Isoniazid plus sulphadoxine-pyrimethamine can reduce morbidity of HIV-positive patients treated for tuberculosis in Africa: a controlled clinical trial

Anti-Tuberculosis Mur Inhibitors: Structural Insights and the Way Ahead for Development of Novel Agents

Mur enzymes serve as critical molecular devices for the synthesis of UDP-MurNAc-pentapeptide, the main building block of bacterial peptidoglycan polymer. These enzymes have been extensively studied for bacterial pathogens such as Escherichia coli and Staphylococcus aureus. Various selective and mixed Mur inhibitors have been designed and synthesized in the past few years. However, this class of enzymes remains relatively unexplored for Mycobacterium tuberculosis (Mtb), and thus offers a promising approach for drug design to overcome the challenges of battling this global pandemic. This review aims to explore the potential of Mur enzymes of Mtb by systematically scrutinizing the structural aspects of various reported bacterial inhibitors and implications concerning their activity. Diverse chemical scaffolds such as thiazolidinones, pyrazole, thiazole, etc., as well as natural compounds and repurposed compounds, have been reviewed to understand their in silico interactions with the receptor or their enzyme inhibition potential. The structural diversity and wide array of substituents indicate the scope of the research into developing varied analogs and providing valuable information for the purpose of modifying reported inhibitors of other multidrug-resistant microorganisms. Therefore, this provides an opportunity to expand the arsenal against Mtb and overcome multidrug-resistant tuberculosis.

Management of active tuberculosis in adults with HIV

Every year, about 1 million people living with HIV worldwide develop tuberculosis. Although the drug regimens used to treat tuberculosis in these patients are the same as those used in HIV-negative patients, cotreatment of tuberculosis with antiretroviral therapy involves challenges including the optimal timing of antiretroviral initiation, drug-drug interactions, drug tolerability, and the prevention and treatment of tuberculosis-associated immune reconstitution syndrome. Furthermore, mortality is high in people with HIV who are diagnosed with tuberculosis during a hospital admission, and in those with tuberculous meningitis. Studies in this field have better characterised these challenges and informed optimal management and guideline revisions. In patients with tuberculosis, antiretroviral therapy improves survival, is well tolerated, and can be adjusted to manage drug-drug interactions with rifampicin. Prednisone is effective in both preventing and treating the paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome.

Body mass index variation over time and associated factors among HIV-positive adults on second-line ART in north-west Ethiopia: a retrospective follow-up study

OBJECTIVES

This study aimed to assess the evolution of body mass index (BMI) of HIV-positive adults on second-line antiretroviral therapy (ART) over time and factors affecting it in north-west Ethiopia.

DESIGN

An institution-based retrospective follow-up study was conducted using data extracted from 1016 patient cards from February 2008 to February 2016.

SETTING

Eight referral hospitals from Amhara region, Ethiopia were included.

PARTICIPANTS

HIV patients who started second-line ART.

OUTCOME MEASURES

Change in BMI since starting second-line ART.

RESULTS

Five hundred and thirty-eight (52.95%) participants were males and the median age of the participants was 33 years (IQR: 28; 39). The median follow-up time was 18 months (IQR: 5.2; 32.2). The average change of BMI showed linear increase over time. The amount of BMI increment or decrement according to each variable was shown as β coefficients. Treatment duration (β=0.013, 95% CI 0.004 to 0.022), isoniazid prophylaxis (β=0.87, 95% CI 0.32 to 1.42), cotrimoxazole prophylaxis (β=0.63, 95% CI 0.08 to 1.19), ambulatory functional status (β=-1.16, 95% CI -1.95 to 1.31), bedridden functional status (β=-1.83, 95% CI -2.47 to 1.21), WHO stage III (β=-0.42, 95% CI -0.65 to 0.20), WHO stage IV (β=-0.62, 95% CI -1.02 to 0.22), CD4 count (β=0.001, 95% CI 0.0008 to 0.0015), and time interaction of variables like tertiary educational status (β=0.02, 95% CI 0.01 to 0.04), ambulatory functional status (β=0.03, 95% CI 0.01 to 0.05) and WHO stages III (β=0.01, 95% CI 0.007 to 0.02) were found to be significant predictors.

CONCLUSION

The BMI of patients has shown linear increment over the treatment time. Factors affecting it have been identified but its effect on cardiovascular disease needs further study.

Repurposing of FDA-approved drugs to target MurB and MurE enzymes in Mycobacterium tuberculosis

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) is one amongst the top 10 causes of death worldwide. The growing rise in antibiotic resistance compounded with slow and expensive drug discovery has further aggravated the situation. 'Drug repurposing' is a promising approach where known drugs are examined for a new indication. In the present study, we have attempted to identify drugs that could target MurB and MurE enzymes involved in the muramic acid synthesis pathway (Mur Pathway) in Mtb. FDA-approved drugs from two repositories i.e. Drug Bank (1932 drugs) and e-LEA3D (1852 drugs) were screened against these proteins. Several criteria were applied to study the protein-drug interactions and the consensus drugs were further studied by molecular dynamics (MD) simulation. Our study found Sulfadoxine (-7.3 kcal/mol) and Pyrimethamine (-7.8 kcal/mol) to show stable interaction with MurB while Lifitegrast (-10.5 kcal/mol) and Sildenafil (-9.1 kcal/mol) showed most reliable interaction with MurE. Furthermore, binding free energy (ΔG_bind), RMSD and RMSF data and the number of hydrogen bonds corroborated the stability of interactions and hence these drugs for repurposing should be explored further.Communicated by Ramaswamy H. Sarma.

Effect of secondary preventive therapy on recurrence of tuberculosis in HIV-infected individuals: a systematic review

Human immunodeficiency virus (HIV)-infected individuals successfully treated for tuberculosis (TB) remain at risk of recurrence of the disease, especially in high TB incidence settings. We performed a systematic review, investigating whether secondary preventive therapy (sPT) with anti-TB drugs (preventive therapy in former TB patients with treatment success) is an effective strategy to prevent recurrence of TB in this patient group. We searched the databases PubMed, Cochrane Library, EMBASE, Web of Science and Google Scholar using the keywords HIV-infections, HIV, human immunodeficiency virus, AIDS, isoniazid, isoniazid preventive therapy (IPT), tuberculosis, TB, recurrence and recurrent disease, resulting in 253 potential publications. We identified eight publications for full text assessment, after which four articles qualified for inclusion in this systematic review. The quality of the included articles was rated using the GRADE system. All but one study were rated as having a high quality. In all included studies, sPT significantly decreased the incidence of recurrent TB in HIV-infected individuals to a substantial degree in comparison to non-treatment or placebo. Relative reductions varied from 55.0% to 82.1%. These data showed that the use of sPT to prevent recurrent TB in HIV-infected individuals was highly beneficial. These findings need to be confirmed in prospective studies with an adequate assessment of the effect of antiretroviral therapy (ART) and the occurrence of drug resistance.

Recognizing drug targets using evolutionary information: implications for repurposing FDA-approved drugs against Mycobacterium tuberculosis H37Rv

Drug repurposing to explore target space has been gaining pace over the past decade with the upsurge in the use of systematic approaches for computational drug discovery. Such a cost and time-saving approach gains immense importance for pathogens of special interest, such as Mycobacterium tuberculosis H37Rv. We report a comprehensive approach to repurpose drugs, based on the exploration of evolutionary relationships inferred from the comparative sequence and structural analyses between targets of FDA-approved drugs and the proteins of M. tuberculosis. This approach has facilitated the identification of several polypharmacological drugs that could potentially target unexploited M. tuberculosis proteins. A total of 130 FDA-approved drugs, originally intended against other diseases, could be repurposed against 78 potential targets in M. tuberculosis. Additionally, we have also made an attempt to augment the chemical space by recognizing compounds structurally similar to FDA-approved drugs. For three of the attractive cases we have investigated the probable binding modes of the drugs in their corresponding M. tuberculosis targets by means of structural modelling. Such prospective targets and small molecules could be prioritized for experimental endeavours, and could significantly influence drug-discovery and drug-development programmes for tuberculosis.

Progress in tuberculosis vaccine development and host-directed therapies--a state of the art review

Tuberculosis continues to kill 1·4 million people annually. During the past 5 years, an alarming increase in the number of patients with multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis has been noted, particularly in eastern Europe, Asia, and southern Africa. Treatment outcomes with available treatment regimens for drug-resistant tuberculosis are poor. Although substantial progress in drug development for tuberculosis has been made, scientific progress towards development of interventions for prevention and improvement of drug treatment outcomes have lagged behind. Innovative interventions are therefore needed to combat the growing pandemic of multidrug-resistant and extensively drug-resistant tuberculosis. Novel adjunct treatments are needed to accomplish improved cure rates for multidrug-resistant and extensively drug-resistant tuberculosis. A novel, safe, widely applicable, and more effective vaccine against tuberculosis is also desperately sought to achieve disease control. The quest to develop a universally protective vaccine for tuberculosis continues. So far, research and development of tuberculosis vaccines has resulted in almost 20 candidates at different stages of the clinical trial pipeline. Host-directed therapies are now being developed to refocus the anti-Mycobacterium tuberculosis-directed immune responses towards the host; a strategy that could be especially beneficial for patients with multidrug-resistant tuberculosis or extensively drug-resistant tuberculosis. As we are running short of canonical tuberculosis drugs, more attention should be given to host-directed preventive and therapeutic intervention measures.

Recurrent tuberculosis in HIV-infected patients in Rio de Janeiro, Brazil

BACKGROUND/OBJECTIVE

The risk of recurrent tuberculosis may increase in HIV-infected patients due to exogenous reinfection. We measured the frequency of and determined risk factors for recurrent tuberculosis in a cohort of HIV-infected patients in Rio de Janeiro, Brazil.

METHODS

Data were abstracted from medical records of HIV-infected patients attending 29 HIV clinics between 1998 and 2007. Patients analyzed were those who had no tuberculosis history prior to their first HIV clinic visit and who had at least one episode of tuberculosis after entry. Incidence rate ratios compared incidence rates between risk groups and Cox proportional hazards regression models evaluated unadjusted and adjusted associations.

RESULTS

Among 1080 HIV-infected patients with tuberculosis, 96 (8.9%) developed a recurrent diagnosis. The median time between diagnoses was 2.4 years. Fewer patients with recurrent tuberculosis had completed their initial 6-month course of tuberculosis treatment compared with patients without recurrence (78 versus 86%; P = 0.02). For patients who completed therapy, the incidence rate of recurrence was 2.5/100 versus 9.0/100 person-years for noncompleters (incidence rate ratio, 3.60; 95% confidence interval, 1.92-6.32). In multivariate modeling, initial tuberculosis treatment completion, receipt of antiretroviral therapy, and CD4 cell count more than 200 mm any time after the initial diagnosis were associated with a significantly decreased hazard of recurrence.

CONCLUSION

Tuberculosis recurrence rates were high in this HIV-infected population. Completion of initial tuberculosis therapy, use of antiretroviral therapy, and increases in CD4 cell counts were associated with lower recurrence rates. Use of secondary preventive therapy might be warranted to reduce the burden of tuberculosis in patients with HIV infection.

Tuberculosis preventive therapy in the era of HIV infection: overview and research priorities

The recognition of tuberculosis (TB) as a major cause of morbidity and mortality among human immunodeficiency virus (HIV)-infected persons has led to renewed interest in TB preventive therapy and its incorporation into the essential package of health care for these individuals. Despite convincing data regarding its efficacy, TB preventive therapy has not been widely implemented. Further work is needed to determine how to overcome the barriers to the implementation of such therapy, including how best to exclude the presence of active TB before providing preventive therapy. Such issues as the optimal duration of preventive therapy for and the role of TB preventive therapy in the treatment of individuals receiving antiretroviral therapy remain to be defined. Ongoing research will help to determine how best to use this intervention in the care of HIV-infected persons and in the control of TB on a wider basis.

Structure-based design, synthesis and preliminary evaluation of selective inhibitors of dihydrofolate reductase from Mycobacterium tuberculosis

Tuberculosis is an increasing threat, owing to the spread of AIDS and to the development of resistance of the causative organism, Mycobacterium tuberculosis, to the currently available drugs. Dihydrofolate reductase (DHFR) is an important enzyme of the folate cycle; inhibition of DHFR inhibits growth and causes cell death. The crystal structure of M. tuberculosis DHFR revealed a glycerol tightly bound close to the binding site for the substrate dihydrofolate; this glycerol-binding motif is absent from the human enzyme. A series of pyrimidine-2,4-diamines was designed with a two-carbon tether between a glycerol-mimicking triol and the 6-position of the heterocycle; these compounds also carried aryl substituents at the 5-position. These, their diastereoisomers, analogues lacking two hydroxy groups and analogues lacking the two-carbon spacing linker were synthesised by acylation of the anions derived from phenylacetonitriles with ethyl (4S,5R)-4-benzyloxymethyl-2,2-dimethyl-1,3-dioxolane-4-propanoate, ethyl (4S,5S)-4-benzyloxymethyl-2,2-dimethyl-1,3-dioxolane-4-propanoate, tetrahydrooxepin-2-one and 2,3-O-isopropylidene-d-erythronolactone, respectively, to give the corresponding alpha-acylphenylacetonitriles. Formation of the methyl enol ethers, condensation with guanidine and deprotection gave the pyrimidine-2,4-diamines. Preliminary assay of the abilities of these compounds to inhibit the growth of TB5 Saccharomyces cerevisiae carrying the DHFR genes from M. tuberculosis, human and yeast indicated that 5-phenyl-6-((3R,4S)-3,4,5-trihydroxypentyl)pyrimidine-2,4-diamine selectively inhibited M. tuberculosis DHFR and had little effect on the human or yeast enzymes.

Efficacy of secondary isoniazid preventive therapy among HIV-infected Southern Africans: time to change policy?

OBJECTIVE

To determine the efficacy of secondary preventive therapy against tuberculosis (TB) among gold miners working in South Africa.

DESIGN

An observational study.

SETTING

Health service providing comprehensive care for gold miners.

METHODS

The incidence of recurrent TB was compared between two cohorts of HIV-infected miners: one cohort (n = 338) had received secondary preventive therapy with isoniazid (IPT) and the other had not (n = 221).

RESULTS

The overall incidence of recurrent TB was reduced by 55% among men who received IPT compared with those who did not (incidence rates 8.6 and 19.1 per 100 person-years, respectively; incidence rate ratio, 0.45; 95% confidence interval 0.26-0.78). The efficacy of isoniazid preventive therapy was unchanged after controlling for CD4 cell count and age. The number of person-years of IPT required to prevent one case of recurrent TB among individuals with a CD4 cell count < 200 x 106 cells/l, and > or = 200 x 106 cells/l was 5 and 19, respectively.

CONCLUSION

Secondary preventive therapy reduces TB recurrence: the absolute impact appears to be greatest among individuals with low CD4 cell counts. International TB preventive therapy guidelines for HIV-infected individuals need to be expanded to include recommendations for secondary preventive therapy in settings where TB prevalence is high.

Cotrimoxazole prophylaxis for opportunistic infections in adults with HIV

BACKGROUND

The prevention and early treatment of infections are the mainstay of the medical management of the majority of people with HIV infection, who live in low income countries without access to antiretroviral drugs. Cotrimoxazole is cheap and effective against a wide range of organisms. However, routine prophylactic treatment is difficult to deliver in low-resource settings, and could also lead to increased resistance to the drug.

OBJECTIVES

To assess the effects of routinely administered cotrimoxazole on death and illness episodes in HIV infected adults.

SEARCH STRATEGY

We searched the Cochrane HIV/AIDS Group register, the Cochrane Controlled Trials Register, MEDLINE, LILACS, AIDSLINE, AIDSTRIALS and AIDSDRUGS databases, and proceedings and abstracts from AIDS and tuberculosis (TB) conferences (search date July 2001). We checked reference lists for trials and other pertinent articles, and contacted pharmaceutical companies and experts in the field.

SELECTION CRITERIA

Randomised or quasi randomised trials comparing routinely administered cotrimoxazole versus placebo or no treatment in adults (age greater than 13 years).

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial eligibility and quality, and extracted data. Where data were incomplete or unclear trial authors were contacted for further details.

MAIN RESULTS

Four trials involving 1476 people were identified. Three trials (1416 people) studied heterosexual men and women in West Africa. A fourth trial was of homosexual men on chemotherapy for Kaposi's sarcoma, in the United States. Meta-analysis of the three African trials showed a significant beneficial effect of cotrimoxazole for death: relative risk 0.69 (95% confidence interval 0.55 to 0.87); for morbid events: 0.76 (0.64 to 0.9); and for hospitalisation: 0.66 (0.48 to 0.92). There was no significantly greater risk of adverse effects: relative risk 1.28 (0.47 to 3.51). Effects were similar in people with early and advanced HIV disease. Insufficient evidence was found on effects in areas with higher bacterial resistance or in people on antiretroviral therapy.

REVIEWER'S CONCLUSIONS

In the trials included in the review, cotrimoxazole prophylaxis had a beneficial effect in preventing death and illness episodes in adults with both early and advanced HIV disease. However, the wider applicability of these findings is unclear, in particular to areas with higher background bacterial resistance to cotrimoxazole. Further trials would be required in differing settings to widen applicability.

Experimental in vitro efficacy study on the interaction of epiroprim plus isoniazid against Mycobacterium tuberculosis

Thirty Mycobacterium tuberculosis strains (8: INH(R)/INH(R), 12: INH(R)/RIF(S), 10: INH(S)/RIF(S)) were examined against MICs of epiroprim (EPM) and isoniazid (INH) separately or in association. EPM alone proved to be insufficiently active against the various mycobacterial isolates (MIC > or =256 microg/ml). The observed average sensitivity to the association of EPM plus INH was, in contrast, considerably increased, as reflected by reduced MICs and lower percentages of resistant strains. MICs ranged between 16 and 32 microg/ml EPM and 2 and 4 microg/ml INH for INH(R) strains. All INH(S) isolates were inhibited by a concentration of 0.125 microg/ml EPM and 0.06 microg/ml INH. The fractional inhibitory concentration indices indicated an additive activity on INH(R)/RIF(R) strains and a synergistic activity on INH(R)/RIF(S) and INH(S)/RIF(S) strains. The synergistic activity of this drug association needs to be confirmed in an animal model.