Tuberculosis and HIV infection: a global perspective

Protective CD4 T cells targeting cryptic epitopes of Mycobacterium tuberculosis resist infection-driven terminal differentiation

CD4 T cells are crucial to the control of Mycobacterium tuberculosis infection and are a key component of current vaccine strategies. Conversely, immune-mediated pathology drives disease, and recent evidence suggests that adaptive and innate responses are evolutionarily beneficial to M. tuberculosis. We compare the functionality of CD4 T cell responses mounted against dominant and cryptic epitopes of the M. tuberculosis 6-kDa early secreted Ag (ESAT-6) before and postinfection. Protective T cells against cryptic epitopes not targeted during natural infection were induced by vaccinating mice with a truncated ESAT-6 protein, lacking the dominant epitope. The ability to generate T cells that recognize multiple cryptic epitopes was MHC-haplotype dependent, including increased potential via heterologous MHC class II dimers. Before infection, cryptic epitope-specific T cells displayed enhanced proliferative capacity and delayed cytokine kinetics. After aerosol M. tuberculosis challenge, vaccine-elicited CD4 T cells expanded and recruited to the lung. In chronic infection, dominant epitope-specific T cells developed a terminal differentiated KLRG1(+)/PD-1(lo) surface phenotype that was significantly reduced in the cryptic epitope-specific T cell populations. Dominant epitope-specific T cells in vaccinated animals developed into IFN-γ- and IFN-γ,TNF-α-coproducing effector cells, characteristic of the endogenous response. In contrast, cryptic epitope-specific CD4 T cells maintained significantly greater IFN-γ(+)TNF-α(+)IL-2(+) and TNF-α(+)IL-2(+) memory-associated polyfunctionality and enhanced proliferative capacity. Vaccine-associated IL-17A production by cryptic CD4 T cells was also enhanced, but without increased neutrophilia/pathology. Direct comparison of dominant/cryptic epitope-specific CD4 T cells within covaccinated mice confirmed the superior ability of protective cryptic epitope-specific T cells to resist M. tuberculosis infection-driven T cell differentiation.

Multidrug resistant tuberculosis diagnosed by synovial fluid analysis

Tuberculosis remains a major public health problem worldwide. HIV co-infection is contributing to an increased incidence of the disease, particularly that caused by multidrug resistant strains of Mycobacterium tuberculosis (MT). We describe an HIV-infected patient with pleural and lymph node tuberculosis diagnosed by pleural effusion characteristics and biopsy specimens, without MT identification, that further presented with knee-joint involvement. Arthrocentesis allowed MT isolation and drug susceptibility testing, resulting in a diagnosis of multidrug-resistant tuberculosis and an appropriate treatment regimen. MT identification and drug susceptibility tests are very important, especially for HIV co-infected patients.

Pharmacophore mapping and electronic feature analysis for a series of nitroaromatic compounds with antitubercular activity

A five point pharmacophore was generated using PHASE for a series of nitroaromatic compounds and their congeners as antitubercular agents. The generated pharmacophore yielded significant 3D-QSAR model with r(2) of 0.890 for a training set of 92 molecules. The model also showed excellent predictive power with correlation coefficient Q(2) of 0.857 for a test set of 31 compounds. The pharmacophore indicated that presence of a nitro group, a piperazine moiety, one aromatic ring feature and two acceptor features are necessary for potent antitubercular activity. The pharmacophore was supported by electronic property analysis using density functional theory (DFT) at B3LYP/3-21*G level. Molecular electrostatic profile of the compounds was consistent with the generated pharmacophore model, particularly appearance of localized negative potential regions near both the oxygen atoms of nitro group extending laterally to the isoxazole ring system/amide bond in the most active compounds. Calculated data further revealed that all active compounds have smaller LUMO energies located over the nitro group, furan ring, and isoxazole ring/amide bond attached to it. Higher negative values of LUMO energies concentrated over the nitro group are indicative of the electron acceptor capacity of the compounds, suggesting that these compounds are prodrugs and must be activated by TB-nitroreductase. The results obtained from this study should aid in efficient design and development of nitroaromatic compounds as antitubercular agents.

Synthesis, optimization and structure-activity relationships of 3,5-disubstituted isoxazolines as new anti-tuberculosis agents

In the course of the development of a potent series of nitrofuranylamide anti-tuberculosis agents, we investigated if the exceptional activity resulted in part from the isoxazoline core and if it possessed any intrinsic anti-tuberculosis activity. This led to the discovery of an isoxazoline ester with appreciable anti-tuberculosis activity. In this study we explored the anti-tuberculosis structure-activity relationship of the isoxazoline ester compound through systematic modification of the 3,5-di-substituted isoxazoline core. Two approaches were used: (i) modification of the potentially metabolically labile ester functionality at the 3 position with acids, amines, amides, reverse amides, alcohols, hydrazides, and 1,3,4-oxadiazoles; (ii) substitution of the distal benzyl piperazine ring in the 5 position of the isoxazoline ring with piperazyl-ureas, piperazyl-carbamates, biaryl systems, piperidines and morpholine. Attempts to replace the ester group at C-3 position of isoxazoline with a variety of bioisosteric head groups led to significant loss of the tuberculosis inhibition indicating that an ester is required for anti-tuberculosis activity. Optimization of the isoxazoline C-5 position produced compounds with improved anti-tuberculosis activity, most notably the piperazyl-urea and piperazyl-carbamate analogs.

Vaccine-elicited 10-kilodalton culture filtrate protein-specific CD8+ T cells are sufficient to mediate protection against Mycobacterium tuberculosis infection

The 10-kDa culture filtrate protein (CFP-10) and 6-kDa early secretory antigen of T cells (ESAT-6) are secreted in abundance by Mycobacterium tuberculosis and are frequently recognized by T cells from infected people. The genes encoding these proteins have been deleted from the genome of the vaccine strain Mycobacterium bovis bacillus Calmette-Guérin (BCG), and it is hypothesized that these proteins are important targets of protective immunity. Indeed, vaccination with ESAT-6 elicits protective CD4+ T cells in C57BL/6 mice. We have previously shown that M. tuberculosis infection of C3H mice elicits CFP-10-specific CD8+ and CD4+ T cells. Here we demonstrate that immunization with a CFP-10 DNA vaccine stimulates a specific T-cell response only to the H-2K(k)-restricted epitope CFP-10(32-39). These CFP-10(32-39)-specific CD8+ cells undergo a rapid expansion and accumulate in the lung following challenge of immunized mice with aerosolized M. tuberculosis. Protective immunity is induced by CFP-10 DNA vaccination as measured by a CFU reduction in the lung and spleen 4 and 8 weeks after challenge with M. tuberculosis. These data demonstrate that CFP-10 is a protective antigen and that CFP-10(32-39)-specific CD8+ T cells elicited by vaccination are sufficient to mediate protection against tuberculosis.

Connecting with the larger purpose of our work

Organizations and people that are able to connect their daily work with a larger overall purpose will be rewarded with higher levels of fulfillment, accomplishment, employee engagement, and job satisfaction. Those who work in the field of the life sciences have a direct opportunity to achieve positive impact on the human condition. For BD (Becton, Dickinson and Co.), this opportunity has manifested itself through medical technology advances that have contributed to human health for over a century. These competencies are currently being applied to help address some of the most important health challenges facing the developing world, such as pandemic disease, child health, and the need to establish sufficient and sustainable access to health and laboratory services. This work is being pursued through commercial activity, technical training and support, public-private sector collaboration, philanthropy, and volunteerism.

Inhibition of Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium avium by Novel Dideoxy Nucleosides

The prevalence of tuberculosis (TB) and mutidrug-resistant tuberculosis (MDR-TB) has been increasing, leading to serious infections, high mortality, and a global health threat. Here, we report the identification of a novel class of dideoxy nucleosides as potent and selective inhibitors of Mycobacterium bovis, Mycobacterium tuberculosis, and drug-resistant Mycobacterium tuberculosis. A series of 5-acetylenic derivatives of 2',3'-dideoxyuridine (3-8) and 3'-fluoro-2',3'-dideoxyuridine (22-27) were synthesized and tested for their antimycobacterial activity against M. bovis, M. tuberculosis, and M. avium. 2',3'-Dideoxyuridine possessing 5-decynyl, 5-dodecynyl, 5-tridecynyl, and 5-tetradecynyl substituents (4-7) exhibited the highest antimycobacterial activity against all three mycobacteria. In contrast, in the 3'-fluoro-2',3'-dideoxyuridine series, a 5-tetradecynyl analogue (26) displayed the most potent activity against these mycobacteria. Among other derivatives, 5-bromo-2',3'-dideoxycytidine (11), 5-methyl-2',3'-dideoxycytidine (12), and 5-chloro-4-thio-2',3'-dideoxyuridine (19) exhibited modest inhibition of M. bovis and M. tuberculosis. In the series of dideoxy derivatives of adenosine, guanosine, and purines, 2-amino-6-mercaptoethyl-9-(2,3-dideoxy-beta-d-glyceropentofuranosyl)purine (32) and 2-amino-4-fluoro-7-(2,3-dideoxy-beta-d-glyceropentofuranosyl)pyrrolo[2,3-d]pyrimidine (35) were the most efficacious against M. bovis and M. tuberculosis, and M. avium, respectively.

Access to diagnostics in support of HIV/AIDS and tuberculosis treatment in developing countries

Access to necessary diagnostic tests in support of HIV/AIDS and tuberculosis treatment, such as CD4 cell counts, viral load, tuberculosis culture, and susceptibility testing, has significantly lagged the provision of drug therapy in developing countries. This is an outcome of the fundamental limitations in overall access to basic health services in the developing world, particularly in sub-Saharan Africa. Among health services, laboratory capacity and access are particularly deficient, and often non-existent in rural settings. As such, treatment is commonly administered in the absence of diagnostic testing, potentially accelerating the incidence of drug-related toxicity and the onset of drug resistance if therapy results in incomplete viral suppression. Factors constraining the expansion of necessary diagnostic testing include a severe shortage of qualified laboratory personnel, limited access to training for specific diagnostic tests, and a lack of national standards and systems for laboratory accreditation, proficiency testing, quality control and logistics. Additional factors include insufficient funding for improvements in laboratory services, limited availability of technical support, and the cost of diagnostic instrumentation and consumables. As a result, laboratory tests that are routine and expected in the industrialized world are often not performed in developing countries, despite the massive scale-up in treatment access for HIV/AIDS. This results in unintended consequences such as higher levels of mortality among patients who have not been properly diagnosed, additional costs for providing ART to patients who may not yet require drug therapy, and earlier onset of resistance to first-line therapies among patients predisposed to drug resistance.

Growth Inhibition of Mycobacterium bovis, Mycobacterium tuberculosis and Mycobacterium avium In Vitro: Effect of 1-β-d-2‘-Arabinofuranosyl and 1-(2‘-Deoxy-2‘-fluoro-β-d-2‘-ribofuranosyl) Pyrimidine Nucleoside Analogs

The resurgence of tuberculosis and the emergence of multiple-drug-resistant strains of Mycobacteria necessitate the search for new classes of antimycobacterial agents. We synthesized a series of 1-beta-D-2'-arabinofuranosyl and 1-(2'-deoxy-2'-fluoro-beta-D-ribofuranosyl) pyrimidine nucleosides possessing diverse sets of alkynyl, alkenyl, alkyl, and halo substituents at the C-5 position of the uracil and investigated their effect on activity against M. tuberculosis, M. bovis, and M. avium. Among these molecules, 5-alkynyl-substituted derivatives emerged as potent inhibitors of M. bovis, M. tuberculosis, and M. avium. Nucleosides 1-beta-D-2'-arabinofuranosyl-5-dodecynyluracil (5), 1-(2'-deoxy-2'-fluoro-beta-D-ribofuranosyl)-5-dodecynyluracil (24), and 1-(2'-deoxy-2'-fluoro-beta-D-ribofuranosyl)-5-tetradecynyluracil (25) showed the highest antimycobacterial potency against M. bovis and M. tuberculosis. The MIC90 exhibited by compounds 5, 24, and 25 was similar or close to that of the reference drug rifampicin. The most active compounds 5, 24, and 25 were also found to retain sensitivity against a rifampicin-resistant strain of M. tuberculosis H37Rv at similar concentrations. Some of these analogs also revealed in vitro antimicrobial effect against several other gram-positive pathogens.

Host innate immune response to Mycobacterium tuberculosis

This review focuses on recent progress in our understanding of Mycobacterium tuberculosis survival in macrophages, the interaction of M. tuberculosis with Toll-like receptors (TLRs) and the establishment of the link between innate and adaptive immunity, and TLRs and interferon-gamma-mediated antimicrobial pathways in macrophages. We also propose a paradigm that TLR2 signaling regulates the magnitude of the host Th1 response leading to either M. tuberculosis persistence and latent infection or replication and disease.

Synthesis and in vitro anti-mycobacterial activity of 5-substituted pyrimidine nucleosides

Mycobacterium tuberculosis and Mycobacterium avium infections cause the two most important mycobacterioses, leading to increased mortality in patients with AIDS. Various 5-substituted 2'-deoxyuridines, uridines, 2'-O-methyluridine, 2'-ribofluoro-2'-deoxyuridines, 3'-substituted-2',3'-dideoxy uridines, 2',3'-dideoxyuridines, and 2',3'-didehydro-2',3'-dideoxyuridines were synthesized and evaluated for their in vitro inhibitory activity against M. bovis and M. avium. 5-(C-1 Substituted)-2'-deoxyuridine derivatives emerged as potent inhibitors of M. avium (MIC90 = 1-5 microg/mL range). The nature of C-5 substituents in the 2'-deoxyuridine series appeared to be a determinant of anti-mycobacterial activity. This new class of inhibitors could serve as useful compounds for the design and study of new anti-tuberculosis agents.

Design and Studies of Novel 5-Substituted Alkynylpyrimidine Nucleosides as Potent Inhibitors of Mycobacteria

We herein report a new category of 5-substituted pyrimidine nucleosides as potent inhibitors of mycobacteria. A series of 5-alkynyl derivatives of 2'-deoxyuridine (1-8), 2'-deoxycytidine (9-14), uridine (15-17), and 2'-O-methyluridine (18, 19) were synthesized and evaluated for their antimycobacterial activity in vitro. 5-Decynyl, 5-dodecynyl, and 5-tetradecynyl derivatives showed the highest antimycobacterial potency against M. bovis and M. avium, with the 2'-deoxyribose derivatives being more effective than the ribose analogues. Nucleosides bearing short alkynyl side chains 5-ethynyl, 5-propynyl, 5-pentynyl, and 5-heptynyl were mostly not inhibitory. Incorporation of a phenylethynyl function at the 5-position diminished the antimicrobial effect. Furthermore, related bicyclic analogues (20-24) were devoid of antimycobacterial activity, indicating that an acyclic side chain at the C-5 position of the pyrimidine ring is essential for potent activity. Compounds 1-17 were synthesized by the Pd-catalyzed coupling reactions of respective alkynes with 5-iodo derivatives of 2'-deoxyuridine, 2'-deoxycytidine, and uridine. Intramolecular cyclization of 1 and 3-6 in the presence of Cu afforded the corresponding bicyclic compounds 20-24. The investigated nucleosides are recognized here for the first time to be potent inhibitors of mycobacteria. This class of compounds could be of interest for lead optimization as antimycobacterial agents.

Lack of an Association between Interleukin-12 Receptor β1 Polymorphisms and Tuberculosis in Koreans

BACKGROUND

The fact that only 10% of people infected with Mycobacterium tuberculosis develop clinical tuberculosis (TB) suggests the presence of genetic factors in the pathogenesis of TB. To date, a number of single nucleotide polymorphisms (SNPs) in several candidate genes have been proposed as genetic risk factors of TB; however, reports are conflicting.

OBJECTIVES

We investigated whether SNPs in the interleukin (IL)-12 receptor beta1 gene are associated with TB in Koreans.

METHODS

One hundred and fifteen patients with bacteriologically or pathologically confirmed TB and 151 healthy anonymous blood donors were enrolled. The genotypes of 5 SNPs on IL-12 receptor beta1 gene, +705A/G (Q214R), +1158T/C (M365T), +1196G/C (G378R), +1637G/A (A525T) and +1664 C/T (P534S), were determined by PCR-RFLP.

RESULTS

No difference was observed between TB patients and controls in terms of the genotype frequencies of the 5 SNPs of the IL-12 receptor beta1 gene or of their haplotypes.

CONCLUSIONS

In view of the finding that these SNPs have been reported to be associated with TB in the Japanese and Moroccan populations, our results may reflect racial differences in genetic susceptibility to TB.

[Current diagnosis and treatment of the osteoarticular tuberculosis]

In 1993, tuberculosis was recognized as global medical problem by WHO. Recurring flare-up of this disease was triggered by difficult socioeconomic situation of the countries in transition, current development of immunocompromising diseases, and some other factors have contributed, too. The osteoarticular tuberculosis has been always postprimary and localized form of the disease, which, due to certain similarity to some other osteoarticular diseases, has been challenge for orthopaedic surgeons both from diagnostic and treatment aspects. Bacteriological diagnostics has had a limited value due to application of recommended tuberculostatic medication before obtaining specimens from bones or joints; and, on the other hand, rapid bacteriological methods, because of their expensive equipment, could be carried out in large mycobacteriology laboratories only. New visualizing methods, CT and MRI, have been particularly important for detection and monitoring of tuberculosis process in the spine during the early stage of the disease, what is impossible to achieve with native radiograms. Programmed administration of tuberculostatic drugs both in non-operative and surgical treatment has been proven necessary.

Synthesis and evaluation of nitrofuranylamides as novel antituberculosis agents

In an effort to develop new and more potent therapies to treat tuberculosis, a library of compounds was screened for M. tuberculosis UDP-Gal mutase inhibition. Nitrofuranylamide 1 was identified as a hit in this screen, possessing good antituberculosis activity. This paper describes the synthesis and evaluation of an expanded set of nitrofuranylamides. We have discovered a number of nitrofuranylamides with submicromolar M. tuberculosis MIC values and acceptable therapeutic indexes. The MIC activity did not correlate with UDP-Gal mutase inhibition, suggesting an alternative primary cellular target was responsible for the antituberculosis activity. The compounds were only active against mycobacteria of the tuberculosis complex. On the basis of these results, four compounds were selected for in vivo testing in a mouse model of tuberculosis infection, and of these compounds one showed significant antituberculosis activity.

The value of polymerase chain reaction detection of Mycobacterium tuberculosis in granulomas isolated by laser capture microdissection

AIMS

The aim of this study was to investigate the usefulness of polymerase chain reaction (PCR) detection of Mycobacterium tuberculosis in granulomas isolated by laser capture microdissection (LCM).

METHODS

The PCR DNA amplification method was used to detect M. tuberculosis in granulomas microdissected from one section stained by haematoxylin and eosin (H&E) from a formalin-fixed paraffin-embedded specimen. The results were compared to those obtained from PCR performed from 10 whole paraffin sections of 5 micro m each, and with the histology, culture and the patient's clinical findings.

RESULTS

Forty-nine formalin-fixed and paraffin-embedded samples from 49 patients with a histological suspicion of a mycobacterial infection were investigated. Using culture as the reference method, the sensitivity for the detection of M. tuberculosis was 92% and the specificity was 100% using PCR from microdissected granulomas and were similar to those obtained by using PCR from 10 whole sections.

CONCLUSIONS

The PCR method of examination of microdissected granulomas from deparaffinised sections is a sensitive, specific and rapid method for the detection of M. tuberculosis in formalin-fixed and paraffin-embedded samples. The method is as sensitive as that using PCR on 10 whole tissue sections, thus making it suitable for small biopsies. However, although these methods reduce the delay in diagnosis, culture remains the gold standard for identification of mycobacteria in tissue. Culture also allows for the testing of antibiotic sensitivity of any isolated species, in this way determining appropriate treatment.

Inhibition of Pneumocystis carinii, Toxoplasma gondii, and Mycobacterium avium dihydrofolate reductases by 2,4-diamino-5-[2-methoxy-5-(omega-carboxyalkyloxy)benzyl]pyrimidines: marked improvement in potency relative to trimethoprim and species selectivity relative to piritrexim

A series of previously undescribed 2,4-diamino-5-[2-methoxy-5-alkoxybenzyl]pyrimidines (3a-e) and 2,4-diamino-5-[2-methoxy-5-(omega-carboxyalkyloxy)benzyl]pyrimidines (3f-k) with up to eight CH2 groups in the alkoxy or omega-carboxyalkyloxy side chain were synthesized and tested for the ability to inhibit partially purified dihydrofolate reductase (DHFR) from Pneumocystis carinii (Pc), Toxoplasma gondii (Tg), Mycobacterium avium (Ma), and rat liver in comparison with two standard inhibitors, trimethoprim (1) and piritrexim (2). The latter drug is known to be extremely potent but shows a marked preference for binding to mammalian DHFR, whereas the former is very selective for the parasite enzymes but is a much weaker inhibitor. The underlying strategy for the synthesis of compounds 3a-k was that a hybrid structure embodying some features of both 1 and 2 might possess a more favorable combination of potency and selectivity than either parent drug. The choice of analogues 3f-k was based on the idea that the acidic omega-carboxyl group might interact preferentially with a basic center in the active site of DHFR from any of the parasite species relative to the active site of mammalian DHFR. In addition, the omega-carboxyl group was expected to improve water solubility relative to 1 or 2. In standardized spectrophotometric assays with dihydrofolate as the substrate and NADPH as the cofactor, 2,4-diamino-5-[(2-methoxy-4-carboxybutyloxy)benzyl]pyrimidine (3g) inhibited Pc DHFR with an IC(50) of 0.049 microM and rat DHFR with IC(50) of 3.9 microM. Its potency against Pc DHFR was 140-fold greater than that of 1 and close to that of 2, and its selectivity index, defined as the ratio IC(50)(rat liver)/IC(50)(P. carinii), was 8-fold higher than that of 1 and >10(4)-fold higher than that of 2. Although it was less potent and less selective against Tg than Pc DHFR, it was very potent as well as highly selective against Ma DHFR, with an IC(50) of 0.0058 microM and an IC(50)(rat liver)/IC(50)(M. avium) ratio of >600. Because of this favorable combination of potency and selectivity relative to 1 and 2, compound 3g may be viewed as a promising lead in the search for new antifolates with potential clinical activity against P. carinii and other opportunistic pathogens in patients with AIDS.

Glucocorticoids suppress human immunodeficiency virus type-1 long terminal repeat activity in a cell type-specific, glucocorticoid receptor-mediated fashion: direct protective effects at variance with clinical phenomenology

Glucocorticoid administration and/or excess secretion have been associated with increased Human Immunodeficiency Virus Type-1 (HIV-1) replication and AIDS progression. The HIV-1 long terminal repeat (LTR) promoter contains glucocorticoid-responsive element (GRE)-like sequences that could mediate a positive effect of glucocorticoids on HIV-1. In addition, we recently demonstrated that the HIV-1 accessory protein Vpr is a potent coactivator of the glucocorticoid receptor, which, like the host coactivator p300, potentiates the effect of glucocorticoids on GRE-containing, glucocorticoid-responsive genes. Such an effect may increase the sensitivity of several host target tissues to glucocorticoids by several fold, and may, thus, contribute to a positive effect of glucocorticoids on the HIV-1-LTR in infected host cells. In this study, we determined the direct effect of glucocorticoids on HIV-1-LTR by examining the ability of dexamethasone to modulate the activity of this promoter coupled to the luciferase reporter gene in human cell lines. Dexamethasone markedly inhibited Tat-stimulated, p300- or Vpr-enhanced luciferase activities in a cell-type specific, dose-dependent, and glucocorticoid receptor-mediated fashion. This effect of dexamethasone was not potentiated by Vpr, was antagonized by the glucocorticoid receptor antagonist RU 486 and required the DNA-binding domain of the receptor. These data suggest that the inhibitory effect of glucocorticoids on the HIV-1-LTR may be exerted via non-GRE-dependent inhibition of the strongly positive host transcription factor NF-kappaB, which interacts with the DNA- and ligand-binding domains of the receptor. Alternatively, it is also possible that dexamethasone-activated glucocorticoid receptor competes with other transcription factors for their binding sites on the promoter region or squelches transcription factors shared by HIV-1-LTR and glucocorticoid-responsive promoters. We conclude that glucocorticoids suppress, rather than stimulate, the HIV-1 promoter, thus acting, protectively for the host. Their apparent negative clinical association with AIDS is most likely due to immunosuppression of the host.

Impact of HIV infection on tuberculosis

Tuberculosis is increasing in prevalence in many countries and is now the leading infectious cause of death world wide, being responsible for three million deaths annually. Infection with HIV, likewise increasing in prevalence, has emerged as the most important predisposing factor for developing overt tuberculosis in people co-infected with Mycobacterium tuberculosis. Owing to the widespread geographical overlap of these two infections, it is estimated that in 1999, HIV related tuberculosis will reach one million cases and will cause 30% of the expected 2.5 million AIDS related deaths. Tuberculosis in HIV infected individuals may have unusual clinical features and can cause diagnostic difficulties. Despite the effectiveness of modern short course treatment, the mortality of HIV related tuberculosis during and after treatment remains high, and this may be due to other HIV related infections. The "cursed duet" of infection with both HIV and M tuberculosis is generating a threat to human health of unparalleled proportions which, if not taken seriously by health workers and decision makers, could become totally unmanageable.