Disease extent and anti‐tubercular treatment response correlates with Mycobacterium tuberculosis‐specific CD4 T‐cell phenotype regardless of HIV‐1 status

Abstract

Objectives. The development of non-sputum-based assays for tuberculosis (TB) diagnosis and treatment monitoring is a key priority. Recent data indicate that whole blood-based assays to assess the phenotype of Mycobacterium tuberculosis (Mtb)-specific CD4 T cells hold promise for this purpose and require further investigation in well-characterised TB cohorts. In this study, we investigated the relationship between the phenotypic signature of Mtb-specific CD4 responses, TB disease extent and treatment response. Methods. Using flow cytometry, we measured the expression of phenotypic and functional markers (HLA-DR, CD27, CD153, KLRG1, IL-2, MIP-1b, TNF-a and IFN-c) on Mtb-specific CD4 T-cells in whole blood from 161 participants of varying TB and HIV status. TB disease extent was graded as a continuum using the Xpert ct value, C-reactive protein, Timika radiographic score and monocyte/lymphocyte ratio. Results. The phenotypic profile of Mtb-specific CD4 T cells pre-anti-tubercular treatment (ATT) strongly correlated with disease extent, irrespective of HIV status. ATT associated with major changes in the phenotype of Mtbspecific CD4 T cells, with decreased expression of HLA-DR and increased CD27 and CD153 expression. Principal component analysis showed an almost complete separation between latent TB infection (LTBI) and active TB (aTB) pre-ATT groups, whereas the profile of the aTB post-ATT group overlapped with the LTBI group. However, in patients experiencing treatment failure or relapse, no significant changes were observed in Mtb-specific CD4

Immune profiling of Mycobacterium tuberculosis-specific T cells in recent and remote infection

“…Finally, we showed that of all the immunological features that were different between recent and remote M.tb infection, T cell activation was the best biomarker for differentiating between infection states. Overall, the T cell activation biomarker appears very robust, regardless of mycobacterial antigen specificity (M.tb lysate or CFP-10/ESAT-6) or the assay used for detection (PBMC-ICS, tetramer staining or, as previously reported, whole blood stimulation [17] , [18] , [19] , [20] , [21] , [22] ). This study focused on understanding T cell immunobiology during acquisition of M.tb infection and the discovery of potential biomarkers to distinguish between recent and remote M.tb infection.…”

“…Expression of HLA-DR, a member of the MHC class II family typically expressed by antigen-presenting cells, is often used as a marker of T cell activation [ 15 , 16 ]. In the context of tuberculosis, studies have shown that disease, regardless of HIV status, is associated with significantly higher levels of T cell activation than M.tb infection, and that activation is reduced upon successful antimicrobial treatment [17] , [18] , [19] , [20] , [21] , [22] . These studies suggest that antigen-specific T cell activation could be used as a biomarker of microbial burden, and potentially infer in vivo antigen exposure during different stages of infection and disease.…”

“…TST and IGRAs have a low predictive value for tuberculosis [26] . Other functional assays that measure M.tb-specific T cell properties such as Th1 cytokine co-expression profiles [ 27 , 28 ], T cell differentiation (CD27, [ 29 , 30 ]) and T cell activation [17] , [18] , [19] , [20] , [21] , [22] have been proposed as new potential immunodiagnostic concepts that can distinguish between M.tb infection and disease. In line with this principle, potential biomarkers of recent M.tb infection based on proportions of TNF-only (IFN-γ-IL-2-) T E (CD45RA-CCR7-CD127-) CD4 T cells or T cell proliferation, as well as a blood transcriptomic signature, have been described [31] , [32] , [33] .…”

Immune profiling of Mycobacterium tuberculosis-specific T cells in recent and remote infection

“…Expression of HLA-DR, a member of the MHC class II family typically expressed by antigen-presenting cells, is often used as a marker of T cell activation [15,16]. In the context of tuberculosis, studies have shown that disease, regardless of HIV status, is associated with significantly higher levels of T cell activation than M.tb infection, and that activation is reduced upon successful antimicrobial treatment [17][18][19][20][21][22]. These studies suggest that antigen-specific T cell activation could be used as a biomarker of microbial burden, and potentially infer in vivo antigen exposure during different stages of infection and disease.…”

“…TST and IGRAs have a low predictive value for tuberculosis [26]. Other functional assays that measure M.tbspecific T cell properties such as Th1 cytokine co-expression profiles [27,28], T cell differentiation (CD27, [29,30]) and T cell activation [17][18][19][20][21][22] have been proposed as new potential immunodiagnostic concepts that can distinguish between M.tb infection and disease. In line with this principle, potential biomarkers of recent M.tb infection based on proportions of TNF-only (IFN--IL-2-) TE (CD45RA-CCR7-CD127-) CD4 T cells or T cell proliferation, as well as a blood transcriptomic signature, have been described [31][32][33].…”