Duration of efficacy of treatment of latent tuberculosis infection in HIV-infected adults

Loss to follow up from isoniazid preventive therapy among adults attending HIV voluntary counseling and testing sites in Uganda

Among HIV-infected adults attending non-governmental organization voluntary counseling and testing (VCT) sites in Uganda that provide a nine-month course of isoniazid preventive treatment (IPT), we report on loss to follow-up (LTFU) and its associated risk factors. The design was a retrospective cohort study of program data spanning a three year period (2006-2008). A total of 586 IPT patients were enrolled of whom 335 (57.1%) were females with a mean age of 34 years. Of those starting IPT, 341 (58.1%) were lost to follow-up, 197 (33.6%) completed IPT, 29 (4.9%) were discontinued and 19 (3.2%) died. The return rates at one, three, five and seven months were 78.0% (457), 62.1% (364), 52.9% (310) and 33.6% (197) respectively. Being less than 30 years of age, widowed, separated, or divorced were found to be associated with a higher risk of loss to follow-up. Sudden improvement in retention on IPT was observed between the years 2006 and 2007, although causes of the improvement are poorly understood hence the need for more research. At non-governmental VCT sites in Uganda, six out of ten individuals enrolled on IPT are lost to follow-up and efforts to reduce this attrition including systems strengthening might play a critical role in the success of IPT programs.

Epidemiology of tuberculosis and HIV: recent advances in understanding and responses

Although tuberculosis (TB) continues to cause enormous suffering and overwhelm health care systems in areas with high HIV prevalence, there have been a number of recent significant advances in knowledge regarding the epidemiology, management, and control of HIV-related TB. TB remains the most common serious opportunistic infection in people with HIV infection and the leading cause of death. However, there is some reason for optimism. First, two trials addressing when to start antiretroviral therapy (ART) in HIV-infected adults with newly diagnosed TB have shown that earlier initiation of ART reduces mortality significantly. Second, there is trial evidence of efficacy in giving long-term isoniazid preventive treatment (IPT) to HIV-infected adults in high HIV-prevalence settings where TB reinfection is frequent (much like cotrimoxazole). Third, the search for an inexpensive, rapid, sensitive, and specific TB diagnostic that is able to replace smear and delayed mycobacterial culture has yielded promising results. Responding to massive TB epidemics in high HIV-prevalence settings, the World Health Organization has supplemented its directly observed treatment short-course strategy with one called the 3I's to actively screen and diagnose TB cases (intensified case finding), prevent new cases of TB with IPT, and prevent transmission of TB in congregate settings such as hospitals and clinics (infection control). Combating TB in high HIV-prevalence settings requires rapid and massive implementation of the 3I's with initiation of antiretrovirals and more effective efforts to prevent new HIV infections.

An evaluation of factors associated with taking and responding positive to the tuberculin skin test in individuals with HIV/AIDS

BACKGROUND

The tuberculin skin test (TST) is still the standard test for detecting latent infection by M tuberculosis (LTBI). Given that the Brazilian Health Ministry recommends that the treatment of latent tuberculosis (LTBI) should be guided by the TST results, the present study sets out to describe the coverage of administering the TST in people living with HIV at two referral health centers in the city of Recife, where TST is offered to all patients. In addition, factors associated with the non-application of the test and with positive TST results were also analyzed.

METHODS

A cross-sectional study was carried out with HIV patients, aged 18 years or over, attending outpatient clinics at the Correia Picanço Hospital/SES/PE and the Oswaldo Cruz/UPE University Hospital, who had been recommended to take the TST, in the period between November 2007 and February 2010. Univariate and multivariate logistic regression analyses were carried out to establish associations between the dependent variable - taking the TST (yes/no), at a first stage analysis, and the independent variables, followed by a second stage analysis considering a positive TST as the dependent variable. The odds ratio was calculated as the measure of association and the confidence interval (CI) at 95% as the measure of accuracy of the estimate.

RESULTS

Of the 2,290 patients recruited, 1087 (47.5%) took the TST. Of the 1,087 patients who took the tuberculin skin test, the prevalence of TST ≥ 5 mm was 21.6% among patients with CD4 ≥ 200 and 9.49% among those with CD4 < 200 (p = 0.002). The patients most likely not to take the test were: men, people aged under 39 years, people with low educational levels and crack users. The risk for not taking the TST was statiscally different for health service. Patients who presented better immunity (CD4 ≥ 200) were more than two and a half times more likely to test positive that those with higher levels of immunodeficiency (CD4 < 200).

CONCLUSIONS

Considering that the TST is recommended by the Brazilian health authorities, coverage for taking the test was very low. The most serious implication of this is that LTBI treatment was not carried out for the unidentified TST-positive patients, who may consequently go on to develop TB and eventually die.

New regimens to prevent tuberculosis in adults with HIV infection

BACKGROUND

Treatment of latent tuberculosis in patients infected with the human immunodeficiency virus (HIV) is efficacious, but few patients around the world receive such treatment. We evaluated three new regimens for latent tuberculosis that may be more potent and durable than standard isoniazid treatment.

METHODS

We randomly assigned South African adults with HIV infection and a positive tuberculin skin test who were not taking antiretroviral therapy to receive rifapentine (900 mg) plus isoniazid (900 mg) weekly for 12 weeks, rifampin (600 mg) plus isoniazid (900 mg) twice weekly for 12 weeks, isoniazid (300 mg) daily for up to 6 years (continuous isoniazid), or isoniazid (300 mg) daily for 6 months (control group). The primary end point was tuberculosis-free survival.

RESULTS

The 1148 patients had a median age of 30 years and a median CD4 cell count of 484 per cubic millimeter. Incidence rates of active tuberculosis or death were 3.1 per 100 person-years in the rifapentine-isoniazid group, 2.9 per 100 person-years in the rifampin-isoniazid group, and 2.7 per 100 person-years in the continuous-isoniazid group, as compared with 3.6 per 100 person-years in the control group (P>0.05 for all comparisons). Serious adverse reactions were more common in the continuous-isoniazid group (18.4 per 100 person-years) than in the other treatment groups (8.7 to 15.4 per 100 person-years). Two of 58 isolates of Mycobacterium tuberculosis (3.4%) were found to have multidrug resistance.

CONCLUSIONS

On the basis of the expected rates of tuberculosis in this population of HIV-infected adults, all secondary prophylactic regimens were effective. Neither a 3-month course of intermittent rifapentine or rifampin with isoniazid nor continuous isoniazid was superior to 6 months of isoniazid. (Funded by the National Institute of Allergy and Infectious Diseases and others; ClinicalTrials.gov number, NCT00057122.).

Comparison of the bactericidal activity of various fluoroquinolones against Mycobacterium tuberculosis in an in vitro experimental model

OBJECTIVES

To compare the bactericidal activity of various fluoroquinolones against Mycobacterium tuberculosis in the latent and exponential growth phases.

METHODS

Ciprofloxacin, levofloxacin and moxifloxacin were tested against 16 M. tuberculosis clinical isolates (4 resistant and 12 susceptible to fluoroquinolones) from Elche, Spain, isolated between 1992 and 2009. To study bactericidal activity, an inoculum of approximately 10(5) cfu of each isolate was cultured in Middlebrook 7H9 broth. The broth was previously acidified to pH 4.6 to obtain the microorganism in the stationary phase. Cultures with different concentrations (0.1 to 50 mg/L) of antibiotic and antibiotic-free controls were incubated for 48 h then plated onto Middlebrook 7H11 to detect bacterial killing. In all stages of the process the M. tuberculosis strain ATCC 41323 was included as a quality control to ensure reproducible results.

RESULTS

Moxifloxacin and levofloxacin were found to exhibit bactericidal activity at lower concentrations and against more strains in both the latent and the exponential growth phases compared with ciprofloxacin. The bactericidal activity of moxifloxacin was greater than that of levofloxacin against microorganisms in the exponential growth phase, but the opposite was true in the latent phase.

CONCLUSIONS

Our data confirm the usefulness of moxifloxacin in the treatment of tuberculosis and suggest that levofloxacin may be used as an alternative drug in the treatment of latent tuberculosis when it is not possible to use isoniazid. Based on the results presented, ciprofloxacin appears to be a poor choice.

6-month versus 36-month isoniazid preventive treatment for tuberculosis in adults with HIV infection in Botswana: a randomised, double-blind, placebo-controlled trial

BACKGROUND

In accordance with WHO guidelines, people with HIV infection in Botswana receive daily isoniazid preventive therapy against tuberculosis without obtaining a tuberculin skin test, but duration of prophylaxis is restricted to 6 months. We aimed to assess effectiveness of extended isoniazid therapy.

METHODS

In our randomised, double-blind, placebo-controlled trial we enrolled adults infected with HIV aged 18 years or older at government HIV-care clinics in Botswana. Exclusion criteria included current illness such as cough and an abnormal chest radiograph without antecedent tuberculosis or pneumonia. Eligible individuals were randomly allocated (1:1) to receive 6 months' open-label isoniazid followed by 30 months' masked placebo (control group) or 6 months' open-label isoniazid followed by 30 months' masked isoniazid (continued isoniazid group) on the basis of a computer-generated randomisation list with permuted blocks of ten at each clinic. Antiretroviral therapy was provided if participants had CD4-positive lymphocyte counts of fewer than 200 cells per μL. We used Cox regression analysis and the log-rank test to compare incident tuberculosis in the groups. Cox regression models were used to estimate the effect of antiretroviral therapy. The trial is registered at ClinicalTrials.gov, number NCT00164281.

FINDINGS

Between Nov 26, 2004, and July 3, 2009, we recorded 34 (3·4%) cases of incident tuberculosis in 989 participants allocated to the control group and 20 (2·0%) in 1006 allocated to the continued isoniazid group (incidence 1·26% per year vs 0·72%; hazard ratio 0·57, 95% CI 0·33-0·99, p=0·047). Tuberculosis incidence in those individuals receiving placebo escalated approximately 200 days after completion of open-label isoniazid. Participants who were tuberculin skin test positive (ie, ≥5 mm induration) at enrolment received a substantial benefit from continued isoniazid treatment (0·26, 0·09-0·80, p=0·02), whereas participants who were tuberculin skin test-negative received no significant benefit (0·75, 0·38-1·46, p=0·40). By study completion, 946 (47%) of 1995 participants had initiated antiretroviral therapy. Tuberculosis incidence was reduced by 50% in those receiving 360 days of antiretroviral therapy compared with participants receiving no antiretroviral therapy (adjusted hazard ratio 0·50, 95% CI 0·26-0·97). Severe adverse events and death were much the same in the control and continued isoniazid groups.

INTERPRETATION

In a tuberculosis-endemic setting, 36 months' isoniazid prophylaxis was more effective for prevention of tuberculosis than was 6-month prophylaxis in individuals with HIV infection, and chiefly benefited those who were tuberculin skin test positive.

FUNDING

US Centers for Disease Control and Prevention and US Agency for International Development.

Costs and consequences of additional chest x-ray in a tuberculosis prevention program in Botswana

RATIONALE

Isoniazid preventive therapy is effective in reducing the risk of tuberculosis (TB) in persons living with HIV (PLWH); however, screening must exclude TB disease before initiating therapy. Symptom screening alone may be insufficient to exclude TB disease in PLWH because some PLWH with TB disease have no symptoms. The addition of chest radiography (CXR) may improve disease detection.

OBJECTIVES

The objective of the present analysis was to compare the costs and effects of the addition of CXR to the symptom screening process against the costs and effects of symptom screening alone.

METHODS

Using data from Botswana, a decision analytic model was used to compare a "Symptom only" policy against a "Symptom+CXR" policy. The outcomes of interest were cost, death, and isoniazid- and multidrug-resistant TB in a hypothetical cohort of 10,000 PLWH.

MEASUREMENTS AND MAIN RESULTS

The Symptom+CXR policy prevented 16 isoniazid- and 0.3 multidrug-resistant TB cases; however, because of attrition from the screening process, there were 98 excess cases of TB, 15 excess deaths, and an additional cost of U.S. $127,100. The Symptom+CXR policy reduced deaths only if attrition was close to zero; however, to eliminate attrition the cost would be U.S. $2.8 million per death averted. These findings did not change in best- and worst-case scenario analyses.

CONCLUSIONS

In Botswana, a policy with symptom screening only preceding isoniazid-preventive therapy initiation prevents more TB and TB-related deaths, and uses fewer resources, than a policy that uses both CXR and symptom screening.

Association of isoniazid preventive therapy with lower early mortality in individuals on antiretroviral therapy in a workplace programme

OBJECTIVE

To describe the association between isoniazid preventive therapy (IPT) and mortality among individuals starting antiretroviral therapy (ART) in a workplace programme in South Africa where tuberculosis (TB) incidence is very high.

METHODS

ART-naive individuals starting ART from January 2004 to December 2007 were followed for up to 12 months. Deaths were ascertained from clinic and human resource data. The association between IPT and mortality was assessed using Cox regression.

RESULTS

A total of 3270 individuals were included (median age 45; 93% men; median baseline CD4 cell count 155 cells/μl (interquartile range 87-221); and 45% with WHO stage 3/4]. Nine hundred twenty-two (28%) individuals started IPT either prior to or within 3 months of starting ART. Individuals who started IPT tended to have less advanced HIV disease at ART initiation. Two hundred fifty-nine (7.9%) deaths were observed with overall mortality rate 8.9 per 100 person-years [95% confidence interval (CI) 7.9-10.6]. The unadjusted mortality rate was lower among those who received IPT compared with those who did not [3.7/100 vs. 11.1/100 person-years, respectively, hazard ratio 0.34 (95% CI 0.24-0.49)]; this association remained after adjustment for age, baseline CD4 cell count, baseline WHO stage, year of ART start, and individual company (hazard ratio 0.51, 95% CI 0.32-0.80). In sensitivity analyses restricted to those with no previous history of TB (n = 3036) or with no TB symptoms at ART initiation (n = 2251), IPT remained associated with reduced mortality [adjusted hazard ratios 0.51 (95% CI 0.32-0.81) and 0.48 (95% CI 0.24-0.96), respectively].

CONCLUSION

Mortality was lower among individuals receiving IPT with or prior to ART start. These results support routine use of IPT in conjunction with ART.

Tuberculosis case-contact research in endemic tropical settings: design, conduct, and relevance to other infectious diseases

The study of the contacts of patients with tuberculosis has a long history. Where tuberculosis is endemic, regular recruitment of tuberculosis cases and their household contacts can be done for research and strategic intervention. This recruitment provides a platform whereby host, pathogen, and environmental factors related to tuberculosis can be investigated and new interventions can be assessed. We describe the types of study possible within a tuberculosis case-contact study platform and its essential components, including recruitment and follow-up of the patients with tuberculosis, their household contacts and community controls, assessments and sampling, and data management and processing. Sample handling and storage, local engagement, ethical challenges, and the strengths and weaknesses of study design are all important issues in case-contact research. A case-contact study platform is a powerful research tool to answer fundamental questions in tuberculosis and has relevance to the study of other major infectious diseases.

T cell reactivity against mycolyl transferase antigen 85 of M. tuberculosis in HIV-TB coinfected subjects and in AIDS patients suffering from tuberculosis and nontuberculous mycobacterial infections

The mycolyl transferase antigen 85 complex is a major secreted protein family from mycobacterial culture filtrate, demonstrating powerful T cell stimulatory properties in most HIV-negative, tuberculin-positive volunteers with latent M.tuberculosis infection and only weak responses in HIV-negative tuberculosis patients. Here, we have analyzed T cell reactivity against PPD and Ag85 in HIV-infected individuals, without or with clinical symptoms of tuberculosis, and in AIDS patients with disease caused by nontuberculous mycobacteria. Whereas responses to PPD were not significantly different in HIV-negative and HIV-positive tuberculin-positive volunteers, responses to Ag85 were significantly decreased in the HIV-positive (CDC-A and CDC-B) group. Tuberculosis patients demonstrated low T cell reactivity against Ag85, irrespective of HIV infection, and finally AIDS patients suffering from NTM infections were completely nonreactive to Ag85. A one-year follow-up of twelve HIV-positive tuberculin-positive individuals indicated a decreased reactivity against Ag85 in patients developing clinical tuberculosis, highlighting the protective potential of this antigen.

Interpreting meta-analysis according to the adequacy of sample size. An example using isoniazid chemoprophylaxis for tuberculosis in purified protein derivative negative HIV-infected individuals

Objective:

To illustrate the utility of statistical monitoring boundaries in meta-analysis, and provide a framework in which meta-analysis can be interpreted according to the adequacy of sample size. To propose a simple method for determining how many patients need to be randomized in a future trial before a meta-analysis can be deemed conclusive.

Study design and setting:

Prospective meta-analysis of randomized clinical trials (RCTs) that evaluated the effectiveness of isoniazid chemoprophylaxis versus placebo for preventing the incidence of tuberculosis disease among human immunodeficiency virus (HIV)-positive individuals testing purified protein derivative negative. Assessment of meta-analysis precision using trial sequential analysis (TSA) with LanDeMets monitoring boundaries. Sample size determination for a future trials to make the meta-analysis conclusive according to the thresholds set by the monitoring boundaries.

Results:

The meta-analysis included nine trials comprising 2,911 trial participants and yielded a relative risk of 0.74 (95% CI, 0.53–1.04, P = 0.082, I² = 0%). To deem the meta-analysis conclusive according to the thresholds set by the monitoring boundaries, a future RCT would need to randomize 3,800 participants.

Conclusion:

Statistical monitoring boundaries provide a framework for interpreting meta-analysis according to the adequacy of sample size and project the required sample size for a future RCT to make a meta-analysis conclusive.

Tuberculosis as part of the natural history of HIV infection in developing countries

An enhanced, refocused research agenda is critical to reducing the burden of tuberculosis (TB) in the human immunodeficiency virus (HIV) epidemic in developing countries. TB threatens HIV-infected patients before and after initiation of antiretroviral therapy, is difficult to diagnose, is rapidly fatal when it is drug resistant, and is being spread in clinics and hospitals. Research priorities include improved and point-of-care TB diagnostics; TB treatment and prevention during HIV infection, drug-resistant TB, and childhood TB; and optimization of TB and HIV program integration. With new TB diagnostics and drugs reaching approval, research must focus on effectively deploying these advancements. Research must include evaluations of individual, household, health care, and community approaches. Studies must apply implementation science to determine how to increase and adapt effective interventions to reduce TB burden in the context of HIV infection. Investment in this research will improve the lives of persons infected with HIV and contribute to efforts to reduce the global TB burden.

Tuberculosis and survival of HIV-infected individuals by time since seroconversion

In a cohort of 1950 HIV-positive men with known dates of HIV seroconversion, 399 developed tuberculosis. Mortality rates following tuberculosis were greatly increased (hazard ratio, adjusted for age at seroconversion, 4.7, 95% confidence interval 3.7-6.1), and this ratio was similar at different times following seroconversion. Overall mortality was similar to that in western seroconverter cohorts with much lower rates of tuberculosis, suggesting that tuberculosis is more a marker of HIV progression than a cause of it.

Treatment of latent Mycobacterium tuberculosis infection in intravenous drug users co-infected with HIV

Objective: This clinical trial, carried out among injection drug users and the HIV-infected with tuberculin skin test ≥ 5 mm, aimed to evaluate the compliance and tolerability of two preventive strategies against tuberculosis (TB).

Methods: Study protocol prospectively compares adherence to nine months of daily therapy with isoniazid (9H) versus two months of daily therapy with rifampin plus pyrazinamide (2RZ) administered randomly. All patients were concurrently admitted to a methadone maintenance programme. To assess toxicity, liver function was monitored monthly.

Results: From 305 assessable patients, those in 2RZ arm showed better adherence (84% vs. 59%, p < 0.0001). Results on liver toxicity did not show significant differences between 9H and 2RZ (4.5% vs. 6.9%; odds ratio = 1.58, 95% confidence interval = 0.42—7.24). Conclusion: 2RZ should be considered an option to prevent TB in selected groups of patients infected with HIV, such as injection drug users on methadone treatment.

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.

[Treatment of latent tuberculosis infection: update of guidelines, 2006]

The Tuberculosis Working Group of the Portuguese Society of Pulmonology, feeling the need to develop guidelines for the diagnosis and treatment of latent tuberculosis infection, compiled a set of recommendations, in view to standardize procedures on this area. This document was prepared in collaboration with the Portuguese Societies of Internal Medicine, Pediatrics and Infectious Diseases, A review and update of guidelines for tracing and treatment of latent tuberculosis infection was made, concerning immunocompetent children and adults, as well as immunocompromised children and adults due to HIV infection. It is understood that these guidelines are to be used as general recommendations, and they should not replace the individual analysis of each case.

The impact of antiretroviral therapy and isoniazid preventive therapy on tuberculosis incidence in HIV-infected patients in Rio de Janeiro, Brazil

BACKGROUND

Tuberculosis is a common complication and leading cause of death in HIV infection. Antiretroviral therapy (ART) lowers the risk of tuberculosis, but may not be sufficient to control HIV-related tuberculosis. Isoniazid preventive therapy (IPT) reduces tuberculosis incidence significantly, but is not widely used.

METHODS

We analysed tuberculosis incidence in 11 026 HIV-infected patients receiving medical care at 29 public clinics in Rio de Janeiro, Brazil, between 1 September 2003 and 1 September 2005. Data were collected through a retrospective medical record review. We determined rates of tuberculosis in patients who received neither ART nor IPT, only ART, only IPT, or both ART and IPT.

RESULTS

The overall tuberculosis incidence was 2.28 cases/100 person-years (PY) [95% confidence interval (CI) 2.06-2.52]. Among patients who received neither ART nor IPT, incidence was 4.01/100 PY. Patients who received ART had an incidence of 1.90/100 PY (95% CI 1.66-2.17) and those treated with IPT had a rate of 1.27/100 PY (95% CI 0.41-2.95). The incidence among patients who received ART and IPT was 0.80/100 PY (95% CI 0.38-1.47). Multivariate Cox proportional hazards modeling revealed a 76% reduction in tuberculosis risk among patients receiving both ART and IPT (adjusted relative hazard 0.24; P < 0.001) after adjusting for age, previous tuberculosis diagnosis, and CD4 cell counts at baseline.

CONCLUSION

The use of both IPT and ART in HIV-infected patients is associated with significantly reduced tuberculosis incidence. In conjunction with expanded access to ART, the wider use of IPT in patients with HIV will improve tuberculosis control in high burden areas.

Pathogenesis and management of HIV/TB co-infection in Asia

HIV infection increases the risk of reactivation of latent tuberculosis (TB), progression of a new infection or re-infection to active disease, and acceleration of the natural course of the disease with a more rapid spread of strains, including those that are drug resistant, in the community. TB also accelerates the course of HIV-induced disease by activating viral replication and accentuating the decline in CD4 T cell counts. In this chapter, TB-HIV co-infection is discussed in the context of the situation in Vietnam, particularly Ho Chi Minh City, the creation of a well-integrated TB control and research programs in Cambodia, and the broad principles of the co-management of TB/HIV particularly in the context of the associated atypical forms of pulmonary TB (PTB), increased non-PTB and the frequency of acid fast smear negative cases.

Dynamic variation in the cellular origin of HIV type 1 during treatment of tuberculosis in dually infected subjects

HIV-1 replication remains elevated in dually infected HIV-1/TB subjects at completion of antituberculosis therapy. A viral immunocapture assay was used to examine the cellular origin of HIV-1 within plasma from HIV-1/TB subjects at time of diagnosis of pulmonary TB, at end of TB treatment, and 6 months after completion of treatment. Asymptomatic HIV-1-infected subjects without TB (HIV-1/C) served as controls. Both activated immature macrophage (CD36(+)) and CD4 T cell (CD26(+)) compartments contributed to viral load. Changes in the activation status of either cellular compartment paralleled their contribution to viral load. Levels of HIV-1 originating from activated (HLA-DR(+)) cells and from CD36(+) and CD26(+) mononuclear cells resolved to levels observed in HIV-1/C by the end of treatment. HIV-1 isolated by anti-CD3 immunocapture from HIV-1/TB patients remained significantly higher than from HIV-1/C patients at the end of TB treatment and at 12 months follow-up. Therefore, viral production by lymphocytes extends well beyond the completion of TB treatment.

Towards universal access to HIV prevention, treatment, care, and support: the role of tuberculosis/HIV collaboration

Tuberculosis is the oldest of the world's current pandemics and causes 8.9 million new cases and 1.7 million deaths annually. The disease is among the most common causes of morbidity and mortality in people living with HIV. However, tuberculosis is more than just part of the global HIV problem; well-resourced tuberculosis programmes are an important part of the solution to scaling-up towards universal access to comprehensive HIV prevention, diagnosis, care, and support. This article reviews the impact of the interactions between tuberculosis and HIV in resource-limited settings; outlines the recommended programmatic and clinical responses to the dual epidemics, highlighting the role of tuberculosis/HIV collaboration in increasing access to prevention, diagnostic, and treatment services; and reviews progress in the global response to the epidemic of HIV-related tuberculosis.

Effect of tuberculosis preventive therapy on HIV disease progression and survival in HIV-infected adults

PURPOSE

To determine whether tuberculosis (TB) preventive therapies alter the rate of disease progression to AIDS or death and to identify significant prognostic factors for HIV disease progression to AIDS.

METHOD

In a randomized placebo-controlled trial in Kampala, Uganda, 2,736 purified protein derivative (PPD)-positive and anergic HIV-infected adults were randomly assigned to four and two regimens, respectively. PPD-positive patients were treated with isoniazid (INH) for 6 months (6H; n = 536), INH plus rifampicin for 3 months (3HR; n = 556), INH plus rifampicin plus pyrazinamide for 3 months (3HRZ; n = 462), or placebo for 6 months (n = 464). Anergic participants were treated with 6H (n = 395) or placebo (n = 323).

RESULTS

During follow-up, 404 cases progressed to AIDS and 577 deaths occurred. The cumulative incidence of the AIDS progression was greater in the anergic cohort compared to the PPD-positive cohort (p < .0001). Among PPD-positive patients, the relative risk of the AIDS progression with INH alone was 0.95 (95% CI 0.68-1.32); with 3HR it was 0.83 (95% CI 0.59-1.17); and with 3HRZ it was 0.76 (95% CI 0.52-1.08), controlling for significant baseline predictors. Among anergic patients, the relative risk of the AIDS progression was 0.81 (95% CI 0.56-1.15). Survival was greater in the PPD-positive cohort compared to the anergic cohort (p = .0001).

CONCLUSION

The number of signs or symptoms at baseline and anergic status are associated with increasing morbidity and mortality. Even though the tuberculosis preventive therapies were effective in reducing the incidence of TB for HIV-infected adults, their benefit of delaying HIV disease progression to AIDS was not observed.

Isoniazid preventive therapy and risk for resistant tuberculosis

In the context of tuberculosis (TB) resurgence, isoniazid preventive therapy (IPT) is increasingly promoted, but concerns about the risk for development of isoniazid-resistant tuberculosis may hinder its widespread implementation. We conducted a systematic review of data published since 1951 to assess the effect of primary IPT on the risk for isoniazid-resistant TB. Different definitions of isoniazid resistance were used, which affected summary effect estimates; we report the most consistent results. When all 13 studies (N = 18,095 persons in isoniazid groups and N = 17,985 persons in control groups) were combined, the summary relative risk for resistance was 1.45 (95% confidence interval 0.85-2.47). Results were similar when studies of HIV-uninfected and HIV-infected persons were considered separately. Analyses were limited by small numbers and incomplete testing of isolates, but findings do not exclude an increased risk for isoniazid-resistant TB after IPT. The diagnosis of active TB should be excluded before IPT. Continued surveillance for isoniazid resistance is essential.

Tuberculosis in sub-Saharan Africa: opportunities, challenges, and change in the era of antiretroviral treatment

Rapid scale-up of antiretroviral treatment programmes is happening in Africa, driven by international advocacy and policy directives and supported by unprecedented donor funding and technical assistance. This welcome development offers hope to millions of HIV-infected Africans, among whom tuberculosis is the major cause of serious illness and death. Little in the way of HIV diagnosis or care was previously offered to patients with tuberculosis, by either national tuberculosis or AIDS control programmes, with tuberculosis services focused exclusively on diagnosis and treatment of rising numbers of patients. Tuberculosis control in Africa has yet to adapt to the new climate of antiretroviral availability. Many barriers exist, from drug interactions to historic differences in the way that tuberculosis and HIV are perceived, but failure to successfully integrate HIV and tuberculosis control will threaten the viability of both programmes. Here, we review tuberculosis epidemiology in Africa and policy implications of HIV/AIDS treatment scale-up.

Review editorial: prevention of tuberculosis in resource-poor countries with increasing access to highly active antiretroviral treatment

The administration of isoniazid (INH) has been proposed, evaluated and implemented to prevent tuberculosis (TB) disease among patients who are infected with the human immunodeficiency virus (HIV). This strategy has been developed in communities where TB is highly endemic and at a time when antiretroviral (ARV) treatment was not, or was rarely available. Although INH prevention programmes were somewhat pushed to the background due to the worldwide advocacy for ARV drugs, prevention of TB remains of paramount importance. The dual HIV-TB infection poses problems, not only for the individual and his/her clinician but also for the programme manager. We review various aspects of TB preventive treatment in countries with a high prevalence of HIV-TB co-infection and limited resources but with increasing access to ARV treatment.

Immunogenicity of the Mycobacterium tuberculosis PPE55 (Rv3347c) protein during incipient and clinical tuberculosis

Clinical tuberculosis (TB), whether noncavitary or cavitary, is the late stage of a chronic disease process, since Mycobacterium tuberculosis is a slowly growing organism. Our studies have shown that the profiles of antigenic proteins expressed by the in vivo bacteria that elicit antibodies differ in cavitary and noncavitary TB. To gain insight into antigenic proteins expressed during incipient, subclinical TB, an expression library of M. tuberculosis genomic DNA was screened with sera obtained during subclinical TB from guinea pigs infected with aerosols of M. tuberculosis H37Rv. One of the proteins recognized by antibodies elicited during subclinical TB infection of guinea pigs is the 309-kDa PPE55 (Rv3347c) protein. Genomic hybridization studies suggest that the PPE55 gene is specific to the M. tuberculosis complex and is present in a majority of clinical isolates tested. Antibodies to the C-terminal, approximately 100-kDa fragment of PPE55 (PPE-C) were detectable in sera from 29/30 (97%) human immunodeficiency virus-negative/TB-positive (HIV(-) TB(+)) patients and 17/24 (71%) HIV(+) TB(+) patients tested but not in sera from purified-protein derivative-positive healthy controls, suggesting that the in vivo expression of PPE55 protein correlates with active M. tuberculosis infection. Anti-PPE-C antibodies were also detected in retrospective sera obtained months prior to manifestation of clinical TB from 17/21 (81%) HIV(+) TB(+) individuals tested, providing evidence that the protein is expressed during incipient, subclinical TB in HIV-infected humans. Thus, PPE55 is a highly immunogenic protein that may be useful for differentiating between latent TB and incipient, subclinical TB.

Antigens of Mycobacterium tuberculosis recognized by antibodies during incipient, subclinical tuberculosis

Serum samples obtained from human immunodeficiency virus (HIV)-infected tuberculosis (TB) patients months prior to clinical TB were used to delineate the profile of Mycobacterium tuberculosis culture filtrate proteins recognized during subclinical TB. A subset of approximately 12 antigens was recognized by antibodies in these serum samples. Antibodies to two of these antigens (81 [88]-kDa malate synthase [GlcB] and MPT51) were present in serum samples obtained during incipient subclinical TB in 19 (approximately 90%) of the 21 HIV-infected TB patients tested. These antigens will be useful for devising diagnostic tests that can identify HIV-positive individuals who are at a high risk for developing clinical TB.

High rates of clinical and subclinical tuberculosis among HIV-infected ambulatory subjects in Tanzania

BACKGROUND

We sought to determine the prevalence of active tuberculosis among ambulatory HIV-infected persons in Tanzania with CD4 cell counts of > or =200 cells/mm3 and a bacille Calmette-Guerin vaccination scar.

METHODS

Subjects who volunteered for a tuberculosis booster vaccine trial were screened for active tuberculosis by obtainment of a history, physical examination, chest radiography, sputum culture and acid fast bacillus (AFB) stain, and blood culture. All subjects underwent a tuberculin skin test (TST) and lymphocyte proliferation assays (LPAs) for detection of responses to mycobacterial antigens.

RESULTS

Active tuberculosis was identified at baseline in 14 (15%) of the first 93 subjects who were enrolled: 10 (71%) had clinical tuberculosis (symptoms or chest radiograph findings), and 4 (29%) had subclinical tuberculosis (positive sputum AFB stain or culture results but no symptoms or chest radiograph findings). An additional 6 subjects with subclinical tuberculosis were identified subsequently. The 10 subjects with subclinical tuberculosis included 3 with positive sputum AFB stains results and 7 who were only identified by a positive sputum culture result. Compared with subjects who did not have tuberculosis, the 10 subjects with subclinical tuberculosis were more likely to have peripheral lymphadenopathy, positive TST results, and elevated LPA responses to early secreted antigenic target-6 (ESAT). Eight of 10 patients had received isoniazid because of a positive TST result before active tuberculosis was recognized.

CONCLUSIONS

Clinical and subclinical tuberculosis are common among ambulatory HIV-infected persons, and some cases can only be identified by sputum culture. World Health Organization guidelines for screening for latent tuberculosis before treatment do not recommend sputum culture and, therefore, may fail to identify a substantial number of HIV-infected persons with subclinical, active tuberculosis.

Treatment of latent tuberculosis infection in HIV infected persons

BACKGROUND

Individuals with HIV infection are at an increased risk of developing active tuberculosis. It is known that treatment of latent tuberculosis infection (LTBI), also referred to as preventive therapy or chemoprophylaxis, helps to prevent progression to active disease in human immunodeficiency virus (HIV) negative populations. However, the extent and magnitude of protection (if any) associated with preventive therapy in those infected with HIV should be quantified.

OBJECTIVES

To determine the effectiveness of tuberculosis preventive therapy in reducing the risk of active tuberculosis and death in persons infected with HIV.

SEARCH STRATEGY

We searched the Cochrane Controlled Trials Register (CCTR), MEDLINE, EMBASE, AIDSLINE, AIDSTRIALS and AIDSDRUGS. We also scanned reference lists of articles and contacted authors and other researchers in the field.

SELECTION CRITERIA

We included studies in which HIV positive individuals were randomly allocated to preventive therapy for TB and placebo, or to alternative TB preventive therapy regimens. Participants could be tuberculin skin test positive or negative, but without active tuberculosis.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied study selection criteria, assessed study quality and extracted data. Effects were assessed using relative risk for dichotomous data and weighted mean difference for continuous data.

MAIN RESULTS

11 trials were included with a total of 8,130 randomized participants. Preventive therapy (any anti-TB drug) versus placebo was associated with a lower incidence of active tuberculosis (RR 0.64, 95% CI 0.51 to 0.81). This benefit was more pronounced in individuals with a positive tuberculin skin test (RR 0.38, 95% CI 0.25 to 0.57) than in those who had a negative test (RR 0.83, 95% CI 0.58 to 1.18.). Limited data suggest that the initial protective effect against tuberculosis may decline over the short to medium term. Efficacy was similar for all regimens (regardless of drug type, frequency or duration of treatment). However, compared to INH monotherapy, short -course multi-drug regimens were much more likely to require discontinuation of treatment due to adverse effects. Overall, there was no evidence that preventive therapy versus placebo reduced all-cause mortality (RR 0.95, 95% CI 0.85 to 1.06), although a favourable trend was found in people with a positive tuberculin test (RR 0.80, 95% CI 0.63 to 1.02).

REVIEWER'S CONCLUSIONS

Treatment of latent tuberculosis infection (LTBI) reduces the risk of active tuberculosis in HIV positive individuals with a positive tuberculin skin test. The choice of regimen will depend on factors such as cost, adverse effects, adherence and drug resistance. Future studies should assess these aspects. In addition, trials evaluating the long-term effects of anti-tuberculosis chemoprophylaxis and the influence of level of immunocompromise on effectiveness are needed.

Tuberculosis

Among communicable diseases, tuberculosis is the second leading cause of death worldwide, killing nearly 2 million people each year. Most cases are in less-developed countries; over the past decade, tuberculosis incidence has increased in Africa, mainly as a result of the burden of HIV infection, and in the former Soviet Union, owing to socioeconomic change and decline of the health-care system. Definitive diagnosis of tuberculosis remains based on culture for Mycobacterium tuberculosis, but rapid diagnosis of infectious tuberculosis by simple sputum smear for acid-fast bacilli remains an important tool, and more rapid molecular techniques hold promise. Treatment with several drugs for 6 months or more can cure more than 95% of patients; direct observation of treatment, a component of the recommended five-element DOTS strategy, is judged to be the standard of care by most authorities, but currently only a third of cases worldwide are treated under this approach. Systematic monitoring of case detection and treatment outcomes is essential to effective service delivery. The proportion of patients diagnosed and treated effectively has increased greatly over the past decade but is still far short of global targets. Efforts to develop more effective tuberculosis vaccines are under way, but even if one is identified, more effective treatment systems are likely to be required for decades. Other modes of tuberculosis control, such as treatment of latent infection, have a potentially important role in some contexts. Until tuberculosis is controlled worldwide, it will continue to be a major killer in less-developed countries and a constant threat in most of the more-developed countries.

Can we control tuberculosis in high HIV prevalence settings?

The overlap between the epidemiology of HIV and tuberculosis and consequent rapid rise in numbers of patients with tuberculosis in many African countries has put a huge burden on health systems. The stigma of HIV has increased the existing stigma surrounding tuberculosis. There are three mechanisms by which we may reduce the number of cases of tuberculosis in a community: reducing transmission of tuberculosis, reducing reactivation of latent tuberculosis infection and reducing HIV transmission. Reinforcing the existing health service to find more cases, active case-finding in communities or enhanced case-finding in specific groups will reduce transmission of tuberculosis. However, health services that find it difficult to find cases efficiently will also find it difficult to support patients throughout treatment to achieve a cure. Partnership with traditional healers, community-based organizations and private practitioners could reduce this burden. Reactivation of tuberculosis among people living with HIV can be reduced by tuberculosis preventive therapy or by antiretroviral therapy. Programmes that identify people living with HIV can also implement enhanced tuberculosis case-finding increasing the benefits of the programme. However, the impact of widespread use of antiretroviral therapy may be to increase the number of people in a community who are mildly immunocompromised and the incidence of tuberculosis at a community level might rise. Any strategy that successfully reduces HIV transmission will benefit tuberculosis control, since around a third of all HIV-positive individuals will develop tuberculosis before they die. To control tuberculosis in high HIV prevalence settings, we must strengthen health systems to include not only expansion of the DOTS strategy but also full-blooded implementation of voluntary counselling and testing, enhanced and active tuberculosis case-finding, preventive therapy and better care for people living with HIV including antiretroviral therapy. The approach needed to control tuberculosis needs also to be integrated into broader development and poverty reduction goals.

Current thinking on the management of tuberculosis

High-income countries are moving toward tuberculosis (TB) elimination. Sophisticated diagnostic tests and effective treatment regimens are readily available. The range of available resources even makes effective treatment of multidrug-resistant tuberculosis (MDRTB) possible. The introduction of highly active antiretroviral therapy and specific TB control measures has reduced the incidence of HIV-associated TB disease. Unfortunately, the situation in low-income countries that carry 95% of the global TB burden is less positive. TB diagnosis still relies upon sputum smear microscopy. The management of MDRTB remains problematic though guidelines for DOTS-plus programs have been developed, and cheaper second-line drugs are becoming available. The HIV epidemic continues to confound TB control efforts, particularly in sub-Saharan Africa. The appropriate package of interventions for controlling HIV/TB disease remains undefined and unimplemented. The international community must provide the funding and technical support to address the alarming dichotomy in TB control that exists between rich and poor countries.

HIV-related pulmonary infections: a review of the recent literature

Antimicrobial prophylaxis and highly active antiretroviral therapy have changed the epidemiology and impact of pulmonary infection in patients infected with the human immunodeficiency virus (HIV). However, pulmonary infection remains a significant contributor to the morbidity and mortality of such patients. Bacterial pneumonia and tuberculosis remain common lung infections in this setting, especially where appropriate prophylaxis is unavailable or when compliance with such therapy is poor. Pneumonia related to Pneumocystis carinii also remains a significant problem, especially as a presenting illness in patients not yet known to be infected with HIV. Recrudescence of "treated" infection as a manifestation of the immune reconstitution syndrome may become more commonly encountered as more patients are treated with highly active therapy.

HIV/AIDS treatment and HIV vaccines for Africa

Increased support from the global HIV/AIDS community is driving advances in HIV treatment and vaccine development in the developing world. Care of patients with AIDS includes many biomedical, nutritional, psychosocial, and behavioural interventions. In resource-poor settings, antiretroviral drugs should be given with use of standardised treatment regimens and streamlined algorithms for monitoring use. A safe and effective HIV vaccine will supplement prevention efforts to protect uninfected people against infection, or might possibly be able to modify the course of HIV infection. Advances have been made in understanding the immune response and immunisation to HIV, and new ideas for candidate vaccines have been developed, including several based on HIV-1 strains prevalent in Africa. HIV vaccine efficacy trials are needed in Africa to determine whether these advances can be translated into clinical and public health benefits. In this review, we discuss the prospects for use of treatment and vaccines in resource-poor settings.

Tuberculosis in the tropics

Tropical countries bear the brunt of the global TB burden. Young children are at high risk and suffer the most severe forms of TB; adults with pulmonary cavities are the main sources of transmission. The incidence in sub-Saharan Africa is increasing as a consequence of the HIV pandemic. Smear-negative TB, which is common in children and patients who have HIV infection, is becoming a major problem in resource-poor settings where access to mycobacterial culture and histopathology is limited. Clinical case definitions are being developed to address this problem. Short courses of rifampin-based therapy are not universally available, but access is increasing. DOTS is the main strategy that the WHO is promoting to improve TB control. This is particularly important for sputum smear-positive patients. Unfortunately, the DOTS targets set by the WHO have not yet been met. Innovative, low-cost ways of supervising therapy have been developed using family members or lay supervisors. Preventive therapy in tropical countries is limited to high-risk cases (young children and HIV-infected patients who are tuberculin skin test-positive). An improved TB vaccine would dramatically improve TB control.