RESUMEN

The genomic sequences of 20 Leishmania infantum isolates collected in northeastern Brazil were compared with each other and with the available genomic sequences of 29 L. infantum/donovani isolates from Nepal and Turkey. The Brazilian isolates were obtained in the early 1990s or since 2009 from patients with visceral or non-ulcerating cutaneous leishmaniasis, asymptomatic humans, or dogs with visceral leishmaniasis. Two isolates were from the blood and bone marrow of the same visceral leishmaniasis patient. All 20 genomic sequences display 99.95% identity with each other and slightly less identity with a reference L. infantum genome from a Spanish isolate. Despite the high identity, analysis of individual differences among the 32 million base pair genomes showed sufficient variation to allow the isolates to be clustered based on the primary sequence. A major source of variation detected was in chromosome somy, with only four of the 36 chromosomes being predominantly disomic in all 49 isolates examined. In contrast, chromosome 31 was predominantly tetrasomic/pentasomic, consistent with its regions of synteny on two different disomic chromosomes of Trypanosoma brucei. In the Brazilian isolates, evidence for recombination was detected in 27 of the 36 chromosomes. Clustering analyses suggested two populations, in which two of the five older isolates from the 1990s clustered with a majority of recent isolates. Overall the analyses do not suggest individual sequence variants account for differences in clinical outcome or adaptation to different hosts. For the first known time, DNA of isolates from asymptomatic subjects were sequenced. Of interest, these displayed lower diversity than isolates from symptomatic subjects, an observation that deserves further investigation with additional isolates from asymptomatic subjects.

Asunto(s)

Enfermedades de los Perros/parasitología , Leishmania infantum/genética , Leishmaniasis Visceral/veterinaria , Animales , ADN Protozoario/genética , Enfermedades de los Perros/epidemiología , Perros , Variación Genética , Genoma de Protozoos , Humanos , Leishmaniasis Visceral/epidemiología , Leishmaniasis Visceral/parasitología , Polimorfismo de Nucleótido Simple

RESUMEN

Mapping murine genes controlling cutaneous leishmaniasis (CL) identified Fli1 as a candidate influencing resistance to L. major and enhanced wound healing. We examine FLI1 as a gene controlling CL and mucosal leishmaniasis (ML) caused by L. braziliensis in humans. Intron 1 single nucleotide polymorphisms tagging promoter and enhancer elements were analysed in 168 nuclear families (250 CL; 87 ML cases) and replicated in 157 families (402 CL; 39 ML cases). Robust case-pseudocontrol logistic regression analysis showed association between allele C (odds ratio (OR) 1.65; 95% confidence interval 1.18-2.29; P=0.003) of FLI1_rs7930515 and CL in the primary sample that was confirmed (OR 1.60; 95% confidence interval 1.10-2.33; P=0.014) in the replication set (combined P=1.8 × 10(-4)). FLI1_rs7930515 is in linkage disequilibrium with the functional GAn microsatellite in the proximal promoter. Haplotype associations extended across the enhancer, which was not polymorphic. ML associated with inverse haplotypes compared with CL. Wound healing is therefore important in CL, providing potential for therapies modulating FLI1.

Asunto(s)

Predisposición Genética a la Enfermedad , Leishmaniasis Cutánea/genética , Polimorfismo de Nucleótido Simple , Proteína Proto-Oncogénica c-fli-1/genética , Alelos , Brasil , Frecuencia de los Genes , Haplotipos , Humanos , Intrones , Grupos Raciales/genética

RESUMEN

Congenital Toxoplasma gondii infection can result in intracranial calcification, hydrocephalus and retinochoroiditis. Acquired infection is commonly associated with ocular disease. Pathology is characterized by strong proinflammatory responses. Ligation of ATP by purinergic receptor P2X(7), encoded by P2RX7, stimulates proinflammatory cytokines and can lead directly to killing of intracellular pathogens. To determine whether P2X(7) has a role in susceptibility to congenital toxoplasmosis, we examined polymorphisms at P2RX7 in 149 child/parent trios from North America. We found association (FBAT Z-scores +/-2.429; P=0.015) between the derived C(+)G(-) allele (f=0.68; OR=2.06; 95% CI: 1.14-3.75) at single-nucleotide polymorphism (SNP) rs1718119 (1068T>C; Thr-348-Ala), and a second synonymous variant rs1621388 in linkage disequilibrium with it, and clinical signs of disease per se. Analysis of clinical subgroups showed no association with hydrocephalus, with effect sizes for associations with retinal disease and brain calcifications enhanced (OR=3.0-4.25; 0.004

Asunto(s)

Coriorretinitis/genética , Predisposición Genética a la Enfermedad/genética , Receptores Purinérgicos P2/genética , Toxoplasmosis Congénita/genética , Adulto , Brasil , Preescolar , Coriorretinitis/etiología , Femenino , Estudio de Asociación del Genoma Completo , Haplotipos/genética , Humanos , Patrón de Herencia/genética , Desequilibrio de Ligamiento , Modelos Logísticos , Masculino , América del Norte , Polimorfismo de Nucleótido Simple/genética , Receptores Purinérgicos P2X7 , Toxoplasmosis Congénita/complicaciones

RESUMEN

Ninety per cent of the 500,000 annual new cases of visceral leishmaniasis (VL) occur in India/Bangladesh/Nepal, Sudan and Brazil. Importantly, 80-90% of human infections are sub-clinical or asymptomatic, usually associated with strong cell-mediated immunity. Understanding the environmental and genetic risk factors that determine why two people with the same exposure to infection differ in susceptibility could provide important leads for improved therapies. Recent research using candidate gene association analysis and genome-wide linkage studies (GWLS) in collections of families from Sudan, Brazil and India have identified a number of genes/regions related both to environmental risk factors (e.g. iron), as well as genes that determine type 1 vs. type 2 cellular immune responses. However, until now all of the allelic association studies carried out have been underpowered to find genes of small effect sizes (odds ratios or OR < 2), and GWLS using multicase pedigrees have only been powered to find single major genes, or at best oligogenic control. The accumulation of large DNA banks from India and Brazil now makes it possible to undertake genome-wide association studies (GWAS), which are ongoing as part of phase 2 of the Wellcome Trust Case Control Consortium. Data from this analysis should seed research into novel genes and mechanisms that influence susceptibility to VL.

Asunto(s)

Predisposición Genética a la Enfermedad , Genoma Humano , Estudio de Asociación del Genoma Completo , Leishmania donovani/patogenicidad , Leishmaniasis Visceral/genética , Animales , Asia Occidental/epidemiología , Brasil/epidemiología , Estudio de Asociación del Genoma Completo/métodos , Humanos , Hipersensibilidad Tardía/genética , Leishmaniasis Visceral/epidemiología , Leishmaniasis Visceral/inmunología , Leishmaniasis Visceral/parasitología , Ratones , Ratones Endogámicos BALB C , Sudán/epidemiología

RESUMEN

Visceral leishmaniasis (VL) caused by Leishmania chagasi is endemic to northeast Brazil. A positive delayed-type hypersensitivity skin test response (DTH+) is a marker for acquired resistance to disease, clusters in families and may be genetically controlled. Twenty-three single nucleotide polymorphisms (SNPs) were genotyped in the cytokine 5q23.3-q31.1 region IRF1-IL5-IL13-IL4-IL9-LECT2-TGFBI in 102 families (323 DTH+; 190 DTH-; 123 VL individuals) from a VL endemic region in northeast Brazil. Data from 20 SNPs were analyzed for association with DTH+/- status and VL using family-based, stepwise conditional logistic regression analysis. Independent associations were observed between the DTH+ phenotype and markers in separate linkage disequilibrium blocks in LECT2 (OR 2.25; P=0.005; 95% CI=1.28-3.97) and TGFBI (OR 1.94; P=0.003; 95% CI=1.24-3.03). VL child/parent trios gave no evidence of association, but the DTH- phenotype was associated with SNP rs2070874 at IL4 (OR 3.14; P=0.006; 95% CI=1.38-7.14), and SNP rs30740 between LECT2 and TGFBI (OR 3.00; P=0.042; 95% CI=1.04-8.65). These results indicate several genes in the immune response gene cluster at 5q23.3-q31.1 influence outcomes of L. chagasi infection in this region of Brazil.

Asunto(s)

Cromosomas Humanos Par 5/genética , Hipersensibilidad Tardía/genética , Leishmania infantum , Leishmaniasis Visceral/genética , Leishmaniasis Visceral/inmunología , Polimorfismo de Nucleótido Simple , Alelos , Animales , Brasil , Estudios de Casos y Controles , Biología Computacional , Femenino , Predisposición Genética a la Enfermedad , Genotipo , Humanos , Leishmaniasis Visceral/parasitología , Modelos Logísticos , Masculino , Fenotipo , Alineación de Secuencia

RESUMEN

The region on chromosome 6 encoding the major histocompatibility complex (MHC) is associated with a number of autoimmune and infectious diseases. Primary susceptibility to many of these has been localized to a region containing the human leukocyte antigen (HLA)-DR and -DQ genes. A recent study of sarcoidosis has provided evidence of an independent effect, associated with a truncating single nucleotide polymorphism (SNP) of a nearby gene, BTNL2. This gene may encode an immune receptor involved in costimulation. Sarcoidosis, tuberculoid leprosy, tuberculosis (TB) and Crohn's disease all have similar immunological features, including a Th1 response with granuloma formation. In addition mycobacteria have been identified or suggested to be causative pathogens in such conditions. We genotyped the truncating BTNL2 SNP in 92 TB and 72 leprosy families from Brazil and carried out family-based association studies. We could not find evidence of overtransmission of the truncating allele in TB. There was an association with susceptibility to leprosy (P=0.04), however, this is most likely due to linkage disequilibrium with HLA-DR. We also genotyped 476 UK Caucasian cases of Crohn's disease with 760 geographically matched controls and found no evidence of a disease association. We conclude that the truncating BTNL2 SNP is not important in this group of Th1 dominated granulomatous diseases.

Asunto(s)

Enfermedad de Crohn/genética , Lepra/genética , Glicoproteínas de Membrana/genética , Mutación Puntual , Polimorfismo de Nucleótido Simple , Sitios de Empalme de ARN/genética , Tuberculosis/genética , Alelos , Brasil , Butirofilinas , Cromosomas Humanos Par 6/genética , Femenino , Antígenos HLA-DQ/genética , Antígenos HLA-DR/genética , Humanos , Desequilibrio de Ligamiento , Masculino , Reino Unido

RESUMEN

A genome-wide scan was conducted for visceral leishmaniasis (VL) in Brazil. Initially, 405 markers were typed in 22 multicase pedigrees (28 nuclear families; 174 individuals; 66 affected). Non-parametric multipoint analysis detected nine chromosomal regions with provisional evidence (logarithm of the odds (LOD) scores 0.95-1.66; 0.003

Asunto(s)

Predisposición Genética a la Enfermedad , Genoma Humano , Leishmaniasis Visceral/genética , Leishmaniasis Visceral/inmunología , Brasil , Quimiocina CCL1 , Quimiocinas CC/genética , Humanos , Desequilibrio de Ligamiento , Polimorfismo de Nucleótido Simple

RESUMEN

Here we report the results from a genome-wide linkage scan to identify genes and chromosomal regions that influence quantitative immune response traits, using multi-case leprosy and tuberculosis families from north-eastern Brazil. Total plasma IgE, antigen-specific IgG to Mycobacterium leprae soluble antigen (MLSA), M. tuberculosis soluble antigen (MTSA) and M. tuberculosis purified protein derivative (PPD), and antigen-specific lymphocyte proliferation (stimulation index or SI) and interferon-gamma (IFN-gamma) release to MLSA and PPD, were measured in 16 tuberculosis (184 individuals) and 21 leprosy (177 individuals) families. The individuals were genotyped at 382 autosomal microsatellite markers across the genome. The adjusted immune-response phenotypes were analysed using a variety of variance components and regression-based methods. These analyses highlighted a number of practical issues and problems with regard to implementation of the methods and, interestingly, differences were observed between several standard statistical and genetic analysis packages used. From this we determined that, for this set of traits in these pedigrees, significant p values for linkage using variance components analysis, supported by significance using the Visscher-Hopper modification of the Haseman-Elston method, provided the most compelling evidence for linkage. Using these criteria, linkage (5.8 x 10(-5) < p < 0.008) was seen for: total plasma IgE on chromosome 2; IgG to MLSA on chromosomes 8, 17 and 21; IgG to PPD on chromosome 12; SI to PPD on chromosome 1; IFN-gamma to MLSA on chromosomes 6, 7, 10, 12 and 14; and IFN-gamma to PPD on chromosomes 1, 16 and 19.

Asunto(s)

Ligamiento Genético , Genoma Humano , Inmunidad/genética , Lepra/inmunología , Sitios de Carácter Cuantitativo/inmunología , Tuberculosis/inmunología , Análisis de Varianza , Antígenos Bacterianos/sangre , Antígenos Bacterianos/inmunología , Brasil , Ensayo de Inmunoadsorción Enzimática , Familia , Genómica/métodos , Genotipo , Humanos , Inmunoglobulina E/sangre , Inmunoglobulina E/inmunología , Inmunoglobulina G/sangre , Inmunoglobulina G/inmunología , Interferón gamma/sangre , Interferón gamma/inmunología , Lepra/genética , Repeticiones de Microsatélite/genética , Sitios de Carácter Cuantitativo/genética , Análisis de Regresión , Tuberculina/sangre , Tuberculina/inmunología , Tuberculosis/genética

RESUMEN

The region of conserved synteny on mouse chromosome 11/human 17q11-q21 is known to carry a susceptibility gene(s) for intramacrophage pathogens. The region is rich in candidates including NOS2A, CCL2/MCP-1, CCL3/MIP-1alpha, CCL4/MIP-1beta, CCL5/RANTES, CCR7, STAT3 and STAT5A/5B. To examine the region in man, we studied 92 multicase tuberculosis (627 individuals) and 72 multicase leprosy (372 individuals) families from Brazil. Multipoint nonparametric analysis (ALLEGRO) using 16 microsatellites shows two peaks of linkage for leprosy at D17S250 (Z(lr) score 2.34; P=0.01) and D17S1795 (Z(lr) 2.67; P=0.004) and a single peak for tuberculosis at D17S250 (Z(lr) 2.04; P=0.02). Combined analysis shows significant linkage (peak Z(lr) 3.38) at D17S250, equivalent to an allele sharing LOD score 2.48 (P=0.0004). To determine whether one or multiple genes contribute, 49 informative single nucleotide polymorphisms were typed in candidate genes. Family-based allelic association testing that was robust to family clustering demonstrated significant associations with tuberculosis susceptibility at four loci separated by intervals (NOS2A-8.4 Mb-CCL18-32.3 kb-CCL4-6.04 Mb-STAT5B) up to several Mb. Stepwise conditional logistic regression analysis using a case/pseudo-control data set showed that the four genes contributed separate main effects, consistent with a cluster of susceptibility genes across 17q11.2.

Asunto(s)

Cromosomas Humanos Par 17/genética , Predisposición Genética a la Enfermedad , Lepra/genética , Proteínas de la Leche , Tuberculosis/genética , Animales , Brasil , Estudios de Casos y Controles , Quimiocina CCL3 , Quimiocina CCL4 , Quimiocinas CC/genética , Proteínas de Unión al ADN/genética , Femenino , Frecuencia de los Genes , Marcadores Genéticos , Pruebas Genéticas/estadística & datos numéricos , Genotipo , Humanos , Lepra/etiología , Proteínas Inflamatorias de Macrófagos , Masculino , Ratones , Familia de Multigenes , Mutación Puntual , Proteínas/genética , Factor de Transcripción STAT5 , Transactivadores/genética , Tuberculosis/etiología , Proteínas Supresoras de Tumor

RESUMEN

Genome-wide scans were conducted for tuberculosis and leprosy per se in Brazil. At stage 1, 405 markers (10 cM map) were typed in 16 (178 individuals) tuberculosis and 21 (173 individuals) leprosy families. Nonparametric multipoint analysis detected 8 and 9 chromosomal regions respectively with provisional evidence (P<0.05) for linkage. At stage 2, 58 markers from positive regions were typed in a second set of 22 (176 individuals) tuberculosis families, with 22 additional markers typed in all families; 42 positive markers in 50 (192 individuals) new leprosy families, and 30 additional markers in all families. Three regions (10q26.13, 11q12.3, 20p12.1) retained suggestive evidence (peak LOD scores 1.31, 1.85, 1.78; P=0.007, 0.0018, 0.0021) for linkage to tuberculosis, 3 regions (6p21.32, 17q22, 20p13) to leprosy (HLA-DQA, 3.23, P=5.8 x 10(-5); D17S1868, 2.38, P=0.0005; D20S889, 1.51, P=0.004). The peak at D20S889 for leprosy is 3.5 Mb distal to that reported at D20S115 for leprosy in India. (151 words).

Asunto(s)

Cromosomas Humanos Par 15/genética , Predisposición Genética a la Enfermedad , Lepra/genética , Tuberculosis/genética , Brasil , Mapeo Cromosómico , Cromosomas Humanos Par 4/genética , Cromosomas Humanos Par 6/genética , Femenino , Ligamiento Genético , Marcadores Genéticos , Pruebas Genéticas , Genoma Humano , Humanos , India , Masculino

RESUMEN

The region of conserved synteny on mouse chromosome 11/human 17q11-q21 is known to carry a susceptibility gene(s) for intramacrophage pathogens. The region is rich in candidates including NOS2A, CCL2/MCP-1, CCL3/MIP-1 alpha, CCL4/MIP-1 beta, CCL5/RANTES, CCR7, STAT5A/5B. To examine the region in man, we studied 92 multicase tuberculosis (627 individuals) and 72 multicase leprosy (372 indiciduals) families from Brazil. Multipoint nonparametric analysis (ALLEGRO) using 16 microsatellites shows two peaks of linkage for leprosy at D17S250 (Zir score 2.34; P=0.01) and D17S1795 (Zir 2.67; P=O.004) and a single peack for tuberculosis at D17S250 (Zir 2.04; P=0.02). Combined analysis shows significant linkage (peak Zir 3.38) at D17S250, equivalent to an allele sharing LOD score 2.48 (P=0.0004). To determine whether one or multiple genes contribute, 49 informative single nucleotide polymorphisms were typed in candidate genes. Family-based allelic association testing that was robust to family clustering demonstrated significant associations with tuberculosis susceptibility at four loci separated by intervals (NOS2A-8.4 Mb-CCL 18-32.3 kb-CCL4-6.04 Mb-STAT5B) up to several Mb. Stepwise conditional logistic regression analysis using a case/pseudo-control data set showed that the four genes contributed separate main effects, consistent with a cluster of susceptibilitty genes acros 17q11.2

Asunto(s)

Humanos , /inmunología , /inmunología , Lepra/genética , Lepra/inmunología , Tuberculosis/genética , Tuberculosis/inmunología , Genética de Población

RESUMEN

Genome-wide scans were conducted for tuberculosis and leprosy per se in Brazil. At stage 1,405 markers (10 cM map) were typed in 16 (178 individuals) tuberculosis and 21 (173 individuals) leprosy families. Nonparametric multipoint analysis detected 8 and 9 chromosomal regions respectively with provisional evidence (P<0.05) for linkage. A stage 2, 58 markers from positive regions were typed in a second set of 22 (176 individuals) tuberculosis families, with 22 additional markers types in all families; 42 positive markers in 50 (192 individuals) new leprosy families, and 30 additional markers in all families. Three regions (10q26.13, 11q12.3, 20p12.1) retained suggestive evidence (peak LOD scores 1.31, 1.78, 1.78; P=0.007, 0.0018, 0.0021) for linkage to tuberculosis, 3 regions (6p21.32, 17q22, 20p13) to leprosy (HLA-DQA, 3.23, P=5.8 x 10-5; D17S1868.2.38, P=0.0005; D20S889, 1.51, P=0.004). The peak at D20S889 for leprosy is 3.5 Mb distal to that reported at D20S115 for leprosy in India

Asunto(s)

Lepra/genética , Mycobacterium leprae , Mycobacterium tuberculosis , Predisposición Genética a la Enfermedad , Tuberculosis/genética , Mycobacterium leprae/inmunología , Mycobacterium leprae/metabolismo , Mycobacterium tuberculosis/inmunología , Mycobacterium tuberculosis/metabolismo

RESUMEN

Familial aggregation, high relative risk to siblings, and segregation analysis, suggest genetic control of visceral leishmaniasis in Brazil. Class II gene effects in mice, and high circulating tumour necrosis factor alpha in humans, provide reasons to target HLA. Fifteen polymorphic markers across 1.03 Mb (DQB1 to TNFa) were genotyped (87 multicase families; 638 individuals). Model-based parametric analyses using single-point combined segregation and linkage in COMDS, or multi-point linkage in ALLEGRO, failed to detect linkage. Model-free nonparametric affected sibling pair (SPLINK) or NPL(all) score (ALLEGRO) analyses also failed to detect linkage. Information content mapping confirmed sufficient marker information to detect linkage. Analysis of simulated data sets demonstrated that these families had 100% power to detect NPL(all) scores of 5 to 6 (>LOD4; P < 0.00001) over the range (7% to 61%) of age-related penetrances for a disease susceptibility gene. The extended transmission disequilibrium test (TDT) showed no consistent allelic associations between disease and the 15 loci. TDT also failed to detect significant associations between extended haplotypes and disease, consistent with failure to detect significant linkage disequilibrium across the region. Linkage disequilibrium between adjacent groups of markers (HLADQ/DR; 82-1/82-3/-238bpTNFA; LTA/62/TNFa) was not accompanied by significant global haplotype TDT associations with disease. The data suggest that class II/III regions of HLA do not contain major disease gene(s) for visceral leishmaniasis in Brazil.

Asunto(s)

Predisposición Genética a la Enfermedad , Antígenos de Histocompatibilidad Clase II/genética , Leishmania donovani/inmunología , Leishmaniasis Visceral/genética , Leishmaniasis Visceral/inmunología , Animales , Brasil , Marcadores Genéticos , Antígenos de Histocompatibilidad Clase II/inmunología , Humanos , Escala de Lod

RESUMEN

Previous analyses indicate major gene control of susceptibility to leprosy per se and the HLA class II region has been implicated in determining susceptibility and control of clinical phenotype. Segregation analysis using data from 76 Brazilian leprosy multi-case pedigrees (1166 individuals) supported a two locus model as the best fit: a recessive major gene and a recessive modifier gene(s) (single locus vs two locus model, P = 0.0007). Combined segregation and linkage analysis to the major locus, showed strong linkage to HLA class II (HLA-DQB1 P = 0.000002, HLA-DQA1 P = 0.000002, HLA-DRB1 P = 0.0000003) and tumour necrosis factor genes (TNF P = 0.00002, LTA P = 0.003). Extended transmission disequilibrium testing, using multiple affected family members, demonstrated that the common allele TNF*1 of the -308 promoter region polymorphism showed linkage and/or association with disease per se, at a high level of significance (P < 0.0001). Two locus transmission disequilibrium testing suggested susceptibility (TNF*1/LTA*2) and protective (TNF*2/LTA*2) haplotypes in the class iii region. Taken together the segregation and HLA analyses suggest the possibility of more than one susceptibility locus in the MHC.

Asunto(s)

Genes MHC Clase II , Ligamiento Genético , Lepra/genética , Factor de Necrosis Tumoral alfa/genética , Brasil/epidemiología , Humanos , Lepra/epidemiología , Fenotipo

RESUMEN

Familial clustering of disease, racial differences in asymptomatic:disease ratios, and studies of mice all point to a genetic component for disease susceptibility in visceral leishmaniasis. Analysis of 87 multi-case pedigrees (824 individuals; 138 nuclear families) from a region of northeastern Brazil endemic for Leishmania chagasi demonstrates a high relative risk ratio (lambda(2S) = 34) to further siblings of affected sibling pairs. Complex segregation analysis using POINTER and COMDS show that all single locus models, as well as polygenic and multifactorial models, provide a significantly (P < 0.001) better fit to the data than a sporadic model. Of the genetic models, the general single locus model was not significantly different from additive or dominant single locus models, all of which gave a gene frequency for the putative disease susceptibility allele of approximately 0.002. The general single locus model was strongly favored (P < 0.001) over a recessive single gene model. Using POINTER, polygenic and multifactorial models were clearly rejected (P < 0.001 in all cases) in favor of the general single locus model. Using COMDS, the analysis was extended to consider two locus models. Results under a general two-locus model did not differ significantly from the dominant, additive, or general single locus models. Under this model, one locus was estimated at a gene frequency of 0.0017, i.e., in the same range as the disease susceptibility locus for the most favored single gene models, with the second locus at a much lower frequency of 0.0002. Hence, the data support the hypothesis that a single major gene may be important in determining disease susceptibility in this population. To identify the gene(s) involved, a genome scan with replication using two subsets of these larger pedigrees with power to detect linkage is in progress.

Asunto(s)

Leishmaniasis Visceral/genética , Adolescente , Adulto , Brasil/epidemiología , Niño , Preescolar , Interpretación Estadística de Datos , Femenino , Predisposición Genética a la Enfermedad , Humanos , Lactante , Leishmaniasis Visceral/diagnóstico , Leishmaniasis Visceral/epidemiología , Masculino , Modelos Genéticos , Linaje

Asunto(s)

Factor de Necrosis Tumoral alfa/genética , Fenotipo , Genes MHC Clase II , Lepra/epidemiología , Lepra/genética , Ligamiento Genético

RESUMEN

Amazonian localized cutaneous leishmaniasis (LCL) is caused by parasites of the subgenera Leishmania and Viannia. Respectively, these parasites may cause diffuse cutaneous leishmaniasis (DCL) and mucocutaneous leishmaniasis (MCL). This, together with differing skin test responses, suggests some species-specificity in cell mediated immunity. In this study, T cell responses (proliferative and interferon-gamma) to crude and defined antigens were examined in paired samples pre and post chemotherapy. Untreated L. (L.) amazonensis LCL patients showed lower responses to crude leishmanial antigens than the L. (V.) spp. group. L. (V.) braziliensis antigen was a more potent stimulator of T cell responses than L. (L.) amazonensis antigen in all patient groups. Few positive responses were seen to the L. (L.) amazonensis glycoprotein GP46. A substantial proportion of LCL patients did respond to the L. (L.) pifanoi amastigote antigens A2, and the surface membrane glycoprotein P8. DCL patients were poor responders to all leishmanial antigens, except GP46. In contrast, MCL patients were good responders to all antigens except GP46 and A2. A significant rise in the response to P8 and A2 antigen was seen post treatment across all LCL and MCL patients, indicating that these antigens might provide suitable vaccine candidates.

Asunto(s)

Antígenos de Protozoos/inmunología , Leishmania/inmunología , Leishmaniasis Cutánea/inmunología , Linfocitos T/inmunología , Adulto , Animales , Antiprotozoarios/uso terapéutico , Brasil/epidemiología , División Celular , Femenino , Humanos , Interferón gamma/análisis , Interferón gamma/inmunología , Interferón gamma/metabolismo , Leishmaniasis Cutánea/tratamiento farmacológico , Leishmaniasis Cutánea/epidemiología , Leucocitos Mononucleares/inmunología , Masculino , Meglumina/uso terapéutico , Antimoniato de Meglumina , Compuestos Organometálicos/uso terapéutico , Vacunas Antiprotozoos/inmunología , Especificidad de la Especie , Linfocitos T/citología , Linfocitos T/metabolismo

RESUMEN

Genetic analysis of disease phenotypes segregating in recombinant inbred, congenic and recombinant haplotype mouse strains permitted us to effectively "scan" the murine genome for genes controlling resistance and susceptibility to leishmanial infections. Five major regions were implicated which, because they show conserved synteny with regions of the human genome, immediately provide candidate gene regions for human disease susceptibility genes. A common intramacrophage niche for leishmanial and mycobacterial pathogens, and a similar spectrum of immune response and disease phenotypes, also led to the prediction that the same genes/candidate gene regions might be responsible for genetic susceptibility to mycobacterial infections such as leprosy and tuberculosis. Indeed, one of the murine genes (Nramp1) was identified for its role in controlling a range of intramacrophage pathogens, including leishmanial, salmonella and mycobacterial infections. In recent studies, multicase families of visceral leishmaniasis, tuberculosis and leprosy, from north-eastern Brazil have been analysed to determine the role of these candidate genes/regions in humans. Complex segregation analysis provides evidence for one or two major genes controlling susceptibility to these diseases in this population. Family-based linkage analyses (e.g., combined segregation and linkage analysis; sib-pair analyses) and transmission disequilibrium testing have been used to examine the role of four regions in disease susceptibility and/or immune response phenotypes. Results to date demonstrate: (1) the major histocompatibility complex (MHC:H-2 in mouse, HLA in humans: mouse chromosome 17/human 6p; candidates class II and class III including tumour necrosis factor alpha/beta genes) shows both linkage to, and allelic association with, leprosy per se, but is only weakly associated with visceral leishmaniasis and shows neither linkage to, nor allelic association with, tuberculosis; (2) no evidence for linkage between NRAMP1, the positionally cloned candidate for the murine macrophage resistance gene Ity/Lsh/Bcg (mouse chromosome 1/human 2q35), and susceptibility to tuberculosis or visceral leishmaniasis; (3) the region of human chromosome 17q (candidates NOS2A, SCYA2-5) homologous with distal mouse chromosome 11 is linked to tuberculosis susceptibility; and (4) the "T helper 2" cytokine gene cluster (proximal murine chromosome 11/human 5p; candidates IL4, IL5, IL9, IRF1, CD14) is not linked to human disease susceptibility for any of the three infections, but shows linkage to and highly significant allelic association with ability to mount an immune response to mycobacterial antigens. The demonstration of an allelic association between IL4 and immune response to mycobacterial antigen may provide a genetic explanation for the inverse association recently demonstrated between delayed hypersensitivity T helper 1 responses to mycobacterial antigen and atopic disorder in Japanese children. These studies demonstrate that the "mouse-to-human" strategy, refined by our knowledge of the human immune response to infection, can lead to the identification of important candidate gene regions in humans.

Asunto(s)

Mapeo Cromosómico , Leishmaniasis/genética , Lepra/genética , Tuberculosis/genética , Animales , Brasil , Femenino , Ligamiento Genético , Predisposición Genética a la Enfermedad , Humanos , Inmunidad Innata/genética , Leishmaniasis/inmunología , Lepra/inmunología , Masculino , Ratones , Linaje , Fenotipo , Tuberculosis/inmunología

RESUMEN

In the 1970s and 1980s, analysis of recombinant inbred, congenic and recombinant haplotype mouse strains permitted us to effectively 'scan' the murine genome for genes controlling resistance and susceptibility to leishmanial infections. Five major regions of the genome were implicated in the control of infections caused by different Leishmania species which, because they show conserved synteny with regions of the human genome, immediately provides candidate gene regions for human disease susceptibility genes. A common intramacrophage niche for leishmanial and mycobacterial pathogens, and a similar spectrum of immune response and disease phenotypes, also led to the prediction that the same genes/candidate gene regions might be responsible for genetic susceptibility to mycobacterial infections such as leprosy and tuberculosis. Indeed, one of the murine genes (Nramp1) was identified for its role in controlling a range of intramacrophage pathogens including leishmania, salmonella and mycobacterium infections. In recent studies, multicase family data on visceral leishmaniasis and the mycobacterial diseases, tuberculosis and leprosy, have been collected from north-eastern Brazil and analysed to determine the role of these candidate genes/regions in determining disease susceptibility. Complex segregation analysis provides evidence for one or two major genes controlling susceptibility to tuberculosis in this population. Family-based linkage analyses (combined segregation and linkage analysis; sib-pair analysis), which have the power to detect linkage between marker loci in candidate gene regions and the putative disease susceptibility genes over 10-20 centimorgans, and transmission disequilibrium testing, which detects allelic associations over 1 centimorgan (ca. 1 megabase), have been used to examine the role of four regions in determining disease susceptibility and/or immune response phenotype. Our results demonstrate: (i) the major histocompatibility complex (MHC: H-2 in mouse, HLA in man: mouse chromosome 17/human 6p; candidates class II and class III including TNF alpha/beta genes) shows both linkage to, and allelic association with, leprosy per se, but is only weakly associated with visceral leishmaniasis and shows neither linkage to nor allelic association with tuberculosis; (ii) no evidence for linkage between NRAMP1, the positionally cloned candidate for the murine macrophage resistance gene Ity/Lsh/Bcg (mouse chromosome 1/human 2q35), and susceptibility to tuberculosis or visceral leishmaniasis could be demonstrated in this Brazilian population; (iii) the region of human chromosome 17q (candidates NOS2A, SCYA2-5) homologous with distal mouse chromosome 11, originally identified as carrying the Scl1 gene controlling healing versus nonhealing responses to Leishmania major, is linked to tuberculosis susceptibility; and (iv) the 'T helper 2' cytokine gene cluster (proximal murine chromosome 11/human 5q; candidates IL4, IL5, IL9, IRF1, CD14) controlling later phases of murine L. major infection, is not linked to human disease susceptibility for any of the three infections, but shows linkage to and highly significant allelic association with ability to mount an immune response to mycobacterial antigens. These studies demonstrate that the 'mouse-to-man' strategy, refined by our knowledge of the human immune response to infection, can lead to the identification of important candidate gene regions in man.

Asunto(s)

Proteínas de Transporte de Catión , Leishmaniasis Cutánea/genética , Leishmaniasis Cutánea/inmunología , Infecciones por Mycobacterium/genética , Infecciones por Mycobacterium/inmunología , Animales , Antígenos Bacterianos/inmunología , Enfermedades Autoinmunes/genética , Brasil , Proteínas Portadoras/genética , Cromosomas Humanos Par 17 , Femenino , Ligamiento Genético , Predisposición Genética a la Enfermedad , Antígenos HLA/genética , Humanos , Interleucina-4/genética , Lepra/genética , Lepra/inmunología , Masculino , Proteínas de la Membrana/genética , Ratones , Linaje , Polimorfismo Genético , Programas Informáticos , Tuberculosis/genética , Tuberculosis/inmunología

RESUMEN

SETTING: A study of multicase tuberculosis pedigrees from Northern Brazil. OBJECTIVE: To determine the model of inheritance for genetic susceptibility to tuberculosis, and to test the hypothesis that TNFA and NRAMP1 are candidate susceptibility genes. DESIGN: The study sample included 98 pedigrees, 704 individuals and 205 nuclear families. Segregation analyses were performed using the programs POINTER and COMDS. Combined segregation and linkage analysis was carried out within COMDS. Non-parametric linkage analyses were performed using BETA. RESULTS: A sporadic model for disease distribution in families was strongly rejected, as were polygenic and multifactorial models. A codominant single gene model provided the best fit (P < 0.001) to the data using POINTER. COMDS extended the analysis to compare single-gene and two-gene models. A general two-locus model for disease control was marginally favoured (0.01 < P < 0.05) over the codominant single-gene model. No evidence was found for linkage between susceptibility to disease per se and the TNF gene cluster. Weak linkage was observed using COMDS for genes (IL8RB, P = 0.039; D2S1471, P = 0.025) tightly linked (< 150 kb) to NRAMP1, but not for NRAMP1 itself. CONCLUSIONS: Tuberculosis susceptibility in this region of Brazil is under oligogenic control. Although a minor role for TNFA and NRAMP1 cannot be excluded, our data suggest that neither is a major gene involved in this oligogenic control.

Asunto(s)

Proteínas Portadoras/genética , Proteínas de Transporte de Catión , Proteínas de la Membrana/genética , Tuberculosis/genética , Factor de Necrosis Tumoral alfa/genética , Adolescente , Adulto , Distribución por Edad , Brasil , Niño , Preescolar , Mapeo Cromosómico , Susceptibilidad a Enfermedades , Ligamiento Genético , Humanos , Lactante , Persona de Mediana Edad , Modelos Genéticos , Linaje , Programas Informáticos