Kasha Singh

Metabolic regulation of hepatitis B immunopathology by myeloid-derived suppressor cells

Infection with hepatitis B virus (HBV) results in disparate degrees of tissue injury: the virus can either replicate without pathological consequences or trigger immune-mediated necroinflammatory liver damage. We investigated the potential for myeloid-derived suppressor cells (MDSCs) to suppress T cell–mediated immunopathology in this setting. Granulocytic MDSCs (gMDSCs) expanded transiently in acute resolving HBV, decreasing in frequency prior to peak hepatic injury. In persistent infection, arginase-expressing gMDSCs (and circulating arginase) increased most in disease phases characterized by HBV replication without immunopathology, whilst L-arginine decreased. gMDSCs expressed liver-homing chemokine receptors and accumulated in the liver, their expansion supported by hepatic stellate cells. We provide in vitro and ex vivo evidence that gMDSCs potently inhibited T cells in a partially arginase-dependent manner. L-arginine–deprived T cells upregulated system L amino acid transporters to increase uptake of essential nutrients and attempt metabolic reprogramming. These data demonstrate the capacity of expanded arginase-expressing gMDSCs to regulate liver immunopathology in HBV infection.

Expanding Access to Treatment for Hepatitis C in Resource-Limited Settings: Lessons From HIV/AIDS

The need to improve access to care and treatment for chronic hepatitis C virus (HCV) infection in resource-limited settings is receiving increasing attention. Key priorities for scaling up HCV treatment and care include reducing the cost of current and future treatment; simplifying the package of care; identifying opportunities to shift specific tasks to nonspecialists to overcome human resource constraints; service integration with human immunodeficiency virus (HIV) clinics, prison health services, and needle syringe and oral substitution therapy programs; improving surveillance, monitoring, and research; encouraging patient and community engagement; focusing specifically on the needs of vulnerable groups; and increasing financial and political commitment. Many of these obstacles have been addressed in rolling out treatment for human immunodeficiency virus during the last decade, and a number of lessons can be drawn to help improve access to HCV care.

Assessment of the sensitivity and specificity of Xpert MTB/RIF assay as an early sputum biomarker of response to tuberculosis treatment

BACKGROUND An accurate biomarker is urgently needed to monitor the response to treatment in patients with pulmonary tuberculosis. The Xpert MTB/RIF assay is a commercially available real-time PCR that can be used to detect Mycobacterium-tuberculosis-specific DNA sequences in sputum samples. We therefore evaluated this assay with serial sputum samples obtained over 26 weeks from patients undergoing treatment for tuberculosis. METHODS We analysed sputum samples from 221 patients with smear-positive tuberculosis enrolled at two sites (Cape Town, South Africa, and Mbeya, Tanzania) of a multicentre randomised clinical trial REMoxTB of antituberculosis treatment on a weekly basis (weeks 0 to 8), then at weeks 12, 17, 22, and 26 after treatment initiation. The Xpert MTB/RIF results over time were compared with the results of standard smear microscopy and culture methods. FINDINGS We obtained and analysed 2741 sputum samples from 221 patients. The reduction in positivity rates with Xpert MTB/RIF were slower than those with the standard methods. At week 8, positive results were obtained for 62 (29%) of 212 sputum samples with smear microscopy, 46 (26%) of 175 with solid culture (Löwenstein-Jensen medium), 77 (42%) of 183 with liquid culture (Bactec MGIT960 system), and 174 (84%) of 207 with Xpert MTB/RIF; at 26 weeks, positive results were obtained for ten (5%) of 199, four (3%) of 157, seven (4%) of 169, and 22 (27%) of 83 sputum samples, respectively. The reduction in detection of quantitative M tuberculosis DNA with Xpert MTB/RIF correlated with smear grades (ρ=-0·74; p<0·0001), solid culture grades (ρ=-0·73; p<0·0001), and time to liquid culture positivity (ρ=0·73; p<0·0001). Compared with the combined binary smear and culture results as a reference standard, the Xpert MTB/RIF assay had high sensitivity (97·0%, 95% CI 95·8-97·9), but poor specificity (48·6%, 45·0-52·2). INTERPRETATION The poor specificity precludes the use of the Xpert MTB/RIF assay as a biomarker for monitoring tuberculosis treatment, and should not replace standard smear microscopy and culture. FUNDING Global Alliance for TB Drug Development, Bill & Melinda Gates Foundation, UK Medical Research Council, German Ministry of Science and Technology.

Chronic hepatitis C treatment outcomes in low- and middle-income countries: a systematic review and meta-analysis

OBJECTIVE To assess the effectiveness of treatment for hepatitis C virus (HCV) infection in low- and middle-income countries and identify factors associated with successful outcomes. METHODS We performed a systematic review and meta-analysis of studies of HCV treatment programmes in low- and middle-income countries. The primary outcome was a sustained virological response (SVR). Factors associated with treatment outcomes were identified by random-effects meta-regression analysis. FINDINGS The analysis involved data on 12 213 patients included in 93 studies from 17 countries. The overall SVR rate was 52% (95% confidence interval, CI: 48-56). For studies in which patients were predominantly infected with genotype 1 or 4 HCV, the pooled SVR rate was 49% (95% CI: 43-55). This was significantly lower than the rate of 59% (95% CI: 54-64) found in studies in which patients were predominantly infected with other genotypes (P = 0.012). Factors associated with successful outcomes included treatment with pegylated interferon and ribavirin, infection with an HCV genotype other than genotype 1 or 4 and the absence of liver damage or human immunodeficiency virus infection at baseline. No significant difference in the SVR rate was observed between weight-adjusted and fixed-dose ribavirin treatment. Overall, 17% (95% CI: 13-23) of adverse events resulted in treatment interruption or dose modification, but only 4% (95% CI: 3-5) resulted in treatment discontinuation. CONCLUSION The outcomes of treatment for HCV infection in low- and middle-income countries were similar to those reported in high-income countries.

Causes of false-positive HIV rapid diagnostic test results

HIV rapid diagnostic tests have enabled widespread implementation of HIV programs in resource-limited settings. If the tests used in the diagnostic algorithm are susceptible to the same cause for false positivity, a false-positive diagnosis may result in devastating consequences. In resource-limited settings, the lack of routine confirmatory testing, compounded by incorrect interpretation of weak positive test lines and use of tie-breaker algorithms, can leave a false-positive diagnosis undetected. We propose that heightened CD5+ and early B-lymphocyte response polyclonal cross-reactivity are a major cause of HIV false positivity in certain settings; thus, test performance may vary significantly in different geographical areas and populations. There is an urgent need for policy makers to recognize that HIV rapid diagnostic tests are screening tests and mandate confirmatory testing before reporting an HIV-positive result. In addition, weak positive results should not be recognized as valid except in the screening of blood donors.

Treatment Outcomes of Treatment-Naïve Hepatitis C Patients Co-Infected with HIV: A Systematic Review and Meta-Analysis of Observational Cohorts

Introduction Co-infection with Hepatitis C (HCV) and HIV is common and HIV accelerates hepatic disease progression due to HCV. However, access to HCV treatment is limited and success rates are generally poor. Methods We conducted a systematic review and meta-analysis to assess HCV treatment outcomes in observational cohorts. Two databases (Medline and EMBASE) were searched using a compound search strategy for cohort studies reporting HCV treatment outcomes (as determined by a sustained virological response, SVR) in HIV-positive patients initiating HCV treatment for the first time. Results 40 studies were included for review, providing outcomes on 5339 patients from 17 countries. The pooled proportion of patients achieving SVR was 38%. Significantly poorer outcomes were observed for patients infected with HCV genotypes 1 or 4 (pooled SVR 24.5%), compared to genotypes 2 or 3 (pooled SVR 59.8%). The pooled proportion of patients who discontinued treatment due to drug toxicities (reported by 33 studies) was low, at 4.3% (3.3–5.3%). Defaulting from treatment, reported by 33 studies, was also low (5.1%, 3.5–6.6%), as was on-treatment mortality (35 studies, 0.1% (0–0.2%)). Conclusions These results, reported under programmatic conditions, are comparable to those reported in randomised clinical trials, and show that although HCV treatment outcomes are generally poor in HIV co-infected patients, those infected with HCV genotypes 2 or 3 have outcomes comparable to HIV-negative patients.

XDR-TB, what is it; how is it treated; and why is therapeutic failure so high?

Drug resistance is a major hurdle in the global battle against tuberculosis (TB). In tackling this problem it is important to understand both how resistance emerges as well as the ways in which multi-drug and extensively drug-resistant TB (M/XDR-TB) may be successfully treated. The biggest problem with treatment is the lack of effective drugs. Exciting developments have been made in this area over recent years with useful drugs being found from older agents as well as new discoveries. Patent applications are being made for novel agents and are also possible as new use for older agents such as thioridazine. A flourishing drug pipeline is critical if we are to make progress in the management of M/XDR-TB.

The two-edged sword: vasculitis associated with HIV and hepatitis C coinfection

Vasculitis has long been associated with chronic viral infections, thus the twin perils of the infection and the immune response against it that bedevils the specialties of infection and immunity. After HIV was identified, it too became associated with vasculitic syndromes. Later, hepatitis C virus was also isolated, identified and described with its own spectrum of vasculitic diseases, including hepatitis C virus-associated cryoglobulinaemia. With the increasing prevalence of HIV and hepatitis C virus coinfection, there has come an increasing recognition of the range of vasculitides that can occur in this population leading to significant morbidity, diagnostic and treatment challenges. In this review, we examine the epidemiology, pathogenesis and general principles of treatment of these systemic diseases in HIV/hepatitis C virus coinfected individuals.

Moxifloxacin for tuberculosis

We believe Helen Cox and colleagues’ proposal to restrict moxifl oxacin use to multidrug-resistant tuberculosis is based on fl awed logic. In a clinical trial of the present fi rst-line regimen for drug-susceptible tuberculosis, cure rates were greater than 95% and no new regimen is likely to improve on this rate. However, reducing treatment duration with moxifl oxacincontaining regimens would lead to a decreased risk of default and consequent drug resistance. Moxifl oxacin-containing regimens render sputum cultures sterile more rapidly than standard therapy, and so reduce onward transmission. A resultant decline in incident cases has been estimated by modelling studies. Cox and colleagues suggest that reserving moxifl oxacin for use in drugresistant tuberculosis will decrease future drug resistance. Restriction might be feasible in government programmes but is unrealistic in private practice, which is a common setting for tuberculosis treatment in countries with a high tuberculosis burden, including India. Furthermore, that all drugs in this class can be restricted is unlikely because of their widespread use and low cost. Those drugs with poorer anti-tuberculosis activity are more likely to select for resistance—for example, exposure to subinhibitory ciprofl oxacin concentrations increased mycobacterial mutation rates by up to 200 times compared with the rates without the antibiotic. Cross-resistance among fl uoroquinolones is common. Therefore, restriction of one drug in the class would not achieve a useful result. Cox and colleagues note that treatment-shortening trials are underway, and we advocate that patients with uncomplicated susceptible disease should not be treated with moxifl oxacin until results of these trials are known. In cases of drug resistance or poor tolerance, fl uoroquinolones should be used only in settings where susceptibility results are available to prevent the risk of increasing resistance.

TRAIL regulatory receptors constrain human hepatic stellate cell apoptosis

The TRAIL pathway can mediate apoptosis of hepatic stellate cells to promote the resolution of liver fibrosis. However, TRAIL has the capacity to bind to regulatory receptors in addition to death-inducing receptors; their differential roles in liver fibrosis have not been investigated. Here we have dissected the contribution of regulatory TRAIL receptors to apoptosis resistance in primary human hepatic stellate cells (hHSC). hHSC isolated from healthy margins of liver resections from different donors expressed variable levels of TRAIL-R2/3/4 (but negligible TRAIL-R1) ex vivo and after activation. The apoptotic potential of TRAIL-R2 on hHSC was confirmed by lentiviral-mediated knockdown. A functional inhibitory role for TRAIL-R3/4 was revealed by shRNA knockdown and mAb blockade, showing that these regulatory receptors limit apoptosis of hHSC in response to both oligomerised TRAIL and NK cells. A close inverse ex vivo correlation between hHSC TRAIL-R4 expression and susceptibility to apoptosis underscored its central regulatory role. Our data provide the first demonstration of non-redundant functional roles for the regulatory TRAIL receptors (TRAIL-R3/4) in a physiological setting. The potential for these inhibitory TRAIL receptors to protect hHSC from apoptosis opens new avenues for prognostic and therapeutic approaches to the management of liver fibrosis.