Differential gene expression of activating Fcγ receptor classifies active tuberculosis regardless of human immunodeficiency virus status or ethnicity

Abstract

New diagnostics and vaccines for tuberculosis (TB) are urgently needed, but require an understanding of the requirements for protection from/susceptibility to TB. Previous studies have used unbiased approaches to determine gene signatures in single-site populations. The present study utilized a targeted approach, reverse transcriptase multiplex ligation-dependent probe amplification (RT-MLPA), to validate these genes in a multisite study. We analysed ex vivo whole blood RNA from a total of 523 participants across four sub-Saharan countries (Ethiopia, Malawi, South Africa, and The Gambia) with differences in TB and human immunodeficiency virus (HIV) status. We found a number of genes that were expressed at significantly lower levels in participants with active disease than in those with latent TB infection (LTBI), with restoration following successful TB treatment. The most consistent classifier of active disease was FCGR1A (high-affinity IgG Fc receptor 1 (CD64)), which was the only marker expressed at significantly higher levels in participants with active TB than in those with LTBI before treatment regardless of HIV status or genetic background. This is the first study to identify a biomarker for TB that is not affected by HIV status or geo-genetic differences. These data provide valuable clues for understanding TB pathogenesis, and also provide a proof-of-concept for the use of RT-MLPA in rapid and inexpensive validation of unbiased gene expression findings.

Role of B Cells and Antibodies in Acquired Immunity against Mycobacterium tuberculosis

“…This is consistent with the well-established data that Ag-Ab interactions with FcR can modulate the immune response, which has been exploited in the treatment of a variety of diseases, most notably neoplastic and autoimmune disorders (Kalergis and Ravetch 2002;Rafiq et al 2002;Clynes 2005;Dhodapkar et al 2005). In fact, a recent multisite human gene expression study found that expression of FcyRIA was significantly and consistently higher in subjects with TB compared with those with LTBI, regardless of HIV coinfection (Sutherland et al 2013). These findings were consistent with another study showing a significant reduction in FcyRIA expression in TB cases after antituberculous treatment when compared with pretreatment expression (Cliff et al 2013).…”

Clinical Immunology and Multiplex Biomarkers of Human Tuberculosis

“…As the assay is high-throughput, it is exceptionally suited to determine biomarker signatures on a population scale. We have used dcRT-MLPA to characterize the human immune response in the peripheral blood during TB infection as well as in the response to curative treatment in several cohort studies in genetically and geographically diverse populations (Sutherland et al 2011(Sutherland et al , 2013Joosten et al 2012). Biomarker signatures were identified and validated with excellent classifying values between TB cases versus healthy infected or uninfected controls.…”

“…In a follow-up study with 523 participants across four sub-Saharan countries (Ethiopia, Malawi, South Africa, and The Gambia), differing also in TB and HIV status, we found a number of genes to be expressed at lower levels in active diseased compared with latently infected individuals, which normalized during treatment. A remarkably consistent classifier of active disease appeared to be the high-affinity IgG Fc receptor 1 FCGR1A (CD64), which was expressed at significantly higher levels in active TB regardless of HIV status or genetic background (Sutherland et al 2013).…”

Focused human gene expression profiling using dual-color reverse transcriptase multiplex ligation-dependent probe amplification

“…Host biomarkers within the signatures included the high-affinity IgG Fc receptor 1 FCGR1A (CD64), apoptosis-related genes, and T-cell/B-cell markers, suggesting important contributions of adaptive immunity to TB pathogenesis [4]. Moreover, FCGR1A expression levels appeared not affected by HIV status or geo-genetic differences, categorizing it as a remarkably consistent classifier of active TB disease [19].…”

“…We have used dcRT-MLPA to characterize the human innate and adaptive immune response in peripheral blood during infection with mycobacteria (both Mycobacterium leprae and Mycobacterium tuberculosis, the causative agents of leprosy and tuberculosis (TB), respectively) as well as in the response to curative TB treatment in genetically and geographically diverse populations [4,[17][18][19][20]. Host biomarker signatures with the highest discriminatory power between active TB disease (TB cases) and latent infection were identified and validated using a lasso logistic regression model, which is a shrinkage and selection method for logistic regression [21].…”