Biomedical subjects

J Convit

Publications and source records attributed to J Convit.

At least 37 records · Page 2Linked to original sources

PubMed1994

Coexistence of two species of Leishmania in the digestive tract of the vector Lutzomyia ovallesi.

Leishmania isolated from the digestive tract of a naturally infected Lutzomyia ovallesi sand fly were cultured in blood agar for rapid growth, cloning, and subsequent identification through schizodeme analysis, dot-blot hybridization, use of monoclonal antibodies with various specificities and absorbed polyclonal antibodies. Twenty-three clones isolated from the primary culture were identified. The results showed that parasites belonging to some clones corresponded to the L. mexicana complex, while others belonged to the L. braziliensis complex. These results clearly establish the coexistence of two Leishmania species in the digestive tract of a single Lu. ovallesi sand fly.

Animals↗

PubMed1994

A longitudinal study of immunologic reactivity in leprosy patients treated with immunotherapy.

More than 150 leprosy patients treated with multidrug therapy (MDT) plus immunotherapy (IMT) with a mixture of heat-killed Mycobacterium leprae plus live BCG were studied in relation to humoral and cell-mediated immune responses. Many previously had received prolonged sulfone monotherapy. Patients received 2 to 10 doses of IMT in a period of 1 to 3 years, depending upon their clinical form of leprosy. The patients were followed up for 5 to 10 years with repeated determinations of antibody levels to phenolic glycolipid-I; lymphoproliferative (LTT) responses to soluble extract of M. leprae, to whole bacilli and to BCG, skin-test responses and bacterial indexes (BIs). After MDT plus IMT there was a statistically significant decrease of antibody levels in the multibacillary (MB) group. The BI decreased proportionally to the ELISA results. LTT increased to M. leprae antigens, especially to soluble extract, in a high percentage of these patients (34% of LL patients positive). Lepromin positivity in MB patients increased from 5% initially positive to 75% at the cut-off during this follow up. These results show substantial early and persistent cell-mediated reactivity to M. leprae in many MB patients treated with MDT-IMT, confirming and expanding previously published data.

Antibodies, Bacterial↗

PubMed1993

Determination of the cytokine profile in American cutaneous leishmaniasis using the polymerase chain reaction.

The lymphokine profiles were determined in the skin lesions of the three distinct clinical forms of American cutaneous leishmaniasis (ACL), using a reverse transcriptase polymerase chain reaction (RT-PCR) and primers for various lymphokines. The message for interferon-gamma (IFN-gamma), tumour necrosis factor-beta (TNF-beta), and IL-8 was expressed in the three clinical forms of ACL. IL-1 beta mRNA was expressed in most localized (LCL) and mucocutaneous (MCL) leishmaniasis, but in only few of the diffuse cutaneous leishmaniasis (DCL). IL-2 mRNA was detected in about half of the lesions, with more prominent values for MCL. IL-4 mRNA was present in most lesions from the three clinical forms, but markedly increased in DCL. IL-5 and IL-10 mRNAs were expressed in all MCL and in half of the DCL lesions and weakly expressed in LCL lesions. IL-10 mRNA was more abundant in MCL lesions. In contrast, IL-6 and TNF-alpha mRNAs were expressed in a large number of LCL. In MCL, IL-6 mRNA was expressed in most cases and TNF-alpha mRNA in all the cases. In DCL, IL-6 mRNA was absent and TNF-alpha mRNA was weakly expressed. These results suggest that most T cells present in the MCL and DCL lesions secrete a mixture of type 1 and type 2 cytokine patterns, but in DCL granulomas type 2 cytokines predominate. In LCL the cytokine patterns show a mixture of type 1 and type 0 with a preponderance of IFN-gamma over IL-4, and low levels of IL-5 and IL-10. The lack of IL-6 and TNF-alpha mRNAs, and the low expression of IL-1 beta in DCL lesions suggest a defect in the antigen-processing cells that may account for the state of unresponsiveness in these patients.

Base Sequence↗

PubMed1993

Antigen-specific immunodeficiency and its relation to the spectrum of American cutaneous leishmaniasis.

Delayed-type hypersensitivity (DTH) and antibodies against Leishmania have been studied in 207 Venezuelan patients with localized, muco-cutaneous and diffuse forms of American cutaneous leishmaniasis, representing the clinical spectrum of this disease. Muco-cutaneous disease appears to be related to inadequate immunomodulation or defective killing mechanisms; about 40% of these patients show exaggerated DTH, which is inversely related to antibody levels and is more pronounced in less extensive lesions. Patients with diffuse disease present severe antigen-specific immunodeficiency, apparently limited to T cell-mediated protection, DTH and its in vitro correlates. Treatment of patients with diffuse cutaneous leishmaniasis using a combination of chemotherapy and combined vaccine immunotherapy (heat-killed promastigotes plus BCG) has induced clinical inactivity and positive DTH in about one third of these patients, accompanied by marked lowering of antibody levels. These results are discussed in terms of Type 1 T cell responses, protective in cell-mediated immune reactions, and Type 2 T cell responses, non-protective in cell-mediated reactions, in the spectrum of leishmaniasis. Factors related to the induction of favorable Type 1 responses to intracellular pathogens are discussed in terms of a possible mechanism of the combined vaccine efficacy and priorities in vaccine development.

Animals↗

PubMed1993

The cutaneous lesion in American leishmaniasis: leukocyte subsets, cellular interaction and cytokine production.

Interactions between immunocompetent cells require the participation of T cell antigen receptor (TCR) and the integrin lymphocyte function-associated molecule-1 (LFA-1, CD11a/CD18). These interactions are mediated by interlinking cytokines, which are important in determining the type of immune response. In the present study, we have shown that in American cutaneous leishmaniasis (ACL) lesions, most infiltrating T cells expressed the alpha beta TCR including those selectively migrating to the epidermis. In contrast, gamma delta T cells were abundant in localized (LCL) and scarce in muco-cutaneous (MCL) and diffuse (DCL) cutaneous leishmaniasis, suggesting a role in effective granulomas. There were differences in the expression of LFA-1 alpha and beta subunits, with most cells expressing LFA-1 beta. The ratio LFA-1 beta/LFA-1 alpha was higher in LCL (11.8:1) than in MCL (3.3:1) and DCL (2.4:1). Similar results were observed in Leishmania mexicana-infected C57BL/6 mice. DCL lesions showed a higher proportion of LFA-1 alpha+ cells than MCL and LCL lesions. A reverse-transcriptase polymerase chain reaction (RT-PCR) analysis of the cytokine profiles showed that most T cells present in the MCL and DCL lesions secrete a mixture of Type 1 and Type 2 cytokine patterns, but in DCL granulomas predominate the Type 2 cytokines. In LCL the cytokine patterns show a preponderance of INF gamma over IL-4, and low levels of IL-5 and IL-10, suggesting a Type 1 cytokine profile.

Animals↗

PubMed1993

Serum levels of tumor necrosis factor in patients with American cutaneous leishmaniasis.

The purpose of this study was to evaluate serum levels of TNF-alpha in patients with either of the three clinical forms of American cutaneous leishmaniasis. The 86 patients examined were classified as having either the localized (LCL: 22 patients), mucocutaneous (MCL: 45 patients), or the rare diffuse (DCL: 19 patients) form of the disease. Our results show a significant increase in the mean level of TNF-alpha in the three groups of patients when compared to controls. MCL patients produce significantly higher levels of TNF-alpha than DCL patients. The proportion of individuals positive for serum TNF-alpha was significantly higher in both MCL and DCL patients than in the controls. No significant differences were found in the level of TNF-alpha when compared between before and after cure of 12 patients with MCL. There were no significant correlations between the level of TNF-alpha and the skin test diameter. The results will be discussed in terms of the pathogenesis of the disease in its different clinical forms.

Adolescent↗

PubMed1993

BCG vaccination protects against leprosy in Venezuela: a case-control study.

A total of 64,570 household and other close contacts of about 2000 leprosy cases were screened for eligibility for entry into a trial of a new leprosy vaccine. The screening procedure included a clinical examination for leprosy and for the presence of BCG and lepromin scars. Ninety-five new cases of leprosy were identified, and the prevalence of BCG and lepromin scars among them was compared with similar data from matched controls selected from among those with no evidence of leprosy. The difference in the prevalence of BCG scars in the two groups was used to estimate the protection against leprosy conferred by BCG vaccination. One or more BCG scars was associated with a protective efficacy of 56% (95% confidence limits 27% to 74%). There was a trend of increasing protection with four or more BCG scars, but this was not statistically significant. There was no evidence that the efficacy of BCG varied with age or according to whether or not the contact lived in the same household as a case. The protective effect was significantly higher among males, and was significantly greater for multibacillary than for paucibacillary leprosy.

Adolescent↗

PubMed1992

Immunoprophylactic trial with combined Mycobacterium leprae/BCG vaccine against leprosy: preliminary results.

In an attempt to find a vaccine that gives greater and more consistent protection against leprosy than BCG vaccine, we compared BCG with and without killed Mycobacterium leprae in Venezuela. Close contacts of prevalent leprosy cases were selected as the trial population since they are at greatest risk of leprosy. Since 1983, 29,113 contacts have been randomly allocated vaccination with BCG alone or BCG plus 6 x 10(8) irradiated, autoclaved M leprae purified from the tissues of infected armadillos. We excluded contacts with signs of leprosy at screening and a proportion of those whose skin-test responses to M leprae soluble antigen (MLSA) were 10 mm or more (positive reactions). By July, 1991, 59 postvaccination cases of leprosy had been confirmed in 150,026 person-years of follow-up through annual clinical examinations of the trial population (31 BCG, 28 BCG/M leprae). In the subgroup for which we thought an effect of vaccination was most likely (onset more than a year after vaccination, negative MLSA skin-test response before vaccination), leprosy developed in 11 BCG recipients and 9 BCG/M leprae recipients; there were 18% fewer cases (upper 95% confidence limit [CL] 70%) in the BCG/M leprae than in the BCG alone group. For all cases with onset more than a year after vaccination irrespective of MLSA reaction the relative efficacy was 0% (upper 95% CL 54%; 15 cases in each vaccine group). Retrospective analysis of data on the number of BCG scars found on each contact screened suggested that BCG alone confers substantial protection against leprosy (vaccine efficacy 56%, 95% CL 27-74%) and there was a suggestion that several doses of BCG offered additional protection. There is no evidence in the first 5 years of follow-up of this trial that BCG plus M leprae offers substantially better protection against leprosy than does BCG alone, but the confidence interval on the relative efficacy estimate is wide.

BCG Vaccine↗

PubMed1992

A major T cell antigen of Mycobacterium leprae is a 10-kD heat-shock cognate protein.

Several mycobacterial antigens, identified by monoclonal antibodies and patient sera, have been found to be homologous to stress or heat-shock proteins (hsp) defined in Escherichia coli and yeast. A major antigen recognized by most Mycobacterium leprae-reactive human T cell lines and cell wall-reactive T cell clones is a 10-kD protein that has now been cloned and sequenced. The predicted amino acid sequence of this protein is 44% homologous to the hsp 10 (GroES) of E. coli. The purified native and recombinant 10-kD protein was found to be a stronger stimulator of peripheral blood T cell proliferation than other native and recombinant M. leprae proteins tested. The degree of reactivity paralleled the response to intact M. leprae throughout the spectrum of leprosy. Limiting-dilution analysis of peripheral blood lymphocytes from a patient contact and a tuberculoid patient indicated that approximately one third of M. leprae-reactive T cell precursors responded to the 10-kD antigen. T cell lines derived from lepromin skin tests were strongly responsive to the 10-kD protein. T cell clones reactive to both the purified native and recombinant 10-kD antigens recognized M. leprae-specific epitopes as well as epitopes crossreactive with the cognate antigen of M. tuberculosis. Further, the purified hsp 10 elicited strong delayed-type hypersensitivity reactions in guinea pigs sensitized to M. leprae. The strong T cell responses against the M. leprae 10-kD protein suggest a role for this heat-shock cognate protein in the protective/resistant responses to infection.

Amino Acid Sequence↗

PubMed1992

Parasitic oligosaccharide residues recognized by patients with mucocutaneous and localized cutaneous leishmaniasis.

Humoral immune responses were studied in 118 Venezuelan patients with either active mucocutaneous (MCL) or localized cutaneous leishmaniasis (LCL). Most patients had elevated antibody levels to the six promastigote oligosaccharide residues studied: galactosyl(alpha 1-2)galactose, galactosyl(alpha 1-3)galactose, galactosyl(alpha 1-6)galactose, galactosyl(alpha 1-3)mannose, galactofuranosyl(beta 1-3)mannose, and galactocerebroside. Significantly higher antibody levels were found in patients with MCL against galactosyl(alpha 1-3)galactose and Leishmania tropica glycoinositol phospholipid (GIPL)-1, GIPL-2, and GIPL-3 compared with patients with LCL. For both clinical forms of American cutaneous leishmaniasis (ACL), the most reactive antigen was galactosyl(alpha 1-3)galactose, with elevated levels found in 63% and 79% of MCL and LCL patients, respectively. In patients with MCL and LCL, no significant relationship was found between antibody levels against a given oligosaccharide residue and clinical parameters such as age, leishmanin diameter, number of skin lesions, or time of evolution. It is noteworthy that 33% and 15% of MCL and LCL patients, respectively, did not have elevated antibody levels against the six different oligosaccharide residues studied. This suggests the presence of a subpopulation of non-humoral immunoreactive ACL patients. The relationship between abnormal levels of oligosaccharide antibodies and the final outcome of the disease remains to be established.

Adult↗

PubMed1992

Albendazole in the treatment of onchocerciasis: double-blind clinical trial in Venezuela.

A double-blind clinical trial was conducted in Monagas State, Venezuela to assess the tolerance and efficacy of albendazole in the therapy of Onchocerca volvulus infection. Forty-nine patients (26 treated and 23 controls) received a 10-day course of albendazole (400 mg/day) or a placebo. Consistent with the excellent tolerance observed, albendazole did not kill microfilariae. However, analysis of changes in microfilarial densities (mf/mg of skin) over one year showed that albendazole was active against O. volvulus, presumably by interfering with embryogenesis. The nature, degree, and duration of this effect remain to be determined.

Adolescent↗

PubMed1992

Preliminary study of cellular immunity to Mycobacterium leprae protein in contacts and leprosy patients.

Because of the good results obtained in the mononuclear cell (T lymphocyte) proliferative response in tuberculoid leprosy patients and family contacts and healthy Mitsuda-positive volunteers using Mycobacterium leprae soluble extract, we prepared different protein fractions from the soluble extract. We used the T-cell Western blot technique with separation by electrophoresis in SDS-polyacrylamide gels and transfer onto nitrocellulose membranes. Each unstained blot was converted into 18 fractions of antigen-bearing particles and tested with peripheral blood mononuclear cells from 21 individuals including Mitsuda-positive contacts, vaccinated lepromatous leprosy (LL) patients, borderline tuberculoid (BT) patients, and unvaccinated lepromatous patients. The stimulation index (SI) of the contacts was higher to the different fractions in comparison with the leprosy patients. They showed four peaks of stimulation to fractions 66-55, 45-29, 22-18, and 14 kDa. The second highest responders were BT patients, followed by vaccinated LL patients. The unvaccinated patients did not respond significantly to any of the fractions (SI less than 1).

Bacterial Proteins↗

PubMed1991

Differing lymphokine profiles of functional subsets of human CD4 and CD8 T cell clones.

Functional subsets of human T cells were delineated by analyzing patterns of lymphokines produced by clones from individuals with leprosy and by T cell clones of known function. CD4 clones from individuals with strong cell-mediated immunity produced predominantly interferon-gamma, whereas those clones that enhanced antibody formation produced interleukin-4. CD8 cytotoxic T cells secreted interferon-gamma. Interleukin-4 was produced by CD8 T suppressor clones from immunologically unresponsive individuals with leprosy and was found to be necessary for suppression in vitro. Both the classic reciprocal relation between antibody formation and cell-mediated immunity and resistance or susceptibility to certain infections may be explained by T cell subsets differing in patterns of lymphokine production.

Antibody Formation↗

PubMed1991

Immunological suppression by human CD8+ T cells is receptor dependent and HLA-DQ restricted.

Mechanisms of specific immunologic unresponsiveness or tolerance and their regulation by the major histocompatibility complex remain central issues in immunology. Recent findings that potentially reactive anti-self T cells are not completely clonally deleted in the thymus and that specific immunological unresponsiveness can be acquired in certain infectious diseases, such as leprosy, suggest that peripheral unresponsiveness can be developed and maintained in adults. Human antigen-specific T suppressor cells represent one mechanism of peripheral tolerance. Clones of CD8+ T suppressor cells have been derived from blood or lesions of patients with lepromatous leprosy who are selectively unable to mount cellular immunity to Mycobacterium leprae. Using a panel of M. leprae-specific CD4+ and CD8+ T-cell clones of differing major histocompatibility complex class II haplotypes, suppression in vitro was found to be restricted by HLA-DQ and not by HLA-DR and inhibited by antibodies to HLA-DQ. In addition, antigen-induced suppression could be inhibited by antibodies specific to appropriate polymorphic T-cell receptor beta chains of the CD8+ clones. The results establish that activation of specific T suppressor cells is dependent on their polymorphic T-cell receptors and suggest that HLA-DQ serves as the preferred restricting element for suppression.

Antibodies, Monoclonal↗

PubMed1991

Immunocytochemical characterization of immune cells in lesions of American cutaneous leishmaniasis using novel T cell markers.

Some recently defined lymphocyte immunophenotypes were determined in lesions of patients with American cutaneous leishmaniasis (ACL). New monoclonal antibodies have allowed the demonstration of cell surface antigens of T lymphocytes, such as CD45RA and CD45RO, which recognize different maturational stages of the same T CD4+ cell subgroup: 'virgin' (CD4+CD45RA+) and 'memory' (CD4+CD45RO+) T cells respectively. The CD4/CD8 cell ratios were higher in mucocutaneous leishmaniasis (MCL) than in localized cutaneous leishmaniasis (LCL) lesions. Diffuse cutaneous leishmaniasis (DCL) has the highest values of 'virgin' T cells; LCL and MCL patients have lower values, similar to each other. 'Memory' T cells were higher in MCL than in LCL or DCL. The ratio of 'memory'/'virgin' T cells was 7.9 for LCL, 9.6 for MCL and 2.5 for DCL. The highest value for IL-2 receptor positive cells (CD25) was observed in LCL, whereas single CD45RO-immunoreactive cells showed a peak value in DCL patients. HLA-DR+ cells were present in all three clinical forms of ACL. MCL patients showed a lack of epithelial Langerhans cell (CD1a+) in the nasal mucosa.

Antigens, CD↗

PubMed1991

IgM antibodies to native phenolic glycolipid-I in contacts of leprosy patients in Venezuela: epidemiological observations and a prospective study of the risk of leprosy.

In a randomized, double-blind vaccine trial in Venezuela, about 29,000 contacts of leprosy patients have been vaccinated with either a mixture of heat-killed Mycobacterium leprae and BCG or BCG alone, and are being re-surveyed annually to detect new cases of leprosy. All contacts had a serum sample collected at the time of entry into the trial, and 13,020 of these sera have been analyzed for antibodies to phenolic glycolipid-I (PGL-I). Antibody levels have been related to various characteristics of the contacts and to their risk of developing leprosy in the following 4 years. A strong association was found between PGL-I antibody level and the risk of developing leprosy, in spite of possible modification of the incidence rate induced by vaccination. Antibody levels were higher in females than in males, and declined progressively with age. Household contacts had higher levels than did non-household contacts, and levels were higher in individuals from the state in Venezuela which has the highest incidence of the disease. No substantial differences were found in antibody levels between contacts of multibacillary and paucibacillary patients, which may in part reflect the influence of treatment, and there was no clear association with the presence of BCG or lepromin scars or with skin-test responses to PPD and leprosy soluble antigen. The assay of antibodies to PGL-I seems unlikely to provide a sensitive or specific test for infection with M. leprae, and measuring PGL-I antibody levels as a screening procedure to identify those at high risk of developing leprosy is unlikely to be particularly useful in most leprosy control programs. Such assays may be useful for the epidemiological monitoring of changes in the intensity of infection with M. leprae in a community and for the study of carefully defined groups of contacts during some phases of control programs.

Adolescent↗

PubMed1990

Sinefungin as treatment for American Leishmania in sensitive BALB/c and resistant C57BL/6 mice.

Using inbred BALB/c and C57BL/6 mice as animal models for American cutaneous leishmaniasis, we evaluated the inhibitory effect of sinefungin on foot-pad infection produced by 5 different Leishmania isolates. When treatment was initiated a few days, or even 2 weeks, after infection, an obvious leishmanicidal effect was detected on mice infected with Leishmania mexicana or L. braziliensis isolates, which lasted at least 50 weeks for all isolates studied. The optimal dose schedule was 4 mg/kg body weight/day, injected ip for 10 consecutive days; lower doses produced only a short leishmanistatic effect. The optimal dose found was 50-fold lower than the LD50. In vitro studies using Leishmania-infected murine peritoneal macrophages showed sinefungin as a powerful inhibitory drug, mean ED50 for the several Leishmania isolates studied being 50 ng/ml. No correlation was found between in vitro sensitivity of culture promastigotes and in vivo sensitivity to sinefungin of an American Leishmania isolate.

Adenosine↗

PubMed1989

Characterization of Mycobacterium leprae cell wall-associated proteins with the use of T lymphocyte clones.

Development of a vaccine against leprosy depends on the identification of Ag that stimulate cell-mediated immune responses. We have previously demonstrated that cell wall proteins of Mycobacterium leprae are highly immunogenic. By using human cell wall-specific T cell clones we have begun to characterize soluble proteins that integrate into the cell wall skeleton. T cells from leprosy lesions were expanded with IL-2 in vitro yet retained specificity to Ag of the insoluble cell wall core (CWC) in vitro, indicating that T cells had been activated by CWC Ag in vivo. A cell wall protein-peptidoglycan complex and cell wall protein preparations lacking carbohydrates and lipids from CWC retained T cell reactivity. To identify immunogenic protein component(s) of cell wall protein, T cell lines were established to cell walls and tested against M. leprae proteins separated by SDS-PAGE and transferred to nitrocellulose. Greatest T cell reactivity was observed to proteins of Mr 7 kDa, 16 kDa, and 28 kDa. T cell clones reactive with 7-kDa and 16-kDa Ag from gels failed to respond to proteins of other Mr separated under either reducing or nonreducing conditions, indicating that these molecules are not subunits of larger proteins and may represent monomeric units polymerized into cell walls. The approaches described herein for characterization of immunodominant T cell Ag of M. leprae may be useful for study of T cell Ag in cell walls of bacterial pathogens of man.

Bacterial Proteins↗