Association study between B- and T-lymphocyte attenuator gene and type 1 diabetes mellitus or systemic lupus erythematosus in the Japanese population

Beyond the anti-PD-1/PD-L1 era: promising role of the BTLA/HVEM axis as a future target for cancer immunotherapy

Recent introduction of monoclonal antibodies targeting immune checkpoints to harness antitumor immunity has revolutionized the cancer treatment landscape. The therapeutic success of immune checkpoint blockade (ICB)-based therapies mainly relies on PD-1/PD-L1 and CTLA-4 blockade. However, the limited overall responses and lack of reliable predictive biomarkers of patient´s response are major pitfalls limiting immunotherapy success. Hence, this reflects the compelling need of unveiling novel targets for immunotherapy that allow to expand the spectrum of ICB-based strategies to achieve optimal therapeutic efficacy and benefit for cancer patients. This review thoroughly dissects current molecular and functional knowledge of BTLA/HVEM axis and the future perspectives to become a target for cancer immunotherapy. BTLA/HVEM dysregulation is commonly found and linked to poor prognosis in solid and hematological malignancies. Moreover, circulating BTLA has been revealed as a blood-based predictive biomarker of immunotherapy response in various cancers. On this basis, BTLA/HVEM axis emerges as a novel promising target for cancer immunotherapy. This prompted rapid development and clinical testing of the anti-BTLA blocking antibody Tifcemalimab/icatolimab as the first BTLA-targeted therapy in various ongoing phase I clinical trials with encouraging results on preliminary efficacy and safety profile as monotherapy and combined with other anti-PD-1/PD-L1 therapies. Nevertheless, it is anticipated that the intricate signaling network constituted by BTLA/HVEM/CD160/LIGHT involved in immune response regulation, tumor development and tumor microenvironment could limit therapeutic success. Therefore, in-depth functional characterization in different cancer settings is highly recommended for adequate design and implementation of BTLA-targeted therapies to guarantee the best clinical outcomes to benefit cancer patients.

Regulatory role of BTLA and HVEM checkpoint inhibitors in T cell activation in a perciform fish Larimichthys crocea

The BTLA and HVEM are two well-characterized immune checkpoint inhibitors in humans and other mammalian species. However, the occurrence and functionality of these two molecules in non-mammalian species remain poorly understood. In the present study, we identified the BTLA and HVEM homologs from large yellow croaker (Larimichthys crocea), an economically important marine species of the perciform fish family. The Larimichthys crocea BTLA and HVEM (LcBTLA and LcHVEM) share conserved structural features to their mammalian counterparts, and they were expressed in various tissues and cells examined at different transcriptional levels, with particular abundance in immune-relevant tissues and splenic leukocytes. Immunofluorescence staining and flow cytometry analysis showed that LcHVEM and LcBTLA proteins were distributed on MHC-II⁺ APCs and CD4-2⁺ T cells, and a strong interaction between LcBTLA and LcHVEM was detected in splenic leukocytes in the mixed lymphocyte reaction (MLR). By blockade assays using anti-LcBTLA and anti-LcHVEM Abs as well as recombinant soluble LcBTLA and LcHVEM proteins in different combinations, it was found that LcBTLA-LcHVEM interactions play an important inhibitory role in the activation of alloreactive T cells using MLR as a model, and APC-initiated antigen-specific CD4-2⁺ T cells in response to A. hydrophila (A. h) stimulation. These observations highlight the extensive functional roles of LcBTLA and LcHVEM immune-checkpoint inhibitors in allogeneic T cell reactions, and CD4-2⁺ T cell-mediated adaptive immune responses in Larimichthys crocea. Thus, the BTLA-HVEM checkpoint may represent an ancient coinhibitory pathway, which was originated in fish and was conserved from fish to mammals throughout the vertebrate evolution.

BTLA Expression and Function Are Impaired on SLE B Cells

B- and T-lymphocyte attenuator (BTLA/CD272) is an inhibitory checkpoint molecule expressed on T and B cells. Prior studies reported defective function of BTLA by T cells in patients with systemic lupus erythematosus (SLE), whereas nothing is known about its role on B cells in SLE, a disease with various B cell abnormalities. Peripheral blood mononuclear cells (PBMCs) from 23 healthy donors (HD) and 34 SLE patients were stained for BTLA and its expression on B cells was assessed. PBMCs or CD27^-IgD⁺ naive B cells were stimulated together with an activating anti-BTLA antibody or an inhibitor of spleen tyrosine kinase (SYK) and differentiation as well as the expression of activation markers CD71, PD-1 and CD86 were analyzed. Our phenotypic and functional studies revealed reduced BTLA expression on CD27^-IgD⁺ naïve B cells from SLE patients (p=0.0017) related to anti-dsDNA antibody titers (p=0.0394) and SIGLEC-1/CD169 expression on monocytes (p=0.0196), a type I interferon marker related to disease activity. BTLA engagement was found to control CpG/TLR9 activation limiting plasmablast (p=0.0156) and B cell memory induction (p=0.0078) in normal B cells in contrast to other B cell activation pathways (CD40, BCR). These BTLA functions were impaired in SLE B cells. Inhibition of SYK was found to mimic the effects of BTLA activity in vitro. Thus, is it possible that reduced BTLA expression and function of CD27-IgD+ antigen- and T cell-inexperienced SLE B cells could be overcome by SYK inhibition which should be tested in future studies as potential therapeutic principle.

Roles of BTLA in Immunity and Immune Disorders

B and T lymphocyte attenuator (BTLA) is one of the most important cosignaling molecules. It belongs to the CD28 superfamily and is similar to programmed cell death-1 (PD-1) and cytotoxic T lymphocyte associated antigen-4 (CTLA-4) in terms of its structure and function. BTLA can be detected in most lymphocytes and induces immunosuppression by inhibiting B and T cell activation and proliferation. The BTLA ligand, herpesvirus entry mediator (HVEM), does not belong to the classic B7 family. Instead, it is a member of the tumor necrosis factor receptor (TNFR) superfamily. The association of BTLA with HVEM directly bridges the CD28 and TNFR families and mediates broad and powerful immune effects. Recently, a large number of studies have found that BTLA participates in numerous physiopathological processes, such as tumor, inflammatory diseases, autoimmune diseases, infectious diseases, and transplantation rejection. Therefore, the present work aimed to review the existing knowledge about BTLA in immunity and summarize the diverse functions of BTLA in various immune disorders.

Immune Checkpoint Molecules-Inherited Variations as Markers for Cancer Risk

In recent years, immunotherapy has been revolutionized by a new approach that works by blocking receptors called immune checkpoints (IC). These molecules play a key role in maintaining immune homeostasis, mainly by suppressing the immune response and by preventing its overactivation. Since inhibition of the immune response by IC can be used by cancer to avoid recognition and destruction by immune system, blocking them enhances the anti-tumor response. This therapeutic approach has brought spectacular clinical effects. The ICs present heterogeneous expression patterns on immune cells, which may affect the effectiveness of immunotherapy. The inherited genetic variants in regulatory regions of ICs genes can be considered as potential factors responsible for observed inter-individual differences in ICs expression levels on immune cells. Additionally, polymorphism located in exons may introduce changes to ICs amino acid sequences with potential impact on functional properties of these molecules. Since genetic variants may affect both expression and structure of ICs, they are considered as risk factors of cancer development. Inherited genetic markers such as SNPs may also be useful in stratification patients into groups which will benefit from particular immunotherapy. In this review, we have comprehensively summarized the current understanding of the relationship between inherited variations of CTLA-4, PDCD1, PD-L1, BTLA, TIM-3, and LAG-3 genes in order to select SNPs which can be used as predictive biomarkers in personalized evaluation of cancer risk development and outcomes as well as possible response to immunotherapy.

Association of BTLA rs1982809 polymorphism with lung cancer risk in Tunisian population

B and T lymphocyte attenuator (BTLA) is an immune-inhibitory receptor that negatively regulates the lymphocyte activation. A few studies have been devoted to the relationship between BTLA gene variations and cancer's risk. It has been essentially demonstrated to be involved in increasing cancer risk in chronic lymphocyte leukaemia, renal cell carcinoma, breast and colorectal cancer predispositions in Asian population. The aim of this study was to evaluate the association between BTLA gene polymorphisms and the risk of lung cancer in the Tunisian population. In a case-control study, three BTLA single-nucleotide polymorphism (SNP): rs1982809 (A > G), rs9288952 (G > A) and rs9288953(C > T) were genotyped with the use of TaqMan probes in 169 lung cancer patients and in 300 controls. The rs1982809 SNP was significantly associated with an increased risk of lung cancer compared with controls in codominant and dominant models. The heterozygous rs1982809-AG genotype carriers had a higher risk of developing lung cancer when compared to AA genotype carriers in Tunisian population (OR (95%CI) = 1.63 (1.09-2.42), p = .01]. The AG genotype is an important risk factor associated with lymphatic invasion (OR = 3.71) and large-sized lung tumour (OR = 1.80). It is also a risk factor for the development of an adenocarcinoma subtype (OR = 2.08). However, the BTLA rs9288953 and rs9288952 SNPs were not associated with susceptibility for lung cancer (p > .05). Haplotype comparison did not show any significant association in our research. For the survival analysis, there was no impact of BTLA SNPs on the mortality risk associated to lung cancer in Tunisian patients. The current study is the first to demonstrate an association between BTLA rs1982809 polymorphism and an increased lung cancer risk in the Tunisian population.

Association between BTLA polymorphisms and susceptibility to esophageal squamous cell carcinoma in the Chinese population

Background

Growing evidence suggested that B‐ and T‐lymphocyte attenuator (BTLA) polymorphisms raised the susceptibility to a wide range of cancers. This study aimed to evaluate whether BTLA variants were related to the risk of esophageal squamous cell carcinoma (ESCC).

Methods

A total of 721 ESCC patients and 1208 matched non‐cancer controls were included in this research, and four tagging BTLA polymorphisms (rs2171513 G > A, rs3112270 A > G, rs1982809 G > A, and rs16859629 T > C) were selected and genotyped using SNPscan™ Assays.

Results

In the present study, no significant relationship between BTLA polymorphisms and ESCC was observed. However, stratified analyses suggested that the variant of BTLA rs3112270 A > G reduced the risk of ESCC in the male subgroup (AG vs AA: adjusted OR = 0.78, 95% CI = 0.61‐0.99, P = .042), BMI < 24 kg/m² subgroup (AG vs AA: adjusted OR = 0.72, 95% CI = 0.55‐0.93, P = .012; AG/GG vs AA: adjusted OR = 0.77, 95% CI = 0.60‐0.98, P = .032), and ever drinking subgroup (AG vs AA: adjusted OR = 0.61, 95% CI = 0.38‐0.97, P = .037). But when stratified by BMI ≥ 24 kg/m², the rs3112270 A > G polymorphism increased the susceptibility to ESCC (GG vs AA: adjusted OR = 1.91, 95% CI = 1.02‐3.59, P = .045). Besides, we demonstrated that BTLA rs2171513 G > A polymorphism was protective of ESCC in the ever drinking subgroup (GA/AA vs GG: adjusted OR = 0.62, 95% CI = 0.39‐0.97, P = .037).

Conclusion

Taken together, our initial investigation postulated that the rs3112270 A > G and rs2171513 G > A variants in the BTLA gene are candidates for the risk of ESCC, which might be helpful for the early diagnosis and treatment of ESCC.

BTLA-HVEM Checkpoint Axis Regulates Hepatic Homeostasis and Inflammation in a ConA-Induced Hepatitis Model in Zebrafish

The BTLA-HVEM checkpoint axis plays extensive roles in immunomodulation and diseases, including cancer and autoimmune disorders. However, the functions of this checkpoint axis in hepatitis remain limited. In this study, we explored the regulatory role of the Btla-Hvem axis in a ConA-induced hepatitis model in zebrafish. Results showed that Btla and Hvem were differentially expressed on intrahepatic Cd8⁺ T cells and hepatocytes. Knockdown of Btla or Hvem significantly promoted hepatic inflammation. Btla was highly expressed in Cd8⁺ T cells in healthy liver but was downregulated in inflamed liver, as evidenced by a disparate proportion of Cd8⁺Btla⁺ and Cd8⁺Btla^- T cells in individuals without or with ConA stimulation. Cd8⁺Btla⁺ T cells showed minimal cytotoxicity to hepatocytes, whereas Cd8⁺Btla^- T cells were strongly reactive. The depletion of Cd8⁺Btla^- T cells reduced hepatitis, whereas their transfer enhanced hepatic inflammation. These observations indicate that Btla endowed Cd8⁺Btla⁺ T cells with self-tolerance, thereby preventing them from attacking hepatocytes. Btla downregulation deprived this tolerization. Mechanistically, Btla-Hvem interaction contributed to Cd8⁺Btla⁺ T cell tolerization, which was impaired by Hvem knockdown but rescued by soluble Hvem protein administration. Notably, Light was markedly upregulated on Cd8⁺Btla^- T cells, accompanied by the transition of Cd8⁺Btla⁺Light^- to Cd8⁺Btla^-Light⁺ T cells during hepatitis, which could be modulated by Cd4⁺ T cells. Light blockade attenuated hepatitis, thereby suggesting the positive role of Light in hepatic inflammation. These findings provide insights into a previously unrecognized Btla-Hvem-Light regulatory network in hepatic homeostasis and inflammation, thus adding a new potential therapeutic intervention for hepatitis.

Associations between HVEM/LIGHT/BTLA/CD160 polymorphisms and the occurrence of antibody-mediate rejection in renal transplant recipients

Antibody-mediated rejection (ABMR) is a serious complications that can occur following renal transplantation. The production of donor-specific antibodies by the humoral immune response can trigger costimulatory signals, which are crucial in activating immune cells, and therefore, playing a potential role in ABMR. To investigate the role of HVEM/LIGHT/BTLA/CD160 polymorphisms in ABMR, we retrospectively analyzed 200 renal transplant recipients. We adopted next-generation sequencing (NGS) to identify HVEM/LIGHT/BTLA/CD160 single-nucleotide polymorphisms (SNPs) in the genotypes of these patients. We divided the patients into two groups: those with ABMR and those who were stable. We adopted multiple models and performed regression analysis after adjusting for multiple confounding variables, to determine the correlation between the SNPs and ABMR. We obtained 41 high-quality SNPs readouts. However, we did not observe any significant association between these polymorphisms and the pathogenesis of ABMR in any of the models.Nevertheless, since there is evidence suggesting the involvement of costimulatory signals in graft rejection, further research should be conducted to better understand how genetic polymorphisms may be involved in ABMR.

Intragenic Variations in BTLA Gene Influence mRNA Expression of BTLA Gene in Chronic Lymphocytic Leukemia Patients and Confer Susceptibility to Chronic Lymphocytic Leukemia

The aim of this study was to determine the association between polymorphisms in gene encoding B- and T-lymphocyte attenuator (BTLA) and susceptibility to chronic lymphocytic leukemia (CLL) and their influence on mRNA expression of BTLA gene in T and B cells from CLL patients (pts.). The following BTLA single-nucleotide polymorphisms (SNPs): rs2705511, rs1982809, rs9288952, rs76844316, rs16859633, rs9288953, rs2705535, rs1844089, rs2705565, rs2633580 were genotyped with use of TaqMan probes in 321 CLL pts. and in 470 controls. The mRNA levels of human BTLA were determined in subpopulations of T and B cells from 37 CLL patients with use of Applied Biosystems assays. Three SNPs: rs1982809, rs2705511 and rs9288953 were associated with susceptibility to CLL. The frequency of rs1982809[G] allele and rs2705511[C] allele carriers was higher in patients compared to the controls (0.51 vs. 0.41, OR 1.51, 95% CI 1.14-2.02, p = 0.004 and 0.56 vs. 0.44, OR 1.62, 95% CI 1.22-2.16, p = 0.0009, respectively). Furthermore, rs9288953[TT] genotype was overrepresented in CLL pts. compared to the controls (0.22 vs. 0.14, OR 1.74, 95% CI 1.20-2.53, p = 0.004). The evaluation of the influence of BTLA SNPs on BTLA mRNA expression in CLL pts. showed that the presence of rs1982809[G] allele was associated with lower median (±SD) BTLA mRNA expression in T cells (expressed as 2-delta Ct) in CLL pts. as compared to [AA] homozygotes (0.009 ± 0.013 vs. 0.026 ± 0.012, p = 0.03). Our results indicate that rs1982809 BTLA gene polymorphism is associated with mRNA expression level and that variations in the BTLA gene might be considered as potentially low-penetrating CLL risk factor.

Association of 3' nearby gene BTLA polymorphisms with the risk of renal cell carcinoma in the Polish population

OBJECTIVE

T cells play an important role in antitumor immunity, and molecules regulating T-cell activity could influence cancer susceptibility. The distinct role of coinhibitory receptors in immunosurveillance has been considered. B- and T-lymphocyte attenuator (BTLA) is one of these receptors, which negatively regulate immune responses. The aim of this study was to investigate the association between BTLA gene polymorphisms and susceptibility to renal cell carcinoma (RCC) in the Polish population.

METHODS

Altogether 282 patients with RCC and 480 healthy subjects were genotyped for the following polymorphisms: rs2705511, rs1982809, rs9288952, rs16859633, rs9288953, rs2705535, and rs1844089 using the TaqManSNP Genotyping Assays.

RESULTS

Here, we found that the presence of rs1982809G allele (genotype GG+AG) is associated with increased risk of RCC (odds ratio = 1.38; 95% CI: 1.03-1.86; P = 0.03). In patients with clear-cell RCC (ccRCC) with high-grade (3 and 4) tumors, the frequency of rs1982809[GG] genotype was significantly higher as compared to those with low-grade (1 and 2) tumors and to the controls (0.14 vs. 0.06, P = 0.05 and 0.14 vs. 0.06, P = 0.04, respectively). Moreover, we have noticed the trend for overrepresentation of carriers of rs2705511C allele in patients with RCC as compared with the controls (0.51 vs. 0.44, P = 0.08) Haplotype rs2705511C/rs1982809G/rs9288952A/rs9288953T/rs2705535C/rs1844089G (CGATCG) increased the risk of RCC of 46% (odds ratio = 1.46; 95% CI: 1.08-1.96; Pcorrected = 0.05).

CONCLUSION

Our results indicate that polymorphisms rs1982809 situated in 3' UTR nearby region of BTLA gene might be considered as low-penetrating risk factor for RCC, but results have to be confirmed in further studies.

Association between BTLA polymorphisms and genetic susceptibility to chronic HBV infection

AIM: To investigate the association between BTLA polymorphisms and genetic susceptibility to chronic hepatitis B virus (HBV) infection in a Chinese Han population.

METHODS: The rs2633562 and rs2952323 single nucleotide polymorphisms (SNPs) of the BTLA gene were genotyped by Multiplex SNaPshot technique in patients with chronic HBV infection and other family members (HBsAg negative). Genotype and allele frequencies were calculated and analyzed. The association between the gene polymorphisms of BTLA and genetic susceptibility to chronic HBV infection was analyzed by a family-based association method.

RESULTS: Association or linkage was detected among 431 patients. Univariate family-based association tests (FBATs) demonstrated that the G/G genotype in rs2952323 of the BTLA gene was associated with chronic HBV infection, and the variant allele G at rs2952323 was significantly associated with genetic susceptibility to chronic HBV infection in additive model (Z = 2.689, P = 0.0007174) and recessive model (Z = 2.731, P = 0.006308). Transmission/disequilibrium test (TDT) and sibship disequilibuium test (SDT) analysis showed no increased transmission for the major alleles (A, C or G) from heterozygous parents to affected offspring (P = 1.000000, P = 0.151590, respectively). Furthermore, haplotype-specific FBATs showed that AG haplotype (70.0%) was more frequently transmitted in chronic HBV infection than other haplotypes in additive model (Z = 3.093, P = 0.001979) and recessive model (Z = 2.825, P = 0.004721).

CONCLUSION: The gene polymorphisms of BTLA may participate in chronicity of HBV infection in the Chinese Han population.

Gene polymorphisms of novel immunotolerant molecule BTLA: distribution of alleles, genotypes and haplotypes in Polish Caucasian population

B and T lymphocyte attenuator (BTLA) is one of the members of immunoglobulin superfamily which, like CTLA-4 and PD-1, is involved in down regulation of immune response. Despite the important role of BTLA in maintaining immune homeostasis, relatively little studies were devoted to the relationship of polymorphisms in the gene encoding BTLA with susceptibility to autoimmune disease and cancer. Moreover, all published works were done in Asian populations. BTLA gene is located on chromosome 3 in q13.2 and consists of five exons. The aim of this study was to investigate the alleles, genotypes and haplotypes frequency of selected BTLA gene polymorphisms in Caucasian population originating from Poland. For this study, the single-nucleotide polymorphisms (SNPs) were chosen on the basis of literature data. Additionally, the tag dSNP under linkage equilibrium r² > 0.8 and available at the National Center for Biotechnology Information (NCBI) for Caucasian population of rare alleles at a frequency greater than 5 % have been chosen using the NCBI database. The ten BTLA SNPs investigated were: rs1844089, rs2705535, rs9288952, rs9288953, rs1982809, rs2633580, rs2705511, rs2705565, rs76844316, rs16859633. For all SNPs selected on the basis of literature data the significantly different distributions of genotypes between Asian and Caucasian populations were observed.

Slow down and survive: Enigmatic immunoregulation by BTLA and HVEM

B and T lymphocyte associated (BTLA) is an Ig domain superfamily protein with cytoplasmic immunoreceptor tyrosine-based inhibitory motifs. Its ligand, herpesvirus entry mediator (HVEM), is a tumor necrosis factor receptor superfamily member. The unique interaction between BTLA and HVEM allows for a system of bidirectional signaling that must be appropriately regulated to balance the outcome of the immune response. HVEM engagement of BTLA produces inhibitory signals through SH2 domain-containing protein tyrosine phosphatase 1 (Shp-1) and Shp-2 association, whereas BTLA engagement of HVEM produces proinflammatory signals via activation of NF-kappaB. The BTLA-HVEM interaction is intriguing and quite complex given that HVEM has four other ligands that also influence immune responses, the conventional TNF ligand LIGHT and lymphotoxin alpha, as well as herpes simplex virus glycoprotein D and the glycosylphosphatidylinositol-linked Ig domain protein CD160. BTLA-HVEM interactions have been shown to regulate responses in several pathogen and autoimmune settings, but our understanding of this complex system of interactions is certainly incomplete. Recent findings of spontaneous inflammation in BTLA-deficient mice may provide an important clue.