Heparin-binding hemagglutinin as a composition antigen of tuberculosis vaccine exerts protective immune effects by inducing IL-17 / 中华预防医学杂志

To explore the protective immune effect induced by mucosal delivery heparin-binding hemagglutinin (HBHA)-a candidate vaccine antigen of Mycobacterium tuberculosis. Female C57BL/6 mice were between 6 and 8 weeks of age before experimental use. Thirty mice received different immunization strategies and were randomly divided into the control group, the early secreting antigen target-6 (ESAT-6) intranasal immunization group, the HBHA intranasal immunization group, the BCG priming PBS control group, or BCG priming HBHA boost group, 6 mice in each group. In order to analyzed the immune effect, the concentrations of plasma Interleukin-17A (IL-17A) and other cytokines were measured by ELISA. Quantitative real-time PCR analyses were performed to detect the relative quantity (RQ) mRNA of IL-17A in the lung. The lung tissue sections were stained to detect the formation of the tertiary lymphoid structures. The chemokines contributed to formation of the tertiary lymphoid structures were also measured. Flow cytometry was used to detect the frequency of Th1 and Th17 cells in the system. Sixty mice in the BCG priming PBS control group and the BCG priming HBHA boost group were sacrificed at different time points after infection to count the lung bacterial burden. The concentrations of plasma IL-17A and relative quantity of lung IL-17A mRNA were highest in the BCG priming HBHA boost group [(14.76±4.73) pg/mL,RQ (12.27±6.71)], which was significantly higher than the control group [(5.57±2.95) pg/mL,RQ (1.30±0.97)] (t=4.213, P<0.001; t=5.984, P<0.001), and also significantly higher than the BCG priming PBS control group [(6.81±2.18) pg/mL,RQ (1.44±1.16)] (t=3.646 P=0.001; t=6.185 P<0.001). Compared with the BCG priming PBS control group (0.38±0.38)% the frequency of spleen Th17 cells were also significantly increased (t=-0.280 , P=0.048) in the BCG-primary HBHA boost group (1.02±0.34)%. In addition, HBHA boosting could promote better formation of the tertiary lymphoid structures in the lung, and decrease the bacterial load on the early stage after BCG challenge. Collectively, mucosal delivery of HBHA can effectively enhance the protective effect after BCG vaccination, and it is a potential candidate vaccine component.

Immunogenicity of Whole / 生物医学与环境科学（英文）

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Genes y determinantes de virulencia de Mycobacterium tuberculosis que contribuyen a la evasión de la respuesta inmune / Mycobacterium tuberculosis genes and virulence determinants that contribute to the immune response evasion

La tuberculosis pulmonar es un problema de salud pública a nivel mundial. La Organización Mundial de la Salud en el año 2018 reportó alrededor de 10 millones de enfermos y 1,5 millones de muertes. Mycobacterium tuberculosis es un patógeno intracelular y el agente causal de la enfermedad. Estudios experimentales de virulencia han permitido determinar un conjunto de genes de virulencia, que le confieren la capacidad de resistir el ambiente hostil en el macrófago, superar la actividad de la respuesta inmune y persistir en el hospedero. El objetivo de la publicación es presentar una revisión de las investigaciones de los últimos 20 años que han demostrado los genes o factores de virulencia de M. tuberculosis que contribuyen a la evasión de la respuesta inmune. Según los resultados de las investigaciones, existen múltiples factores y genes de virulencia que participan en la evasión de la respuesta inmune innata como ESAT-6, PknG, PhoP, ManLAM, SapM, katG, tpx, nuoG, sodA/secA2, pknE y Rv3654c/Rv3655c, mientras existen elementos capaces de modular la respuesta inmune adaptativa. La comprensión de la interacción entre los genes de virulencia y la actividad del sistema inmune, son importantes para estudiar nuevos métodos de diagnóstico, el diseño de nuevas vacunas y por ende, mejorar las medidas de control, prevención y tratamiento de la tuberculosis(AU)

Pulmonary tuberculosis is a public health problem worldwide. The World Health Organization in 2018 reported about 10 million patients and 1.5 million deaths. Mycobacterium tuberculosis, an intracellular pathogen, is the causative agent of the disease. Experimental virulence studies have allowed to determine a set of virulence genes that confer the ability to resist the hostile environment in the macrophage, overcome the activity of the immune response and persist in the host. The objective of the publication is to present a review of the last 20 years investigations that have shown the genes or virulence factors of M. tuberculosis that contribute to the evasion of the immune response. According to the results of the investigations, there are multiple virulence factors and genes that participate in the evasion of the innate immune response such as ESAT-6, PknG, PhoP, ManLAM, SapM, katG, tpx, nuoG, sodA/secA2, pknE and Rv3654c/Rv3655c, while there are elements capable of modulating the adaptive immune response. The understanding of the interaction between the virulence genes and the activity of the immune system, are important to study new diagnostic methods, the design of new vaccines and therefore, to improve the control, prevention and treatment measures of tuberculosis(AU)

Priorización de nuevas vacunas e innovación al servicio de estrategias de vacunación / New vaccines prioritization and immunization-related innovation

La vacunación es el medio más efectivo para controlar la morbilidad y mortalidad relacionadas con enfermedades infecciosas. Para lograr esto, necesitamos vacunas inmunogénicas y seguras que faciliten y mejoren sus condiciones de transporte, almacenamiento y administración. Gracias a los avances en inmunología y bioinformática, es posible impulsar el descubrimiento de nuevas vacunas para enfrentar la tuberculosis, el virus respiratorio sincicial, el Streptococcus agalactiae, la enfermedad meningocócica invasora, entre otros. Así también, nuevas tecnologías, como la producción de vacunas utilizando plantas transgénicas y parches de microagujas, los cuales podrían facilitar la producción, disminuir los costos y efectos adversos. Sin embargo, no solo necesitamos las vacunas, sino que debemos conocer la epidemiología de las enfermedades prevenibles con vacuna para tomar decisiones fundadas, con el objetivo de planificar estrategias sanitarias, medir su impacto y evaluar la seguridad de su utilización, para alcanzar las metas de salud pública y la confianza de la población.

Vaccination is the most effective strategy to avoid morbidity and mortality related to infectious diseases. To achieve this, we need immunogenic and safe vaccines that facilitate and improve its transport, storage and administration conditions. Thanks to current advances in immunology and bioinformatics, it is possible to boost the discovery of new vaccines to deal with tuberculosis, the respiratory syncytial virus, Streptococcus agalactiae, meningococcal invasive disease, among others. In addition to new technologies such as the production of plant-based vaccines, and microneedles patches, which can facilitate its production, reducing costs and adverse effects. However, vaccines is not the only thing that we need, because we must know the epidemiology and burden of disease to take informed decisions to design optimal strategies, measuring their impact and assessing the safety of their use in order to achieve the goals health and population confidence.

Mycobacterium tuberculosis recombinant protein Rv2626c expressed in Streptomyces lividans. Physico-chemical and Immunological characterization as potential vaccine antigen

Mycobacterium tuberculosis (Mtb) is a leading cause of death globally. Latent tuberculosis infection threatens 1.7 billion people. Mtb latency is mediated by a group of proteins, mainly coded by the Dormancy Safety Regulator (DosR). The protein Rv2626c is the strongest regulated member of this operon. Previous results, including ours, indicate a strong potential of Rv2626c as antigen in a new multiple tuberculosis vaccine. Objectives of this study were to purify the rRv2626c protein and characterize it physico-chemically and immunologically. The purified protein migrates as a sole band after a non-reductive PAGE-silver staining. Under reductive conditions, the dimer isoform appearing at 30.9 kDa prevails over the monomer 15.6 kDa. Mass spectrometry corroborates electrophoresis results regarding dimer molecular weight, of approximately 32 kDa. Six of its digested peptides matched those of HRP-1 protein (Rv2626c) of Mtb whereas 92.1 percent of its amino acid sequence contains three mutations and the addition of an amino acid. With respect to native Mtb protein, 12 of the 13 main epitopes are conserved. Antigenicity was corroborated in volunteers, the antibody responses were significantly higher in a number of infected tuberculosis patients in comparison to healthy Mantoux negative donors as well as in mice immunized with reference Rv2626c, while the immune identification pattern was as expected. The purified protein was able to elicit strong immune response in mice and the resulting antibodies recognized the reference Rv2626c protein. Lastly, the productive specific yield of the Streptomyces lividans strain is sustainable. Taking these results altogether, corroborates our rRv2626c as a promising candidate as antigen for new tuberculosis vaccine formulations(AU)

Mycobacterium tuberculosis (Mtb) es una de las principales causas de muerte globalmente, la tuberculosis latente amenaza a 1,7 mil millones de personas. En combinación con el VIH-SIDA y otras enfermedades, la tuberculosis puede ser reactivada. La latencia de Mtb está mediada por un grupo de proteínas, principalmente codificadas por el Regulador de Seguridad de Latencia (DosR). La proteína Rv2626c es el miembro más fuertemente regulado de este operón. Los resultados previos, incluidos los nuestros, indican una gran potencialidad de Rv2626c como antígeno en una nueva vacuna múltiple contra la tuberculosis. Los objetivos de este estudio fueron purificar la proteína Rv2626c y caracterizarla fisicoquímica e inmunológicamente. La proteína purificada migra como una banda única después de PAGE con tinción de plata en condiciones no reductoras. En condiciones reductoras, el dímero, de 30,9 kDa, es la isoforma prevaleciente sobre el monómero, de 15,6 kDa. La espectrometría de masas corrobora el peso molecular del dímero, de aproximadamente 32 kDa. Seis de sus péptidos digeridos coincidieron con los de la proteína Rv2626c de Mtb, mientras que se confirmó coincidencia del 92,1 por ciento de su secuencia de aminoácidos, detectándose tres mutaciones y la adición de un aminoácido. Con respecto a la proteína Mtb nativa, se conservan 12 de los 13 epítopes principales. La antigenicidad se corroboró en voluntarios, las respuestas de anticuerpos fueron significativamente mayores en un número de pacientes infectados con tuberculosis en comparación con los donantes negativos de Mantoux sanos, así como en ratones inmunizados con la referencia Rv2626c, mientras que el patrón de identificación inmune fue el esperado. La proteína purificada fue capaz de provocar una fuerte respuesta inmune en ratones y los anticuerpos resultantes reconocieron la proteína de referencia Rv2626c. Por último, el rendimiento productivo específico de la cepa de Streptomyces lividans es sostenible. Tomando estos resultados en conjunto, corrobora nuestra rRv2626c como un candidato prometedor como antígeno para nuevas formulaciones de vacunas contra la tuberculosis(AU)

Cellular and humoral immunogenicity of recombinant Mycobacterium smegmatis expressing Ag85B epitopes in mice

Objective/background: The search for new vaccines more efficacious than bacille Calmette-Guerin for tuberculosis prevention is of paramount importance for the control of the disease. The expression of Mycobacterium tuberculosis antigens in Mycobacterium smegmatis is one of the current strategies for the development of new-generation vaccines against tuberculosis. The objective of this study was to evaluate the immunogenicity in mice of M. smegmatis expressing epitopes from Ag85B antigen

Methods: M. smegmatis expressing three T cell epitopes from M. tuberculosis Ag85B [P21, P26, and P53] was constructed [rMs064]. rMs064 was used to immunize BALB/C mice for immunogenicity evaluation. The present study investigates the capacity of rMs064 to induce specific cellular and humoral immune responses against the expressed epitopes. Cytokine production upon stimulation with Ag85B peptides and specific total immunoglobulin G and immunoglobulin G subclasses were determined

Results: The results showed a significant production of interleukin-12 and interleukin-23 when splenocytes were stimulated with P21, P26, and P53 peptides, and interferon-gamma after stimulation with P21 in animals immunized with rMs064 compared with controls. The total immunoglobulin G and its subclasses showed significant increases against the Ag85B epitapes in the sera of rMs064-immunized mice compared with the control groups

Conclusion: The results of this study support the future evaluation of rMs064 as a vaccine candidate against tuberculosis in challenge experiments

Assessment of phagosomes infected with Mycobacterium tuberculosis as a vaccine candidate against tuberculosis.

The present study describes a novel and simple vaccination strategy that involve culturing of M. tuberculosis in the macrophage cells. Isolation of phagosome from macrophage (cell line J774) infected with M. tuberculosis (H37) and M. bovis (BCG) at early and late phase of infection was done ensuing the identification and characterization of these phagosome. In vitro study of apoptosis induced by phagosome infected with (H37) and (BCG) was performed. The vaccine candidate with H37 MOI- 1:10 at 3 h, MOI- 1:20 at 1, 1.5, 2.5 and 3 h and BCG MOI- 1:20 at 3.5 h showed percentage apoptosis as 38.64, 39.93, 34.66, 22.56,34.59 and 37.81% respectively. The results designates that macrophages provide cellular niche during infection and illustrate considerable immunogenic property. Novel antigens expressed or secreted by H37 in infected macrophages can provide evidence to be a successful vaccine candidate as it endures enhanced immune response than BCG.

Tuberculosis, Bacillus Calmette-Guérin (BCG) y vacunas de tuberculosis: análisis de patentes / Tuberculosis, Bacillus Calmette-Guérin (BCG) and tuberculosis vaccines: a patent analysis

La relación de la tuberculosis, el Bacillus Calmette-Guérin y las vacunas de tuberculosis como dominio bajo estudio, parte del hecho de que la única vacuna disponible hoy para prevenir la tuberculosis en humanos es la BCG, y el mejoramiento de ella o el desarrollo de nuevas vacunas es estratégico para el control de esta enfermedad. Este estudio pretende contribuir con estas importantes investigaciones a partir de los estudios patentométricos, y tiene como objetivo realizar un análisis métrico que permita describir la productividad de patentes sobre tuberculosis, Bacillus Calmette-Guérin y vacunas de tuberculosis en un determinado periodo de tiempo. Para el estudio de la productividad se analizó el comportamiento de indicadores temporales y geográficos en el dominio, en el que se utilizaron técnicas y herramientas apropiadas para los documentos de patentes. A la investigación de la tuberculosis como enfermedad infecciosa transmisible se le han dedicado grandes esfuerzos. La tuberculosis fue considerada hasta hace poco un problema de salud de los países en desarrollo, mientras hoy, con la reemergencia de la enfermedad, los países desarrollados han acaparado su investigación; sin embargo, estos esfuerzos no han sido proporcionales con la investigación dedicada a una nueva generación de vacunas contra esta enfermedad y no existen nuevas patentes que lo demuestren...

As an object of study, the relationship between tuberculosis, Bacillus Calmette-Guérin and tuberculosis vaccines starts from the fact that the only vaccine currently available to prevent tuberculosis in humans is BCG, and its improvement or the development of new vaccines is a key strategy to control the disease. The present study intends to make a contribution to such important research from a patent metrics perspective. Its purpose is to conduct a metric analysis allowing to describe the productivity of patents for tuberculosis, Bacillus Calmette-Guérin and tuberculosis vaccines in a given time period. For the productivity study, an analysis was carried out of the behavior of temporal and geographic indicators in the domain, using techniques and tools suitable for patent documents. Research into tuberculosis as an infectious communicable disease has received great attention. Until recently, tuberculosis was considered to be a health problem in the developing world. However, after its re-emergence, research has been mainly conducted in developed countries. But such efforts have not been in proportion to research aimed at developing a new generation of vaccines against the disease, and there are no new patents supporting them...

Extracellular forms of Mycobacterium bovis BCG in the mucosal lymphatic tissues following oral vaccination

Oral vaccination with BCG provides protective systemic immunity against pathogenic mycobacterial challenge. In this study, the anatomical distribution of Mycobacterium bovis BCG following oral vaccination was investigated. Replicating bacteria in the Peyer's patches and mesenteric lymph nodes were present as solitary rods or clusters of two to three bacteria, the majority of which were isolated ex vivo as extracellular forms. Only a minority were shown to be associated with typical antigen-presenting cells. Acid-fast staining of mast cell granules in lymphoid tissues revealed a potential pitfall for these analyses and may explain previous reports of acid-fast 'coccoid' forms of mycobacteria in tissues

Construction, identification and immunoreactivity of Mycobacterium tuberculosis DNA vaccine pVAX1/ESAT-6 plasmid / 南方医科大学学报

<p><b>OBJECTIVE</b>To construct a Mycobacterium tuberculosis DNA vaccine pVAX1/ESAT-6 plasmid and investigate its immunoreactivity.</p><p><b>METHODS</b>The ESAT-6 gene fragment amplified from Mycobacterium tuberculosis genome was inserted into pVAX1 vector to construct the recombinant plasmid pVAX1/ESAT-6, which was identified by restriction enzyme digestion and sequencing. The recombinant plasmid was transformed into Hela cells using Sofast® Transfection reagent, and the cellular expressions of ESAT-6 mRNA and protein were analyzed by RT-PCR and immunofluorescence assay, respectively. The recombinant plasmid pVAX1/ESAT-6 was also transfected into mouse by electronic pulse method, and the mouse serum IFN-γ level and anti-ESAT-6 IgG antibody level were detected by ELISA, mouse lymphocyte proliferation assessed with flow cytometry, and IFN-γ-secreting lymphocytes counted using ELISPOT.</p><p><b>RESULTS</b>Double restriction-enzyme digestion and sequencing showed that the inserted fragment in the recombinant plasmid pVAX1/ESAT-6 was identical to ESAT-6 gene with an inframe insertion. RT-PCR yielded the target band as expected on agarose gel, and immunofluorescence assay of the transfected cells showed specific green fluorescence signals. The mice transfected with the recombinant plasmid showed significantly elevated serum level of anti-ESAT-6 IgG antibody and increased serum IFN-γ level, spleen cell proliferation, and number of IFN-γ-secreting lymphocytes.</p><p><b>CONCLUSION</b>The Mycobacterium tuberculosis DNA vaccine pVAX1/ESAT-6 plasmid we constructed can induce high levels of cellular and humoral immunoreactivity in mice.</p>

BCG vaccine in Korea

The anti-tuberculosis Bacille de Calmette et Guerin (BCG) vaccine was developed between 1905 and 1921 at Pasteur Institutes of Lille in France, and was adopted by many countries. BCG strains comprise natural mutants of major virulence factors of Mycobacterium tuberculosis and that BCG sub-strains differ markedly in virulence levels. The tuberculosis became endemic in Korea after the Korean War (1950s). The BCG strain, which was donated by Pasteur Institutes, was brought to Korea in 1955, and the first domestic BCG vaccine was produced by the National Defense Research Institute (NDRI), current Korea Centers for Disease Control and Prevention (KCDC), in 1960. Since 1987, BCG manufacture work was handed over to the Korean Institute of Tuberculosis (KIT), the freeze-dried BCG vaccine was manufactured at a scale required to meet the whole amount of domestic consumption. However, since 2006, the manufacture of BCG vaccine suspended and the whole amount of BCG was imported at this point of time. Now KIT is planning to re-produce the BCG vaccine in Korea under the supervision of KCDC, this will be render great role to National Tuberculosis Control Program (NTP) and provide initiating step for developing new tuberculosis vaccines in Korea.

Antigen-presenting cells transfected with Hsp65 messenger RNA fail to treat experimental tuberculosis

In the last several years, the use of dendritic cells has been studied as a therapeutic strategy against tumors. Dendritic cells can be pulsed with peptides or full-length protein, or they can be transfected with DNA or RNA. However, comparative studies suggest that transfecting dendritic cells with messenger RNA (mRNA) is superior to other antigen-loading techniques in generating immunocompetent dendritic cells. In the present study, we evaluated a new therapeutic strategy to fight tuberculosis using dendritic cells and macrophages transfected with Hsp65 mRNA. First, we demonstrated that antigen-presenting cells transfected with Hsp65 mRNA exhibit a higher level of expression of co-stimulatory molecules, suggesting that Hsp65 mRNA has immunostimulatory properties. We also demonstrated that spleen cells obtained from animals immunized with mock and Hsp65 mRNA-transfected dendritic cells were able to generate a mixed Th1/Th2 response with production not only of IFN-γ but also of IL-5 and IL-10. In contrast, cells recovered from mice immunized with Hsp65 mRNA-transfected macrophages were able to produce only IL-5. When mice were infected with Mycobacterium tuberculosis and treated with antigen-presenting cells transfected with Hsp65 mRNA (therapeutic immunization), we did not detect any decrease in the lung bacterial load or any preservation of the lung parenchyma, indicating the inability of transfected cells to confer curative effects against tuberculosis. In spite of the lack of therapeutic efficacy, this study reports for the first time the use of antigen-presenting cells transfected with mRNA in experimental tuberculosis.

Producción in vitro de interferón gamma en ratones vacunados con ´Mycobacterium habana´ frente a antígenos de Mycobacterium tuberculosis / In vitro interferon gamma production in mice vaccinated with ´Mycobacterium habana´ against Mycobacterium tuberculosis antigens

Introducción: el desarrollo de nuevas vacunas antituberculosas requiere de la caracterización de la respuesta de inmunidad celular, inducida por el nuevo candidato vacunal frente a los antígenos principales de Mycobacterium tuberculosis. Objetivo: determinar el potencial inmunogénico de ´Mycobacterium habana´ TMC-5135, cuando se usa como vacuna subcutánea en ratones Balb/c. Métodos: en este estudio se inocularon subcutáneamente ratones Balb/c con la cepa viva ´Mycobacterium habana´ TMC-5135 y se determinó la producción in vitro de IFN gamma en cultivos celulares de pulmón, bazo y ganglios inguinales estimulados con antígenos solubles totales y el antígeno 85b. Como grupo control se vacunaron ratones con BCG subcepa Phipps. Resultados: particularmente en los ganglios linfáticos inguinales, ambos antígenos indujeron mayor producción de IFN gamma en los ratones vacunados con ´Mycobacterium habana´que con BCG. Conclusiones: los resultados justifican la realización de nuevas investigaciones usando ´Mycobacterium habana´ TMC-5135 como candidato vacunal para prevenir la tuberculosis.

Introduction: development of new antituberculosis vaccines requires the characterization of the cell-mediated immune responses induced by mycobacterial antigens. Objective: to determine the immunogenic potential of ´Mycobacterium habana´ TMC-5135 when using subcutaneous vaccine in Balb/c mice. Methods: in this study, Balb/c mice were inoculated subcutaneously with live ´Mycobacterium habana´ TMC-5135. The production of IFN gamma in cell suspensions obtained from the lungs, the spleen and the lymph nodes after stimulation with mycobacterial antigens Ag85b or culture filtrate antigens (CFA) was recorded. Results: the production of IFN gamma after stimulation with CFA and Ag85b was higher in mice vaccinated with ´M. habana´ than in animals immunized with BCG. Conclusions: these results encourage new research on ´M. habana´ as vaccinal candidate against tuberculosis.

Rational design of diagnostic and vaccination strategies for tuberculosis

The development of diagnostic tests which can readily differentiate between vaccinated and tuberculosis-infected individuals is crucial for the wider utilization of bacillus Calmette-Guérin (BCG) as vaccine in humans and animals. BCG_0092 is an antigen that elicits specific delayed type hypersensitivity reactions similar in size and morphological aspects to that elicited by purified protein derivative, in both animals and humans infected with the tubercle bacilli. We carried out bioinformatics analyses of the BCG_0092 and designed a diagnostic test by using the predicted MHC class I epitopes. In addition, we performed a knockout of this gene by homologous recombination in the BCG vaccine strain to allow differentiation of vaccinated from infected individuals. For that, the flanking sequences of the target gene (BCG_0092)were cloned into a suicide vector. Spontaneous double crossovers, which result in wild type revertants or knockouts were selected using SacB. BCG_0092 is present only in members of the Mycobacterium tuberculosis complex. Eight predicted MHC class I epitopes with potential for immunological diagnosis were defined, allowing the design of a specific diagnostic test. The strategy used to delete the (BCG_0092) gene from BCG was successful. The knockout genotype was confirmed by PCR and by Southern blot. The mutant BCG strain has the potential of inducing protection against tuberculosis without interfering with the diagnostic test based on the use of selected epitopes from BCG_0092.

Progress in research on molecular biology and application in dominant antigens ESAT6 and CFP10 of TB vaccine / 生物医学工程学杂志

As the dominant antigens, early secreted antigenic target 6 (ESAT6, E6) and culture filtrate protein 10 (CFP10, C10) had once been the focus of tuberculosis (TB) vaccine due to their capability of inducing strong cell immune response in the host. They are also endowed with promising future of prevention against and diagnosis of TB. In this review, we systematically introduce recent research progress of E6 and C10, especially in structure-function, biological characteristics, protein expression and secretion, host immunity and vaccine development, and the prospects of their application are also discussed.

Factores de virulencia de Mycobacterium tuberculosis / Virulence factors of Mycobacterium tuberculosis

Mycobacterium tuberculosis, the etiological agent of human tuberculosis, causes annually three million deaths and latently infects about two billion people. Immunodeficiency caused by malnutrition, senescence or co-infection with HIVenhances the risk of developing active tuberculosis, either from a primary infection or by reactivation of a latent infection. The increasing appearance of multidrug-resistant strains to existing drugs is worrisome, since it leaves patients practically without treatment options. The understanding of the mechanisms of transmission, pathogenesis and virulence of M. tuberculosis is important. The analysis of its genome shows the presence of alternative sigma factors, transcriptional repressors and activators, two component signaling systems, metabolic enzymes and cellular secretory systems, that are associated with virulence in a series of pathogenic micro-organisms. Environmental stimuli such as pH, temperature, osmolality, oxygen availability are processed, activating or repressing virulence genes. The molecular mechanisms of action of these genes have been elucidated in in vitro and in vivo models.