Research progress on genetic control of host susceptibility to tuberculosis / 浙江大学学报·医学版

The "Lübeck disaster", twins studies, adoptees studies, and other epidemiological observational studies have shown that host genetic factors play a significant role in determining the host susceptibility to Mycobacterium tuberculosis infection and pathogenesis of tuberculosis. From linkage analyses to genome-wide association studies, it has been discovered that human leucocyte antigen (HLA) genes as well as non-HLA genes (such as SLC11A1, VDR, ASAP1 as well as genes encoding cytokines and pattern recognition receptors) are associated with tuberculosis susceptibility. To provide ideas for subsequent studies about risk prediction of MTB infection and the diagnosis and treatment of tuberculosis, we review the research progress on tuberculosis susceptibility related genes in recent years, focusing on the correlation of HLA genes and non-HLA genes with the pathogenesis of tuberculosis. We also report the results of an enrichment analysis of the genes mentioned in the article. Most of these genes appear to be involved in the regulation of immune system and inflammation， and are also closely related to autoimmune diseases.

Polimorfismos genéticos asociados a la inmunidad innata y la susceptibilidad genética a la tuberculosis / Genetic polymorphisms associated with innate immunity and to genetic susceptibility to tuberculosis

Resumen La tuberculosis es un problema de salud mundial exacerbado por la ausencia de una vacuna eficaz y la emergencia de cepas multidrogo resistentes. La inmunidad innata, clave en la susceptibilidad a tuberculosis, está asociada a polimorfismos genéticos en TLRs (Toll Like Receptors), VDR (Vitamin D Receptor), INF-γ, TNF-α, entre otros. Recientemente, también a nueve genes causantes de susceptibilidad mendeliana a enfermedades micobacterianas (MSMD), incluyendo genes autosómicos y ligados al cromosoma X. Después de décadas de exitoso manejo, Chile reportó mantención de la mortalidad, aumento en la incidencia de tuberculosis en todas sus formas y casos multidrogo resistentes. La incidencia es mayor en Norte y Centro, donde la Región Metropolitana mostró incremento de población migrante latinoamericana. Consecuentemente, la alta persistencia de la incidencia en tales zonas geográficas, podría asociarse a poblaciones portadoras de polimorfismos de un solo nucleótido (SNP)s y/o MSMD, confiriendo susceptibilidad genética a tuberculosis y/o a BCG diseminada y otros patógenos intramacrofágicos, similar a lo descrito en poblaciones de Europa, Asia, África y América. En conclusión, proponemos considerar la predisposición genética de la población actual, al momento de diseñar políticas nacionales de salud pública para erradicar la tuberculosis.

Tuberculosis is a global health problem exacerbated by the absence of an effective vaccine and emergence of extensive antibiotic-resistant strains. Innate immunity is key to tuberculosis susceptibility, since it is associated with genetic polymorphisms in TLRs (Toll Like Receptors), VDR (Vitamin D Receptor), INF-γ, TNF-α, among others. Recently, also to nine Mendelian Susceptibility Mycobacterial Diseases (MSMD) -causing genes, including autosomal and X-linked genes. After decades of successful management, Chile reported maintenance of mortality and increase in tuberculosis under 15 years and multidrug resistant cases incidence. Moreover, incidence is higher in the North and the Center, where Metropolitan Region showed a sustained increment of the Latin American migrant population. Consequently, the high incidence persistence in such geographic areas could be associated with populations carrying SNPs genetic polymorphisms types and/or MSMD that confer genetic susceptibility to tuberculosis and/or BCG dissemination and other intramacrophagic pathogens, similar to that described in certain populations in Europe, Asia, Africa and America. Corollary, we propose to consider genetic predisposition of the current population, at the time of designing national public health policies to eradicate tuberculosis.

Identification of the Mycobacterium tuberculosis Beijing lineage in Ecuador / Detección de Mycobacterium tuberculosis , linaje Beijing, en Ecuador

ABSTRACT Introducción. Los aislamientos de Mycobacterium tuberculosis pertenecientes al linaje Beijing se consideran especialmente virulentos y transmisibles, y con mayor tendencia a la adquisición de resistencia. El linaje Beijing se ha reportado en todo el mundo; sin embargo, en Latinoamérica los estudios al respecto son más escasos. En el único estudio multinacional llevado a cabo en la región, se detectó una distribución heterogénea del linaje, y no se le encontró en Chile, Colombia y Ecuador, aunque en estudios nacionales posteriores se identificaron aislamientos en Chile y Colombia. Objetivo. Rastrear la presencia del linaje Beijing de M. tuberculosis en Ecuador, único país en la región en el que aún no se reporta. Materiales y métodos. Se analizó una muestra de conveniencia (2006-2012) en dos hospitales que atendían poblaciones diferentes. La genotipificación de los aislamientos de M. tuberculosis se hizo mediante la plataforma 24-MIRU-VNTR. La asignación de linajes se hizo mediante la comparación de los patrones genotípicos con los incluidos en la plataforma MIRU-VNTRplus, y aquellos pertenecientes al linaje Beijing fueron confirmados mediante reacción en cadena de la polimerasa específica de alelo. Resultados. Se detectó el primer aislamiento Beijing en Ecuador, en una circunstancia epidemiológica inesperada: un paciente de la región andina, proveniente de una comunidad con escasa movilidad y alejada de las fronteras con los países limítrofes, Perú y Colombia, en los que ya se han identificado aislamientos de M. tuberculosis pertenecientes al linaje Beijing. Conclusiones. En este trabajo se reporta por primera vez la presencia del linaje Beijing de M. tuberculosis en Ecuador en un contexto epidemiológico inusual que merece especial atención.

RESUMEN Introduction: Mycobacterium tuberculosis Beijing lineage isolates are considered to be especially virulent, transmissible and prone to acquire resistances. Beijing strains have been reported worldwide, but studies in Latin America are still scarce. The only multinational study performed in the region indicated a heterogeneous distribution for this lineage, which was absent in Chile, Colombia and Ecuador, although further studies found the lineage in Chile and Colombia. Objective: To search for the presence of the Beijing lineage in Ecuador, the only country in the region where it remains unreported. Materials and methods: We obtained a convenience sample (2006-2012) from two hospitals covering different populations. The isolates were genotyped using 24-MIRU-VNTR. Lineages were assigned by comparing their patterns to those in the MIRU-VNTRplus platform. Isolates belonging to the Beijing lineage were confirmed by allele-specific PCR. Results: We identified the first Beijing isolate in Ecuador in an unexpected epidemiological scenario: A patient was infected in the Andean region, in a population with low mobility and far from the borders of the neighboring countries where Beijing strains had been previously reported. Conclusion: This is the first report of the presence of the Beijing lineage in Ecuador in an unusual epidemiological context that deserves special attention.

DEFB1 gene polymorphisms and tuberculosis in a Northeastern Brazilian population

Abstract β-Defensin-1, an antimicrobial peptide encoded by the DEFB1 gene, is known to play an important role in lung mucosal immunity. In our association study we analyzed three DEFB1 functional polymorphisms -52G>A (rs1799946), -44C>G (rs1800972) and -20G>A (rs11362) in 92 tuberculosis patients and 286 healthy controls, both from Northeast Brazil: no association was found between the studied DEFB1 polymorphisms and the disease. However we cannot exclude that this lack of association could be due to the low number of subjects analyzed, as suggested by the low statistical power achieved for the three analyzed SNPs (values between 0.16 and 0.50).

Microarray analysis of the in vitro granulomatous response to Mycobacterium tuberculosis H37Ra / Análisis con Micromatrices de la respuesta granulomatosa in vitro a Mycobacterium tuberculosis H37Ra

Background: The hallmark of tuberculosis is the granuloma, an organized cellular accumulation playing a key role in host defense against Mycobacterium tuberculosis. These structures sequester and contain mycobacterial cells preventing active disease, while long term maintenance of granulomas leads to latent disease. Clear understanding on mechanisms involved in granuloma formation and maintenance is lacking. Objective: To monitor granuloma formation and to determine gene expression profiles induced during the granulomatous response to M. tuberculosis (H37Ra). Methods: We used a previously characterized in vitro human model. Cellular aggregation was followed daily with microscopy and Wright staining for 5 days. Granulomas were collected at 24h, RNA extracted and hybridized to Affymetrix human microarrays. Results: Daily microscopic examination revealed gradual formation of granulomas in response to mycobacterial infection. Granulomatous structures persisted for 96 h, and then began to disappear. Conclusions: Microarray analysis identified genes in the innate immune response and antigen presentation pathways activated during the in vitro granulomatous response to live mycobacterial cells, revealing very early changes in gene expression of the human granulomatous response.

Antecedentes: La marca histológica de la tuberculosis es el granuloma, una acumulación celular organizada que cumple funciones claves en la defensa del hospedero contra Mycobacterium tuberculosis. Estas estructuras secuestran y confinan a las micobacterias previniendo el desarrollo de enfermedad activa; el mantenimiento a largo plazo de los granulomas conlleva al establecimiento de latencia. Un mejor entendimiento de los mecanismos involucrados en la formación y mantenimiento del granuloma es necesario. Objetivo: Monitorear la formación del granuloma y determinar los patrones de expresión génica inducidos durante la respuesta granulomatosa a M. tuberculosis (H37Ra). Métodos: En este estudio se empleó un modelo in vitro humano previamente caracterizado. La agregación celular fue examinada diariamente mediante microscopia óptica y tinción de Wright por 5 días. Para analizar la expresión génica, los granulomas fueron colectados a las 24 h, se extrajo el RNA sometiéndolo a hibridación a micromatrices de Affymetrix. Resultados: Se observó la formación gradual de granulomas en respuesta a la infección. Los granulomas persistieron por 96 h, y luego se desvanecieron. Conclusiones: Se identificaron genes de la respuesta inmune innata y vías de presentación antigénica activadas durante la respuesta granulomatosa in vitro a células micobacteriales vivas, lo cual reveló alteraciones tempranas de la expresión génica en el inicio de la respuesta granulomatosa humana.

Análisis molecular del cáncer de colon esporádico / Molecular analysis of sporadic colon cancer

Background: In Chile, colorectal cancer (CRC) is often diagnosed in late stages. Thus, surgical treatment must be complemented with chemotherapy. KRAS mutations and microsatellite instability have been detected in these tumors. However, the response to treatment in patients without KRAS mutations varies and requires a better understanding. Aim: To determine the frequency and distribution of somatic point mutations in KRAS, BRAF and PIK3CA genes and microsatellite instability status (MSI) in patients with colon cancer (CC). Material and Methods: A prospective observational study of patients undergoing surgery for colon cancer. Tumor-derived DNA was analyzed by polymerase chain reaction (PCR) for the most frequent mutations of KRAS, BRAF and PIK3CA. PCR was also used to analyze MSI. Results: Fifty-eight patients with sporadic CC were analyzed, 16 showed KRAS mutations (G12R, G12D, G12V, G13D) and out of the 42 patients that did not show any mutation, 10 had mutations in BRAF (V600E) and PIK3CA (E542K, E545D, E545K, Q546E, H1047R). BRAF mutations alone or in combination with PIK3CA mutations were observed in 27% of high MSI tumors and in 2% of tumors without instability (p < 0.049). A higher percentage of high MSI tumors were located in the right colon (p < 0.001), and showed BRAF mutation (p < 0.020). Conclusions: The highest percentage of high MSI and BRAF mutations was observed in the right colon. Therefore, this study suggests the presence of different molecular features between right and left colon tumors that should be considered when defining the therapeutic management.

Sequence comparison of six human microRNAs genes between tuberculosis patients and healthy individuals

Objective/Background: MicroRNAs [miRNAs] play an important role in diseases development. Therefore, human miRNAs may be able to inhibit the survival of Mycobacterium tuberculosis [Mtb] in the human host by targeting critical genes of the pathogen. Mutations within miRNAs can alter their target selection, thereby preventing them from inhibiting Mtb genes, thus increasing host susceptibility to the disease

Methods: This study was undertaken to investigate the genetic association of pulmonary tuberculosis [TB] with six human miRNAs genes, namely, hsa-miR-370, hsa-miR-520d, hsamiR- 154, hsa-miR-497, hsa-miR-758, and hsa-miR-593, which have been predicted to interact with Mtb genes. The objective of the study was to determine the possible sequence variation of selected miRNA genes that are potentially associated with the inhibition of critical Mtb genes in TB patients

Results: The study did not show differences in the sequences compared with healthy individuals without antecedents of TB

Conclusion: This result could have been influenced by the sample size and the selection of miRNA genes, which need to be addressed in future studies

Genetic polymorphism and immune response to tuberculosis in indigenous populations: a brief review

We systematically reviewed studies of the immune response to tuberculosis and the genetic polymorphisms associated with Th1-or Th2-mediated cytokine expression in indigenous populations. A bibliographic search was performed on the Medline and ISI databases and included studies published between January 1980 and October 2011. The search terms were tuberculosis, American Indians, Amerindian, indigenous, Indians, native people, aboriginal, immun*, host immune, immune response, cytokine*, polymorphism*, and gene. Regardless of their design, studies that evaluated immunoglobulin, cytokine levels and genetic polymorphisms that altered cytokine expression were included. Thirteen studies met the inclusion criteria. The majority of studies were performed in Latin America, and five investigated the Warao ethnic group of Venezuela. Most of the investigations indirectly evaluated the immune response. Higher anergy to the tuberculin skin test, higher IgG4 and IgM levels, higher IL-5 production and lower TNF-a, IL-12p40 and IFN-I production were found in the indigenous populations. The studies also reported a predominantly Th2-type response in these populations and a possibly higher susceptibility to tuberculosis. A better understanding of the relevant genetic polymorphisms and their role in immune regulation would help to clarify the immunogenetic mechanisms of TB infection in these populations. This information would be useful for identifying new treatments and preventing infection and progression to active disease.

Kinetics of IFN-Gamma and TNF-Alpha Gene Expression and Their Relationship with Disease Progression after Infection with Mycobacterium Tuberculosis in Guinea Pigs

PURPOSE: Guinea pig is one of the most suitable animal models for Mycobacterium tuberculosis (M. tb) infection since it shows similarities to pulmonary infection in humans. Although guinea pig shows hematogenous spread of M. tb infection into the whole body, immunological studies have mainly focused on granulomatous tissues in lungs and spleens. In order to investigate the time-course of disease pathogenesis and immunological profiles in each infected organ, we performed the following approaches with guinea pigs experimentally infected with M. tb over a 22-week post-infection period. MATERIALS AND METHODS: We examined body weight changes, M. tb growth curve, cytokine gene expression (IFN-gamma and TNF-alpha), and histopathology in liver, spleen, lungs and lymph nodes of infected guinea pigs. RESULTS: The body weights of infected guinea pigs did not increase as much as uninfected ones and the number of M. tb bacilli in their organs increased except bronchotracheal lymph node during the experimental period. The gene expression of IFN-gamma and TNF-alpha was induced between 3 and 6 weeks of infection; however, kinetic profiles of cytokine gene expression showed heterogeneity among organs over the study period. Histophathologically granulomatous lesions were developed in all four organs of infected guinea pigs. CONCLUSION: Although IFN-gamma and TNF-alpha gene expression profiles showed heterogeneity, the granuloma formation was clearly observed in every organ regardless of whether the number of bacilli increased or decreased. However, this protective immunity was accompanied with severe tissue damage in all four organs, which may lead to the death of guinea pigs.

A pilot study to determine genetic polymorphism in Mycobacterium tuberculosis isolates in Central India.

This study was carried out to identify predominant spoligotypes responsible for transmission and prevalence of tuberculosis in central India since there is no data available about the genetic biodiversity of Mycobacterium tuberculosis isolates from patients with tuberculosis in this region. 35 strains of Mycobacterium tuberculosis were subjected to spoligotyping according to the standard protocol. A total of 25 strains out of the 35 (71.42%) could be grouped in to 6 clusters. The largest cluster comprised 8 isolates. Unique (Non-clustered) spoligotypes were seen in 10 isolates, Nine strains did not match the data base (Spol DB-4 data base). The results indicate that there may be a number of orphan strains unique to this geographical area. Further studies on a larger sample size derived from this area would help us delineate the epidemiology of Mycobacterium tuberculosis infection in this area.

Novos aspectos da patogenia da tuberculose / The Pathogenesis of Tuberculosis: Novel Aspects

A tuberculose continua a assombrar a humanidade como uma das doenças infecciosas que mais incapacita e mata. Nosso objetivo foi rever a patogenia da tuberculose, um processo complexo, que envolve tanto o agente etiológico Mycobacterium tuberculosis como os mecanismos de defesa do hospedeiro. Os novos instrumentos de biologia molecular permitiram grandes avanços na compreensão da epidemiologia da doença, assim como na identificação de possíveis alvos farmacológicos e de moléculas que podem ser usadas no diagnóstico das diversas fases da infecção. Estudos da patogenia da tuberculose nos sítios ativos dos pulmões mostraram níveis significativamente mais elevados demediadores que prejudicam a imunidade do tipo Th1 e inata, incluindo mediadores intracelulares e extracelulares. Esses e outros achados têm permitido aplicações no manejo da tuberculose. A proteína early secretory antigenic target-6, presente em micobactérias patogênicas e ausente no BCG, permitiu o desenvolvimento de testes diagnósticos úteis na identificação de infecção tuberculosa latente mesmo em vacinados com BCG. Há uma correlação entre altos níveis de IL-10 ao final de tratamento antituberculose e recidiva da doença ao longo de avaliação, apontando um possível nexo entre essa citocina anti-inflamatória e o risco de recaída por tuberculose

Tuberculosis (TB) still looms as one of the most incapacitating and lethal infectious diseases worldwide. The objective of this article was to review the pathogenesis of tuberculosis, a complex process that involves the interaction between the etiologic agent Mycobacterium tuberculosis and host defense mechanisms. New molecular biology methods have allowed great advances in the understanding of tuberculosis epidemiology, as well as in the identiication of possible pharmacologic targets and molecules that can be used in the diagnosis during the various stages of the infection. Studies of the pathogenesis of tuberculosis at active disease sites in the lungs have demonstrated increased levels of mediators that impair Th1-mediated and innate immunity, including intracellular and extracellular mediators. Such indings have facilitated the application of new techniques in tuberculosis management. The discovery of early secretory antigenic target-6, which is present in pathogenic mycobacteria and absent from BCG, allowed the development of useful diagnostic tests for the identiication of latent tuberculosis infection even in BCG-vaccinated individuals. There is a correlation between high IL-10 levels at the end of anti-tuberculosis treatment and tuberculosis recurrence, showing a possible link between this anti-inlammatory cytokine and the risk of tuberculosis recurrence

Human leucocyte antigens and cytokine gene polymorphisms and tuberculosis.

Purpose: Several genes encoding different cytokines and human leucocyte antigens (HLA) may play crucial roles in host susceptibility to tuberculosis (TB). Our objective was to investigate whether these genes might be associated with protection from or susceptibility to TB. Materials and Methods: Genomic DNA from patients with TB (n = 30) and ethnically matched controls (n = 30) was genotyped by using sequence-specific primers-polymerase chain reaction and sequence-specific oligonucletid methods. Results: Our results demonstrated that HLA-Cw*01 [P = 0.05, odds ration (OR) (95% confidence interval) = 2.269 (1.702-3.027)] allele frequency was significantly more common in TB patients than in healthy controls, and HLA-Cw*01 may be associated with susceptibility to TB. Analysis of cytokine allele frequencies showed that interleukin (IL)-10, -819 C and -592 C alleles was significantly more common in TB patients than in controls (pc: 0.038 and 0.017, respectively). From the IL-10 cluster, a positive significant difference was found at positions -1082 and -592 C/C (pc: 0.027 and 0.054, respectively) genotypes. Although these differences could be explained by the highest frequency of C/C and G/G homozygous patients with TB, in contrast to the control group, statistically significant differences for the C/C genotype however were lost after Bonferroni correction of the P-values. Conclusion: Altogether, our results suggest that the polymorphisms in HLA (class I) and cytokine (IL-10) genes may affect the susceptibility to TB and increase the risk of developing the disease.

CCR2, MCP-1, SDF-1α & DC-sign gene polymorphisms in HIV-1 infected patients with & without tuberculosis.

Background & objectives: Variability in the clinical outcome of persons exposed to and infected with HIV-1 and tuberculosis (TB) is determined by multiple factors including host genetic variations. The aim of the present study was to find out whether chemokine, chemokine receptor and DC-SIGN gene polymorphisms were associated with susceptibility or resistance to HIV and HIV-TB in south India. Methods: CCR2 V64I (G/A), monocyte chemoattractant protein-1 (MCP-1) -2518 A/G, stromal cell derived factor-1α (SDF-1α) 3’UTR G/A and DC-SIGN gene polymorphisms were studied by polymerase chain reaction based methods in HIV-1 infected patients without TB (n=151), with pulmonary TB (PTB) (n=81) and extrapulmonary TB (n=31), 155 PTB patients without HIV and 206 healthy controls. Results: The genotype frequencies of CCR2 V64I, MCP-1 -2518 and DC-SIGN polymorphisms did not differ significantly between the study groups. A significantly increased frequency of GG genotype of SDF-1α polymorphism was observed among HIV+PTB+ patients compared to healthy controls (P=0.009, Pc=0.027). Interpretation & conclusions: Our data suggest that GG genotype of SDF-1α 3’UTR polymorphism may be associated with susceptibility to PTB in HIV-1 infected patients. A better understanding of genetic factors that are associated with TB could help target preventive strategies to those HIV patients likely to develop tuberculosis.

Variantes genéticas da N-acetiltransferase 2, CYP2E1 e glutationa S-transferase: relação com a segurança terapêutica em pacientes com tuberculose / Genetic variants of N-acetyltransferase 2, CYP2E1 and glutathione S-transferase: relation with therapeutic safety in patients with tuberculosis

Polimorfismos nos genes da n-acetiltransferase 2 (NAT2), CYP2E1 e glutationa S-transferase (GST) têm sido associados a diferenças na resposta ao tratamento da tuberculose. O papel de variantes dos genes NAT2, CYP2E1 e GSTM1/GSTT1, no perfil de segurança do tratamento da tuberculose, foi avaliado em 99 pacientes com tuberculose, sem co-infecção por HIV ou vírus da hepatite, tratados por 6 meses. Amostras de sangue foram colhidas antes e durante o tratamento para avaliação de marcadores de lesão hepatocelular (ASL T e AST), colestase (ALP, GGT e bilirrubinas) e função renal (creatinina). O DNA genômico foi extraído de sangue colhido em EDTA pelo método precipitação salina. Os polimorfismos NAT2 foram analisados por PCR-RFLP e seqüenciamento de DNA. Os polimorfismos da região promotora do CYP2E1 foram detectados por PCR-RFLP e para a análise dos genótipos nulos de (GSTM1*0) foi utilizada a PCR multiplex. Durante o tratamento, 59,6% dos pacientes apresentaram reações adversas aos medicamentos (RAM) e alterações nos marcadores de lesão hepatocelular e colestase, com aumento de 1 a 4 vezes o limite superior de referência. Foi observada forte relação entre RAM e alterações nos marcadores séricos (p< 0,05) e também com o uso de medicação concomitante (p< 0,001)...

Molecular diversity of Mycobacterium tuberculosis strains in a slum area of Rio de Janeiro, Brazil / Diversidade molecular de cepas de Mycobacterium tuberculosis em uma região de favela da cidade do Rio de Janeiro

This retrospective molecular study involving restriction fragment length polymorphism, using insertion sequence 6110 as a marker, was conducted in order to provide an initial insight into the genetic diversity of Mycobacterium tuberculosis strains isolated in the slums of the Complexo de Manguinhos, located in the city of Rio de Janeiro, Brazil. Of the 67 strains evaluated, 23 (34.3 percent) were found to belong to clusters (total clusters, 10). Household and social chains of transmission were associated with clustering, in 20 percent and 60 percent, respectively. Living in the Conjunto Habitacional Programado 2 slum was associated with clustering. Although not significant, it is relevant that 26 percent of the clustered strains presented primary resistance. These findings, although possibly underestimating the prevalence due to the failure to analyze all strains, could help improve the local tuberculosis control program.

Este estudo retrospectivo envolvendo polimorfismo de fragmento de restrição e utilizando como marcador a seqüência de inserção 6110, foi realizado para fornecer informações iniciais quanto à diversidade genética das cepas de Mycobacterium tuberculosis isoladas em favelas do Complexo de Manguinhos, na cidade do Rio de Janeiro. Das 67 cepas isoladas, 23 (34,3 por cento) foram agrupadas em clusters (total de clusters, 10). A transmissão entre comunicantes domiciliares e extra-domicialiares estave associada a 20 por cento e 60 por cento dos clusters, respectivamente. Ser morador do Conjunto Habitacional Programado 2 foi associado à presença de clusters. Embora não significativo, é relevante o fato de que 26 por cento das cepas em cluster apresentaram resistência primária. Estes achados, embora possivelmente subestimados devido à impossibilidade de analisar todas as cepas, fornecem subsídios para a melhoria do programa local de controle da tuberculose.

Differential association of tumour necrosis factor-alpha single nucleotide polymorphism (-308) with tuberculosis and bronchial asthma.

BACKGROUND: Tumour necrosis factor (TNF)-alpha is a pleiotropic, pro-inflammatory cytokine of 17 kDa, whose gene is localized on the short arm of chromosome 6. It has a G-308A polymorphism in the promoter region, which is known to be associated with its differential production; the A allele being the high producer. The circulating level of TNF-alpha is under genetic control and implicated in the pathophysiology of asthma and tuberculosis. Since raised levels of TNF-alpha have been found in asthma and tuberculosis, we looked for the association of TNF-alpha G-308A polymorphism in patients with these diseases. METHODS: A total of 300 blood samples from patients (155 with asthma, 145 tuberculosis) and 211 normal healthy controls were collected. The G-308A polymorphism was studied using amplification refractory mutation system analysis. RESULTS: The distribution of G/A alleles in the two patient groups when compared with normal controls revealed a statistically significant association with asthma (p = 0.016) but not with tuberculosis (p = 0.178). CONCLUSION: The data support the common variant common disease hypothesis, which emphasizes that common genetic variations may participate as critical players in inciting common diseases.