Advances in development of new tuberculosis vaccines.

PURPOSE OF REVIEW: Tuberculosis (TB) remains a global public health emergency and caused 1.6 million deaths in 2021. The aim of this review is to provide recent updates on advances in TB vaccine development for prevention and adjunct therapy. RECENT FINDINGS: Targets use indications guiding late stage TB vaccine development have been established, namely: (i) Prevention of disease (PoD), (ii) Prevention of recurrent disease (PoR), (iii) Prevention of established infection in previously uninfected patients (PoI), and (iv) Adjunctive immunotherapy. Novel approaches include vaccines designed to induce immune responses beyond established CD4+, Th1-biased T cell immunity, novel animal models for use in challenge/protection studies, and controlled human infection models to generate vaccine efficacy data. SUMMARY: Recent efforts at developing effective TB vaccines for prevention and adjunct treatment utilising new targets and technologies have yielded 16 candidate vaccines demonstrating proof of concept for inducing potentially protective immune responses to TB which is currently under evaluation in different stages of clinical trials.

Pharmacokinetics of Pyrazinamide and Optimal Dosing Regimens for Drug-Sensitive and -Resistant Tuberculosis.

Pyrazinamide is used in the treatment of tuberculosis (TB) because its sterilizing effect against tubercle bacilli allows the shortening of treatment. It is part of standard treatment for drug-susceptible and drug-resistant TB, and it is being considered as a companion drug in novel regimens. The aim of this analysis was to characterize factors contributing to the variability in exposure and to evaluate drug exposures using alternative doses, thus providing evidence to support revised dosing recommendations for drug-susceptible and multidrug-resistant tuberculosis (MDR-TB). Pyrazinamide pharmacokinetic (PK) data from 61 HIV/TB-coinfected patients in South Africa were used in the analysis. The patients were administered weight-adjusted doses of pyrazinamide, rifampin, isoniazid, and ethambutol in fixed-dose combination tablets according to WHO guidelines and underwent intensive PK sampling on days 1, 8, 15, and 29. The data were interpreted using nonlinear mixed-effects modeling. PK profiles were best described using a one-compartment model with first-order elimination. Allometric scaling was applied to disposition parameters using fat-free mass. Clearance increased by 14% from the 1st day to the 29th day of treatment. More than 50% of patients with weight less than 55 kg achieved lower pyrazinamide exposures at steady state than the targeted area under the concentration-time curve from 0 to 24 h of 363 mg · h/liter. Among patients with drug-susceptible TB, adding 400 mg to the dose for those weighing 30 to 54 kg improved exposure. Average pyrazinamide exposure in different weight bands among patients with MDR-TB could be matched by administering 1,500 mg, 1,750 mg, and 2,000 mg to patients in the 33- to 50-kg, 51- to 70-kg, and greater than 70-kg weight bands, respectively.

Model-Based Evaluation of Higher Doses of Rifampin Using a Semimechanistic Model Incorporating Autoinduction and Saturation of Hepatic Extraction.

Rifampin is a key sterilizing drug in the treatment of tuberculosis (TB). It induces its own metabolism, but neither the onset nor the extent of autoinduction has been adequately described. Currently, the World Health Organization recommends a rifampin dose of 8 to 12 mg/kg of body weight, which is believed to be suboptimal, and higher doses may potentially improve treatment outcomes. However, a nonlinear increase in exposure may be observed because of saturation of hepatic extraction and hence this should be taken into consideration when a dose increase is implemented. Intensive pharmacokinetic (PK) data from 61 HIV-TB-coinfected patients in South Africa were collected at four visits, on days 1, 8, 15, and 29, after initiation of treatment. Data were analyzed by population nonlinear mixed-effects modeling. Rifampin PKs were best described by using a transit compartment absorption and a well-stirred liver model with saturation of hepatic extraction, including a first-pass effect. Autoinduction was characterized by using an exponential-maturation model: hepatic clearance almost doubled from the baseline to steady state, with a half-life of around 4.5 days. The model predicts that increases in the dose of rifampin result in more-than-linear drug exposure increases as measured by the 24-h area under the concentration-time curve. Simulations with doses of up to 35 mg/kg produced results closely in line with those of clinical trials.

Reduced antituberculosis drug concentrations in HIV-infected patients who are men or have low weight: implications for international dosing guidelines.

Reduced antituberculosis drug concentrations may contribute to unfavorable treatment outcomes among HIV-infected patients with more advanced immune suppression, and few studies have evaluated pharmacokinetics of the first-line antituberculosis drugs in such patients given fixed-dose combination tablets according to international guidelines using weight bands. In this study, pharmacokinetics were evaluated in 60 patients on 4 occasions during the first month of antituberculosis therapy. Multilevel linear mixed-effects regression analysis was used to examine the effects of age, sex, weight, drug dose/kilogram, CD4(+) lymphocyte count, treatment schedule (5 versus 7 days/week), and concurrent antiretrovirals (efavirenz plus lamivudine plus zidovudine) on the area under the concentration-time curve from 0 to 12 h (AUC(0-12)) of the respective antituberculosis drugs and to compare AUC(0-12)s at day 8, day 15, and day 29 with the day 1 AUC(0-12). Median (range) age, weight, and CD4(+) lymphocyte count were 32 (18 to 47) years, 55.2 (34.4 to 98.7) kg, and 252 (12 to 500)/µl. For every 10-kg increase in body weight, the predicted day 29 AUC(0-12) increased by 14.1% (95% confidence interval [CI], 7.5, 20.8), 14.1% (95% CI, -0.7, 31.1), 6.1% (95% CI, 2.7, 9.6) and 6.0% (95% CI, 0.8, 11.3) for rifampin, isoniazid, pyrazinamide, and ethambutol, respectively. Males had day 29 AUC(0-12)s 19.3% (95% CI, 3.6, 35.1) and 14.0% (95% CI, 5.6, 22.4) lower than females for rifampin and pyrazinamide, respectively. Level of immune suppression and concomitant antiretrovirals had little effect on the concentrations of the antituberculosis agents. As they had reduced drug concentrations, it is important to review treatment responses in patients in the lower weight bands and males to inform future treatment guidelines, and revision of doses in these patients should be considered.

Africa Centres for Disease Control and Prevention Is Closing Gaps in Disease Detection.

In 2017, the African Union established a new continent-wide public health agency, the Africa Centres for Disease Control and Prevention (Africa CDC). Many outbreaks are never detected in Africa, and among outbreaks that are detected, countries often respond slowly and ineffectively. To address these problems, Africa CDC is working to increase early detection and reporting, improve access to diagnostic tests, promote novel laboratory approaches, help establish national public health institutes, improve information exchange between health agencies, and enhance recording and reporting of acute public health events and vital statistics. The health security of Africa will be strengthened by this new public health agency's ability to build comprehensive, timely disease surveillance that rapidly detects and contains health threats.

Drug resistant tuberculosis in Africa: Current status, gaps and opportunities.

BACKGROUND: The World Health Organization End TB Strategy targets for 2035 are ambitious and drug resistant tuberculosis is an important barrier, particularly in Africa, home to over a billion people. OBJECTIVE: We sought to review the current status of drug resistant tuberculosis in Africa and highlight key areas requiring improvement. METHODS: Available data from 2016 World Health Organization global tuberculosis database were extracted and analysed using descriptive statistics. RESULTS: The true burden of drug resistant tuberculosis on the continent is poorly described with only 51% of countries having a formal survey completed. In the absence of this data, modelled estimates were used and reported 92 629 drug resistant tuberculosis cases with 42% of these occurring in just two countries: Nigeria and South Africa. Of the cases estimated, the majority of patients (70%) were not notified, representing 'missed cases'. Mortality among patients with multi-drug resistant tuberculosis was 21%, and was 43% among those with extensively drug resistant tuberculosis. Policies on the adoption of new diagnostic tools was poor and implementation was lacking. A rifampicin result was available for less than 10% of tuberculosis cases in 23 of 47 countries. Second-line drug resistance testing was available in only 60% of countries. The introduction of the short multi-drug resistant tuberculosis regimen was a welcome development, with 40% of countries having implemented it in 2016. Bedaquiline has also been introduced in several countries. CONCLUSION: Drug resistant tuberculosis is largely missed in Africa and this threatens prospects to achieve the 2035 targets. Urgent efforts are required to confirm the true burden of drug resistant tuberculosis in Africa. Adoption of new tools and drugs is essential if the 2035 targets are to be met.

Laboratory medicine in Africa since 2008: then, now, and the future.

The Maputo Declaration of 2008 advocated for commitment from global stakeholders and national governments to prioritise support and harmonisation of laboratory systems through development of comprehensive national laboratory strategies and policies in sub-Saharan Africa. As a result, HIV laboratory medicine in Africa has undergone a transformation, and substantial improvements have been made in diagnostic services, networks, and institutions, including the development of a competent workforce, introduction of point-of-care diagnostics, and innovative quality improvement programmes that saw more than 1100 laboratories enrolled and 44 accredited to international standards. These improved HIV laboratories can now be used to combat emerging continental and global health threats in the decades to come. For instance, the unprecedented Ebola virus disease outbreak in west Africa exposed the severe weaknesses in the overall national health systems in affected countries. It is now possible to build robust health-care systems in Africa and to combat emerging continental and global health threats in the future. In this Personal View, we aim to describe the remarkable transformation that has occurred in laboratory medicine to combat HIV/AIDS and improve global health in sub-Saharan Africa since 2008.

Improving laboratory efficiencies to scale-up HIV viral load testing.

PURPOSE OF REVIEW: Viral load measurement is a key indicator that determines patients' response to treatment and risk for disease progression. Efforts are ongoing in different countries to scale-up access to viral load testing to meet the Joint United Nations Programme on HIV and AIDS target of achieving 90% viral suppression among HIV-infected patients receiving antiretroviral therapy. However, the impact of these initiatives may be challenged by increased inefficiencies along the viral load testing spectrum. This will translate to increased costs and ineffectiveness of scale-up approaches. This review describes different parameters that could be addressed across the viral load testing spectrum aimed at improving efficiencies and utilizing test results for patient management. RECENT FINDINGS: Though progress is being made in some countries to scale-up viral load, many others still face numerous challenges that may affect scale-up efficiencies: weak demand creation, ineffective supply chain management systems; poor specimen referral systems; inadequate data and quality management systems; and weak laboratory-clinical interface leading to diminished uptake of test results. SUMMARY: In scaling up access to viral load testing, there should be a renewed focus to address efficiencies across the entire spectrum, including factors related to access, uptake, and impact of test results.

Implementation of quality management systems and progress towards accreditation of National Tuberculosis Reference Laboratories in Africa.

BACKGROUND: Laboratory services are essential at all stages of the tuberculosis care cascade, from diagnosis and drug resistance testing to monitoring response to treatment. Enabling access to quality services is a challenge in low-resource settings. Implementation of a strong quality management system (QMS) and laboratory accreditation are key to improving patient care. OBJECTIVES: The study objective was to determine the status of QMS implementation and progress towards accreditation of National Tuberculosis Reference Laboratories (NTRLs) in the African Region. METHOD: An online questionnaire was administered to NTRL managers in 47 World Health Organization Regional Office for Africa member states in the region, between February and April 2015, regarding the knowledge of QMS tools and progress toward implementation to inform strategies for tuberculosis diagnostic services strengthening in the region. RESULTS: A total of 21 laboratories (43.0%) had received SLMTA/TB-SLMTA training, of which 10 had also used the Global Laboratory Initiative accreditation tool. However, only 36.7% of NTRLs had received a laboratory audit, a first step in quality improvement. Most NTRLs participated in acid-fast bacilli microscopy external quality assurance (95.8%), although external quality assurance for other techniques was lower (60.4% for first-line drug susceptibility testing, 25.0% for second-line drug susceptibility testing, and 22.9% for molecular testing). Barriers to accreditation included lack of training and accreditation programmes. Only 28.6% of NTRLs had developed strategic plans and budgets which included accreditation. CONCLUSION: Good foundations are in place on the continent from which to scale up accreditation efforts. Laboratory audits should be conducted as a first step in developing quality improvement action plans. Political commitment and strong leadership are needed to drive accreditation efforts; advocacy will require clear evidence of patient impact and cost-benefit.

Integrating laboratory networks, surveillance systems and public health institutes in Africa.

The Ebola outbreak in West Africa underlined the urgent need for integration of public health systems, including the establishment of national laboratory networks, surveillance systems, and health research institutions at all levels of service delivery. The integration schema presented here would assist in driving the immediate steps needed for integration of public health systems, particularly laboratory networks, in support of the implementation of International Health Regulations and the Global Health Security Agenda in the African region. Increased funding, political willingness from countries, and coordination through enhanced technical assistance from international partners, are critical in achieving this objective.

The WHO AFRO external quality assessment programme (EQAP): Linking laboratory networks through EQA programmes.

External Quality Assessment (EQA) surveys performed by the World Health Organization Regional Office for Africa (WHO AFRO) revealed the need for the strengthening of public health microbiology laboratories, particularly for testing of epidemic-prone diseases in the African Region. These surveys revealed common issues such as supply chain management, skilled personnel, logistical support and overall lack of quality standards. For sustainable improvements to health systems as well as global health security, deficiencies identified need to be actively corrected through robust quality assurance programmes and implementation of laboratory quality management systems. Given all the pathogens of public health importance, an external quality assessment programme with a focus on vaccine-preventable diseases and emerging and re-emerging dangerous pathogens is important, and should not be stand-alone, but integrated within laboratory networks as seen in polio, measles, yellow fever and rubella. In 2015, WHO AFRO collaborated with the US Centers for Disease Control and Prevention, the London School of Hygiene & Tropical Medicine and partners in a series of consultations with countries and national and regional EQA providers for the development of quality assurance models to support HIV point-of-care testing and monitoring. These consultations revealed similar challenges as seen in the WHO AFRO surveys. WHO AFRO brought forth its experience in implementing quality standards for health programmes, and also opened discussions on how lessons learned through such established programmes can be utilised to supporting and strengthening the introduction of early infant diagnosis of HIV and viral load point-of-care testing. An optimised external quality assessment programme will impact the ability of countries to meet core capacities, providing improved quality management systems, improving the confidence of diagnostic network services in Africa, and including capacities to detect events of international public health importance.

Efficacy and Safety of 'Fixed Dose' versus 'Loose' Drug Regimens for Treatment of Pulmonary Tuberculosis in Two High TB-Burden African Countries: A Randomized Controlled Trial.

BACKGROUND: There are limited data on the performance of the use of fixed-dose combination (FDC) TB drugs when used under programmatic settings in high TB-endemic countries. We evaluated the efficacy and safety of FDC versus loose formulation (LF) TB treatment regimens for treatment of pulmonary TB (PTB) in the context of actual medical practice in prevailing conditions within programmatic settings in five sites in two high TB-burden African countries. METHODS: A two-arm, single-blind, randomized clinical trial comparing FDCs with separate LFs involving 1000 adults newly diagnosed with culture positive PTB was conducted at five sites in two African countries between 2007 and 2011. Participants were randomized to receive daily treatment with anti-TB drugs given as either FDC or separate LFs for 24 weeks (intensive phase- 8 weeks of isoniazid, rifampicin, ethambutol and pyrazinamide; continuation phase- 16 weeks of rifampicin and isoniazid). Primary outcome measures were microbiological cure and safety at the end of six months' treatment; pre-specified non-inferiority margin for difference in cure rate was 4%. The primary efficacy analysis was based on the modified intent to treat (mITT) cohort comprising all randomized patients with a positive baseline culture result for TB and who received at least one dose of study treatment. Patients missing end of treatment culture results were considered failures. Further analyses were done in which mITT patients without an end of treatment (EOT) culture were excluded in a complete case analysis (mITTcc) and a per protocol cohort analysis defined as mITTcc patients who received at least 95% of their intended doses and had an EOT culture result. RESULTS: In the mITT analysis, the cure rate in the FDC group was 86.7% (398/459) and in the LF group 85.2% (396/465) (difference 1.5-% (90% confidence interval (CI) (-2.2%- 5.3%)). Per Protocol analysis showed similar results: FDC 98.9% (359/363) versus LF 96.9% (345/356), (difference 2.0% (90% CI: 0.1%- 3.8%)). The two arms showed no significant differences in terms of safety, early culture conversion and patient adherence to treatment. INTERPRETATION: The comparison of the two drug regimens satisfied the pre-specified non-inferiority criterion. Our results support the WHO recommendations for the use of FDC in the context of actual medical practice within health services in high TB-endemic countries. TRIAL REGISTRATION: ISRCTN Registry 95204603.

Impact of tuberculosis treatment and antiretroviral therapy on serial RD-1-specific quantitative T-cell readouts (QuantiFERON-TB Gold In-Tube), and relationship to treatment-related outcomes and bacterial burden.

BACKGROUND: The impact of anti-tuberculosis treatment with and without antiretroviral therapy (ART) on standardized interferon gamma release assay (IGRA) readouts has been studied inadequately in high-burden countries. METHODS: The QuantiFERON-TB Gold In-Tube (QFT-GIT) test was used to evaluate interferon gamma (IFN-γ) responses longitudinally (0, 3, 6, and 12 months post initiation of tuberculosis (TB)-HIV co-treatment or ART alone) in 82 HIV-infected patients. RESULTS: Of the 65 evaluable participants, 30 were co-infected on ART, 17 were co-infected but not on ART, and 18 were HIV-infected alone and on ART. In HIV-infected and HIV-TB-infected patients on ART, IFN-γ responses increased, whilst they decreased in those not on ART. However, baseline, month 3, and month 6 IFN-γ responses, irrespective of ART, did not differ in TB-HIV co-infected patients who culture-converted compared to those who did not (1.25 vs. 1.05, p=0.5 at baseline; 3.76 vs. 1.15, p=0.2 for month 3; 0.06 vs. 0.7, p=0.3 for month 6). IFN-γ levels did not correlate with the magnitude of sputum bacillary load, smear status, or liquid culture time-to-positivity. CONCLUSION: As IGRAs do not correlate with 2- or 6-month culture conversion or with markers of bacillary burden, they are unlikely to be useful for the prognostication of treatment outcome in co-infected patients.

A 24-well plate assay for simultaneous testing of first and second line drugs against Mycobacterium tuberculosis in a high endemic setting.

BACKGROUND: Early detection of drug resistance is one of the priorities of tuberculosis (TB) control programs as drug resistance is increasing. New molecular assays are only accessible for a minority of the second line drugs and their availability in high endemic settings is also hampered by high cost and logistic challenges. Therefore, we evaluated a previously developed method for drug susceptibility testing (DST) including both first- and second line anti-TB drugs for use in high endemic areas. RESULTS: Baseline mycobacterial isolates from 78 consecutive pulmonary TB patients from Addis Ababa, Ethiopia who were culture positive for Mycobacterium tuberculosis at the end of a two-month directly observed treatment short course (DOTS) were included. The isolates were simultaneously tested for isoniazid, rifampicin, ethambutol, streptomycin, amikacin, kanamycin, capreomycin, ofloxacin, moxifloxacin, ethionamide and para-aminosalicylic acid susceptibility using the indirect proportion method adopted for 24-well agar plates containing Middlebrook 7H10 medium. Applying the 24-well plate assay, 43 (55.1%) isolates were resistant to one or more of the first line drugs tested (isoniazid, rifampicin and ethambutol). MDR-TB was identified in 20.5% of this selected group and there was a perfect correlation for rifampicin resistance with the results from the genotype MTBDRplus assay. All isolates were susceptible to aminoglycosides and fluoroquinolones in agreement with the genotype MTBDRsl assay. The only tested second line drug associated to resistance was ethionamide (14.1% resistant). The method was reproducible with stable results for internal controls (one multi-drug resistant (MDR) and one pan-susceptible strain (H37Rv) and DST results could be reported at two weeks. CONCLUSIONS: The 24-well plate method for simultaneous DST for first- and second line drugs was found to be reproducible and correlated well to molecular drug susceptibility tests. It is likely to be useful in high-endemic areas for surveillance as well as for the detection of second line drug resistance in targeted groups such as in those who fail empirical MDR treatment.

Early versus delayed initiation of highly active antiretroviral therapy for HIV-positive adults with newly diagnosed pulmonary tuberculosis (TB-HAART): a prospective, international, randomised, placebo-controlled trial.

BACKGROUND: WHO guidelines recommend early initiation of antiretroviral therapy (ART) irrespective of CD4 cell count for all patients with tuberculosis who also have HIV, but evidence supporting this approach is poor quality. We assessed the effect of timing of ART initiation on tuberculosis treatment outcomes for HIV-positive patients with CD4 counts of 220 cells per µL or more. METHODS: We did this randomised, placebo-controlled trial between Jan 1, 2008, and April 31, 2013 at 26 treatment centres in South Africa, Tanzania, Uganda, and Zambia. We enrolled HIV-positive patients with culture-confirmed tuberculosis who had tolerated 2 weeks of tuberculosis short course chemotherapy. Participants were randomly allocated (1:1) to early ART (starting after 2 weeks of tuberculosis treatment) or delayed ART (placebo, then starting ART at the end of 6 months of tuberculosis treatment). Randomisation was computer generated, with permuted blocks of size eight, and stratified by CD4 count (220-349 cells per µL vs ≥350 cells per µL). Patients and investigators were masked to treatment allocation until completion of 6-months' tuberculosis treatment, after which the study was open label. The primary endpoint was a composite of failure of tuberculosis treatment, tuberculosis recurrence, and death within 12 months of starting tuberculosis treatment in the modified intention-to-treat population. Secondary endpoints included mortality. The study is registered with controlled-trials.com (ISRCTN77861053). FINDINGS: We screened 13,588 patients and enrolled 1675: 834 assigned early ART, 841 delayed ART. The primary endpoint was reached by 65 (8·5%) of 767 patients in the early ART group versus 71 (9·2%) of 771 in the delayed ART group (relative risk [RR] 0·91, 95% CI 0·64-1·30; p=0·9). Of patients with a CD4 cell count of 220-349 cells per µL, 26 (7·9%) of 331 patients versus 33 (9·6%) of 342 reached the primary endpoint (RR 0·80, 95% CI 0·46-1·39; p=0·6). For those with 350 cells per µL or more, 39 (8·9%) of 436 versus 38 (8·9%) of 429 reached the primary endpoint (RR 1·01, 95% CI 0·63-1·62; p=0·4). Mortality did not differ significantly between treatment groups (RR 1·4, 95% CI 0·8-2·3; p=0·23). Grade 3 and 4 adverse events occurred in 149 (18%) of 834 patients assigned early ART versus 174 (21%) of 841 assigned delayed ART (p=0·37). 87 (10%) of 834 versus 84 (10%) of 841 had immune reconstitution inflammatory syndrome (p=0·56). INTERPRETATION: ART can be delayed until after completion of 6 months of tuberculosis treatment for HIV-positive patients with tuberculosis who have CD4 cell counts greater than 220 cells per µL. WHO guidelines should be updated accordingly. FUNDING: USAID, Zambia Ministry of Health, Tanzania Commission for Science and Technology, WHO-TDR.