PapA1 and PapA2 are acyltransferases essential for the biosynthesis of the Mycobacterium tuberculosis virulence factor sulfolipid-1

Mycobacterium tuberculosis produces numerous exotic lipids that have been implicated as virulence determinants. One such glycolipid, Sulfolipid-1 (SL-1), consists of a trehalose-2-sulfate (T2S) core acylated with four lipid moieties. A diacylated intermediate in SL-1 biosynthesis, SL(1278), has been shown to activate the adaptive immune response in human patients. Although several proteins involved in SL-1 biosynthesis have been identified, the enzymes that acylate the T2S core to form SL(1278) and SL-1, and the biosynthetic order of these acylation reactions, are unknown. Here we demonstrate that PapA2 and PapA1 are responsible for the sequential acylation of T2S to form SL(1278) and are essential for SL-1 biosynthesis. In vitro, recombinant PapA2 converts T2S to 2'-palmitoyl T2S, and PapA1 further elaborates this newly identified SL-1 intermediate to an analog of SL(1278). Disruption of papA2 and papA1 in M. tuberculosis confirmed their essential role in SL-1 biosynthesis and their order of action. Finally, the Delta papA2 and Delta papA1 mutants were screened for virulence defects in a mouse model of infection. The loss of SL-1 (and SL(1278)) did not appear to affect bacterial replication or trafficking, suggesting that the functions of SL-1 are specific to human infection.     

5种结核分枝杆菌特异蛋白质的抗原性分析

目的评价14、16、38kD、mtb81和 ESAT-6等5种结核分枝杆菌特异蛋白质的抗原性。方法利用14、16、38kD、mtb81和 ESAT-6等5种重组蛋白建立ELISA方法,检测120份结核病人、30份非结核呼吸道感染病人和30份健康人血清中相应抗体。结果ELISA显示5种结核杆菌特异性蛋白质的特异性均高于95%;敏感性和准确性则不尽相同,其中38kD的检测敏感性最高,为80.8%;14、16kD、mtb81和 ESAT-6的检测敏感性分别为52.5%、68.3%、35.8%和44.2%。结论5种结核杆菌特异性蛋白质均具有不同程度的抗原性。进一步提高抗原或抗体的检测灵敏度将有利于结核病的诊断。     

Graft-versus-myeloma effect: proof of principle

The presence of a graft-versus-tumor effect has been well established in leukemia but not in multiple myeloma. A 40-year-old patient with myeloma refractory to standard chemotherapy and autologous transplantation received a matched unrelated T-cell-depleted transplant after conditioning with fractionated total-body irradiation, thiotepa, and cyclophosphamide. This procedure resulted in a transient and incomplete response with evidence of rapidly progressive disease within 2.5 months posttransplantation. The patient then received a small number of donor peripheral blood (PB) mononuclear cells (CD3 cells 1.2 x 10(6)/kg) without any further cytotoxic therapy. A complete remission was attained, lasting now for more than 14 months. The procedure was associated with severe acute and subsequently limited chronic graft- versus-host disease (GVHD). This report provides the first direct evidence of a graft-versus-myeloma effect after allogenic transplantation.     

Structural biology of Mycobacterium tuberculosis proteins: the Indian efforts

Among the many different objectives of large scale structural genomics projects are expanding the protein fold space, enhancing understanding of a model or disease-related organism, and providing foundations for structure-based drug discovery. Systematic analysis of protein structures of Mycobacterium tuberculosis has been ongoing towards meeting some of these objectives. Indian participation in these efforts has been enthusiastic and substantial. The proteins of M. tuberculosis chosen for structural analysis by the Indian groups span almost all the functional categories. The structures determined by the Indian groups have led to significant improvement in the biochemical knowledge on these proteins and consequently have started providing useful insights into the biology of M. tuberculosis. Moreover, these structures form starting points for inhibitor design studies, early results of which are encouraging. The progress made by Indian structural biologists in determining structures of M. tuberculosis proteins is highlighted in this review.     

Identification of outer membrane proteins of Mycobacterium tuberculosis

The cell wall of mycobacteria includes an unusual outer membrane of extremely low permeability. While Escherichia coli uses more than 60 proteins to functionalize its outer membrane, only two mycobacterial outer membrane proteins (OMPs) are known. The porin MspA of Mycobacterium smegmatis provided the proof of principle that integral mycobacterial OMPs share the β-barrel structure, the absence of hydrophobic α-helices and the presence of a signal peptide with OMPs of gram-negative bacteria. These properties were exploited in a multi-step bioinformatic approach to predict OMPs of M. tuberculosis. A secondary structure analysis was performed for 587 proteins of M. tuberculosis predicted to be exported. Scores were calculated for the β-strand content and the amphiphilicity of the β-strands. Reference OMPs of gram-negative bacteria defined threshold values for these parameters that were met by 144 proteins of unknown function of M. tuberculosis. Two of them were verified as OMPs by a novel two-step experimental approach. Rv1698 and Rv1973 were detected only in the total membrane fraction of M. bovis BCG in Western blot experiments, while proteinase K digestion of whole cells showed the surface accessibility of these proteins. These findings established that Rv1698 and Rv1973 are indeed localized in the outer membrane and tripled the number of known OMPs of M. tuberculosis. Significantly, these results provide evidence for the usefulness of the bioinformatic approach to predict mycobacterial OMPs and indicate that M. tuberculosis likely has many OMPs with β-barrel structure. Our findings pave the way to identify the set of proteins which functionalize the outer membrane of M. tuberculosis.     

The PE and PPE proteins of Mycobacterium tuberculosis

India already has earned the dubious distinction of being one of the countries with the highest incidence of tuberculosis (TB). The conventional control measures have had little impact on the relentless march of the TB epidemic. Potential solutions to this problem include the development of new drugs and an effective TB vaccine. In this perspective, identification of the mycobacterial components that have important role(s) in the establishment of the infection assumes crucial importance. Mycobacterium tuberculosis is an intracellular pathogen and it resides inside the macrophage, which is considered to be the most important component of the immune system. M. tuberculosis possesses two highly polymorphic sets of genes called the PE and PPE families. These unique families of proteins account for about 10% of the mycobacterial genome and have drawn considerable interest from different schools of M. tuberculosis researchers across the globe. In this review, we discuss the importance of these proteins in the regulation of dendritic cell and macrophage immune-effector functions, as well as the relevance of these proteins in the clinical manifestation of TB. This information may be helpful to better understand the immunological importance of PE/PPE proteins and their roles in mycobacterial virulence.     

Protective immunity against tuberculosis induced by vaccination with major extracellular proteins of Mycobacterium tuberculosis.

Tuberculosis, caused by the intracellular pathogen Mycobacterium tuberculosis, is the world's leading cause of death in humans from a single infectious agent. A safe and effective vaccine against this scourge is urgently needed. This study demonstrates that immunization with the 30-kDa major secretory protein, alone or in combination with other abundant extracellular proteins of M. tuberculosis, induces strong cell-mediated immune responses and substantial protective immunity against aerosol challenge with virulent M. tuberculosis bacilli in the highly susceptible guinea pig model of pulmonary tuberculosis. Protection is manifested by decreased clinical illness including decreased weight loss, reduced mortality, and decreased growth of M. tuberculosis in the lungs and spleens of immunized animals compared with sham-immunized controls. This study demonstrates that purified major extracellular proteins of M. tuberculosis are candidate components of a subunit vaccine against tuberculosis and provides compelling support for the concept that extracellular proteins of intracellular pathogens are key immunoprotective molecules.     

结核分枝杆菌PE/PPE蛋白研究进展

PE/PPE蛋白是分枝杆菌所独有的蛋白家族,因其氨基端分别含有Pro-Glu(PE)和Pro-Pro-Glu(PPE)的基序而得名,其编码基因约占结核分枝杆菌整个基因组的10%。PE/PPE蛋白从被发现开始就引起了人们的广泛兴趣,本文就近年来的研究进展作一综述。     

OsmC proteins of Mycobacterium tuberculosis and Mycobacterium smegmatis protect against organic hydroperoxide stress

Bacterial antioxidants play a critical role in the detoxification of endogenously and host derived oxidative radicals during host-pathogen interactions. Recently, the osmotically induced bacterial protein C (OsmC) is included in the antioxidant category of enzymes as it shows structural and functional relationships with organic hydroperoxide reductase (Ohr) enzyme. A copy of the gene encoding OsmC is conserved across mycobacterial species, including Mycobacterium tuberculosis (Rv2923c) and Mycobacterium smegmatis (MSMEG2421), but its role in protecting these species against oxidative stress is unknown. To determine the role of OsmC in mycobacterial oxidative stress, we overexpressed and purified OsmCs of M. tuberculosis and M. smegmatis and assessed their ability to reduce peroxide substrates like hydrogen peroxide (H(2)O(2)), cumene hydroperoxide (CHP) and t-butyl hydroperoxide (t-BHP) in Ferrous Ion Oxidation in Xylenol (FOX) assay. This revealed that OsmCs from both species were capable of reducing both inorganic (H(2)O(2)) and organic (CHP and t-BHP) peroxides. Further, an M. smegmatis mutant (MS?osmC) deficient in OsmC exhibited reduced reduction of CHP and t-BHP than the parental wild type strain, indicating that OsmC protein contributes significantly for the total peroxide reductase activity of mycobacteria. The MS?osmC strain was also sensitive to organic hydroperoxides, which could be reversed by complementing with a plasmid borne osmC. Plasmid borne osmC also increased the resistance of M. smegmatis wild type strain to isoniazid (INH) but at a relatively lower level than ahpC, an organic hydroperoxide reductase. These results suggest that OsmC plays an important role in peroxide metabolism and protecting mycobacteria against oxidative stress.     

结核分枝杆菌培养滤液蛋白免疫学特性及应用研究进展

结核分枝杆菌培养滤液蛋白(CFP)是结核分枝杆菌培养上清中的分泌蛋白,在结核感染动物模型中能促进保护性免疫的产生,能刺激免疫细胞高效分泌IFN-γ等细胞因子。本文就其组成、生物学和免疫学特性及其在临床诊断和疫苗研制的应用前景做一综述。     

Streptomyces as host for recombinant production of Mycobacterium tuberculosis proteins

The 45/47 kDa APA protein (Rv1860) of Mycobacterium tuberculosis was produced by Streptomyces lividans. The recombinant protein could be recovered from the culture medium of an S. lividans clone containing the apa gene under control of the promoter and signal sequence of the Streptomyces coelicolor agarase gene. The recombinant protein production was further scaled-up using fermentation conditions. The APA protein was subsequently purified from the culture supernatant by means of immunochromatography. About 80 mg of recombinant protein were obtained per liter of culture media. In vivo tests with the APA protein purified from S. lividans TK24/pRGAPA1 revealed that the recombinant protein was antigenic and could induce high titers of specific antibodies in the mouse biological model. Results obtained concerning heterologous production of APA, its immunogenic and antigenic capacity, demonstrated the potential of S. lividans as a valuable host for the production of recombinant proteins from M. tuberculosis.     

重组结核杆菌融合蛋白(EC)用于诊断结核分枝杆菌感染的有效性和安全性系统评价

目的:系统评价重组结核杆菌融合蛋白(EC)相较于结核菌素纯蛋白衍生物(TB-PPD)用于诊断结核分枝杆菌(Mycobacterium tuberculosis,MTB)感染的有效性和安全性。方法:检索临床指南数据库、生物医学文献数据库、卫生行政部门和行业协会官方网站及不良反应监测官方网站,检索时间均自建库截止到2022年2月。英文检索词：Recombinant Mycobacterium tuberculosis fusion protein、CFP10/ESAT6;中文检索词：重组结核分枝杆菌融合蛋白、重组结核杆菌融合蛋白、宜卡、CFP10/ESAT6。收集重组结核杆菌融合蛋白(EC)和结核菌素纯蛋白衍生物(TB-PPD)诊断MTB感染有效性和安全性的指南、共识、团体标准、系统评价和原始研究等。由2名研究者独立筛选文献、提取资料并评价纳入研究的偏倚风险,根据异质性大小采用Meta分析或描述性分析。结果:纳入指南2部、专家共识3篇、团体标准2部,均指出重组结核杆菌融合蛋白(EC)和结核菌素纯蛋白衍生物(TB-PPD)可用于诊断MTB感染和结核病辅助诊断。纳入系统评价1篇,结果显示,重组...