Mycobacterium tuberculosisRv3615c is a highly immunodominant antigen and specifically induces potent Th1-type immune responses in tuberculosis pleurisy

Abstract

T-cell responses have been demonstrated to be essential for preventing infection. The Th1-cytokines produced by T cells, such as INF-γ, IL-2, and TNF-α, not only limit the invasion of but also eliminate the pathogen at the site of infection. Bacillus Calmette-Guérin (BCG) is known to induce Th1-type responses but the protection is inadequate. Identification of immunogenic components, in addition to those expressed in BCG, and induction of a broad spectrum of Th1-type responses provide options for generating sufficient adaptive immunity. Here, we studied human pulmonary T-cell responses induced by the -specific antigen Rv3615c, a protein with a similar size and sequence homology to ESAT-6 and CFP-10, which induced dominant CD4 T-cell responses in human tuberculosis (TB) models. We characterized T-cell responses including cytokine profiling, kinetics of activation, expansion, differentiation, TCR usage, and signaling of activation induced by Rv3615c compared with other -specific antigens. The expanded CD4 T cells induced by Rv3615c predominately produced Th1, but less Th2 and Th17, cytokines and displayed effector/memory phenotypes (CD45ROCD27CD127CCR7). The magnitude of expansion and cytokine production was comparable to those induced by well-characterized the 6 kDa early secreted antigenic target (ESAT-6), the 10 kDa culture filtrate protein (CFP-10) and BCG. Rv3615c contained multiple epitopes Rv3615c, Rv3615c, Rv3615c, Rv3615c and Rv3615c that activated CD4 T cells. The Rv3615c-specific CD4 T cells shared biased of T-cell receptor variable region of β chain (TCR Vβ) 1, 2, 4, 5.1, 7.1, 7.2 and/or 22 chains to promote their differentiation and proliferation respectively, by triggering a signaling cascade. Our data suggest that Rv3615c is a major target of Th1-type responses and can be a highly immunodominant antigen specific for infection.

PD-1 modulating Mycobacterium tuberculosis-specific polarized effector memory T cells response in tuberculosis pleurisy

“…The fresh PFMCs and PBMCs were isolated and prepared following protocol previously described . Shortly, pleural fluids (PFs) from TBP patients were collected and centrifuged at 3000 rpm for 20 min, and the cell pellets were collected.…”

“…The fresh PFMCs and PBMCs were isolated and prepared following protocol previously described. 21 Shortly, pleural fluids (PFs) from TBP patients were collected and centrifuged at 3000 rpm for 20 min, and the cell pellets were collected. The cell pellets from PFs and peripheral blood from healthy donors were suspended and isolated by Ficoll-Hypaque (Tianjin HaoYang Biological Manufacture, Tianjin, China) density gradient centrifugation at 2000 rpm for 20 min.…”

Intranasal immunization with Mycobacterium tuberculosis Rv3615c induces sustained adaptive CD4+ T‐cell and antibody responses in the respiratory tract

“…Detection of cell phenotype and intracellular cytokine expressions using flow cytometry has been previously described . In short, for phenotyping, cells were washed with PBS containing 0.1% BSA and 0.05% sodium azide, and suspended into staining buffer.…”

“…Some of them had a phenotype of CD44 + CD62L low , and produced Th1‐type cytokines, such as IFN‐γ, TNF‐α, and IL‐2. These effector cytokines eliminated the infected cells and controlled M.tb replication . Thus, many vaccine developments have been focused on identifying new CD4 + T‐cell epitopes inducing Th1‐type responses, or modifying BCG to improve efficacy for providing a broader protection .…”

“…The escalating magnitude of T‐cell response and IFN‐γ production induced by BCG did not provide additional protection against M.tb infection . In search for new TB vaccine candidates, we evaluated Rv3615c, a protein whose secretion is dependent on a component of RD1, for potency of inducing T‐cell responses of patients with tuberculosis pleurisy . Rv3615c has previously been identified as an ESX‐1 substrate protein C (EspC) and has been known as a protein with similar amino acid length and homologous sequence as ESAT‐6, CFP‐10, and other members of the ESAT‐6 family .…”