHODS: one hundred and thirty-two patients who underwent routine physical therapy evaluation while waiting for liver transplantation were studied retrospectively. Respiratory muscle strength was assessed by measuring the maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP), and upper-limb strength was evaluated by dynamometry. The patients were divided into two groups: group A, consisting of 51 patients (14 females, 50.1±12.3 years) who died while on the waiting list; and group B, consisting of 81 patients (31 females, 45.0±3.8 years) who survived until the time of liver transplant. Student's t test was used with a 5 percent significance level. RESULTS: The mean MIP values for groups A and B were 65.7±28.0 and 77.5±33.8mmHg (p=0.04), respectively, and the mean MEP values were 72.9±32.9 and 84.4±33.1mmHg (p=0.07), respectively. The mean values for left-hand strength in groups A and B were 18.5±8.1 and 21.5±10.5kgf (p=0.08), and the mean values for right-hand strength were 20.2±9.7 and 23.5±12.5kgf (p=0.10), respectively. CONCLUSIONS: MIP was lower in the patients who died while waiting for liver transplantation. In the same group, it was observed that the MEP values and right and left-hand strength were numerically lower, although they did not reach statistically significant differences.

Prostanoids modulate inflammation and alloimmune responses during graft rejection

Acute rejection of a transplanted organ is characterized by intense inflammation within the graft. Yet, for many years transplant researchers have overlooked the role of classic mediators of inflammation such as prostaglandins and thromboxane (prostanoids) in alloimmune responses. It has been demonstrated that local production of prostanoids within the allograft is increased during an episode of acute rejection and that these molecules are able to interfere with graft function by modulating vascular tone, capillary permeability, and platelet aggregation. Experimental data also suggest that prostanoids may participate in alloimmune responses by directly modulating T lymphocyte and antigen-presenting cell function. In the present paper, we provide a brief overview of the alloimmune response, of prostanoid biology, and discuss the available evidence for the role of prostaglandin E2 and thromboxane A2 in graft rejection.

Long-term ethanol intoxication reduces inflammatory responses in rats

The anti-inflammatory effects of long-term ethanol intoxication were determined during ethanol treatment and withdrawal on the basis of neutrophil and eosinophil migration, hind paw edema and mast cell degranulation. Male Wistar rats (180-200 g, around 2 months of age) were exposed to increasing concentrations of ethanol vapor over a 10-day period. One group was evaluated immediately after exposure (treated group - intoxicated), and another was studied 7 h later (withdrawal group). Ethanol inhalation treatment significantly inhibited carrageenan- (62 percent for the intoxicated group, N = 5, and 35 percent for the withdrawal group, N = 6) and dextran-induced paw edema (32 percent for intoxicated rats and 26 percent for withdrawal rats, N = 5 per group). Ethanol inhalation significantly reduced carrageenan-induced neutrophil migration (95 percent for intoxicated rats and 41 percent for withdrawn rats, N = 6 per group) into a subcutaneous 6-day-old air pouch, and Sephadex-induced eosinophil migration to the rat peritoneal cavity (100 percent for intoxicated rats and 64 percent for withdrawn rats, N = 6 per group). A significant decrease of mast cell degranulation was also demonstrated (control, 82 percent; intoxicated, 49 percent; withdrawn, 51 percent, N = 6, 6 and 8, respectively). Total leukocyte and neutrophil counts in venous blood increased significantly during the 10 days of ethanol inhalation (leukocytes, 13, 27 and 40 percent; neutrophils, 42, 238 and 252 percent, respectively, on days 5, 9 and 10, N = 7, 6 and 6). The cell counts decreased during withdrawal, but were still significantly elevated (leukocytes, 10 percent; neutrophils, 246 percent, N = 6). These findings indicate that both the cellular and vascular components of the inflammatory response are compromised by long-term ethanol intoxication and remain reduced during the withdrawal period.

Immunoglobulin E and systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by intense polyclonal production of autoantibodies and circulating immune complexes. Some reports have associated SLE with a Th2 immune response and allergy. In the present study 21 female patients with SLE were investigated for total IgE and IgE antibodies to dust house aeroallergens by an automated enzyme-linked fluorescent assay, and were also evaluated for antinuclear IgE autoantibodies by a modified indirect immunofluorescence test using HEp-2 cells as antigen substrate. Additionally, immunocapture ELISA was used to investigate serum anti-IgE IgG autoantibodies. Serum IgE above 150 IU/ml, ranging from 152 to 609 IU/ml (median = 394 IU IgE/ml), was observed in 7 of 21 SLE patients (33 percent), 5 of them presenting proteinuria, urinary cellular casts and augmented production of anti-dsDNA antibodies. While only 2 of 21 SLE patients (9.5 percent) were positive for IgE antibodies to aeroallergens, all 10 patients with respiratory allergy (100 percent) from the atopic control group (3 males and 7 females), had these immunoglobulins. SLE patients and healthy controls presented similar anti-IgE IgG autoantibody titers (X = 0.37 ± 0.20 and 0.34 ± 0.18, respectively), differing from atopic controls (0.94 ± 0.26). Antinuclear IgE autoantibodies were detected in 17 of 21 (81 percent) sera from SLE patients, predominating the fine speckled pattern of fluorescence, that was also observed in IgG-ANA. Concluding, SLE patients can present increased IgE levels and antinuclear IgE autoantibodies without specific clinical signs of allergy or production of antiallergen IgE antibodies, excluding a possible association between SLE and allergy.

Identification of immunodominant epitopes of Schistosoma mansoni vaccine candidate antigens using human T cells

Paramyosin and Sm14 are two of the six antigens selected by the World Health Organization as candidates to compose a subunit vaccine against schistosomiasis. Both antigens are recognized by individuals naturally resistant to Schistosoma mansoni infection and induced protective immunity in the murine model. Three Sm14 epitopes and eleven paramyosin epitopes were selected by their ability to bind to different HLA-DR molecules using the TEPITOPE computer program, and these peptides were synthetically produced. The cellular recognition of Sm14 and paramyosin epitopes by peripheral blood mononuclear cells of individuals living in endemic area for schistosomiasis was tested by T cell proliferation assay. Among all Sm14 and paramyosin epitopes studied, Sm14-3 was preferentially recognized by individuals naturally resistant to S. mansoni infection while Para-5 was preferentially recognized by individuals resistant to reinfection. These two peptides represent promising antigens to be used in an experimental vaccine against schistosomiasis, since their preferential recognition by resistant individuals suggest their involvement in the induction of protective immunity.

Antileishmanial IgG and IgE antibodies recognize predominantly carbohydrate epitopes of glycosylated antigens in visceral leishmaniasis

The specificity of human antileishmanial IgG and IgE antibodies to glycosylated antigens of Leishmania chagasi was evaluated. An ELISA was performed with soluble leishmanial antigen (SLA) and a panel of 95 sera including samples from patients with subclinical infection (SC) and visceral leishmaniasis (VL), subjects cured of visceral leishmaniasis (CVL), and from healthy individuals from endemic areas (HIEA). Antileishmanial IgG were verified for 18 (40 percent) of 45 SC subjects (mean absorbance of 0.49 ± 0.17). All nine sera from VL patients had such antibody (0.99 ± 0.21), while 11 (65 percent) of 17 CVL individuals were seropositive (0.46 ± 0.05). Only three (12 percent) of 24 HIEA controls reacted in IgG-ELISA. Antileishmanial IgE was detected in 26 (58 percent) of 45 SC patients (0.35 ± 0.14), and in all VL patients (0.65 ± 0.29). These antibodies were also detected in 13(76 percent) of 17 CVL subjects (0.42 ± 0.14) while all HIEA controls were seronegative. There was no correlation between antileishmanial IgG and IgE antibody absorbances. Mild periodate oxidation at acid pH of SLA carbohydrates drastically diminished its antigenicity in both IgG and IgE-ELISA, affecting mainly the antigens of 125, 102, 94, and 63 kDa as demonstrated by western immunoblotting.

IgG anti-IgE autoantibodies in visceral leishmaniasis

Procedures for IgG depletion in visceral leishmaniasis (VL) and schistosomiasis sera using Sepharose-protein G beads also deplete IgE. In this study, the presence of IgG anti-IgE autoantibodies in sera from patients with VL (n = 10), and hepatic-intestinal schistosomiasis (n = 10) and from healthy individuals (n = 10) was investigated. A sandwich ELISA using goat IgG anti-human IgE to capture serum IgE and goat anti-human IgG peroxidase conjugate to demonstrate the binding of IgG to the IgE captured was performed. VL sera had higher titers (p < 0.05) of IgG anti-IgE autoantibodies (OD = 2.01 ± 0.43) than sera from healthy individuals (OD = 1.35 ± 0.16) or persons infected with Schistosoma mansoni (OD = 1.34 ± 0.18). The immunoblotting carried out with eluates from Sepharose-protein G beads used to deplete IgG from these sera and goat anti-human IgE peroxidase conjugate, showed a similar pattern of bands, predominating the 75 kDa epsilon-heavy chain and also polypeptides resulting from physiological enzymatic digestion of IgE. A frequent additional band immediately above 75 kDa was observed only in VL sera

Detection of specific IgE antibodies in parasite diseases

Activation of Th1 or Th2 cells is associated with production of specific immunoglobulin isotypes, offering the opportunity to use antibody measurement for evaluation of T cell function. Schistosomiasis and visceral leishmaniasis are diseases associated with Th2 activation. However, an IgE response is not always detected in these patients. In the present study we evaluated specific IgE antibodies to S. mansoni and L. chagasi antigens by ELISA after depletion of serum IgG with protein G immobilized on Sepharose beads or RF-absorbent (purified sheep IgG antibodies anti-human IgG). In schistosomiasis patients, specific IgE to SWAP antigen was demonstrable in only 10 of 21 patients (48 percent) (mean absorbance + or - SD = 0.102 + or - 0.195) when unabsorbed serum was used. Depletion of IgG with protein G increased the number of specific IgE-positive tests to 13 (62 percent) and the use of RF-absorbent increased the number of positive results to 20 (95 percent) (mean absorbances + or - SD = 0.303 + or - 0.455 and 0.374 + or - 0.477, respectively). Specific IgE anti-L. chagasi antibodies were not detected in unabsorbed serum from visceral leishmaniasis patients. When IgG was depleted with protein G, IgE antibodies were detected in only 3 (11 percent) of 27 patients, and the use of RF-absorbent permitted the detection of this isotype in all 27 visceral leishmaniasis sera tested (mean absorbance + or - SD = 0.104 + or - 0.03). These data show that the presence of IgG antibodies may prevent the detection of a specific IgE response in these parasite diseases. RF-absorbent, a reagent that blocks IgG-binding sites and also removes rheumatoid factor, was more efficient than protein G for the demonstration of specific IgE antibodies

Regulation of T cell response to leishmania antigens by determinants of histocompatibility leukocyte class I and II molecules

It has been shown that HLA class I molecules play a significant role in the regulation of the proliferation of T cells activated by mitogens and antigens. We evaluated the ability of mAb to a framework determinant of HLA class I molecules to regulate T cell proliferation and interferon gamma (IFN-g) production against leishmania, PPD, C. albicans and tetanus toxoid antigens in patients with tegumentary leishmaniasis and healthy subjects. The anti-major histocompatibility complex (MHC) mAb (W6/32) suppressed lymphocyte proliferation by 90 percent in cultures stimulated with aCD3, but the suppression was variable in cultures stimulated with leishmania antigen. This suppression ranged from 30-67 percent and was observed only in 5 of 11 patients. IFN-g production against leishmania antigen was also suppressed by anti-HLA class I mAb. In 3 patients IFN-g levels were suppressed by more than 60 percent, while in the other 2 cultures IFN-g levels were 36 and 10 percent lower than controls. The suppression by HLA class I mAb to the proliferative response in leishmaniasis patients and in healthy controls varied with the antigens and the patients or donors tested. To determine whether the suppression is directed at antigen presenting cells (APCs) or at the responding T cells, experiments with antigen-primed non-adherent cells, separately incubated with W6/32, were performed. Suppression of proliferation was only observed when the W6/32 mAb was added in the presence of T cells. These data provide evidence that a mAb directed at HLA class I framework determinants can suppress proliferation and cytokine secretion in response to several antigens

Absence of linkage between MHC and a gene involved in susceptibility to human schistosomiasis

Six hundred million people are at risk of infection by Schistosoma mansoni, MHC haplotypes have been reported to segregate with susceptibility to schistosomiasis in murine models. In humans, a major gene related to susceptibility/resistance to infection by S. mansoni (SM1) and displaying the mean fecal egg count as phenotype was detected by segregation analysis. This gene displayed a codominant mode of inheritance with an estimated frequency of 0.20-0.25 for the deleterious allele and accounted for more than 50 percent of the variance of infection levels. To determine if the SM1 gene segregates with the human MHC chromosomal region, we performed a linkage study by the lod score method. We typed for HLA-A, B, C, DR and DQ antigens in 11 informative families from an endemic area for schistosomiasis in Bahia, Brazil, by the microlymphocytotoxicity technique. HLA-DR typing by the polymerase chain reaction with sequence-specific primers (PCR-SSP) and HLA-DQ were confirmed by PCR-sequence-specific oligonucleotide probes (PCR-SSOP). The lod scores for the different theta values obtained clearly indicate that there is no physical linkage between HLA and SM1 genes. Thus, susceptibility or resistance to schistosomiasis, as defined by mean fecal egg count, is not primarily dependent on the host's HLA profile. However, if the HLA molecule plays an important role in specific immune responses to S. mansoni, this may involve the development of the different clinical aspects of the disease such as granuloma formation and development of hepatosplenomegaly.

Cytokine profile and pathology in human leishmaniasis

The clinical spectrum of leishmaniasis and control of the infection are influenced by the parasite-host relationship. The role of cellular immune responses of the Th1 type in the protection against disease in experimental and human leishmaniasis is well established. In humans, production of IFN-gamma is associated with the control of infection in children infected by Leishmania chagasi. In visceral leishmaniasis, an impairment in IFN-gamma production and high IL-4 and IL-10 levels (Th2 cytokines) are observed in antigen-stimulated peripheral blood mononuclear cells (PBMC). Moreover, IL-12 restores IFN-gamma production and enhances the cytotoxic response. IL-10 is the cytokine involved in down-regulation of IFN-gamma production, since anti-IL-10 monoclonal antibody (mAb) restores in vitro IFN-gamma production and lymphoproliferative responses, and IL-10 abrogates the effect of IL-12. In cutaneous and mucosal leishmaniasis, high levels of IFN-gamma are found in L. amazonensis-stimulated PBMC. However, low or absent IFN-gamma levels were observed in antigen-stimulated PBMC from 50 percent of subjects with less than 60 days of disease (24 + 26 pg/ml). This response was restored by IL-12 (308 + 342 pg/ml) and anti-IL-10 mAb (380 + 245 pg/ml) (P<0.05). Later during the disease, high levels of IFN-gamma and TNF-alpha are produced both in cutaneous and mucosal leishmaniasis. After treatment there is a decrease in TNF-alpha levels (366 + 224 pg/ml before treatment vs 142 + 107 pg/ml after treatment, P = 0.02). Although production of IFN-gamma and TNF-alpha might be involved in the control of parasite multiplication in the early phases of Leishmania infection, these cytokines might also be involved in the tissue damage seen in tegumentary leishmaniasis.

Human_Leishmaniasis@cytokines.bahia.br

The cell-mediated immune response is critical in the resistance to and recovery from leishmaniasis. Cytokines are central elements in mounting an immune response and have received a great deal of attention in both human and experimental leishmaniasis. IFN-gamma is responsible for macrophage activation leading to leishmanicidal mechanisms. Understanding the balance of cytokines that lead to enhanced production of or synergize with IFN-gamma, and those cytokines that counterbalance its effects is fundamental for developing rational immunotherapeutic or immunoprophylactic approaches to leishmaniasis. Here we focus on the cytokine balance in human leishmaniasis, particularly IL-10 as an IFN-gamma opposing cytokine, and IL-12 as an IFN-gama inducer. The effects of these cytokines were evaluated in terms of several parameters of the human immune response. IL-10 reduced lymphocyte proliferation, IFN-gamma production and cytotoxic activity of responsive human peripheral blood mononuclear cells. Neutralization of IL-10 led to partial restoration of lymphoproliferation, IFN-gamma production and cytotoxic activity in unresponsive visceral leishmaniasis patients. IL-12 also restored the responses of peripheral blood mononuclear cells from visceral leishmaniasis patients. The responses obtained with IL-12 are higher than those obtained with anti-IL-10, even when anti-IL-10 is combined with anti-IL-4.

The absence of gamma-interferon production of S. mansoni antigens in patients with schistosomiasis

No gamma-interferon production was observed in peripheral blood mononuclear cells (PBMC) cultures from 45 patients living in an endemic area of schistosomiasis in Brazil following in vitro stimulation with schistosomula or adult worm antigens from Schistosoma mansoni (4.9 +/- 24 and 1.0 +/- 3.4 pg/ml, respectively). This immunological abnormality was observed in patients both with a high degree of infection (> or = 400 eggs/g feces) and with a low degree of infection (< 400 eggs/g feces), and was independent of the degree of natural exposure to infection. This absence of gamma-interferon production was antigen specific since high levels of this cytokine were detected in the same patients when their cells were stimulated with PPD (247 +/- 179 pg/ml) or PHA (408 +/- 328 pg/ml). In two of four subjects cured of a previous S. mansoni infection and currently living outside the endemic area, gamma-IFN was produced when their PBMC were stimulated with adult worm antigen (75 +/- 2.5 pg/ml).

Characterization of T cell responses to purified leishmania antigens in subjects infected with Leishmania chagasi

T cell responses to lipophosphoglycan-associated protein (LPG-AP) and the rgp63 antigens were studied in subjects with either asymptomatic L. chagasi infection or cured visceral leishmaniasis. The [3H]-thymidine uptake of lymphocytes stimulated with LPG-AP and rgp63 (mean +/- SD) was 14275 +/- 5048 and 3523 +/- 1678 cpm, respectively, for subjects with asymptomatic L. chagasi infection and 20046 +/- 5102 and 5086 +/- 3500 cpm, respectively, for subjects cured of visceral leishmaniasis. The responses to LPG-AP in both asymptomatic and cured visceral leishmaniasis were higher (P < 0.01) than those observed with rpg63. LPG-AP induced IFN-gamma production in all subjects studied, while rgp63 did not induce lymphocyte proliferation or IFN-gamma production in the majority of the subjects tested. IFN-gamma levels in cultures stimulated with LPG-AP were 103 +/- 81 pg/ml in individuals with asymptomatic L. chagasi infection and 127 +/- 123 pg/ml in subjects cured of visceral leishmaniasis. IFN-gamma levels in cultures stimulated with LPG-AP from subjects with asymptomatic L. chagasi infection were comparable to those observed in subjects cured of visceral leishmaniasis (P > 0.05). These data indicate that LPG-AP is recognized and induces T cell proliferation and IFN-gamma production in subjects with protective immune response against Leishmania chagasi.

Gamma interferon production by lymphocytes from children infected with L. chagasi

The present study was performed to evaluate the ability of lymphocytes from 18 children living in an endemic area of visceral leishmaniasis (VL) to produce gamma-interferon. These children had no previous history of VL and were considered to be infected with Leishmania chagasi based on leishamnial seroconversion. The gamma IFN levels were determined by radioimmunoassay on supernatants of lymphocyte cultures (3 x 10**6/ml). stimulate with PHA (final dilution 1:10) and Leishamnia chagasi antigen (10µg/ml). The gamma-IFN production by lymphocytes from seroconverting children stimulated with PHA (178 ñ 151 U/ml) and Leishmania chagasi (47 ñ 77 U/ml) was significantly higher than that observed in visceral leishmaniasis. For clinical follow-up, these 18 seroconverting children were divided into three groups: asymptomatic infection (N=4); self-healing subclinical illness (N=9), and sublinical infection progressing to VL (N=5). Gamma IFN levels inchildren with either asymptomatic or subclinical infection (65 ñ 85 U/ml were significantly higher (P < 0.003) than those observed in children progressing to VL (9 ñ 6 U/ml). The data demonstrate that there is an association between gamma IFN levels and the clinical course of Leishmania infection