Mycobacterium tuberculosis DosR Regulon Gene Rv2004c Encodes a Novel Antigen with Pro-inflammatory Functions and Potential Diagnostic Application for Detection of Latent Tuberculosis

Abstract

Approximately 1.7 billion people in the world harbor latent Mycobacterium tuberculosis (Mtb) with a substantial risk of progression to clinical outcome. Containment of these seed beds of Mtb is essential to eliminate tuberculosis completely in high burden settings such as India. Hence, there is an urgent need for the identification of new serological markers for detection or vaccine candidates to prevent latent tuberculosis infection (LTBI). DosR regulon antigens of Mtb might serve as attractive targets for LTBI diagnosis or vaccine development as they are specifically expressed and are upregulated during latent phase. In this study, we investigated the role of Rv2004c, a member of DosR regulon (exclusive to Mtb complex), in host–pathogen interaction and its immunogenic potential in LTBI, active TB, and healthy control cohorts. Rv2004c elicited strong antibody response in individuals with LTBI compared to active TB patients and healthy cohorts. Recombinant Rv2004c induced pro-inflammatory cytokine response in human peripheral blood mononuclear cells and THP-1 cells via NF-κB phosphorylation. Interaction of Rv2004c with toll-like receptor (TLR)-2 was confirmed using HEK-Blue hTLR-2 and pull-down assays. Rv2004c enhanced the surface expression of TLR-2 at mRNA and protein levels in THP-1 cells. Our findings revealed that Rv2004c induces strong humoral and cell mediated immune responses. Given these observations, we propose Rv2004c to be a potential diagnostic marker or an attractive vaccine candidate that can be useful against LTBI.

A Systematic Review on Novel Mycobacterium tuberculosis Antigens and Their Discriminatory Potential for the Diagnosis of Latent and Active Tuberculosis

“…In addition 1,507 healthy controls or other controls were included. The majority of studies were in adults only (24/34, 70%;) ( 18 , 20 , 21 , 23 – 27 , 29 – 32 , 35 , 36 , 38 , 39 , 42 , 45 – 51 ), 8/34 (24%) studies were done in adults and children ( 19 , 22 , 28 , 37 , 40 , 41 , 43 , 44 ) and 2/34 (6 %) were done in children only ( 33 , 34 ). Outcomes were measured using enzyme-linked immunosorbent assay (ELISA), enzyme-linked immuno-spot assay (ELISPOT) and flow cytometry (FCM) in 27, 6 and 12 studies, respectively (Table 1 ), and some studies used several different assays for outcome measurement.…”

“…Overall 14/34 (41%) studies included a control group of healthy participants who had negative test results for interferon gamma-release assays /tuberculin skin test and/or no known history of or exposure to aTB ( 19 , 22 , 24 , 28 , 29 , 32 , 34 , 35 , 37 , 38 , 43 , 47 , 48 , 50 ). A further 2/34 (6%) studies included exposed individuals into the control group as long as they stayed healthy (e.g., no symptoms and microbiologically negative or tuberculin skin test negative) ( 32 , 34 ). Another 2/34 (6%) studies included a healthy control group but either no interferon gamma-release assays /tuberculin skin test was done or the community controls were tuberculin skin test positive (no exposure) ( 40 , 49 ).…”

“…Doddam et al characterized the immune-response toward Rv2004c and found that this antigen elicits a strong pro-inflammatory (TNF-α, IL-8, IL-1β, and IL-12) response in LTBI patients compared to aTB and healthy controls ( 32 ). Similarly, Hozumi et al showed that Rv2004c elicits increased IFN-γ producing T cells in a population of LTBI patients compared to aTB and controls in Japan ( 38 ).…”

Roles of Cholesteryl-α-Glucoside Transferase and Cholesteryl Glucosides in Maintenance of Helicobacter pylori Morphology, Cell Wall Integrity, and Resistance to Antibiotics

“…The method we followed for qRT-PCR analysis was described previously ( 31 ). Briefly, RNA was isolated from 10 8 cells of H. pylori strains by TRIzol (Invitrogen, USA).…”

Diagnosis for Latent Tuberculosis Infection: New Alternatives

“…The stimulation of peripheral blood mononuclear cells (PBMC) with Rv1737c and Rv2029c seem to increase the IFNγ or TNF-α-producing CD4 and CD8 T cells in individuals with LTBI compared to active TB (67). The use of RV2004 induced a strong proinflammatory response (TNF-α, IL-8, IL-1b, and IL-12) in LTBI individuals compared with active TB and healthy controls (68). Stimulation with Rv2627c, Rv2629, and Rv2630 induced high concentrations of or TNF-α, IL-6, and IL-10 in patients with active TB.…”