Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) comprises a group of small-vessel inflammatory disorders with largely unknown pathogenesis. AAV is serologically defined by autoantibodies against two specific neutrophil antigens: proteinase 3 and myeloperoxidase (1). Pathologically, AAV is characterized by necrotizing inflammation of vessel walls. Clinically, AAV includes three principal subtypes: granulomatosis with polyangiitis (2), microscopic polyangiitis (MPA) (3, 4), and eosinophilic granulomatosis with polyangiitis (5). Although the exact pathogenesis of AAV is unknown, immune dysregulation, which is influenced by genetic and environmental factors, plays a central role in AAV pathogenesis (6). Genome-wide analyses have identified several predisposing loci, mainly within the major histocompatibility complex region. Specifically, variants in the human leukocyte antigen-DQ segment show strong genetic associations with AAV pathogenesis (7, 8). In Asia, AAV prevalence ranges from 46 to 421 per million (9), and in China, its prevalence is increasing annually, especially among the aging population. The current standard treatment for AAV involves systemic immunosuppressants targeting B and T cells, including glucocorticoids, cyclophosphamide, and rituximab (10); however, many patients with AAV remain unresponsive to the current standard of care and experience disease relapses (11). Therefore, identification of novel therapeutic targets to achieve long-term disease remission is necessary.

Cytotoxic T lymphocyte-associated protein 4 (CTLA-4), a crucial immune checkpoint molecule within the CD28 immunoglobulin superfamily, exhibits predominant expression in T lymphocytes (12). CTLA-4 is an important regulator of T-cell homeostasis and self-tolerance and can modulate the T-cell response by blocking CD28 co-stimulation of T-cells during T-cell activation (13, 14). CTLA-4 expression in T cells is tightly regulated, and the failure of the transport mechanism of CTLA-4 to the cell surface leads to autoimmune susceptibility (14). Given its central role in immune modulation, CTLA-4 has emerged as a promising therapeutic target across multiple disease domains, particularly in autoimmune conditions and oncology. Moreover, CTLA-4-targeted therapies through the successful implementation of CTLA-4 inhibitors have been validated to manage various immune-mediated disorders clinically (12). In AAV, CTLA-4–Ig fusion proteins that block T-cell co-stimulation offer a novel therapeutic strategy potentially advantageous over traditional immunosuppressive regimens (15). However, genetic studies have reported inconsistent associations between CTLA4 polymorphisms and AAV. For instance, a European case–control study identified the association between CTLA4 polymorphism— rs3087243 —and AAV (16). In contrast, a case—control study of the Han Chinese population in Beijing, China, reported no association between CTLA4 polymorphisms (rs231775 and rs5742909) and AAV susceptibility (17). These findings suggest the strong influence of ethnicity, population, and regional variation on genetic susceptibility; however, the association between single-nucleotide polymorphisms (SNPs) at the CTLA4 locus and AAV susceptibility in the Guangxi population has not been reported.

To address this gap, we conducted a case—control study involving 343 patients with AAV from Guangxi and selected three candidate CTLA4 SNPs to evaluate their association with AAV risk in this population.

The pathogenesis of AAV involves the complex interplay of host immunological dysregulation (encompassing both innate and adaptive immunity) and genetic–environmental synergism (4). The breakdown of ANCA tolerance, which is critical to disease initiation, is frequently driven by aberrant immune cell dynamics and humoral immunity deficiencies (25, 26). Nevertheless, emerging evidence from large-scale genomic investigations has substantiated the pivotal role of genetic predisposition in AAV development (7, 9, 27). In this study, we focused on identifying the risk alleles associated with AAV mechanisms and evaluated the correlation between CTLA4 SNPs and AAV risk in the Guangxi population in China. Our findings expand the current understanding of genetic loci associated with AAV susceptibility. CTLA-4 is a master immune checkpoint receptor that delivers co-inhibitory signals crucial for attenuating excessive immune activation (28) and orchestrating immune response termination (29). Although its central regulatory role in maintaining immune homeostasis and preventing autoreactivity is well-established, the precise molecular mechanisms governing CTLA-4-mediated immune modulation remain incompletely elucidated (30). CTLA4 polymorphisms demonstrate significant pleiotropic effects, showing associations with multiple immune-mediated pathologies including systemic lupus erythematosus, rheumatoid arthritis, autoimmune diabetes, and allograft rejection episodes (31–33).

Our data show that CTLA4 rs62182595, rs16840252, and rs5742909 polymorphisms are significantly associated with AAV susceptibility in the Guangxi population under various genetic models. Specifically, the GA genotype of rs62182595 in the codominant and overdominant genetic models and the GA-AA genotype in the dominant genetic model were associated with reduced AAV susceptibility in the Guangxi population. Similarly, the CT-TT and C/T genotypes of rs16840252 (dominant genetic model) and the C/T genotype of rs5742909 (overdominant genetic model) showed association with reduced AAV risk in the Guangxi population.

Next, we analyzed the synergistic effects of haplotype combinations to assess the possible interactions among CTLA4 SNPs and determine the effects of these three SNPs on AAV susceptibility in the Guangxi population. Among the six haplotypes identified, ATT and GCC haplotypes significantly elevated susceptibility, suggesting an interaction between the three SNPs that increases the susceptibility to AAV in the Guangxi population, similar to the results of a previous study on CTLA-4 (34). Furthermore, previous studies suggest that SNP polymorphisms in the 5′ URR region may lead to altered selective splicing (35–37), and alterations in selective splicing can lead to variation in CTLA4. Therefore, we hypothesized that alterations in bases at rs1684025 may alter the selective splicing of both the soluble CTLA-4 (sCTLA-4) and the surface full-length CTLA-4 (flCTLA-4) isoforms, ultimately affecting CTLA-4 gene expression (38). The remaining two SNPs, rs5742909 and rs62182595, located in the promoter region, may lead to different levels of mRNA transcription and protein translation and affect T cell homeostasis, leading to immune dysfunction and ultimately affecting the susceptibility of individuals to AAV (39, 40). Because rs62182595*G, rs16840252*C, and rs5742909*C showed strong LD, we hypothesize that these three loci are likely to amplify the synergistic effects between the loci through gene–gene interactions (formation of different haplotypes). Such interactions could affect the expression level and protein structure of CTLA4, impair T-cell function, and disrupt immune homeostasis, ultimately influencing the susceptibility of individuals to AAV (41–43). Overall, our study demonstrates a significant association between CTLA4 SNPs and AAV risk in the Guangxi population. These findings not only lay the foundation for disease risk stratification (e.g., specific genes can serve as potential genetic markers) to help guide screening of high-risk populations and provide targets for subsequent precise prevention and early intervention, but also explore the potential of CTLA4-targeted precision therapy. It supports the rationale for using CTLA4 as a therapeutic target and provides evidence for “genotype-guided personalized immunotherapy.

Despite its strengths, the present study has certain limitations. First, although haplotype association analysis was conducted, we did not evaluate the expression levels of the CTLA4 gene or protein. As gene expression is affected by numerous factors, such as transcriptional and translational regulations and gene–environmental interactions, our findings require further experimental validation. Second, sample collection was limited due to the rarity of ANCA-associated vasculitis. Third, the study population was restricted to Guangxi, China, which may limit the generalizability of the findings to other populations. In the future, it is planned to carry out cross-regional multi-center collaborative studies. While expanding the sample size, populations of different ethnic groups will be included, and the expression levels of the CTLA4 gene and protein will be detected simultaneously. Combined with the analysis of gene-environment interactions, the research conclusions will be comprehensively verified.