CD8 T cell memory to a viral pathogen requires trans cosignaling between HVEM and BTLA.
ABSTRACT: Defining the molecular interactions required to program activated CD8 T cells to survive and become memory cells may allow us to understand how to augment anti-viral immunity. HVEM (herpes virus entry mediator) is a member of the tumor necrosis factor receptor (TNFR) family that interacts with ligands in the TNF family, LIGHT and Lymphotoxin-?, and in the Ig family, B and T lymphocyte attenuator (BTLA) and CD160. The Ig family members initiate inhibitory signaling when engaged with HVEM, but may also activate survival gene expression. Using a model of vaccinia virus infection, we made the unexpected finding that deficiency in HVEM or BTLA profoundly impaired effector CD8 T cell survival and development of protective immune memory. Mixed adoptive transfer experiments indicated that BTLA expressed in CD8?+ dendritic cells functions as a trans-activating ligand that delivers positive co-signals through HVEM expressed in T cells. Our data demonstrate a critical role of HVEM-BTLA bidirectional cosignaling system in antiviral defenses by driving the differentiation of memory CD8 T cells.
Project description:The B and T lymphocyte attenuator (BTLA) is an Ig super family member that binds to the herpes virus entry mediator (HVEM), a TNF receptor super family (TNFRSF) member. Engagement of BTLA by HVEM triggers inhibitory signals, although recent evidence indicates that BTLA also may act as an activating ligand for HVEM. In this study, we reveal a novel role for the BTLA-HVEM pathway in promoting the survival of activated CD8(+) T cells in the response to an oral microbial infection. Our data show that both BTLA- and HVEM-deficient mice infected with Listeria monocytogenes had significantly reduced numbers of primary effector and memory CD8(+) T cells, despite normal proliferation and expansion compared to controls. In addition, blockade of the BTLA-HVEM interaction early in the response led to significantly reduced numbers of antigen-specific CD8(+) T cells. HVEM expression on the CD8(+) T cells as well as BTLA expression on a cell type other than CD8(+) T lymphocytes, was required. Collectively, our data demonstrate that the function of the BTLA-HVEM pathway is not limited to inhibitory signaling in T lymphocytes, and instead, that BTLA can provide crucial, HVEM-dependent signals that promote survival of antigen activated CD8(+) T cell during bacterial infection.
Project description:The herpesvirus entry mediator (HVEM), a member of the TNF receptor (TNFR) superfamily, can act as a molecular switch that modulates T cell activation by propagating positive signals from the TNF-related ligand LIGHT (TNFR superfamily 14), or inhibitory signals through the Ig superfamily member B and T lymphocyte attenuator (BTLA). Competitive binding analysis and mutagenesis reveals a unique BTLA binding site centered on a critical lysine residue in cysteine-rich domain 1 of HVEM. The BTLA binding site on HVEM overlaps with the binding site for the herpes simplex virus 1 envelope glycoprotein D, but is distinct from where LIGHT binds, yet glycoprotein D inhibits the binding of both ligands, potentially nullifying the pathway. The binding site on HVEM for BTLA is conserved in the orphan TNFR, UL144, present in human CMV. UL144 binds BTLA, but not LIGHT, and inhibits T cell proliferation, selectively mimicking the inhibitory cosignaling function of HVEM. The demonstration that distinct herpesviruses target the HVEM-BTLA cosignaling pathway suggests the importance of this pathway in regulating T cell activation during host defenses.
Project description:Immune cell cosignaling receptors are important modulators of immune cell function. For T cells, cosignaling receptors supply necessary secondary signals supporting activation or attenuation after engagement of antigen-presenting cells. The primary cosignaling receptors belong to either the Ig (CD28-like) or TNF receptor (TNFR) superfamilies. The CD28 family is comprised of coinhibitory and costimulatory receptors. The three coinhibitory receptors are cytotoxic T lymphocyte antigen 4, programmed death-1, and B and T lymphocyte attenuator (BTLA). Although cytotoxic T lymphocyte antigen 4 and programmed death-1 interact with B7-Ig family counter receptors, the ligand for BTLA is less clear. From a protein-protein interaction screen, we identified the TNFR family member herpesvirus entry mediator (HVEM) as a counter receptor for BTLA. Here we show that HVEM binds BTLA with high affinity and can form a ternary complex with its known ligands homologous to lymphotoxin, showing inducible expression, and competing with herpes simplex virus glycoprotein D for HVEM, a receptor expressed by T lymphocytes (LIGHT) or lymphotoxin alpha and BTLA. In addition, binding of HVEM to BTLA attenuates T cell activation, identifying HVEM/BTLA as a coinhibitory receptor pair. This study is a demonstration of a direct interaction between the primary T cell cosignaling receptors of the CD28 and TNFR families.
Project description:The inhibitory cosignaling pathway formed between the TNF receptor herpesvirus entry mediator (HVEM, TNFRSF14) and the Ig superfamily members, B and T lymphocyte attenuator (BTLA) and CD160, limits the activation of T cells. However, BTLA and CD160 can also serve as activating ligands for HVEM when presented in trans by adjacent cells, thus forming a bidirectional signaling pathway. BTLA and CD160 can directly activate the HVEM-dependent NF-kappaB RelA transcriptional complex raising the question of how NF-kappaB activation is repressed in naive T cells. In this study, we show BTLA interacts with HVEM in cis, forming a heterodimeric complex in naive T cells that inhibits HVEM-dependent NF-kappaB activation. The cis-interaction between HVEM and BTLA is the predominant form expressed on the surface of naive human and mouse T cells. The BTLA ectodomain acts as a competitive inhibitor blocking BTLA and CD160 from binding in trans to HVEM and initiating NF-kappaB activation. The TNF-related ligand, LIGHT (homologous to lymphotoxins, exhibits inducible expression, and competes with HSV glycoprotein D for HVEM, a receptor expressed by T lymphocytes, or TNFSF14) binds HVEM in the cis-complex, but NF-kappaB activation was attenuated, suggesting BTLA prevents oligomerization of HVEM in the cis-complex. Genetic deletion of BTLA or pharmacologic disruption of the HVEM-BTLA cis-complex in T cells promoted HVEM activation in trans. Interestingly, herpes simplex virus envelope glycoprotein D formed a cis-complex with HVEM, yet surprisingly, promoted the activation NF-kappaB RelA. We suggest that the HVEM-BTLA cis-complex competitively inhibits HVEM activation by ligands expressed in the surrounding microenvironment, thus helping maintain T cells in the naive state.
Project description:The tumor necrosis factor receptor superfamily member HVEM is one of the most frequently mutated surface proteins in germinal center (GC)-derived B cell lymphomas. We found that HVEM deficiency increased B cell competitiveness during pre-GC and GC responses. The immunoglobulin (Ig) superfamily protein BTLA regulated HVEM-expressing B cell responses independently of B-cell-intrinsic signaling via HVEM or BTLA. BTLA signaling into T cells through the phosphatase SHP1 reduced T cell receptor (TCR) signaling and preformed CD40 ligand mobilization to the immunological synapse, thus diminishing the help delivered to B cells. Moreover, T cell deficiency in BTLA cooperated with B cell Bcl-2 overexpression, leading to GC B cell outgrowth. These results establish that HVEM restrains the T helper signals delivered to B cells to influence GC selection outcomes, and they suggest that BTLA functions as a cell-extrinsic suppressor of GC B cell lymphomagenesis.
Project description:Currently, the pathogenesis of rheumatoid arthritis (RA) is not clearly understood. The LIGHT/HVEM/BTLA co-signaling pathway may be involved in the pathogenesis of RA, although reports on the expression levels of LIGHT, HVEM and BTLA in T lymphocytes from RA patients are limited.In this study, we recruited 30 healthy controls and 21 RA patients. Clinical characteristics were collected for RA patients. The levels of LIGHT, HVEM and BTLA expressed on the surface of circulating T cells of RA patients and healthy controls were measured by flow cytometry.The percentages of CD3+, CD4+ and CD8+ T lymphocytes that expressed BTLA from RA patients were all higher than those of the controls (all p < 0.05), while the percentages of CD3+, CD4+ and CD8+ T lymphocytes that expressed HVEM and LIGHT were all lower than those of the controls (all p < 0.05). The rheumatoid factor and the percentage of HVEM+CD4+ T lymphocytes showed a statistically significant negative correlation in RA patients (r = -0.453, p = 0.039), as did the swollen joint count and the percentage of BTLA+CD8+ T lymphocytes (r = -0.501, p = 0.021).Here, we provide the first report on the increased expression of BTLA in T lymphocytes and on the decreased expression of HVEM and LIGHT in RA patients. BTLA, HVEM and LIGHT might be involved in the pathogenesis of RA and have the potential to be new clinically useful characteristics of RA.
Project description:Immune checkpoints are crucial in the maintenance of antitumor immune responses. The activation or blockade of immune checkpoints is dependent on the interactions between receptors and ligands; such interactions can provide inhibitory or stimulatory signals, including the enhancement or suppression of T-cell proliferation, differentiation, and/or cytokine secretion. B-and T-lymphocyte attenuator (BTLA) is a lymphoid-specific cell surface receptor which is present on T-cells and interacts with herpes virus entry mediator (HVEM), which is present on tumor cells. The binding of HVEM to BTLA triggers an inhibitory signal which attenuates the immune response. This feature is interesting for studying the molecular interactions between HVEM and BTLA, as they may be targeted for novel immunotherapies. This work was based on the crystal structure of the BTLA/HVEM complex showing that BTLA binds the N-terminal cysteine-rich domain of HVEM. We investigated the amino acid sequence of HVEM and used molecular modeling methods to develop inhibitors of the BTLA/HVEM interaction. We synthesized novel compounds and determined their ability to interact with the BTLA protein and inhibit the formation of the BTLA/HVEM complex. Our results suggest that the HVEM (14-39) peptide is a potent inhibitor of the formation of the BTLA/HVEM protein complex.
Project description:The interaction between the tumor necrosis factor (TNF) family member LIGHT and the TNF family receptor herpes virus entry mediator (HVEM) co-stimulates T cells and promotes inflammation. However, HVEM also triggers inhibitory signals by acting as a ligand that binds to B and T lymphocyte attenuator (BTLA), an immunoglobulin super family member. The contribution of HVEM interacting with these two binding partners in inflammatory processes remains unknown. In this study, we investigated the role of HVEM in the development of colitis induced by the transfer of CD4(+)CD45RB(high) T cells into recombination activating gene (Rag)(-/-) mice. Although the absence of HVEM on the donor T cells led to a slight decrease in pathogenesis, surprisingly, the absence of HVEM in the Rag(-/-) recipients led to the opposite effect, a dramatic acceleration of intestinal inflammation. Furthermore, the critical role of HVEM in preventing colitis acceleration mainly involved HVEM expression by radioresistant cells in the Rag(-/-) recipients interacting with BTLA. Our experiments emphasize the antiinflammatory role of HVEM and the importance of HVEM expression by innate immune cells in preventing runaway inflammation in the intestine.
Project description:Antibody based immune-checkpoint blockade therapy is a major breakthrough in oncology, leading to clinical benefit for cancer patients. Among the growing family of inhibitory receptors, the B and T lymphocyte attenuator (BTLA), which interacts with herpes virus entry mediator (HVEM), is a promising target for immunotherapy. Indeed, BTLA inhibits T-cell proliferation and cytokine production. The crystal structure of the BTLA/HVEM complex has shown that the HVEM(26-38) fragment is directly involved in protein binding. We designed and analyzed the capacity of several analogs of this fragment to block the ligation between BTLA and HVEM, using competitive ELISA and cellular assay. We found that the HVEM(23-39) peptide can block BTLA/HVEM ligation. However, the blocking ability was due to the Cys encompassed in this peptide and that even free cysteine targeted the BTLA protein and blocked its interaction with HVEM. These data highlight a Cys-related artefact in vitro, which should be taken in consideration for future development of BTLA/HVEM blocking compounds.
Project description:Dendritic cells (DCs) initiate immunity and also antigen-specific tolerance mediated by extrathymic regulatory T (Treg) cells, yet it remains unclear how DCs regulate induction of such tolerance. Here, we report that efficient induction of Treg cells was instructed by BTLA+DEC205+CD8+CD11c+ DCs and the immunomodulatory functions of BTLA. In contrast, T cell activation in steady state by total CD11c+ DCs that include a majority of DCs that do not express BTLA did not induce Treg cells and had no lasting impact on subsequent immune responses. Engagement of HVEM, a receptor of BTLA, promoted Foxp3 expression in T cells through upregulation of CD5. In contrast, T cells activated in the absence of BTLA and HVEM-mediated functions remained CD5lo and therefore failed to resist the inhibition of Foxp3 expression in response to effector cell-differentiating cytokines. Thus, DCs require BTLA and CD5-dependent mechanisms to actively adjust tolerizing T cell responses under steady-state conditions.