IRF4 ablation in B cells abrogates allogeneic B cell responses and prevents chronic transplant rejection

Bioinformatics and experimental validation were combined to explore lactylation-related biomarkers in HBV-associated acute liver failure

BACKGROUND AND AIM

Currently, hepatitis B virus-related acute liver failure (HBV-ALF) has limited treatment options. Studies have shown that histone lactylation plays a role in the progression of liver-related diseases. Therefore, it is essential to explore lactylation-related gene (LRGs) biomarkers in HBV-ALF to provide new information for the treatment of HBV-ALF.

METHODS

Two HBV-ALF-related datasets (GSE38941 and GSE14668) and 65 LRGs were used. First, the differentially expressed genes (DEGs) were derived from differential expression analysis, the key module genes from weighted gene co-expression network analysis; and LRGs were used to intersect to obtain the candidate genes. Subsequently, the feature genes obtained from least absolute shrinkage and selection operator regression analysis and support vector machine analysis were intersected to obtain the candidate key genes. Among them, genes with consistent and significant expression trends in both GSE38941 and GSE14668 were used as biomarkers. Subsequently, biomarkers were analyzed for functional enrichment, immune infiltration, and sensitive drug prediction.

RESULTS

In this study, five candidate genes (PIGM, PIGA, EGR1, PIGK, and PIGL) were identified by intersecting 6461 DEGs and 2496 key module genes with 65 LRGs. We then screened four candidate key genes from the machine learning algorithm, among which PIGM and PIGA were considered biomarkers in HBV-ALF. Moreover, the results of enrichment analysis showed that the significant enrichment signaling pathways for biomarkers included allograft rejection and valine, leucine, and isoleucine degradation. Thereafter, 11 immune cells differed significantly between groups, with resting memory CD4+ T cells having the strongest positive correlation with biomarkers. Methylphenidate hydrochloride is a potential therapeutic drug for PIGM.

CONCLUSION

Two genes, PIGM and PIGA, were identified as biomarkers related to LRGs in HBV-ALF, providing a basis for understanding HBV-ALF pathogenesis.

Blockade of BLyS inhibits B-cell responses and antibody production for the prevention of chronic transplant rejection

BACKGROUND

Chronic rejection, closely related to the activation of B cells and donor-specific antibody (DSA) production, has unsatisfactory therapeutic outcomes. B lymphocyte stimulator (BLyS) is a major regulatory factor that controls the activation and differentiation of B cells. However, it remains unclear whether BLyS blockade can regulate B and plasma cells in the transplantation setting and affect chronic rejection. Here, we investigated the efficacy of the BLyS inhibitors belimumab and telitacicept in controlling B-cell response and preventing chronic rejection.

METHODS

The effects of belimumab and telitacicept on B-cell activation, differentiation, and antibody production in vitro were determined. A chronic rejection model in mouse was established by allogeneic cardiac transplantation with CTLA4-Ig treatment. Allograft survival, histology, DSA levels, and B-cell responses were analyzed to evaluate the chronic rejection-preventive effects of belimumab and telitacicept.

RESULTS

In vitro experiments confirmed that belimumab and telitacicept inhibited B-cell activation and differentiation and reduced antibody production. In vivo experiments indicated that they significantly prolonged allograft survival, attenuated chronic rejection through significant suppression of myocardial ischemic necrosis and interstitial fibrosis, and reduced DSA-IgG levels, C4d deposition, and inflammatory cell infiltration. Furthermore, the frequencies of B cells, plasma cells, and IgG-producing cells in the recipients' spleen, lymph nodes, bone marrow, and blood were decreased after BLyS inhibitors treatment.

CONCLUSIONS

This study demonstrated that belimumab and telitacicept inhibit B-cell responses and antibody production and alleviate chronic transplant rejection. Therefore, BLyS inhibitors are expected to be used for the prevention of chronic rejection in clinical practice.

CD4+ T cell immunity is dependent on an intrinsic stem-like program

CD4+ T cells are central to various immune responses, but the molecular programs that drive and maintain CD4+ T cell immunity are not entirely clear. Here we identify a stem-like program that governs the CD4+ T cell response in transplantation models. Single-cell-transcriptomic analysis revealed that naive alloantigen-specific CD4+ T cells develop into TCF1hi effector precursor (TEP) cells and TCF1-CXCR6+ effectors in transplant recipients. The TCF1-CXCR6+CD4+ effectors lose proliferation capacity and do not reject allografts upon adoptive transfer into secondary hosts. By contrast, the TCF1hiCD4+ TEP cells have dual features of self-renewal and effector differentiation potential, and allograft rejection depends on continuous replenishment of TCF1-CXCR6+ effectors from TCF1hiCD4+ TEP cells. Mechanistically, TCF1 sustains the CD4+ TEP cell population, whereas the transcription factor IRF4 and the glycolytic enzyme LDHA govern the effector differentiation potential of CD4+ TEP cells. Deletion of IRF4 or LDHA in T cells induces transplant acceptance. These findings unravel a stem-like program that controls the self-renewal capacity and effector differentiation potential of CD4+ TEP cells and have implications for T cell-related immunotherapies.

Continuous Expression of Interferon Regulatory Factor 4 Sustains CD8+ T Cell Immunity against Tumor

T-cell-based immunotherapy is gaining momentum in cancer treatment; however, our comprehension of the transcriptional regulation governing T cell antitumor activity remains constrained. The objective of this study was to explore the function of interferon regulatory factor 4 (IRF4) in antitumor CD8+ T cells using the TRAMP-C1 prostate cancer and B16F10 melanoma model. To achieve this, we generated an Irf4GFP-DTR mouse strain and discovered that CD8+ tumor-infiltrating lymphocytes (TILs) expressing high levels of IRF4.GFP exhibited a more differentiated PD-1high cell phenotype. By administering diphtheria toxin to tumor-bearing Irf4GFP-DTR mice, we partially depleted IRF4.GFP+ TILs and observed an accelerated tumor growth. To specifically explore the function of IRF4 in antitumor CD8+ T cells, we conducted 3 adoptive cell therapy (ACT) models. Firstly, depleting IRF4.GFP+ CD8+ TILs derived from ACT significantly accelerated tumor growth, emphasizing their crucial role in controlling tumor progression. Secondly, deleting the Irf4 gene in antitumor CD8+ T cells used for ACT led to a reduction in the frequency and effector differentiation of CD8+ TILs, completely abolishing the antitumor effects of ACT. Lastly, we performed a temporal deletion of the Irf4 gene in antitumor CD8+ T cells during ACT, starting from 20 days after tumor implantation, which significantly compromised tumor control. Therefore, sustained expression of IRF4 is essential for maintaining CD8+ T cell immunity in the melanoma model, and these findings carry noteworthy implications for the advancement of more potent immunotherapies for solid tumors.

An agent-based model of cardiac allograft vasculopathy: toward a better understanding of chronic rejection dynamics

Cardiac allograft vasculopathy (CAV) is a coronary artery disease affecting 50% of heart transplant (HTx) recipients, and it is the major cause of graft loss. CAV is driven by the interplay of immunological and non-immunological factors, setting off a cascade of events promoting endothelial damage and vascular dysfunction. The etiology and evolution of tissue pathology are largely unknown, making disease management challenging. So far, in vivo models, mostly mouse-based, have been widely used to study CAV, but they are resource-consuming, pose many ethical issues, and allow limited investigation of time points and important biomechanical measurements. Recently, agent-based models (ABMs) proved to be valid computational tools for deciphering mechanobiological mechanisms driving vascular adaptation processes at the cell/tissue level, augmenting cost-effective in vivo lab-based experiments, at the same time guaranteeing richness in observation time points and low consumption of resources. We hypothesize that integrating ABMs with lab-based experiments can aid in vivo research by overcoming those limitations. Accordingly, this work proposes a bidimensional ABM of CAV in a mouse coronary artery cross-section, simulating the arterial wall response to two distinct stimuli: inflammation and hemodynamic disturbances, the latter considered in terms of low wall shear stress (WSS). These stimuli trigger i) inflammatory cell activation and ii) exacerbated vascular cell activities. Moreover, an extensive analysis was performed to investigate the ABM sensitivity to the driving parameters and inputs and gain insights into the ABM working mechanisms. The ABM was able to effectively replicate a 4-week CAV initiation and progression, characterized by lumen area decrease due to progressive intimal thickening in regions exposed to high inflammation and low WSS. Moreover, the parameter and input sensitivity analysis highlighted that the inflammatory-related events rather than the WSS predominantly drive CAV, corroborating the inflammatory nature of the vasculopathy. The proof-of-concept model proposed herein demonstrated its potential in deepening the pathology knowledge and supporting the in vivo analysis of CAV.

B-cell response in solid organ transplantation

The transcriptional regulation of B-cell response to antigen stimulation is complex and involves an intricate network of dynamic signals from cytokines and transcription factors propagated from T-cell interaction. Long-term alloimmunity, in the setting of organ transplantation, is dependent on this B-cell response, which does not appear to be halted by current immunosuppressive regimens which are targeted at T cells. There is emerging evidence that shows that B cells have a diverse response to solid organ transplantation that extends beyond plasma cell antibody production. In this review, we discuss the mechanistic pathways of B-cell activation and differentiation as they relate to the transcriptional regulation of germinal center B cells, plasma cells, and memory B cells in the setting of solid organ transplantation.