A blood RNA signature for tuberculosis disease risk: a prospective cohort study.

BACKGROUND: Identification of blood biomarkers that prospectively predict progression of Mycobacterium tuberculosis infection to tuberculosis disease might lead to interventions that combat the tuberculosis epidemic. We aimed to assess whether global gene expression measured in whole blood of healthy people allowed identification of prospective signatures of risk of active tuberculosis disease. METHODS: In this prospective cohort study, we followed up healthy, South African adolescents aged 12-18 years from the adolescent cohort study (ACS) who were infected with M tuberculosis for 2 years. We collected blood samples from study participants every 6 months and monitored the adolescents for progression to tuberculosis disease. A prospective signature of risk was derived from whole blood RNA sequencing data by comparing participants who developed active tuberculosis disease (progressors) with those who remained healthy (matched controls). After adaptation to multiplex quantitative real-time PCR (qRT-PCR), the signature was used to predict tuberculosis disease in untouched adolescent samples and in samples from independent cohorts of South African and Gambian adult progressors and controls. Participants of the independent cohorts were household contacts of adults with active pulmonary tuberculosis disease. FINDINGS: Between July 6, 2005, and April 23, 2007, we enrolled 6363 participants from the ACS study and 4466 from independent South African and Gambian cohorts. 46 progressors and 107 matched controls were identified in the ACS cohort. A 16 gene signature of risk was identified. The signature predicted tuberculosis progression with a sensitivity of 66·1% (95% CI 63·2-68·9) and a specificity of 80·6% (79·2-82·0) in the 12 months preceding tuberculosis diagnosis. The risk signature was validated in an untouched group of adolescents (p=0·018 for RNA sequencing and p=0·0095 for qRT-PCR) and in the independent South African and Gambian cohorts (p values <0·0001 by qRT-PCR) with a sensitivity of 53·7% (42·6-64·3) and a specificity of 82·8% (76·7-86) in the 12 months preceding tuberculosis. INTERPRETATION: The whole blood tuberculosis risk signature prospectively identified people at risk of developing active tuberculosis, opening the possibility for targeted intervention to prevent the disease. FUNDING: Bill & Melinda Gates Foundation, the National Institutes of Health, Aeras, the European Union, and the South African Medical Research Council

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D3)

AbstractMatrix assisted laser desorption ionization (MALDI) was used to study the organolithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D3) in a mixed solvent system. The mass spectral peak intensities were monitored to determine the effects of polymerization time, initiator concentration, and reaction temperature on the formation of the mono, di, and trisiloxanolate initiator species and the extent of chain redistribution. The three initiator species were formed by reacting n-butyllithium and sec-butyllithium with D3 in nonpolar solvent. The mass spectral results showed that sec-butyllithium and n-butyllithium form different populations of initiator species under the same conditions and that the measured mass spectral peak intensities do not accurately represent the population of siloxanolate initiator species prior to propagation. The changes in peak intensities were attributed to chain redistribution

Construction of a Versatile High Precision Ambient Ionization Source for Direct Analysis and Imaging

The design and construction of a high precision ambient ionization source matrix-assisted laser desorption electrospray ionization (MALDESI) are described in full detail, including a complete parts list. The computer controlled high precision motion control system and high repetition rate Explorer laser are demonstrated during MALDESI-FT-ICR analysis of peptides and proteins ranging from 1 to 17 kDa. The high stability ionization source platform described herein demonstrates both the advantages of the new MALDESI source and versatility for application to numerous desorption and ionization techniques

Remote Mass Spectrometric Sampling of Electrospray- and Desorption Electrospray-Generated Ions Using an Air Ejector

A commercial air ejector was coupled to an electrospray ionization linear ion trap mass spectrometer (LTQ) to transport remotely generated ions from both electrospray (ESI) and desorption electrospray ionization (DESI) sources. We demonstrate the remote analysis of a series of analyte ions that range from small molecules and polymers to polypeptides using the AE-LTQ interface. The details of the ESI-AE-LTQ and DESI-AE-LTQ experimental configurations are described and preliminary mass spectrometric data are presented