Activation Profile of Mycobacterium tuberculosis –Specific CD4+ T Cells Reflects Disease Activity Irrespective of HIV Status

The diagnosis of pulmonary tuberculosis in HIV-infected individuals is particularly 33 challenging, as HIV-induced alterations of the immune system lead to reduced cavitations, 34 limiting the sensitivity of sputum-based assays (1).Thus, alternate markers are needed to 35 distinguish between latent (LTBI) and active TB (aTB) in this high-risk group.Several 36 attributes of Mtb-specific CD4+ T cells have been shown to efficiently delineate LTBI and 37 aTB in HIV-uninfected individuals, including their polyfunctional or memory profiles (2-4).38Moreover, Adekambi et al. recently demonstrated that the activation profile of Mtb-specific 39 CD4+ T cells accurately discriminates between LTBI and aTB (5).As chronic HIV infection 40 is characterized by persistent systemic immune activation (6), it is plausible that these blood-41 based markers may not be relevant for HIV-infected individuals.42We therefore compared the potential of the activation and polyfunctional profiles of 43Mtb-specific CD4+T cells to distinguish between LTBI and aTB in HIV-uninfected and HIV-44 infected individuals.We analyzed 76 participants divided in four groups according to their 45 TB and HIV status (Table S1): LTBI/HIV-(n=17), aTB/HIV-(n=17), LTBI/HIV+ (n=21, 46 median CD4 count: 316 cells/mm 3 , IQR: 231-543) and aTB/HIV+ (n=21, CD4 count: 250 47 cells/mm 3 , IQR: 155-295).LTBI was defined as TST positive, IGRA positive, sputum culture 48 negative and normal CXR.aTB was diagnosed based on symptoms suggestive of tuberculosis 49 and Mtb positive smear and/or sputum culture, as previously described ( 7).All HIV-infected 50 participants were ART-naïve.UCT ethics committee approved the study and written consent 51 was obtained from participants.Cryopreserved PBMCs were stimulated for 16 hours with 52 ESAT-6/CFP-10 peptide pool and intracellular staining using a live/dead marker and 53 antibodies towards CD3, CD4, CD8, HLA-DR, Ki67, CD38, IFN-γ, TNF-α and IL-2 was 54 performed.Positive ESAT-6/CFP-10 responses (defined as twice the background) were 55 detectable in 16 subjects in the LTBI/HIV-and LTBI/HIV+ groups; and in 15 and 18