Understanding inflammatory bowel disease via immunogenetics.

The major inflammatory bowel diseases, Crohn's disease and ulcerative colitis, are both debilitating disorders of the gastrointestinal tract, characterized by a dysregulated immune response to unknown environmental triggers. Both disorders have an important and overlapping genetic component, and much progress has been made in the last 20 years at elucidating some of the specific factors contributing to disease pathogenesis. Here we review our growing understanding of the immunogenetics of inflammatory bowel disease, from the twin studies that first implicated a role for the genome in disease susceptibility to the latest genome-wide association studies that have identified hundreds of associated loci. We consider the insight this offers into the biological mechanisms of the inflammatory bowel diseases, such as autophagy, barrier defence and T-cell differentiation signalling. We reflect on these findings in the context of other immune-related disorders, both common and rare. These observations include links both obvious, such as to pediatric colitis, and more surprising, such as to leprosy. As a changing picture of the underlying genetic architecture emerges, we turn to future directions for the study of complex human diseases such as these, including the use of next generation sequencing technologies for the identification of rarer risk alleles, and potential approaches for narrowing down associated loci to casual variants. We consider the implications of this work for translation into clinical practice, for example via early therapeutic hypotheses arising from our improved understanding of the biology of inflammatory bowel disease. Finally, we present potential opportunities to better understand environmental risk factors, such as the human microbiota in the context of immunogenetics.

Immunogenetics of mycobacterial infections in the North Indian population.

Several lines of evidence highlight the genetic basis of risk to develop mycobacterial diseases. Human leukocyte antigen (HLA)-DR2 alleles (DRB1*1501 and DRB1*1502) have been found to be strongly associated with mycobacterial disease, especially the more severe forms such as lepromatous leprosy and multidrug-resistant pulmonary tuberculosis. In this study, DNA-based high-resolution typing techniques of polymerase chain reaction-sequence-specific oligonucleotide probe were used to determine the distribution of HLA-DR/DQ alleles in patients with leprosy and pulmonary tuberculosis. Analysis of different DR2 subtypes based on valine/glycine dimorphism at codon beta86 in pocket 1 of HLA-DR showed an inverse relationship of DR2 alleles with V/G as the severity of disease increased both in leprosy and in pulmonary tuberculosis.

Immunogenetic association in patients with antineutrophil cytoplasmic antibodies (ANCA) from Mumbai, Maharashtra, India.

Considerable genetic evidence exit for ANCA-associated vasculitis and pathogenesis. HLA A and B alleles identified serologically from 84 ANCA-positive patients were compared with 101 controls. Further subtyping were done in the 27 "pauci-immune" vasculitis patients using the polymerase chain reaction based PCR-SSOP technique and compared with controls (67). The results revealed that HLA A1 (OR=4.00; p value 2.72E-05), B17 (OR=3.38; p value 0.0008) and HLA B40 (OR=2.74; p value 0.001) were significantly increased among ANCA-positive patients when compared with the controls. Further, the molecular subtypes A*0101 (OR=5.04; p value 0.0005), B*5801 (OR=4.47; p value 0.0002) and haplotype A*0101-B*5801 (OR=4.47; p value 0.0001) were significantly increased among the autoimmune patients. The study revealed that HLA A1, B17 and B40 alleles are associated in production of antineutrophil autoantibodies and A*0101-B*5801 haplotype is significantly associated with autoimmune diseases and they may be invariably involved in disease pathogenesis in India.

Estudo de associação entre antígenos HLA e reação hansênica tipo 1 ulcerada / Study of the association of HLA antigens and ulcerated type 1 leprotic reaction

Embora existam associações importantes entre antígenos HLA e várias doenças, os mecanismos de suscetibilidade permanecem obscuros e há evidências de que não esteja envolvido o mesmo loco gênico e nem seja o mesmo mecanismo que atue nas diversas doenças. Estudos de associação com pacientes que apresentam reações hansênicas, em especial naqueles com reações hansênicas tipo 1 ulcerada, não foram realizadas até hoje. O objetivo era investigar uma possível associação entre antígenos HLA da classe II e reação hansênica tipo 1 ulcerada. Antígenos HLA-A, B, DR e DQ foram determinados em 12 pacienes hanseniasnos caucasóides, sendo 11 com hanseníase tuberculóide reacional (MHTR) e um com hanseníase dimorfa reacional (MHDR). O grupo controle doi constituído por amostra da população caucasóide do Estado de São Paulo. A comparação das freqüências dos antígenos HLA entre pacientes e grupos controle não evidenciou nenhum tipo de associação. Entretanto, foi observado aumento significante na freqüência do antígeno HLA-DR2 (63,3 vs 19 por cento, p<0,05). Os resultados obtiidos não mostraram qualquer tipo de associação entre antígenos HLA e reação hansênica tipo 1 ulcerada, mas sugerem uma função dos genes do complexo HLA no direcionamento da forma clínica da hanseníase

Immunogenetics of uveitis in leprosy.

PURPOSE: To identify any possible determinants in the development of uveitis in leprosy patients. METHODS: Human leukocyte antigen (HLA) class I and II antigen, and HLA class II genotypings were analyzed among Japanese leprosy patients. Ninety-three unrelated Japanese leprosy patients (46 patients with a history of uveitis and 47 patients without uveitis) and 114 healthy control subjects were investigated. RESULTS: The occurrence of HLA-DR2 was significantly higher in patients with uveitis (78.3%) than in those without uveitis (57.4%; odds ratio = 2.7, P<.05) and in the controls (33.3%; odds ratio = 7.2, P<.0000005, Pc<.00005). The occurrence of HLA-DR4 was significantly lower in patients with uveitis (15.2%) than in those without it (38.3%; odds ratio = 0.29, P<.05) and in the controls (46.5%; odds ratio = 0.21, P<.0005, Pc<.05). Furthermore, the frequencies of DR2-positive and DR4-negative genotypes were significantly higher in patients with uveitis (69.6%) than in those without it (38.3%; odds ratio = 3.7, P<.005) and in the controls (21.9%; odds ratio = 8.1, P<.00000005). At the genomic level, the occurrence of HLA-DQB1*0302 was significantly lower in the patients with uveitis (8.7%) than in those without it (25.5%; odds ratio = 0.28, P<.05). The distribution of HLA-DRB1 and DQA1 alleles was not significantly different between the patients with and those without uveitis. However, the frequencies of DRB1*1501-positive, as well as DRB1*0405- and DQB1*0302-negative genotypes were significantly higher in the patients with uveitis (47.8%) than in those without it (25.5%; odds ratio = 2.7, P<.05) and in the controls (8.8%; odds ratio = 9.5, P<.00000005). CONCLUSIONS: Our results suggest that HLA Class II genes confer susceptibility to or protection from leprous uveitis.

Association of vitamin D receptor genotype with leprosy type.

Host genetic factors including major histocompatibility complex (MHC) polymorphisms influence both susceptibility to leprosy per se and also to leprosy type. Non-MHC genes may play an important role, but such genes remain undefined. The influence of two non-MHC candidate genes was assessed in a case-control study of Bengali leprosy patients from Calcutta. Recent studies have implicated variation in the vitamin D receptor (VDR) gene in susceptibility to several diseases, including osteoporosis and pulmonary tuberculosis. In this population, homozygotes for the alternate alleles of the VDR polymorphism are associated, respectively, with lepromatous and tuberculoid leprosy. The NRAMP1 (natural resistance associated macrophage protein 1) gene may influence human mycobacterial disease susceptibility based on studies with the murine homologue Nramp1. However, no significant association was found between NRAMP1 and leprosy susceptibility. This study suggests that the VDR polymorphism may influence susceptibility to some diseases by affecting the type and the strength of the host immune response.

Immunogenetics of episcleritis in leprosy.

Human leukocyte antigens (HLA) were analyzed among Japanese leprosy patients to identify any possible determinants in the development of episcleritis in leprosy patients. Seventy-nine Japanese leprosy patients (33 patients with history of episcleritis and 46 patients without episcleritis) and 114 healthy control subjects were investigated. Human leukocyte antigen-class I and class II specificities were determined serologically by the standard microcytotoxicity test. The HLA-DRB1, -DRB5, -DQA1, and -DQB1 genotypings were performed by using the polymerase chain reaction (PCR)-single strand conformation polymorphism and PCR-restriction fragment length polymorphism analyses. The frequency of HLA-Cw3 was significantly increased among the patients with episcleritis (66.7%) compared to patients without episcleritis (43.5%; odds ratio = 2.6, P < 0.05). The frequency of HLA-DR4 was significantly decreased among the patients with episcleritis (15.2%) compared to patients without episcleritis (39.1%; odds ratio = 0.28, P < 0.05) and the controls (46.5%; odds ratio = 0.21, P < 0.001). At the genomic level, frequencies of the HLA-DRB1*0405, -DQB1*0401, and -DQB1*0302 alleles were significantly decreased among the patients with episcleritis (0%, 0%, and 6.1%, respectively) compared to patients without episcleritis (15.2%, 13.0%, and 26.1%, respectively; odds ratio = 0.07, 0.09, and 0.18, P < 0.05). HLA-DRB1*0405 and -DQB1*0401 were also significantly decreased among the patients with episcleritis compared to the controls (29.8% and 29.8%; odds ratio = 0.04, P < 0.0001). Our results suggest that HLA-Cw3 antigen confers the susceptibility to the development of episcleritis among Japanese leprosy patients. Concurrently, the DRB1 (the -DBR1*0405), and/or DQB1 (the -DQB1*0401 and -DQB1*0302) alleles might provide protection against leprous episcleritis.

The immunogenetics of human infectious diseases.

Twin and adoptee studies have indicated that host genetic factors are major determinants of susceptibility to infectious disease in humans. Twin studies have also found high heritabilities for many humoral and cellular immune responses to pathogen antigens, with most of the genetic component mapping outside of the major histocompatibility complex. Candidate gene studies have implicated several immunogenetic polymorphisms in human infectious diseases. HLA variation has been associated with susceptibility or resistance to malaria, tuberculosis, leprosy, AIDS, and hepatitis virus persistence. Variation in the tumor necrosis factor gene promoter has also been associated with several infectious diseases. Chemokine receptor polymorphism affects both susceptibility ot HIV-1 infection and the rate of progression to AIDS. Inactivating mutations of the gamma-interferon receptor lead to increased susceptibility to typical mycobacteria and disseminated BCG infection in homozygous children. The active form of vitamin D has immunomodulatory effects, and allelic variants of the vitamin D receptor appear to be associated with differential susceptibility to several infectious diseases. NRAMP1, a macrophage gene identified by positional cloning of its murine homologue, has been implicated in susceptibility to tuberculosis in Africans. Whole genome linkage analysis of multi-case families is now being used to map and identify new loci affecting susceptibility to infectious diseases. It is likely that susceptibility to most microorganisms is determined by a large number of polymorphic genes, and identification of these should provide insights into protective and pathogenic mechanisms in infectious diseases.

Controle genético da hanseníase e/ou seu subtipos associado aos antígenos HLA / ?

A hanseníase é uma doença infecciosa crônica causada pelo bacilo Mycobacterium leprae (M. leprae). Com base em critérios clínicos, histopatológicos e imunológicos, a hanseníase pode ser classificada com tuberculóide (TT), borderline-tuberculóide (BT), borderline-bordeline (BB), borderline-lepromatosa (BL), lepromatosa (LL) e indeterminada (I). A manifestação da hanseníase e sua gravidade parecem depender de interações entre M. leprae e o sistema imune do hospedeiro infecctado. Estudos de susceptibilidade à hanseníase indicam a participação de fatores genéticos no controle da imunidade humoral e mediada por célula no desenvolvimento das diferentes formas da doença. Vários estudos têm demonsatrado associações entre as especificidades HLA e as formas clínicas TT e LL da hanseníase. O presente trabalho teve como objetivo investigar uma possível associação entre as especificidades HLA e a hanseníase e/ou seus subtipos numa população brasileira. Desta forma, os fenótipos HLA de cento e vite e um pacientes brasileiros com hanseníase foram comparados com aqueles de cento e quarenta e sete indivíduos normais de grupo étnico correspondente. A tipagem HLA-A, B, Cw, DR e DQ dos pacientes e controles foi realizada através da técnica de microlinfocitotoxidade. Os resultados demonstraram um aumento na frequência de HLA-A33(p=0,0395), B5, (p=0,0487), B7 (p=0,02, B51 (p=0,00102), Cw4 (p=0,0496), Cw7 (p=0,0168), Dr2 (p=0,00035), DQ1 (p=0019), DQ3 (p=0,012) e DQ7(p=0,104) no grupo de pacientes comparados aos controles e um descrécimo na frequência de HLA-A9 (p=0,0094, A23(p=0,021, B14 (p=0,0197), B65 (p=0,00454, DR4 (p=0,0569) e DQ2 (p=0,0192. Contudo, após correção das probabilidades pelo número de antígenos testados somente o desvio da frequência de HLA-DR2 (44,2 por cento nos pacientes de 23,3 por cento nos controles; pc=0,0231) permaneceu significante. O risco realtivo (RR), quen indica o grau de associação entre a especificidade HLA-DR2 e a hanseníase foi de 2,6. A anáilse individual das formas clínicas da hanseníase demonstrou que, para a forma LL, as frequências aparecem aumentadas para HLA-B5...

Expressao do antigeno de 18kDa de Mycobacterium leorae na levedura Saccaromyces cerevisisae e estudo das propriedades imunogenicas do antigeno recombinante / Expression of the antigen of 18kDa of Mycobacterium leprae na levedura Saccharomyces cerevisiae and study of imonogenics properties of recombinant antigen

Dois diferentes sistemas de expressao do antigeno de 18 kDa de M. leprae (p18) em S. cerevisiae, um intracelular e outro de secrecao, foram desenvolvidos. Ambos os sistemas mostraram-se efetivos para a expressao, mas a purificacao da p18 secretada mostrou-se mais simples. Comparando diferentes cepas hospedeiras e condicoes de cultivo, foi obtido um sistema de secrecao de alto rendimento (mais de 100 mg de proteina biologicamente ativa por litro). A p18 foi purificada do meio de cultura da levedura por precipitacao, seguida de cromatografias de troca ionica e por filtracao em gel. As propriedades imunologicas da proteina recombinante, nativa ou previamente irradiada com raios 'GAMA' foram analisadas em camundongos. Ambas as preparacoes desencadearam producao de anticorpos e reacao de hipersensibilidade tardia, correspondentes as respostas humoral e celular, respectivamente. Em adicao, a irradiacao previa do antigeno potencializou sua imunogenicidade a nivel celular. Estes resultados demonstram ser esta proteina forte candidata para utilizacao em novos testes cutaneos para a monitorizacao da resposta celular contra M. leprae

Leprosy and immunity: genetics and immune function in multiple case families.

Genetic susceptibility to infection with M. leprae was studied in 10 multiple case families of Australian Aborigines. Of the 87 members available for study, 24 had proven stable clinical leprosy which had been or was still being treated with diamino diphenyl sulphone. Evidence of contact with M. leprae in the remaining 63 members as assessed by ELISA to M. leprae sonicate and phenolic glycolipid (PGL) or by indirect immunofluorescence antibody assay was found in 78%, 64% and 71%, respectively. By contrast, in vitro assays of T cell function (LMAT and LTT) were less reliable indicators of exposure. Evidence was sought for possible linkages between human leucocyte antigen (HLA) or non-HLA genes and four marker phenotypes including clinical leprosy, clinical subtype of leprosy and lymphocyte transformation or leucocyte migration inhibition factor (LIF) production in response to M. leprae antigen. No associations were found with any particular HLA or non-HLA gene. On the other hand, sequential analysis of the data from the 10 families was strongly suggestive of a linkage between HLA haplotype and non-responsiveness to M. leprae as manifest by lack of LIF production but not lymphocyte transformation. The model which best fits the data is for a gene on chromosome 6 in close linkage with the HLA haplotype, with two alleles, autosomal recessive inheritance and penetrance of 90%. On this basis, it can be suggested that disease type (lepromatous leprosy) rather than disease susceptibility may be controlled by genes within or closely linked to the major histocompatibility gene complex.

Immunogenetics of susceptibility to leprosy, tuberculosis, and leishmaniasis. An epidemiological perspective.

The literature on the genetic regulation of susceptibility in leprosy, tuberculosis, amd leishmaniasis is critically reviewed. Of the three groups of diseases, leprosy has received the most attention from the standpoint of human genetics. There is now evidence that genetic factors, some of them HLA-linked, play a role in tuberculoid leprosy. However, the evidence leaves considerable room for environmental determinants in addition to genetic background. Several twin studies of tuberculosis have favored some genetic factors in clinical tuberculosis, but their evidence is mitigated by the many biases underlying such studies. Though very little work has been done on the genetics of leishmaniasis in man, experimental studies in mice have begun to unravel mechanisms controlling successive steps in the course of both L. donovani and L. torpica infections. It is suggested that future work should concentrate on moving from genetics to biochemical genetics in the mouse, should extend family studies in conjunction with markers in man, and should place high priority on confirmation of reported leprosy type discordance among monozygous twins.