Laboratory-based study of drug resistance and genotypic profile of multidrug-resistant tuberculosis isolates in Salvador, Bahia, Brazil.

BACKGROUND: Surveillance of multidrug resistant/extensively drug-resistant tuberculosis (MDR/XDR-TB) is essential to guide disease dissemination control measures. Brazil contributes to a significant fraction of tuberculosis (TB) cases worldwide, but only few reports addressed MDR/XDR-TB in the country. METHODS: This cross-sectional, laboratory-based study describes the phenotypic resistance profiles of isolates obtained between January 2008 and December 2011 in Bahia, Brazil, and sociodemographic, epidemiological, and clinical characteristics (obtained from mandatory national registries) of the corresponding 204 MDR/XDR-TB patients. We analyzed the mycobacterial spoligotyping and variable number of tandem repeats of mycobacterial interspersed repetitive units in 12-loci profiles obtained from Salvador. RESULTS: MDR/XDR-TB patients were predominantly male, had a median age of 43 years, belonged to black ethnicity, and failed treatment before MDR-TB diagnosis. Nearly one-third of the isolates had phenotypic resistance (evaluated by mycobacteria growth indicator tube assay) to second-line anti-TB drugs (64/204, 31%), of which 22% cases (14/64) were diagnosed as XDR-TB. Death was a frequent outcome among these individuals and was associated with resistance to second-line anti-TB drugs. Most isolates successfully genotyped belonged to the Latin-American Mediterranean (LAM) Family, with an unprecedented high proportion of LAM10-Cameroon subfamily bacilli. More than half of these isolates were assigned to a unique cluster by the genotyping methods performed. Large clusters of identical genotypes were also observed among LAM SIT42 and SIT376 strains. CONCLUSIONS: We highlight the need for strengthening local and national efforts to perform early detection of TB drug resistance and to prevent treatment discontinuation to limit the emergence of drug-resistant strains.

Laboratory-based study of drug resistance and genotypic profile of multidrug-resistant tuberculosis isolates in Salvador, Bahia, Brazil

Abstract Background: Surveillance of multidrug resistant/extensively drug-resistant tuberculosis (MDR/XDR-TB) is essential to guide disease dissemination control measures. Brazil contributes to a significant fraction of tuberculosis (TB) cases worldwide, but only few reports addressed MDR/XDR-TB in the country. Methods: This cross-sectional, laboratory-based study describes the phenotypic resistance profiles of isolates obtained between January 2008 and December 2011 in Bahia, Brazil, and sociodemographic, epidemiological, and clinical characteristics (obtained from mandatory national registries) of the corresponding 204 MDR/XDR-TB patients. We analyzed the mycobacterial spoligotyping and variable number of tandem repeats of mycobacterial interspersed repetitive units in 12-loci profiles obtained from Salvador. Results: MDR/XDR-TB patients were predominantly male, had a median age of 43 years, belonged to black ethnicity, and failed treatment before MDR-TB diagnosis. Nearly one-third of the isolates had phenotypic resistance (evaluated by mycobacteria growth indicator tube assay) to second-line anti-TB drugs (64/204, 31%), of which 22% cases (14/64) were diagnosed as XDR-TB. Death was a frequent outcome among these individuals and was associated with resistance to second-line anti-TB drugs. Most isolates successfully genotyped belonged to the Latin-American Mediterranean (LAM) Family, with an unprecedented high proportion of LAM10-Cameroon subfamily bacilli. More than half of these isolates were assigned to a unique cluster by the genotyping methods performed. Large clusters of identical genotypes were also observed among LAM SIT42 and SIT376 strains. Conclusions: We highlight the need for strengthening local and national efforts to perform early detection of TB drug resistance and to prevent treatment discontinuation to limit the emergence of drug-resistant strains.

Distribution of HLA-DRB1 alleles in BRICS countries with a high tuberculosis burden: a systematic review and meta-analysis.

INTRODUCTION: Tuberculosis (TB) is the leading cause of death worldwide caused by a single infectious disease agent. Brazil, Russia, India, China, and South Africa (BRICS) account for more than half of the world's TB cases. Bacillus Calmette-Guérin (BCG) remains the only vaccine available despite its variable efficacy. Promising antigen-based vaccines have been proposed as prophylactic and/or immunotherapeutic approaches to boost BCG vaccination. Relevant antigens must interact with the range of human leukocyte antigen (HLA) molecules present in target populations; yet this information is currently not available. METHODS: MEDLINE and EMBASE were systematically searched for articles published during 2013-2020 to measure the allelic frequencies of HLA-DRB1 in the BRICS. RESULTS: In total, 67 articles involving 3,207,861 healthy individuals were included in the meta-analysis. HLA-DRB1 alleles *03, *04, *07, *11, *13, and *15 were consistently identified at high frequencies across the BRICS, with a combined estimated frequency varying from 52% to 80%. HLA-DRB1 alleles *01, *08, *09, *10, *12, and *14 were found to be relevant in only one or two BRICS populations. CONCLUSIONS: By combining these alleles, it is possible to ensure at least 80% coverage throughout the BRICS populations.

Distribution of HLA-DRB1 alleles in BRICS countries with a high tuberculosis burden: a systematic review and meta-analysis

Abstract INTRODUCTION: Tuberculosis (TB) is the leading cause of death worldwide caused by a single infectious disease agent. Brazil, Russia, India, China, and South Africa (BRICS) account for more than half of the world's TB cases. Bacillus Calmette-Guérin (BCG) remains the only vaccine available despite its variable efficacy. Promising antigen-based vaccines have been proposed as prophylactic and/or immunotherapeutic approaches to boost BCG vaccination. Relevant antigens must interact with the range of human leukocyte antigen (HLA) molecules present in target populations; yet this information is currently not available. METHODS: MEDLINE and EMBASE were systematically searched for articles published during 2013-2020 to measure the allelic frequencies of HLA-DRB1 in the BRICS. RESULTS: In total, 67 articles involving 3,207,861 healthy individuals were included in the meta-analysis. HLA-DRB1 alleles *03, *04, *07, *11, *13, and *15 were consistently identified at high frequencies across the BRICS, with a combined estimated frequency varying from 52% to 80%. HLA-DRB1 alleles *01, *08, *09, *10, *12, and *14 were found to be relevant in only one or two BRICS populations. CONCLUSIONS: By combining these alleles, it is possible to ensure at least 80% coverage throughout the BRICS populations.

Interferon-gamma release assay performance in northeastern Brazil: influence of the IFNG+874 A>T polymorphism

ABSTRACT Introduction Latent tuberculosis infection diagnosis based on the release of interferon-gamma in cultures of peripheral blood cells stimulated with Mycobacterium tuberculosis antigens has replaced the tuberculin skin test in many countries with low tuberculosis prevalence. The IFN-γ production can be influenced by genetic polymorphisms, of which the IFNG + 874 (rs62559044) locus is the most studied. We investigated the possible influence of the IFNG + 874 A/T polymorphism on interferon-gamma test performance. Methods Patients diagnosed with pulmonary tuberculosis (75), volunteers with positive tuberculin skin test (70) and healthy volunteers with negative tuberculin skin test and no history of contact with tuberculosis (57) were evaluated regarding the IFNG + 874 genotype and the IFN-γ levels in whole blood cultures performed using an interferon-gamma commercial kit (QuantiFERON-TB® Gold In-Tube). Results IFN-γ production was not influenced by the IFNG + 874 genotype, regardless of antigen or mitogen-based stimulation, which suggests that other genes may influence IFN-γ production in response to mycobacteria. The IFNG + 874 polymorphism was found to exert no influence over QFT-IT test sensitivity in our study. Conclusions The IFNG + 874 polymorphism was not shown to influence QuantiFERON-TB® Gold In-Tube test performance in an admixed population from northeastern Brazil.

Interferon-gamma release assay performance in northeastern Brazil: influence of the IFNG+874 A>T polymorphism.

INTRODUCTION: Latent tuberculosis infection diagnosis based on the release of interferon-gamma in cultures of peripheral blood cells stimulated with Mycobacterium tuberculosis antigens has replaced the tuberculin skin test in many countries with low tuberculosis prevalence. The IFN-γ production can be influenced by genetic polymorphisms, of which the IFNG+874 (rs62559044) locus is the most studied. We investigated the possible influence of the IFNG+874 A/T polymorphism on interferon-gamma test performance. METHODS: Patients diagnosed with pulmonary tuberculosis (75), volunteers with positive tuberculin skin test (70) and healthy volunteers with negative tuberculin skin test and no history of contact with tuberculosis (57) were evaluated regarding the IFNG+874 genotype and the IFN-γ levels in whole blood cultures performed using an interferon-gamma commercial kit (QuantiFERON-TB® Gold In-Tube). RESULTS: IFN-γ production was not influenced by the IFNG+874 genotype, regardless of antigen or mitogen-based stimulation, which suggests that other genes may influence IFN-γ production in response to mycobacteria. The IFNG+874 polymorphism was found to exert no influence over QFT-IT test sensitivity in our study. CONCLUSIONS: The IFNG+874 polymorphism was not shown to influence QuantiFERON-TB® Gold In-Tube test performance in an admixed population from northeastern Brazil.

A systematic review of East African-Indian family of Mycobacterium tuberculosis in Brazil

ABSTRACT Introduction: The Mycobacterium tuberculosis East African-Indian (EAI) spoligotyping family (belonging to lineage 1, Indo-Oceanic, defined by the region of deletion RD239) is distributed worldwide, but is more prevalent in Southeast Asia, India, and East Africa. Studies in Latin America have rarely identified EAI. In this study, we describe the occurrence of the EAI family in Brazil. Methods: EAI was identified in a systematic literature review of genetic diversity studies pertaining to M. tuberculosis in Brazil, as well as in a survey conducted in Salvador, Bahia, located in the northeastern region of this country. Results: The EAI6-BGD1 spoligotyping family and the EAI5 Spoligotype International Type (SIT) 1983 clade were the most frequently reported, with wide distribution of this particular clade described in Brazil. The distribution of other EAI spoligotyping patterns with broader worldwide distribution was restricted to the southeastern region of the country. Conclusions: EAI may be endemic at a low frequency in Brazil, with some clades indicating increased fitness with respect to this population.

A systematic review of East African-Indian family of Mycobacterium tuberculosis in Brazil.

INTRODUCTION: The Mycobacterium tuberculosis East African-Indian (EAI) spoligotyping family (belonging to lineage 1, Indo-Oceanic, defined by the region of deletion RD239) is distributed worldwide, but is more prevalent in Southeast Asia, India, and East Africa. Studies in Latin America have rarely identified EAI. In this study, we describe the occurrence of the EAI family in Brazil. METHODS: EAI was identified in a systematic literature review of genetic diversity studies pertaining to M. tuberculosis in Brazil, as well as in a survey conducted in Salvador, Bahia, located in the northeastern region of this country. RESULTS: The EAI6-BGD1 spoligotyping family and the EAI5 Spoligotype International Type (SIT) 1983 clade were the most frequently reported, with wide distribution of this particular clade described in Brazil. The distribution of other EAI spoligotyping patterns with broader worldwide distribution was restricted to the southeastern region of the country. CONCLUSIONS: EAI may be endemic at a low frequency in Brazil, with some clades indicating increased fitness with respect to this population.

N-acetyl-cysteine exhibits potent anti-mycobacterial activity in addition to its known anti-oxidative functions.

BACKGROUND: Mycobacterium tuberculosis infection is thought to induce oxidative stress. N-acetyl-cysteine (NAC) is widely used in patients with chronic pulmonary diseases including tuberculosis due to its mucolytic and anti-oxidant activities. Here, we tested whether NAC exerts a direct antibiotic activity against mycobacteria. METHODS: Oxidative stress status in plasma was compared between pulmonary TB (PTB) patients and those with latent M. tuberculosis infection (LTBI) or healthy uninfected individuals. Lipid peroxidation, DNA oxidation and cell death, as well as accumulation of reactive oxygen species (ROS) were measured in cultures of primary human monocyte-derived macrophages infected with M. tuberculosis and treated or not with NAC. M. tuberculosis, M. avium and M. bovis BCG cultures were also exposed to different doses of NAC with or without medium pH adjustment to control for acidity. The anti-mycobacterial effect of NAC was assessed in M. tuberculosis infected human THP-1 cells and bone marrow-derived macrophages from mice lacking a fully functional NADPH oxidase system. The capacity of NAC to control M. tuberculosis infection was further tested in vivo in a mouse (C57BL/6) model. RESULTS: PTB patients exhibited elevated levels of oxidation products and a reduction of anti-oxidants compared with LTBI cases or uninfected controls. NAC treatment in M. tuberculosis-infected human macrophages resulted in a decrease of oxidative stress and cell death evoked by mycobacteria. Importantly, we observed a dose-dependent reduction in metabolic activity and in vitro growth of NAC treated M. tuberculosis, M. avium and M. bovis BCG. Furthermore, anti-mycobacterial activity in infected macrophages was shown to be independent of the effects of NAC on the host NADPH oxidase system in vitro. Short-term NAC treatment of M. tuberculosis infected mice in vivo resulted in a significant reduction of mycobacterial loads in the lungs. CONCLUSIONS: NAC exhibits potent anti-mycobacterial effects and may limit M. tuberculosis infection and disease both through suppression of the host oxidative response and through direct antimicrobial activity.

Revisiting the Heterogeneous IFN-γ Response of Bacille of Calmette-Guérin (BCG)-Revaccinated Healthy Volunteers in a Randomized Controlled Trial: Effect of the Body Mass Index and of the IFNG+874 A/T Polymorphism.

In trials evaluating the immune responses to Bacille of Calmette-Guérin (BCG), the genetic background and the nutritional status are host-related factors that could affect the heterogeneity in these parameters. The IFNG+874 A/T (rs 62559044) polymorphism has been reported to influence the IFN-γ production by BCG-vaccinated individuals challenged in vitro with mycobacterial antigens. The body mass index (BMI) is a proxy for the nutritional status and has been associated both with the susceptibility to tuberculosis and with the IFN-γ response. We show that although the IFNG+874 A/T polymorphism was not associated with the heterogeneity of IFN-γ production in a randomized controlled trial that evaluated long-term immune responses to BCG revaccination previously conducted in Salvador, Bahia, Brazil, the effect of this polymorphism on the observed increase in IFN-γ production among revaccinated subjects was adjusted in individuals with a low BMI.

Heme Oxygenase-1 Regulation of Matrix Metalloproteinase-1 Expression Underlies Distinct Disease Profiles in Tuberculosis.

Pulmonary tuberculosis (TB) is characterized by oxidative stress and lung tissue destruction by matrix metalloproteinases (MMPs). The interplay between these distinct pathological processes and the implications for TB diagnosis and disease staging are poorly understood. Heme oxygenase-1 (HO-1) levels were previously shown to distinguish active from latent TB, as well as successfully treated Mycobacterium tuberculosis infection. MMP-1 expression is also associated with active TB. In this study, we measured plasma levels of these two important biomarkers in distinct TB cohorts from India and Brazil. Patients with active TB expressed either very high levels of HO-1 and low levels of MMP-1 or the converse. Moreover, TB patients with either high HO-1 or MMP-1 levels displayed distinct clinical presentations, as well as plasma inflammatory marker profiles. In contrast, in an exploratory North American study, inversely correlated expression of HO-1 and MMP-1 was not observed in patients with other nontuberculous lung diseases. To assess possible regulatory interactions in the biosynthesis of these two enzymes at the cellular level, we studied the expression of HO-1 and MMP-1 in M. tuberculosis-infected human and murine macrophages. We found that infection of macrophages with live virulent M. tuberculosis is required for robust induction of high levels of HO-1 but not MMP-1. In addition, we observed that CO, a product of M. tuberculosis-induced HO-1 activity, inhibits MMP-1 expression by suppressing c-Jun/AP-1 activation. These findings reveal a mechanistic link between oxidative stress and tissue remodeling that may find applicability in the clinical staging of TB patients.

Interferon-gamma production by mononuclear cells in Bacille Calmette-Guérin-revaccinated healthy volunteers predicted long-term antimycobacterial responses in a randomized controlled trial.

The Bacille Calmette-Guérin (BCG) vaccine is the only vaccine currently available for tuberculosis, and it demonstrates variable efficacy against the disease. The assessment of new vaccine strategies is hindered by the small annual probability that an infected individual will develop tuberculosis, and the lack of simple and reliable surrogate markers of protection. The frequency of cytokine-producing T cells as well as the production of IFN-γ have been disputed as surrogate markers of protection. We evaluated the evolution of these immune parameters in a population from a high burden city where BCG revaccination has been shown to result in mild protection. We found that individuals whose in vitro IFN-γ responses to mycobacterial antigens had increased by more than 3.3-fold were more likely to maintain higher responses after 1 year and to show increased expansion of IFN-γ-producing T lymphocytes than those with lower or null increase of IFN-γ.

SNP typing reveals similarity in Mycobacterium tuberculosis genetic diversity between Portugal and Northeast Brazil.

Human tuberculosis is an infectious disease caused by bacteria from the Mycobacterium tuberculosis complex (MTBC). Although spoligotyping and MIRU-VNTR are standard methodologies in MTBC genetic epidemiology, recent studies suggest that Single Nucleotide Polymorphisms (SNP) are advantageous in phylogenetics and strain group/lineages identification. In this work we use a set of 79 SNPs to characterize 1987 MTBC isolates from Portugal and 141 from Northeast Brazil. All Brazilian samples were further characterized using spolygotyping. Phylogenetic analysis against a reference set revealed that about 95% of the isolates in both populations are singly attributed to bacterial lineage 4. Within this lineage, the most frequent strain groups in both Portugal and Brazil are LAM, followed by Haarlem and X. Contrary to these groups, strain group T showed a very different prevalence between Portugal (10%) and Brazil (1.5%). Spoligotype identification shows about 10% of mis-matches compared to the use of SNPs and a little more than 1% of strains unidentifiability. The mis-matches are observed in the most represented groups of our sample set (i.e., LAM and Haarlem) in almost the same proportion. Besides being more accurate in identifying strain groups/lineages, SNP-typing can also provide phylogenetic relationships between strain groups/lineages and, thus, indicate cases showing phylogenetic incongruence. Overall, the use of SNP-typing revealed striking similarities between MTBC populations from Portugal and Brazil.

Probiotic and postbiotic activity in health and disease: comparison on a novel polarised ex-vivo organ culture model.

BACKGROUND AND AIMS: Probiotics and their metabolic products, here called postbiotics, have been proposed as food supplements for a healthier intestinal homeostasis, but also as therapeutic aids in inflammatory bowel disease (IBD) with, however, very little clinical benefit. This may be due to the lack of reliable preclinical models for testing the efficacy of different strains. METHODS: The activity of three probiotic strains of Lactobacillus (or a postbiotic) was analysed and compared with a pathogenic strain of Salmonella on a novel organ culture system of human healthy and IBD intestinal mucosa developed in our laboratory. The system maintains an apical to basolateral polarity during stimulation due to the presence of a glued cave cylinder. The cylinder is detached at the end of the experiment and the tissue is processed for histology and immunohistochemistry. Cytokines released from the basolateral side are analysed. RESULTS: The model system provides several physiological characteristics typical of a mucosal microenvironment including the presence of an organised mucus layer and an apical to basolateral polarity. Polarised administration of bacteria is critical to control the ensuing immune response as it mimics the physiological entrance of bacteria. The authors show that probiotics are not always beneficial for the healthy host and can also be detrimental in inflamed IBD. This study shows that a potent postbiotic can protect against the inflammatory properties of invasive Salmonella on healthy tissue and also downregulate ongoing inflammatory processes in IBD tissue. CONCLUSIONS: Probiotics can have inflammatory activities in both healthy and IBD tissue. Valid preclinical data on proper model systems should therefore be obtained before specific probiotic strains enter the clinics, especially if administered during acute inflammatory responses. Postbiotics may be a safe alternative for the treatment of patients with IBD in the acute inflammatory phase.

Non-compliance with health surveillance is a matter of Biosafety: a survey of latent tuberculosis infection in a highly endemic setting.

Objective This study aimed at identifying demographic, socio-economic and tuberculosis (TB) exposure factors associated with non-compliance with the tuberculin skin test, the management and prevention of non-compliance to the test. It was carried out in the context of a survey of latent TB infection among undergraduate students taking healthcare courses in two universities in Salvador, Brazil, a city highly endemic for TB. Methods This is a cross-sectional study of 1164 volunteers carried out between October 2004 and June 2008. Bivariate analysis followed by logistic regression was used to measure the association between non-compliance and potential risk factors through non-biased estimates of the adjusted OR for confounding variables. A parallel evaluation of occupational risk perception and of knowledge of Biosafety measures was also conducted. Results The non-compliance rate was above 40% even among individuals potentially at higher risk of disease, which included those who had not been vaccinated (OR 3.33; 95% CI 1.50 to 7.93; p=0.0018), those reporting having had contact with TB patients among close relatives or household contacts (p=0.3673), or those whose tuberculin skin test status was shown within the survey to have recently converted (17.3% of those completing the study). In spite of the observed homogeneity in the degree of Biosafety knowledge, and the awareness campaigns developed within the study focussing on TB prevention, the analysis has shown that different groups have different behaviours in relation to the test. Family income was found to have opposite effects in groups studying different courses as well as attending public versus private universities. Conclusions Although the data presented may not be directly generalisable to other situations and cultural settings, this study highlights the need to evaluate factors associated with non-compliance with routine testing, as they may affect the efficacy of Biosafety programs.

Host-bacteria interactions in the intestine: homeostasis to chronic inflammation.

In the past decade it has become clear that the gut constitutes an important frontier of the body, which not only regulates the selective entry of nutrients while keeping vigilant against pathogens but also is largely responsible for shaping the immune response to educate the organism to recognize self from non-self. The very notion of self has undergone a dramatic change, with the acknowledgment that our 'selves' include a plethora of microbial species that actively participate in our body's homeostasis. The immune system continuously adapts to the microbiota in a cyclic, dynamic cross talk where intestinal epithelial cells play an important role in instructing noninflammatory responses for a steady-state control of bacterial growth, or triggering inflammatory mechanisms that can clear the gut from harmful invaders. The system is complex and robust in the sense that many players with partially overlapping roles act to keep the integrity of the intestinal mucosal barrier. Failure of these mechanisms involves genetic and environmental triggers and leads to inflammatory bowel disease. In this review, we seek to collect the state-of-the-art knowledge about how host and microbiota interact to promote gut homeostasis and provide evidences of malfunctioning of the described mechanisms in human inflammatory bowel disease.

Characterization of the T-cell receptor Vbeta repertoire in the human immune response against Leishmania parasites.

In order to explore a possible presence of hyperreactive T-cell clones in human cutaneous leishmaniasis (CL), we have investigated, by flow cytometry, the expression of Vbeta chains of T-cell receptors (TCRs) in the following types of cells: (i) peripheral blood mononuclear cells (PBMCs) from CL patients, which were then compared to those from normal volunteers; (ii) unstimulated and soluble Leishmania antigen-stimulated draining lymph node cells from CL patients; (iii) PBMCs from volunteers before versus after Leishmania immunization; and (iv) PBMCs from healthy volunteers that were primed in vitro with live Leishmania parasites. Our results show a modulation in the TCR Vbeta repertoire during CL and after antigen stimulation of patients' cells. Vaccination, however, leads to a broad expansion of different Vbeta TCRs. We also observed an association between TCR Vbeta12 expression, T-cell activation, and gamma interferon production upon in vitro priming with Leishmania. Collectively, these results both indicate that infection with live parasites or exposure to parasite antigen can modulate the TCR Vbeta repertoire and suggest that TCR Vbeta12 may be implicated in the response to Leishmania.

Correlation between interleukin-10 and in situ necrosis and fibrosis suggests a role for interleukin-10 in the resolution of the granulomatous response of tuberculous pleurisy patients.

In order to identify mediators involved in immune-mediated disease regression, the pleural cytokine and histopathological profile was evaluated in tuberculous pleurisy patients with varied disease duration and clinical presentation, previous to chemotherapy. Interleukin (IL)-10, interferon (IFN)-gamma and tumor necrosis factor (TNF) levels in pleural fluids were shown to decrease with disease time. IL-10 was positively correlated with IFN-gamma, TNF and necrosis area in pleural sections. To parallel these findings with disease regression, individuals showing fever, anorexia, and progressive exudate in the pleural cavity (active disease) were compared with patients without symptoms and with a decrease in exudate volume (regressive disease). IFN-gamma and TNF levels were lower in regressive disease, as well as reduced necrosis area in pleural sections. Our results indicate that tissue destruction and a prominent Th1 response mark the early phase of tuberculous pleurisy and suggest that down-modulation of this response, with the possible participation of IL-10, is associated with disease resolution.

BCG (Bacille of Calmette-Guérin) revaccination leads to improved in vitro IFN-gamma response to mycobacterial antigen independent of tuberculin sensitization in Brazilian school-age children.

Tuberculin skin test (TST) response and cytokine production in finger stab-derived whole blood cultures from 136 BCG scar-positive school-age children were evaluated before and after BCG revaccination. Fifty-four percent of the children increased in vitro production of IFN-gamma after revaccination, and this increase was highly significant for previously unresponsive children (P<0.0001). No correlation was found between TST response and cytokine production. Our data suggest that the in vitro IFN-gamma response to mycobacterial antigens can be boosted by BCG revaccination and may contribute to the search of correlates of protection to be used for the evaluation of new mycobacterial vaccines.

Papel de mediadores solúveis na resposta imune em modelos de proteção contra o mycobacterium tuberculosis / Paper of soluble mediators in the immune reply in models of protection against mycobacterium tuberculosis

A imunoprofilaxia permanece como uma importante ferramenta para o controle da pandemia tuberculosa. Neste contexto, assume especial importância o estudo de marcadores que possam ser correlacionados à proteção contra a doença, tornando mais viável em termos de custo-benefício a avaliação de novas vacinas e imunoterápicos. A detecção de mediadores solúveis implicados na resposta contra a micobactéria pode revelar potenciais marcadores de proteção, além de constituir um método suficientemente simples para aplicação em grandes grupos populacionais. Escolheu-se avaliar a modulação de mediadores solúveis em duas situações-modelo identificadas com o desenvolvimento de uma resposta eficaz contra o bacilo na infecção humana: a tuberculose pleural, por ser uma forma que apresenta regressão espontânea dos sintomas, e a vacinação com o bacilo de Calmette-Guérin (BCG), que pode ser relacionada a altos índices de proteção pelo menos contra as formas mais graves da doença. Partindo dos pressupostos de que (1) os mecanismos de contenção do bacilo estimulados nestas duas situações estarão também implicados na resposta à infecção primária e (2) mediadores que apresentem uma variação significativa em ambos os estudos poderão ser úteis para estimar a eficácia de novas estratégias vacinais, nós avaliamos a evolução do perfil de mediadores solúveis nestes dois modelos de proteção contra o M. tuberculosis. Nos dois estudos foi possível identificar correlações entre os níveis de citocinas do tipo Th1. Em pacientes com tuberculose pleural, níveis diminuídos de IFN-y e TNF-a foram associados à regressão espontânea dos sintomas e à resolução da reação granulomatosa, sugerindo um papel da modulação negativa da resposta anti-micobacteriana na proteção contra a doença. Também foi evidenciada nos dois estudos a correlação entre os níveis de TNF-a e IL-10, sugerindo um papel para a IL-10 na modulação da resposta imune celular e provavelmente na limitação do dano tecidual associado a esta resposta. O trabalho reforça a aplicabilidade da investigação de mediadores solúveis para a estimativa da eficácia de novas estratégias vacinais, apontando como candidatos de interesse as citocinas IFN-y, TNF-a e IL-10, mediadores implicados em nossos estudos na proteção contra a infecção pelo M. tuberculosis.