Suppression of Eis and expression of Wag31 and GroES in Mycobacterium tuberculosis cytosol under anaerobic culture conditions.

A major impediment in chemotherapy of Tuberculosis (TB) is the persistence of M. tuberculosis in a latent or dormant state, possibly perpetuated by paucity of oxygen within the lung granuloma. Proteome analysis of the anaerobically persisting microbe could therefore provide novel targets for drugs against latent TB infection (LTBI). An Indian clinical isolate of M. tuberculosis was cultured under aerobic and anaerobic conditions following Wayne’s hypoxia model and its cytosolic proteins were resolved by two-dimensional gel electrophoresis (2DE). Peptide mass fingerprinting of 32 differentially expressed spots using MALDI TOF-TOF MS-MS resulted in identification of 23 proteins. Under the anaerobic culture conditions, expression of 12 of these proteins was highly suppressed (>2 fold reduction in spot volumes), with 4 of them (GrpE, CanB, MoxR1 and Eis) appearing as completely suppressed since corresponding spots were not detectable in the anaerobic sample. On the other hand, 4 proteins were highly expressed, with two of them (Wag31 and GroES) being uniquely expressed under anaerobic conditions. Suppression of Eis could make the anaerobically persisting bacilli susceptible to the aminoglycoside antibiotics which are known to be acetylated and inactivated by Eis. Although all 4 over-expressed proteins can be considered as putative drug targets for LTBI, Wag31 appears particularly interesting in view of its role in the cell wall biogenesis.

Resposta imune humoral ao antígeno rGroES do mycobacterium tuberculosis em pacientes com tuberculose e seus contatos domiciliares / Humoral immune response to mycobacterium tuberculosis rGroES antigen in patients with tuberculosis and their household contacts

A tuberculose (TB) continua sendo um dos mais urgentes problemas de saúde pública do mundo, com 8 a 10 milhões de novos casos e 2 a 3 milhões de mortes a cada ano. Cerca de 50 milhõesde pessoas estão infectadas com o Mycobacterium tuberculosis. A fim de desenvolver testes para imunodiagnóstico da TB, vários antígenos têm sido testados na resposta imune humoral de pacientes com TB ativa. O teste imunoenzimático de ELISA realizado com amostras de plasma de 45 pacientes com tuberculose pulmonar e 172 contatos (96 prova tuberculínica negativa e 76, positiva) foi conduzido para avaliação da resposta imune humoral, com pesquisa de anticorpos das classesIgM e IgG contra o antígeno recombinante GroEs do Mycobacterium tuberculosis (MtGroEs). Pacientes com tuberculose pulmonar ativa apresentaram maiores níveis de IgG anti-rGroEs do que indivíduos saudáveis, o que permitiu a discriminação entre os dois grupos e sugeriu resposta imune humoral específica a este antígeno.

Tuberculosis (TB) remains one of the most important public health problems ofthe world, with 8-10 million new cases and 2-3 million deaths each year. About 50 million people are infected with Mycobacterium tuberculosis. In order to develop immunodiagnostic tests for TB, several antigens have been tested for the humoral immune response of patients with active TB. ELISA was performed with plasma samples from 45 patients with pulmonary TB and 172 contacts (96 negative and 76 positive for the tuberculin skin test). The humoral immune response was evaluated through assessment of IgM and IgG antibodies against recombinant Mycobacterium tuberculosis GroES (MtGroEs). Patients with active pulmonary tuberculosis had higher levels of IgG anti-rGroEs than healthy individuals, allowing discriminationbetween the two groups.

Increased expression and purification of soluble iron-regulatory protein 1 from Escherichia coli co-expressing chaperonins GroES and GroEL

Iron is an essential metal for all living organisms. However, iron homeostasis needs to be tightly controlled since iron can mediate the production of reactive oxygen species, which can damage cell components and compromise the integrity and/or cause DNA mutations, ultimately leading to cancer. In eukaryotes, iron-regulatory protein 1 (IRP1) plays a central role in the control of intracellular iron homeostasis. This occurs by interaction of IRP1 with iron-responsive element regions at 5' of ferritin mRNA and 3' of transferrin mRNA which, respectively, represses translation and increases mRNA stability. We have expressed IRP1 using the plasmid pT7-His-hIRP1, which codifies for human IRP1 attached to an NH2-terminal 6-His tag. IRP1 was expressed in Escherichia coli using the strategy of co-expressing chaperonins GroES and GroEL, in order to circumvent inclusion body formation and increase the yield of soluble protein. The protein co-expressed with these chaperonins was obtained mostly in the soluble form, which greatly increased the efficiency of protein purification. Metal affinity and FPLC ion exchange chromatography were used in order to obtain highly purified IRP1. Purified protein was biologically active, as assessed by electrophoretic mobility shift assay, and could be converted to the cytoplasmic aconitase form. These results corroborate previous studies, which suggest the use of folding catalysts as a powerful strategy to increase protein solubility when expressing heterologous proteins in E. coli.