Domingo Palmero

IL-17 and IFN-γ expression in lymphocytes from patients with active tuberculosis correlates with the severity of the disease

Th1 lymphocytes are crucial in the immune response against Mycobacterium tuberculosis. Nevertheless, IFN‐γ alone is not sufficient in the complete eradication of the bacteria, suggesting that other cytokines might be required for pathogen removal. Th17 cells have been associated with M. tuberculosis infection, but the role of IL‐17‐producing cells in human TB remains to be understood. Therefore, we investigated the induction and regulation of IFN‐γ and IL‐17 during the active disease. TB patients were classified as High and Low Responder individuals according to their T cell responses against the antigen, and cytokine expression upon M. tuberculosis stimulation was investigated in peripheral blood and pleural fluid. Afterwards, the potential correlation among the proportions of cytokine‐producing cells and clinical parameters was analyzed. In TB patients, M. tuberculosis induced IFN‐γ and IL‐17, but in comparison with BCG‐vaccinated healthy donors, IFN‐γ results were reduced significantly, and IL‐17 was markedly augmented. Moreover, the main source of IL‐17 was represented by CD4+IFN‐γ+IL‐17+ lymphocytes, a Th1/Th17 subset regulated by IFN‐γ. Interestingly, the ratio of antigen‐expanded CD4+IFN‐γ+IL‐17+ lymphocytes, in peripheral blood and pleural fluid from TB patients, was correlated directly with clinical parameters associated with disease severity. Indeed, the highest proportion of CD4+IFN‐γ+IL‐17+ cells was detected in Low Responder TB patients, individuals displaying severe pulmonary lesions, and longest length of disease evolution. Taken together, the present findings suggest that analysis of the expansion of CD4+IFN‐γ+IL‐17+ T lymphocytes in peripheral blood of TB patients might be used as an indicator of the clinical outcome in active TB.

Mycobacterium avium complex infection in HIV/AIDS patients.

Disseminated Mycobacterium avium complex (MAC) infection is a severe complication of advanced HIV/AIDS disease. Disseminated infection due to MAC appeared later in the natural history of HIV disease and was an independent predictor of mortality in patients before the extended use of highly active antiretroviral therapy (HAART). The use of combination schemes, including three or four antimicrobial agents followed by secondary prophylaxis and HAARTs, improved the survival and reduced mortality rates. However, subjects who ignore their serological status for HIV, or who are not receiving or do not tolerate HAART, are at high risk of developing disseminated MAC disease. In addition, patients who show a good immunological and virological response to HAART can develop episodes of immune reconstitution inflammatory syndrome associated with MAC, including supurative lymphadenitis and subcutaneous or soft-tissue abscesses. In this article, we describe the epidemiological, clinical, immunological, therapeutic and preventive aspects of MAC infection in HIV-seropositive patients in the pre- and post-HAART era.

Respiratory infections in immunocompromised patients.

Purpose of review Immunosuppressive states and therapies are becoming common in clinical practice. Recent advances and trends in bacterial, fungal, viral and parasitic pulmonary infections in immunosuppressed patients are described. Recent findings Pulmonary infections can jeopardize the prognosis of immunosuppressed patients. The number of patients infected with multidrug-resistant bacteria or opportunistic pathogens like rapid-growing environmental mycobacteria, Strongyloides stercoralis or Rhodococcus equi is increasing with the increased numbers of immunosuppressed patients due to HIV/AIDS and the potent immunosuppressive therapies used in solid-organ and haematopoietic transplantations, cancer and systemic illnesses. The slow development of more effective antibiotics underlines the necessity of preventive measures, development of rapid detection tests for pathogens and appropriate treatment regimens to avoid development of further resistance. Summary Adequate prophylaxis, clinical suspicion, microbiological and molecular investigations, drug susceptibility-based antibiotic treatment and new drug development are strategies required to face up to the challenge of pulmonary infections in immunodepressed patients.

HIV Infection and Geographically Bound Transmission of Drug-Resistant Tuberculosis, Argentina

Disease trends are driven by HIV co-infection and transmission of a few strains within narrow geographic niches.

IFNG-mediated immune responses enhance autophagy against Mycobacterium tuberculosis antigens in patients with active tuberculosis

Protective immunity against Mycobacterium tuberculosis (Mtb) requires IFNG. Besides, IFNG-mediated induction of autophagy suppresses survival of virulent Mtb in macrophage cell lines. We investigated the contribution of autophagy to the defense against Mtb antigen (Mtb-Ag) in cells from tuberculosis patients and healthy donors (HD). Patients were classified as high responders (HR) if their T cells produced significant IFNG against Mtb-Ag; and low responders (LR) when patients showed weak or no T cell responses to Mtb-Ag. The highest autophagy levels were detected in HD cells whereas the lowest quantities were observed in LR patients. Interestingly, upon Mtb-Ag stimulation, we detected a positive correlation between IFNG and MAP1LC3B-II/LC3-II levels. Actually, blockage of Mtb-Ag-induced IFNG markedly reduced autophagy in HR patients whereas addition of limited amounts of IFNG significantly increased autophagy in LR patients. Therefore, autophagy collaborates with human immune responses against Mtb in close association with specific IFNG secreted against the pathogen.

Impact of HIV co-infection on the evolution and transmission of multidrug-resistant tuberculosis

The tuberculosis (TB) epidemic is fueled by a parallel Human Immunodeficiency Virus (HIV) epidemic, but it remains unclear to what extent the HIV epidemic has been a driver for drug resistance in Mycobacterium tuberculosis (Mtb). Here we assess the impact of HIV co-infection on the emergence of resistance and transmission of Mtb in the largest outbreak of multidrug-resistant TB in South America to date. By combining Bayesian evolutionary analyses and the reconstruction of transmission networks utilizing a new model optimized for TB, we find that HIV co-infection does not significantly affect the transmissibility or the mutation rate of Mtb within patients and was not associated with increased emergence of resistance within patients. Our results indicate that the HIV epidemic serves as an amplifier of TB outbreaks by providing a reservoir of susceptible hosts, but that HIV co-infection is not a direct driver for the emergence and transmission of resistant strains. DOI: http://dx.doi.org/10.7554/eLife.16644.001

Human pleural B-cells regulate IFN-γ production by local T-cells and NK cells in a Mycobacterium tuberculosis-induced delayed hypersensitivity reaction

DTH (delayed type hypersensitivity) reactions are secondary cellular immune responses that appear 24-72 h after antigen exposure. Tuberculous pleurisy is a common manifestation of extrapulmonary TB (tuberculosis) and is considered a human model of Th1-mediated DTH. In order to identify functional cross-talk among cellular populations sited in this inflammatory microenvironment, we analysed phenotypic and functional features of human B-cells isolated from the PF (pleural fluid) of TB patients. Freshly isolated PF-B-cells displayed a lower expression of CD20, CD1d and HLA-DR, and a higher expression of CD95, CD38, CD25, CXCR3 (CXC chemokine receptor 3) and CXCR4 (CXC chemokine receptor 4) than their PB (peripheral blood) counterparts, suggesting a non-classical in situ activation. Although memory PF-T-cell frequencies were increased, the frequencies of memory PF-B-cells were not. We demonstrated that, upon stimulation with γ-irradiated M. tuberculosis, mycobacterially secreted proteins or a lectin mitogen, PF-B-cells had a strong activation and produced IL-10 by a mechanism that was dependent on bystander activation of CD19(-) PF cells. Besides, within PF cells, B-cells diminished in vitro M. tuberculosis-induced IFN (interferon)-γ production by T-cells and NK (natural killer) cells in an IL-10-dependent manner. Finally, we found that the lower the frequency of B-cells, the higher the ratio of IFN-γ/IL-10 within PF. Thus our results suggest that B-cells can regulate a human DTH reaction induced by M. tuberculosis.

Evaluación de las medidas de control adoptadas frente a la epidemia de tuberculosis multirresistente asociada al sida en un hospital hispanoamericano

Antecedentes Desde 1992 se detectaron pacientes con tuberculosis multirresistente (TBMR) asociada al sida internados en el Hospital Muniz (Buenos Aires). El objetivo del trabajo es evaluar la eficacia de las medidas adoptadas frente a la expansion nosocomial de la TBMR/sida, que afecto a 803 enfermos entre 1992-2002. Metodos Se aplico un plan de accion que incluyo: cribado baciloscopico de admision, habitaciones de aislamiento para TB/sida, sala de aislamiento para TBMR/sida, diagnostico de multirresistencia mediante metodo radiometrico; banco de farmacos de segunda linea y proteccion respiratoria del personal de salud. Resultados Entre 1995 y 2002, se observo una tendencia estadisticamente significativa en la disminucion de casos de TBMR/sida y de los internamientos por TB/sida (33,9% frente a 80,5%, respectivamente), asi como una disminucion significativa en la mortalidad de los primeros. El cribado baciloscopico permitio diagnosticar el 63,4% de los casos de TB/sida internados. Progresivamente fueron empleados los recursos de aislamiento respiratorio y tratamiento eficaz de los casos de TBMR diagnosticados por metodo radiometrico. Respecto de la poblacion susceptible, el ingreso de pacientes con sida al hospital no vario significativamente a lo largo del periodo estudiado, tampoco lo hizo el recuento de linfocitos T CD4+ de los pacientes que requirieron internamiento. Conclusion Se observo una disminucion significativa de la curva epidemica nosocomial de TBMR en pacientes con sida, pese a la persistencia de pacientes susceptibles con bajo nivel de linfocitos T CD4+. Se considera que esta evolucion decreciente de la TBMR/sida puede ser atribuida al impacto de las medidas de control implementadas.

Phosphorylation of Mitogen-Activated Protein Kinases Contributes to Interferon γ Production in Response to Mycobacterium tuberculosis

Immune control of Mycobacterium tuberculosis depends on interferon γ (IFN-γ)-producing CD4(+) lymphocytes. Previous studies have shown that T cells from patients with tuberculosis produce less IFN-γ, compared with healthy donors, in response to mycobacterial antigens, although IFN-γ responses to mitogens are preserved. In this work, we found that M. tuberculosis-induced IFN-γ production by human T cells correlated with phosphorylation of the mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK), and p38. Moreover, the majority of IFN-γ-producing T cells expressed signaling lymphocyte activation molecule (SLAM), and SLAM activation further increased ERK phosphorylation. Interestingly, patients with tuberculosis had delayed activation of ERK and p38, and this was most marked in patients with the poorest IFN-γ responses (ie, low responders). Besides, SLAM signaling failed to phosphorylate ERK in low responders. Our findings suggest that activation of p38 and ERK, in part through SLAM, mediates T-cell IFN-γ production in response to M. tuberculosis, a pathway that is defective in patients with tuberculosis.

The IL-17A rs2275913 single nucleotide polymorphism is associated with protection to tuberculosis but related to higher disease severity in Argentina.

Mycobacterium tuberculosis (Mtb) causes nearly 10 millions of new tuberculosis disease cases annually. However, most individuals exposed to Mtb do not develop tuberculosis, suggesting the influence of a human genetic component. Here, we investigated the association of the rs2275913 SNP (G → A) from IL-17A and tuberculosis in Argentina by a case-control study. Furthermore, we evaluated in vitro the functional relevance of this SNP during the immune response of the host against Mtb and analyzed its impact on clinical parameters of the disease. We found an association between the AA genotype and tuberculosis resistance. Additionally, within the healthy donors population, AA cells stimulated with a Mtb lysate (Mtb-Ag) produced the highest amounts of IL-17A and IFN-γ, which further support the genetic evidence found. In contrast, within the tuberculosis patients population, AA Mtb-Ag stimulated cells showed the lowest immunological parameters and we evidenced an association between the AA genotype and clinical parameters of disease severity, such as severe radiological lesions and higher bacilli burden in sputum. Overall, our findings demonstrated that the AA genotype from the IL-17A rs2275913 SNP is positively associated with protection to active tuberculosis but related to higher disease severity in the Argentinean population.