Diagnostic benefits of adding EspC, EspF and Rv2348-B to the QuantiFERON Gold In-tube antigen combination

Abstract

Interferon (IFN)-γ release assays (IGRAs) are used to diagnose latent tuberculosis (TB) infection (LTBI). To improve the accuracy of these tests, different approaches, such as alternative cytokine detection and using different antigens, are considered. Following this purpose, this study aims to evaluate the addition of EspC, EspF and Rv2348-B to those present in the QuantiFERON-TB Gold In-Tube (QFN-G-IT). We included 115 subjects: 74 active TB patients, 17 LTBI individuals and 24 healthy controls. Whole blood samples were collected in QFN-G-IT and in-house tubes containing different combinations of EspC, EspF and Rv2348-B, together with ESAT-6, CFP-10, and TB7.7. After overnight incubation at 37 ºC, plasma was harvested and IFN-γ quantified. IFN-γ levels in the QFN-G-IT and in-house tubes correlated very good (Spearman Rho(r) > 0.86). In-house antigen combinations distinguished healthy individuals from those with active TB and LTBI (specificities and sensitivities higher than 87.5% and 96.3%, respectively [AUC > 0.938]). Adding EspC, EspF and Rv2348-B, increased the sensitivity of the test, being the addition of EspC and Rv2348-B the combination that yielded a higher sensitivity with no specificity loss. Addition of these antigens could improve diagnosis in patients with impaired or immature immune response who are at high risk of developing TB. Tuberculosis (TB) remains the leading cause of death by a single infectious agent 1. Correct control, as well as proper management of the disease, are of great importance in order to decrease TB burden. For this, early diagnosis as well as correct and efficient preventive measures and anti-TB treatment, are key 2. Screening of latent TB infection (LTBI) and preventive treatment guidance generally relies on the tuberculin test (TST) performance. However, due to its cross-reaction with non-tuberculous mycobacteria and the bacilli Calmette-Guérin (BCG)

Towards Reverse Vaccinology for Bovine TB: High Throughput Expression of Full Length Recombinant Mycobacterium bovis Proteins

“…EspA (Mb3646c) has been suggested to be part, with EspC, of the type VII secretion apparatus (discussed in ( Ates and Brosch, 2017 )) and an obvious candidate for inclusion ( Chiliza et al, 2017 ). Recombinant EspC has been described ( Lou et al, 2017 ; Salemi et al, 2020 ) and used diagnostically ( Yan et al, 2018 ; Srinivasan et al, 2019 ; Villar-Hernández et al, 2020 ), but EspA has proven more difficult ( Garces et al, 2010 ). EspA expression as either a C- or N-terminally His tagged protein was not successful and mutation of the single cysteine reported to drive dimer formation ( Garces et al, 2010 ) had no effect.…”

Genome-to-genome analysis reveals associations between human and mycobacterial genetic variation in tuberculosis patients from Tanzania

“…This suggests that PRDM15 could be involved in regulation of apoptosis, an important defense mechanism that human macrophages employ for M.tb clearance 40,41 . The function of Rv2348c is unknown, other than that it is an antigen that stimulates T cell-mediated responses 42,43 . Since the induction of apoptosis in infected macrophages facilitates the presentation of antigens by dendritic cells and subsequent activation of T cell-mediated responses 44 , it is possible that Rv2348c and PRDM15 jointly determine disease prognosis due to such a process.…”