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Monocyte Transcriptional Networks are Associated with Tuberculin Skin Test Status in Uganda

ABSTRACT: Understanding mechanisms of resistance to M. tuberculosis (M.tb) infection in humans could identify novel therapeutic strategies as it has for other infectious diseases. We hypothesized that monocytes from household contacts of pulmonary tuberculosis patients that failed to convert their tuberculin skin tests (TSTNEG) would respond differently to M.tb infection when compared to matched tuberculin skin test positive controls (TSTPOS). We obtained genome-wide transcriptional profiles of M.tb-infected peripheral blood monocytes from 10 TSTNEG and 18 TSTPOS Ugandans. We used Gene Set Enrichment Analysis and interaction networks to identify cellular processes associated with TST status. We discovered gene sets associated with histone deacetylases that were differentially expressed when comparing TSTPOS and TSTNEG subjects. We used small molecule inhibitors to demonstrate that histone deacetylase function is important for the pro-inflammatory response to M.tb infection in monocytes. Monocytes from individuals who appear to resist M.tb infection differentially activate pathways controlled by histone deacetylase in response to M.tb infection when compared to those who are susceptible to infection. These data identify a potential cellular mechanism underlying the clinical phenomenon of persistently negative tuberculin skin tests despite known exposure to an infectious contact.

ORGANISM(S): Homo sapiens

PROVIDER: GSE76873 | GEO | 2016/01/15

SECONDARY ACCESSION(S): PRJNA308835

REPOSITORIES: GEO

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Project description:Understanding mechanisms of resistance to M. tuberculosis (M.tb) infection in humans could identify novel therapeutic strategies as it has for other infectious diseases. We hypothesized that monocytes from household contacts of pulmonary tuberculosis patients that failed to convert their tuberculin skin tests (TSTNEG) would respond differently to M.tb infection when compared to matched tuberculin skin test positive controls (TSTPOS). We obtained genome-wide transcriptional profiles of M.tb-infected peripheral blood monocytes from 10 TSTNEG and 18 TSTPOS Ugandans. We used Gene Set Enrichment Analysis and interaction networks to identify cellular processes associated with TST status. We discovered gene sets associated with histone deacetylases that were differentially expressed when comparing TSTPOS and TSTNEG subjects. We used small molecule inhibitors to demonstrate that histone deacetylase function is important for the pro-inflammatory response to M.tb infection in monocytes. Monocytes from individuals who appear to resist M.tb infection differentially activate pathways controlled by histone deacetylase in response to M.tb infection when compared to those who are susceptible to infection. These data identify a potential cellular mechanism underlying the clinical phenomenon of persistently negative tuberculin skin tests despite known exposure to an infectious contact. CD14+ monocytes from 18 TSTPOS and 10 TSTNEG subjects were isolated by positive selection. Depending on the yield, between 5E5 and 1E6 monocytes were plated in duplicate in a 24-well tissue culture plate and rested overnight at 37oC, 5% CO2. The next day, cells were mock-infected or infected with virulent M. tuberculosis strain H37Rv at a multiplicity of infection (MOI) 10:1. After a six hour incubation at 37C, 5% CO2, the mycobacteria were killed and total RNA harvested using TRIzol-LS (Invitrogen). TRIzol samples were stored at -80oC until all infections were completed. To minimize batch effects, equal numbers of TSTPOS and TSTNEG subjects were processed on each of six days and frozen aliquots of M.tb were used for infections. RNA was extracted using the RNeasy Mini Kit with on-column DNAse digestion. RNA was transcribed into complementary DNA, labeled, and hybridized onto Illumina HT-12 microarrays according to the manufacturerâs instructions. Probe intensities were quantified using Illumina iScan platform and processed using BeadArray without performing normalization or background correction.

Project description:The aim of the project was to define transcriptional signatures in whole blood of TB patients (before drug treatment) and healthy controls to distinguish the signature of Latent and Active TB patients from each other and from healthy controls. This will help in diagnosis of active tuberculosis which normally relies on culture of the bacilli, which can take up to 6 wks, and sometimes the bacilli cannot be obtained from sputum thus requiring invasive techniques obtaining bronchoalveolar lavage (BAL). In some cases the bacill cannot be grown from sputum or BAL. Secondly the aim was to determine whether Latent patients have a homogeneous or heterogeneous signature, one may expect the latter since it is not possible to determine by the present tests (Tuberculin skin test - TST - or MTb antigen responsiveness of blood cells to produce IFN-gamma - IGRA assay) whether the mycobacteria has been cleared, is still present but is controlled, or if patients are recently infected or reactivated and will develop active TB. The latter situation may be determined if Latent patients have a blood transcriptional signature similar to that in Active patients. The transcriptional signature in Active TB patients may also provide information as to the factors leading to immunopathogenesis, thus possibly identifying therapeutic targets. The transcriptional profile in Latent TB may give information as to the protective factors controlling the infection, thus important for monitoring vaccine development. A further aim was to examine the transcriptional blood profile of active TB patients at the time of recruitment (before drug treatment) and then subsequently at specific time points after drug treatment to determine whether the signature is extingsuihed with treatment and when. London is a site of intermediate burden of TB - the study was initiated in London, across a broad range of ethnicities to obtain a robust signature that could be used in different developing countries where there is a high burden TB disease. Experimental design : Whole blood collected in tempus tubes from patients with different spectra of TB disease and healthy controls. All patients were sampled prior to the initiation of any antimycobacterial therapy. Active Pulmonary TB: PTB - All patients confirmed by isolation of Mycobacterium Tuberculosis on culture of sputum or bronchoalvelolar lavage fluid. Latent TB: LTB - All patients were screened at a tuberculosis clinic, being either new entrants to the UK from endemic countries or being household contacts of infectious cases. All were positive by tuberculin skin test (>14mm if BCG vaccinated, >5mm if not vaccinated) and were also positive by Interferon-Gamma Release assay(IGRA); specifically Quantiferon Gold In-Tube Assay (Cellestis, Australia). Latent patients had no clinical, radiological or microbiological evidence of active infection and were asymptomatic. Healthy controls - these were volunteers without exposure to TB who were negative by both tuberculin skin test (<15mm if BCG vaccinated, <6mm if unvaccinated); who were also negative by IGRA (as described above). In this dataset: PTB n= 13; LTB n = 17; BCG+ n = 6, BCG-, n =6. Experimental variables : Patient group: Active PTB; Latent TB, Healthy controls (BCG vaccinated and unvaccinated). ethnicity - a wide range of ethnic groups is represented. However all controls in this dataset are broadly Caucasian/White. The active PTB group incorporates a range of smear positive and smear negative disease and a spectrum of disease extent/severity.

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Monocyte Transcriptional Networks are Associated with Tuberculin Skin Test Status in Uganda

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