AAV-mediated intramuscular delivery of myotubularin corrects the myotubular myopathy phenotype in targeted murine muscle and suggests a function in plasma membrane homeostasis

Myotubular myopathy (XLMTM, OMIM 310400) is a severe congenital muscular disease due to mutations in the myotubularin gene (MTM1) and characterized by the presence of small myofibers with frequent occurrence of central nuclei. Myotubularin is a ubiquitously expressed phosphoinositide phosphatase with a muscle-specific role in man and mouse that is poorly understood. No specific treatment exists to date for patients with myotubular myopathy. We have constructed an adeno-associated virus (AAV) vector expressing myotubularin in order to test its therapeutic potential in a XLMTM mouse model. We show that a single intramuscular injection of this vector in symptomatic Mtm1-deficient mice ameliorates the pathological phenotype in the targeted muscle. Myotubularin replacement in mice largely corrects nuclei and mitochondria positioning in myofibers and leads to a strong increase in muscle volume and recovery of the contractile force. In addition, we used this AAV vector to overexpress myotubularin in wild-type skeletal muscle and get insight into its localization and function. We show that a substantial proportion of myotubularin associates with the sarcolemma and I band, including triads. Myotubularin overexpression in muscle induces the accumulation of packed membrane saccules and presence of vacuoles that contain markers of sarcolemma and T-tubules, suggesting that myotubularin is involved in plasma membrane homeostasis of myofibers. This study provides a proof-of-principle that local delivery of an AAV vector expressing myotubularin can improve the motor capacities of XLMTM muscle and represents a novel approach to study myotubularin function in skeletal muscle

Delayed Sputum Culture Conversion in Tuberculosis-Human Immunodeficiency Virus-Coinfected Patients With Low Isoniazid and Rifampicin Concentrations

Background The relationship between concentrations of anti-tuberculosis (TB) drugs, sputum conversion and treatment outcome remains unclear. We sought to determine the association between anti-TB drug concentrations and sputum conversion among TB-HIV co-infected patients on first-line anti-TB drugs. Method We enrolled HIV-infected Ugandans with pulmonary TB. Estimation of first-line anti-TB drug concentrations was performed 1, 2, and 4 hours after drug intake at 2, 8, and 24 weeks of TB treatment. Serial sputum cultures were performed at each visit. Time-to-event analysis was used to determine factors associated with sputum culture conversion. Results We enrolled 268 HIV-infected patients. Patients with low isoniazid and rifampicin concentrations were less likely to have sputum culture conversion before the end of TB treatment or by the end of follow-up; Hazard ratio (HR) 0.54: 95% confidence interval (CI): 0.37-0.77, P=0.001 and HR: 0.61, 95% CI: 0.44-0.85, P=0.003, respectively. Patients in the highest AUC quartile for rifampicin and isoniazid were approximately two times more likely to experience sputum conversion. Rifampicin and isoniazid concentrations below the thresholds and being in a weight band <55kg were both risk factors for unfavorable TB treatment outcomes. Only 4.4% of the participants had treatment failure. Conclusion Although low anti-TB drug concentrations did not translate to a high proportion of patients with treatment failure, the association between low concentrations of rifampicin and isoniazid and delayed culture conversion may have implications on TB transmission

Delayed sputum culture conversion in tuberculosis-human immunodeficiency virus-coinfected patients with low isoniazid and rifampicin concentrations

Background. The relationship between concentrations of antituberculosis drugs, sputum culture conversion, and treatment outcome remains unclear. We sought to determine the association between antituberculosis drug concentrations and sputum conversion among patients coinfected with tuberculosis and human immunodeficiency virus (HIV) and receiving first-line antituberculosis drugs. Methods. We enrolled HIV-infected Ugandans with pulmonary tuberculosis. Estimation of first-line antituberculosis drug concentrations was performed 1, 2, and 4 hours after drug intake at 2, 8, and 24 weeks of tuberculosis treatment. Serial sputum cultures were performed at each visit. Time-to-event analysis was used to determine factors associated with sputum culture conversion. Results. We enrolled 268 HIV-infected patients. Patients with low isoniazid and rifampicin concentrations were less likely to have sputum culture conversion before the end of tuberculosis treatment (hazard ratio, 0.54; 95% confidence interval, .37–.77; P = .001) or by the end of follow-up (0.61; .44–.85; P = .003). Patients in the highest quartile for area under the rifampicin and isoniazid concentration-time curves for were twice as likely to experience sputum conversion than those in the lowest quartile. Rifampicin and isoniazid concentrations below the thresholds and weight <55 kg were both risk factors for unfavorable tuberculosis treatment outcomes. Only 4.4% of the participants had treatment failure. Conclusion. Although low antituberculosis drug concentrations did not translate to a high proportion of patients with treatment failure, the association between low concentrations of rifampicin and isoniazid and delayed culture conversion may have implications for tuberculosis transmission