G. Narendran

Diagnosis & treatment of tuberculosis in HIV co-infected patients

Human immunodeficiency virus (HIV) associated tuberculosis (TB) remains a major global public health challenge, with an estimated 1.4 million patients worldwide. Co-infection with HIV leads to challenges in both the diagnosis and treatment of tuberculosis. Further, there has been an increase in rates of drug resistant tuberculosis, including multi-drug (MDR-TB) and extensively drug resistant TB (XDRTB), which are difficult to treat and contribute to increased mortality. Because of the poor performance of sputum smear microscopy in HIV-infected patients, newer diagnostic tests are urgently required that are not only sensitive and specific but easy to use in remote and resource-constrained settings. The treatment of co-infected patients requires antituberculosis and antiretroviral drugs to be administered concomitantly; challenges include pill burden and patient compliance, drug interactions, overlapping toxic effects, and immune reconstitution inflammatory syndrome. Also important questions about the duration and schedule of anti-TB drug regimens and timing of antiretroviral therapy remain unanswered. From a programmatic point of view, screening of all HIV-infected persons for TB and vice-versa requires good co-ordination and communication between the TB and AIDS control programmes. Linkage of co-infected patients to antiretroviral treatment centres is critical if early mortality is to be prevented. We present here an overview of existing diagnostic strategies, new tests in the pipeline and recommendations for treatment of patients with HIV-TB dual infection.

Efficacy of a 6-month versus 9-month intermittent treatment regimen in HIV-infected patients with tuberculosis a randomized clinical trial.

RATIONALE The outcome of fully intermittent thrice-weekly antituberculosis treatment of various durations in HIV-associated tuberculosis is unclear. OBJECTIVES To compare the efficacy of an intermittent 6-month regimen (Reg6M: 2EHRZ(3)/4HR(3) [ethambutol, 1,200 mg; isoniazid, 600 mg; rifampicin, 450 or 600 mg depending on body weight <60 or > or =60 kg; and pyrazinamide, 1,500 mg for 2 mo; followed by 4 mo of isoniazid and rifampicin at the same doses]) versus a 9-month regimen (Reg9M: 2EHRZ(3)/7HR(3)) in HIV/tuberculosis (TB). METHODS HIV-infected patients with newly diagnosed pulmonary or extrapulmonary TB were randomly assigned to Reg6M (n = 167) or Reg9M (n = 160) and monitored by determination of clinical, immunological, and bacteriological parameters for 36 months. Primary outcomes included favorable responses at the end of treatment and recurrences during follow-up, whereas the secondary outcome was death. Intent-to-treat and on-treatment analyses were performed. All patients were antiretroviral treatment-naive during treatment. MEASUREMENTS AND MAIN RESULTS Of the patients, 70% had culture-positive pulmonary TB; the median viral load was 155,000 copies/ml and the CD4(+) cell count was 160 cells/mm(3). Favorable response to antituberculosis treatment was similar by intent to treat (Reg6M, 83% and Reg9M, 76%; P = not significant). Bacteriological recurrences occurred significantly more often in Reg6M than in Reg9M (15 vs. 7%; P < 0.05) although overall recurrences were not significantly different (Reg6M, 19% vs. Reg9M, 13%). By 36 months, 36% of patients undergoing Reg6M and 35% undergoing Reg9M had died, with no significant difference between regimens. All 19 patients who failed treatment developed acquired rifamycin resistance (ARR), the main risk factor being baseline isoniazid resistance. CONCLUSIONS Among antiretroviral treatment-naive HIV-infected patients with TB, a 9-month regimen resulted in a similar outcome at the end of treatment but a significantly lower bacteriological recurrence rate compared with a 6-month thrice-weekly regimen. ARR was high with these intermittent regimens and neither mortality nor ARR was altered by lengthening TB treatment. Clinical Trials Registry Information: ID# NCT00376012 registered at www.clinicaltrials.gov.

Impact of HIV Infection on the Recurrence of Tuberculosis in South India

BACKGROUND There is limited information on the relative proportion of reactivation and reinfection at the time of recurrence among human immunodeficiency virus (HIV)-infected and HIV-uninfected patients who are successfully treated for tuberculosis infection in India. METHODS HIV-infected and HIV-uninfected patients with sputum culture-positive pulmonary tuberculosis were treated with short-course regimens and followed up for 36 months at the Tuberculosis Research Centre, South India. Bacteriologic recurrences were documented, and typing of strains was performed using 3 different genotypic techniques: restriction fragment length polymorphism (RFLP) by IS6110, spoligotyping, and mycobacterial interspersed repeat unit (MIRU)-variable number tandem repeat (VNTR). DNA fingerprints of paired Mycobacterium tuberculosis isolates (baseline and recurrence) were compared. RESULTS Among 44 HIV-infected and 30 HIV-uninfected patients with recurrent tuberculosis during the period July 1999 to October 2005, 25 and 23 paired isolates, respectively, were typed using all 3 methods. Recurrence was due to exogenous reinfection in 88% of HIV-infected and 9% of HIV-uninfected patients (P<.05). Among recurrent isolates, the HIV-infected patients showed more clustering, as well as a higher proportion of drug resistance, including multidrug resistance. CONCLUSIONS In India, a tuberculosis-endemic country, most recurrences after successful treatment of tuberculosis are due to exogenous reinfection in HIV-infected persons and endogenous reactivation in HIV-uninfected persons. Strategies for prevention and treatment of tuberculosis infection must take these findings into consideration.

HIV-Associated Tuberculosis: Clinical Update

The human immunodeficiency virus (HIV) epidemic has led to an increase in the incidence of tuberculosis globally, particularly in sub-Saharan Africa. Coinfection with HIV leads to difficulties in both the diagnosis and treatment of tuberculosis. Because of the poor performance of sputum smear microscopy in HIV-infected patients, more sensitive tests-such as liquid culture systems, nucleic acid amplification assays, and detection of mycobacterial products in various body fluids-are being investigated. The treatment of coinfected patients requires antituberculosis and antiretroviral drugs to be administered concomitantly; challenges include pill burden and patient compliance, drug interactions, overlapping toxic effects, and immune reconstitution syndrome. Both multidrug-resistant and extensively drug-resistant tuberculosis can spread rapidly among an immunocompromised population, with resulting high mortality rates. Current guidelines recommend starting antiretroviral treatment within a few weeks of antituberculosis therapy for patients with CD4 cell counts <350 cells/microL; however, important questions about the drug regimens and timing of antiretroviral therapy remain. Ongoing trials may answer many of these unresolved questions.

CYP2B6 G516T Polymorphism but Not Rifampin Coadministration Influences Steady-State Pharmacokinetics of Efavirenz in Human Immunodeficiency Virus-Infected Patients in South India

ABSTRACT The dose of efavirenz during concomitant rifampin (RMP) administration is a matter of debate. We studied the influence of RMP coadministration on the steady-state pharmacokinetics of efavirenz in human immunodeficiency virus type 1 (HIV-1)-infected patients in South India. Fifty-seven HIV-tuberculosis (TB)-coinfected and 15 HIV-1-infected patients receiving combination antiretroviral therapy (CART) with an efavirenz (600 mg once daily)-containing regimen were recruited. HIV-TB-coinfected patients were receiving treatment with RMP-containing regimens. A complete pharmacokinetic study was conducted with 19 HIV-TB patients on two occasions (with and without RMP). Trough concentrations of efavirenz were measured in the remaining 38 patients during RMP coadministration. The 15 HIV-infected patients underwent complete pharmacokinetic sampling on one occasion. Plasma efavirenz was estimated by high-performance liquid chromatography, and genotyping of CYP2B6 G516T polymorphism was performed by sequencing. Peak and trough concentrations and exposure to efavirenz were significantly higher in TT than in GT and GG genotype patients (P < 0.001). Although RMP coadministration decreased the peak and trough concentrations and exposure to efavirenz by 17.8, 20.4, and 18.6%, respectively, the differences were not statistically significant. The trough concentration of efavirenz was subtherapeutic (less than 1.0 μg/ml) in 6 (8%) of 72 patients. In this South Indian population of HIV-infected patients, CYP2B6 G516T polymorphism but not RMP coadministration significantly influenced the pharmacokinetics of efavirenz; patients with the TT genotype had very high blood levels of efavirenz. While a small proportion of patients had subtherapeutic efavirenz levels, the clinical implications are uncertain, as all had good immunological responses to CART.

HIV and tuberculosis in India.

The global impact of the converging dual epidemics of tuberculosis (TB) and human immunodeficiency virus (HIV) is one of the major public health challenges of our time. The World Health Organization (WHO) reports 9.2 million new cases of TB in 2006 of whom 7.7% were HIV-infected. Tuberculosis is the most common opportunistic infection in HIV-infected patients as well as the leading cause of death. Further, there has been an increase in rates of drug resistant tuberculosis, including multi-drug (MDRTB) and extensively drug resistant TB (XDRTB), which are difficult to treat and contribute to increased mortality. The diagnosis of TB is based on sputum smear microscopy, a 100-year old technique and chest radiography, which has problems of specificity. Extra-pulmonary, disseminated and sputum smear negative manifestations are more common in patients with advanced immunosuppression. Newer diagnostic tests are urgently required that are not only sensitive and specific but easy to use in remote and resource-poor settings. Treatment of HIV-TB co-infection is complex and associated with high pill burden, overlapping drug toxicities, risk of immune reconstitution inflammatory syndrome (IRIS) and challenges related to adherence. From a programmatic point of view, screening of all HIV-infected persons for tuberculosis and vice-versa will help identify co-infected patients who require treatment for both infections. This requires good coordination and communication between the TB and AIDS control programs, in India.

Increasing nevirapine dose can overcome reduced bioavailability due to rifampicin coadministration

Summary: We studied the effect of rifampicin on steady-state pharmacokinetics of nevirapine and the impact of increasing the dose of nevirapine on its peak (Cmax) and trough (Cmin) levels in 13 HIV-infected patients on regular antiretroviral treatment with nevirapine-containing regimens (200 mg twice daily). A baseline pharmacokinetic study was conducted and repeated after 1 week of daily rifampicin (450/600 mg). The study was repeated in 7 of 8 patients who had subtherapeutic Cmin nevirapine levels after increasing nevirapine dose to 300 mg twice daily. Liver function was monitored. Rifampicin caused significant reductions in Cmax (42%), Cmin (53%), and exposure (46%) of nevirapine (P <.01). The Cmin of nevirapine fell below the therapeutic range of 3 &mgr;g/ml in 8 of 13 patients. An increase of nevirapine to 300 mg twice daily raised Cmin to therapeutic range in all 7 patients without exceeding the toxic level of 12 &mgr;g/mL. There were no clinical or laboratory adverse events. Our findings suggest that decreased bioavailability of nevirapine because of rifampicin coadministration could be overcome by increasing the dose of nevirapine from 200 to 300 mg twice daily without short-term adverse events. Further studies to evaluate the long-term safety of higher dose of nevirapine are required.

Efficacy and Safety of Once-Daily Nevirapine- or Efavirenz-Based Antiretroviral Therapy in HIV-Associated Tuberculosis: A Randomized Clinical Trial

BACKGROUND Nevirapine (NVP) can be safely and effectively administered once-daily but has not been assessed in human immunodeficiency virus (HIV)-infected patients with tuberculosis (TB). We studied the safety and efficacy of once-daily NVP, compared with efavirenz (EFV; standard therapy); both drugs were administered in combination with 2 nucleoside reverse-transcriptase inhibitors. METHODS An open-label, noninferiority, randomized controlled clinical trial was conducted at 3 sites in southern India. HIV-infected patients with TB were treated with a standard short-course anti-TB regimen (2EHRZ(3)/4RH(3); [2 months of Ethambutol, Isoniazid, Rifampicin, Pyrazinamide / 4 months of Isoniazid and Rifampicin] thrice weekly) and randomized to receive once-daily EFV at a dose of 600 mg or NVP at a dose of 400 mg (after 14 days of 200 mg administered once daily) with didanosine 250/400 mg and lamivudine 300 mg after 2 months. Sputum smears and mycobacterial cultures were performed every month. CD4+ cell count, viral load, and liver function test results were monitored periodically. Primary outcome was a composite of death, virological failure, default, or serious adverse event (SAE) at 24 weeks. Both intent-to-treat and per protocol analyses were done, and planned interim analyses were performed. RESULTS A total of 116 patients (75% [87 patients] of whom had pulmonary TB), with a mean age of 36 years, a median CD4+ cell count of 84 cells/mm(3), and a median viral load of 310 000 copies/mL, were randomized. At 24 weeks, 50 of 59 patients in the EFV group and 37 of 57 patients in the NVP group had virological suppression (P = .024). There were no deaths, 1 SAE, and 5 treatment failures in the EFV arm, compared with 5 deaths, 2 SAEs, and 10 treatment failures in the NVP arm. The trial was halted by the data and safety monitoring board at the second interim analysis. Favorable TB treatment outcomes were observed in 93% of the patients in the EFV arm and 84% of the patients in the NVP arm (P = .058). CONCLUSIONS Compared with a regimen of didanosine, lamivudine, and EFV, a regimen of once-daily didanosine, lamivudine, and NVP was inferior and was associated with more frequent virologic failure and death. Clinical Trials Registration. NCT00332306.

Mycobacterial Antigen Driven Activation of CD14++CD16- Monocytes Is a Predictor of Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome.

Paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is an aberrant inflammatory response occurring in a subset of TB-HIV co-infected patients initiating anti-retroviral therapy (ART). Here, we examined monocyte activation by prospectively quantitating pro-inflammatory plasma markers and monocyte subsets in TB-HIV co-infected patients from a South Indian cohort at baseline and following ART initiation at the time of IRIS, or at equivalent time points in non-IRIS controls. Pro-inflammatory biomarkers of innate and myeloid cell activation were increased in plasma of IRIS patients pre-ART and at the time of IRIS; this association was confirmed in a second cohort in South Africa. Increased expression of these markers correlated with elevated antigen load as measured by higher sputum culture grade and shorter duration of anti-TB therapy. Phenotypic analysis revealed the frequency of CD14++CD16− monocytes was an independent predictor of TB-IRIS, and was closely associated with plasma levels of CRP, TNF, IL-6 and tissue factor during IRIS. In addition, production of inflammatory cytokines by monocytes was higher in IRIS patients compared to controls pre-ART. These data point to a major role of mycobacterial antigen load and myeloid cell hyperactivation in the pathogenesis of TB-IRIS, and implicate monocytes and monocyte-derived cytokines as potential targets for TB-IRIS prevention or treatment.

Paradoxical Tuberculosis Immune Reconstitution Inflammatory Syndrome (TB-IRIS) in HIV Patients with Culture Confirmed Pulmonary Tuberculosis in India and the Potential Role of IL-6 in Prediction

Background The incidence, manifestations, outcome and clinical predictors of paradoxical TB-IRIS in patients with HIV and culture confirmed pulmonary tuberculosis (PTB) in India have not been studied prospectively. Methods HIV+ patients with culture confirmed PTB started on anti-tuberculosis therapy (ATT) were followed prospectively after anti-retroviral therapy (ART) initiation. Established criteria for IRIS diagnosis were used including decline in plasma HIV RNA at IRIS event. Pre-ART plasma levels of interleukin (IL)-6 and C-reactive protein (CRP) were measured. Univariate and multivariate logistic regression models were used to evaluate associations between baseline variables and IRIS. Results Of 57 patients enrolled, 48 had complete follow up data. Median ATT-ART interval was 28 days (interquartile range, IQR 14–47). IRIS events occurred in 26 patients (54.2%) at a median of 11 days (IQR: 7–16) after ART initiation. Corticosteroids were required for treatment of most IRIS events that resolved within a median of 13 days (IQR: 9–23). Two patients died due to CNS TB-IRIS. Lower CD4+ T-cell counts, higher plasma HIV RNA levels, lower CD4/CD8 ratio, lower hemoglobin, shorter ATT to ART interval, extra-pulmonary or miliary TB and higher plasma IL-6 and CRP levels at baseline were associated with paradoxical TB-IRIS in the univariate analysis. Shorter ATT to ART interval, lower hemoglobin and higher IL-6 and CRP levels remained significant in the multivariate analysis. Conclusion Paradoxical TB–IRIS frequently complicates HIV-TB therapy in India. IL-6 and CRP may assist in predicting IRIS events and serve as potential targets for immune interventions.