BLR1 and FCGR1A transcripts in peripheral blood associate with the extent of intrathoracic tuberculosis in children and predict treatment outcome

Biomarkers reflecting the extent of Mycobacterium tuberculosis-induced pathology and normalization during anti-tuberculosis treatment (ATT) would considerably facilitate trials of new treatment regimens and the identification of patients with treatment failure. Therefore, in a cohort of 99 Indian children with intrathoracic tuberculosis (TB), we performed blood transcriptome kinetic analysis during ATT to explore 1) the association between transcriptional biomarkers in whole blood (WB) and the extent of TB disease at diagnosis and treatment outcomes at 2 and 6 months, and 2) the potential of the biomarkers to predict treatment response at 2 and 6 months. We present the first data on the association between transcriptional biomarkers and the extent of TB disease as well as outcome of ATT in children: Expression of three genes down-regulated on ATT (FCGR1A, FPR1 and MMP9) exhibited a positive correlation with the extent of TB disease, whereas expression of eight up-regulated genes (BCL, BLR1, CASP8, CD3E, CD4, CD19, IL7R and TGFBR2) exhibited a negative correlation with the extent of disease. Baseline levels of these transcripts displayed an individual capacity >70% to predict the six-month treatment outcome. In particular, BLR1 and FCGR1A seem to have a potential in monitoring and perhaps tailoring future antituberculosis therapy.


BCL2
B-cell lymphoma 2, down-regulates cell death (apoptosis). Increased BCL2 expression in infected macrophages may create an immune privileged site for MTB infection and is implicated in poor prognosis for TB patients. 3,4 A, C

BLR1
Belongs to CXC chemokine receptor family (CXCR5), located in lymph node follicles. An increased expression of BLR1 in TB patients might help in sustaining the expression of its ligand CXCL13, which in turn attracts B cells. 5 C

BPI
Bactericidal permeability-increasing protein, found in neutrophil granules and associated with host defence through microbiocidal activity. 6 C

CASP8
Cysteine-aspartic acid protease family, plays a central role in the execution-phase of cell apoptosis and increased expression is seen in TB patients 7,8 C

CCL13
Chemokine (c-c motif) ligand 13, link immune activation to the recruitment of leukocytes in both Th1-and Th2type immune responses. 10 B,C

CCL19
Chemokine (c-c motif) ligand 19, contributes to control of MTB infection through homing of lymphocytes and dendritic cells. 11 B

CCL22
Belongs to CC chemokine family, plays a role in the trafficking of activated T cells to inflammatory sites. 9 C

CCR7
CC chemokine receptor 7, mediates trafficking of dendritic cells and T cells from the lungs to the mediastinal lymph node during TB disease. 12,13 C

CD3E
T-cell glycoprotein CD3 epsilon, plays a role in intracellular signal-transduction pathways.
14 C

CD4
Cluster of differentiation 4, plays a critical role in adaptive immunity to TB.

CD8A
Cluster of differentiation 8A, identifies cytotoxic T-cells that interact with MHC class I targets and may contribute to control of MTB infection. 15 C

CD14
Cluster of differentiation 14, a component of the innate immune system and acts a co-receptor for recognizing MTB. Monocyte/macrophage marker. 16,17 C

CD19
Cluster of differentiation 19, a B cell marker and essential for B cell activation. 18 C

CD163
Cluster of differentiation 163, a hemoglobin scavenger receptor exclusively expressed in macrophages upon inflammation. 19 C

CTLA4
Cytotoxic T-lymphocyte antigen 4 plays a role in the down-regulation of T cell immune responses and involved in the maintenance of T cell homeostasis. CTLA4 gene expression may be associated with severity of pulmonary TB. 20,21 B,C

CXCL10
CXC chemokine 10 or interferon gamma-induced protein 10 (IP-10), secreted by number of cell types in response to IFN-α/β and involved in stimulation of natural killer cells and T-cell migration in MTB infection. 22 A, C

FASLG
Fas ligand, a type II transmembrane protein, belonging to the TNF family involved in immune modulation and pathogenesis of TB. Modulators of Fas/FasL-mediated apoptosis may therefore be clinically useful. 23 C

FCGR1A
The Fc region of immunoglobulin gamma is involved in both innate and adaptive immune responses. It aids to control MTB infection and plays a central role in antibody-dependent cytotoxicity and the clearance of immune complexes. 24 C

FOXP3
Forkhead box P3, belongs to the transcription factor family and is involved in various cellular processes, acts as an important regulator for T-cell development. 25 C

FPR1
Formyl peptide receptor 1, a member of G-protein-coupled receptor family involved in the control of inflammation and neutrophil function. 26 C

IFNγ
Interferon gamma, secreted by several cell types such as NK cells, CD4 + and CD8 + T-cells, essential for control of MTB infection. 27 B

IL2RA
Interleukin 2 receptor gene, plays an important role in the activation and expansion of T-cells. 28 C

IL4
Interleukin 4, the prototypical Th2 cytokine; high levels of expression are associated with poor outcomes in TB.

IL7R
Interleukin-7 receptor, plays a role in the development of immune cells and control of apoptosis. 31 C

IL10
Interleukin-10, an anti-inflammatory cytokine that may contribute to TB pathogenesis. IL-10 blocks phagosome maturation by a STAT3-dependent, p38-independent mechanism, which facilitates MTB survival and outgrowth 32 A

IL22RA1
Interleukin 22 receptor alpha 1belongs to class II cytokine receptor family and activates various signaling pathways. The expression of IL22RA1 was found to be higher in late TB granulomas. 33,34 B

LAG3
Lymphocyte-activation gene 3, an important regulatory molecule involved in controlling the expansion and activation of T-cells. 35 A,C

LTF
Lacto-transferrin also called Lactoferrin (LF), a secreted mediator that connects innate and adaptive immune responses. 36 C

MARCO
Antigen-presenting cell scavenger receptor, involved in TLR activation that mediates phagocytosis of pathogens. 37 C

MMP9
Matrix metallo-peptidase 9, induced by MTB infection and has a role together with MCP-1in recruiting macrophages to the lungs during granuloma formation. 38 C

NCAM1
Neural cell adhesion molecule 1, mediates several intracellular signaling pathways and may be involved in TB pathogenesis. 39,40 A

RAB13
Ras related protein-13, a small GTPase family member, regulates assembly of functional tight junctions in epithelial cells. 41 C

RAB24
Ras related protein-24, a small GTPase family member, regulates intracellular protein trafficking between endoplasmic reticulum and cis-Golgi compartment. 41 C

RAB33A
Ras related protein-33A, a small GTPase family member; Dysregulation of GTPase plays a role in blocking of phagosome maturation, which is a major survival strategy for MTB. 42 C

SEC14L1
SEC14 cytosolic factor family plays a role in lipid metabolism and the intracellular transport system. SEC14L1 also appears to be a negative regulator of some innate immune functions. 43,44 C

SPP1
Secreted phosphoprotein 1, acts as a cytokine that up-regulates the expression of interferon-gamma and interleukin-12, contributes to resistance against mycobacteria by boosting reactive oxygen intermediate production in macrophages. 45,46 C

TGFB1
Transforming growth factor β1, an anti-inflammatory cytokine, performs many cellular functions and is involved in resolution of granulomatous lesions in TB. 47 C

TGFBR2
Transforming growth factor β receptor 2, involved in signal transduction and response to inhibit cell growth and division. 48 C

TIMP2
Tissue inhibitor of metallo-proteinases, involved in pathological changes, tissue remodeling and possibly, pathogenesis of pulmonary TB. 49 C

TNF
Tumor necrosis factor, a cytokine that plays multiple roles in the immunopathology of TB and is essential for controlling MTB infection. 50 B, C

TNFRSF1 A
TNF receptor superfamily member1A, mediates apoptosis and functions as a regulator of inflammation. 51 C

TNFRSF1 8
TNF receptor superfamily member 18, involved in T-cell activation, programmed cell death and pulmonary fibrosis. 49,51 C ABR Active BCR-Related gene contains a GTPase-activating protein domain (used as endogenous control).

B2M
β2 microglobulin, a component of MHC class I molecules (used as endogenous control). C GAPDH Glyceraldehyde 3-phosphate dehydrogenase, involved in quite a few non-metabolic processes (used as endogenous control).

GUSB
Glucuronidase β, regulates lysosomal storage function and co-regulated in response to stress (used as endogenous control).