Recombinant Human AITRL Protein: Therapeutic Potential of a Novel Immunomodulatory Target

Molecular Structure and Biological Characteristics of AITRL Protein
Human AITRL (Activation-Inducible TNF-Related Ligand), also known as TL1A, is a key member of the tumor necrosis factor superfamily (TNFSF15) that plays a critical role in immune regulation. Structurally, AITRL is a type II transmembrane protein with an extracellular TNF homology domain (THD) that forms stable homotrimers. Recombinant human AITRL (rhAITRL) is a soluble extracellular domain fragment expressed through genetic engineering, with a molecular weight of approximately 25-30 kDa, retaining full biological activity. Unlike most TNF family members, AITRL expression is strictly dependent on cellular activation states, primarily induced in antigen-presenting cells (e.g., dendritic cells and macrophages) and vascular endothelial cells. This unique expression pattern suggests AITRL may play a specialized role in fine-tuning immune responses.

The receptor system of rhAITRL exhibits complex pleiotropy. Its primary receptor, DR3 (Death Receptor 3, TNFRSF25), is widely expressed on activated T lymphocytes, particularly Th1, Th17, and regulatory T cells (Treg). Notably, the AITRL-DR3 interaction has an affinity constant (Kd) of ~10-50 nM, enabling dynamic immune regulation. Additionally, AITRL binds the decoy receptor DcR3, forming a balanced signaling network. X-ray crystallography and cryo-EM structures of the AITRL-DR3 complex reveal symmetric trimeric interactions, providing precise templates for therapeutic molecule design.

Molecular Mechanisms of rhAITRL in Immune Regulation
rhAITRL modulates immune cell function through multilayered mechanisms. For T cell activation, rhAITRL-DR3 engagement enhances TCR signaling intensity via NF-κB and MAPK cascades, distinct from CD28 costimulation. Experimental data show rhAITRL increases CD4+ T cell sensitivity to low-dose antigens by 10-100-fold and boosts cytokine production 3-5-fold, with pronounced effects on Th1/Th17 over Th2 subsets. Molecularly, rhAITRL-DR3 signaling upregulates c-FLIP to inhibit caspase-8-mediated apoptosis, prolonging effector T cell survival.

In Treg regulation, rhAITRL displays dual concentration-dependent effects: low doses (0.1-1 ng/mL) promote Treg proliferation/suppression via IL-2 synergy, while high doses (>10 ng/mL) counteract suppression to boost effector responses. Transcriptomics identifies >500 differentially expressed genes in rhAITRL-treated Tregs, including upregulated Foxp3, CTLA-4, and IL-10.

rhAITRL also shapes innate immunity—enhancing dendritic cell MHC II/co-stimulator (CD80/CD86) expression for superior antigen presentation, and driving macrophage polarization toward M1 (elevated IL-12/TNF-α, suppressed arginase-1). Notably, rhAITRL activates lymphoid tissue-inducer (LTi) cells, pivotal for tertiary lymphoid structure (TLS) formation in chronic inflammation and cancer immunity.

Therapeutic Potential of rhAITRL in Disease Models
In autoimmunity, rhAITRL strategies show bidirectional efficacy. DR3 blockade reduces joint swelling/bone erosion by 60-70% in rheumatoid arthritis models, whereas low-dose rhAITRL expands gut Tregs to ameliorate colitis by >50% in IBD—highlighting tissue-specific effects. EAE studies reveal stage-dependent outcomes: DR3 inhibition prevents disease induction, while rhAITRL administration during remission enhances remyelination.

For cancer immunotherapy, intratumoral rhAITRL increases CD8+ T cell infiltration 3-5-fold, elevating PD-1 blockade response rates from 20% to >60% by promoting TLS formation. Efficacy correlates with DR3 genotypes, where high expressers show 2-3× higher response rates, suggesting a predictive biomarker. DR3-engineered CAR-T cells exhibit superior expansion/persistence, with ongoing trials (NCT04503278).

In infectious diseases, rhAITRL expands virus-specific CD8+ T cells 10-fold and reverses exhaustion in chronic LCMV infection. As a vaccine adjuvant, co-administration elevates neutralizing antibodies by 2-3 logs and enhances memory T cell generation, with Th1-skewed responses ideal for TB/HIV vaccines. Safety assessments reveal milder local/systemic reactions versus alum/MF59 adjuvants.

Clinical Translation Status and Challenges of rhAITRL
Multiple AITRL-DR3-targeting therapies are in clinical development. Anti-DR3 antagonist ANB030 achieved 75% PASI75 response in psoriasis Phase II. Anti-AITRL antibody PF-06480605 demonstrates 40% endoscopic improvement in ulcerative colitis Phase II (NCT04501146). Optimized rhAITRL-Fc as a flu vaccine booster (NCT04590950) enhances elderly immunogenicity in Phase I.

Manufacturing challenges center on trimer stability—advanced variants like AITRL-3S (engineered disulfides) extend 37°C half-life from 24 hours to >7 days. Analytics combine SEC-SAXS for trimer integrity with NF-κB reporter/T cell proliferation assays for potency.

Key clinical questions include addressing 100-fold DR3 expression variability, balancing effector/Treg modulation, and mitigating autoimmunity risks. Solutions may involve DR3 companion diagnostics, tissue-targeted prodrugs (e.g., MMP-9-activated), and rational combinations (e.g., with IL-2 variants/PD-1 blockers). Single-cell sequencing is unraveling disease-specific AITRL response heterogeneity for precision stratification.

Future Research Directions and Technological Breakthroughs
       Rational design generates enhanced rhAITRL variants—K150E mutation boosts DR3 affinity 5× without DcR3 engagement. Conditionally activated prodrugs (e.g., MMP-9-cleavable masks) increase therapeutic indices >10×. Fc/PEG fusions extend primate half-life to 5-7 days.

Innovative delivery systems include mRNA-based local expression, injectable hydrogels (4-week sustained release in arthritis), and exosome vehicles (100× higher lymph node targeting for vaccines). CRISPRa-mediated endogenous DR3 upregulation in Tregs enhances therapeutic sensitivity.Omics-AI integration advances mechanistic understanding—single-cell multiomics identifies epigenetic/metabolic signatures predicting responses. Machine learning models quantify AITRL-DR3 signaling to guide dosing. Gut-on-a-chip platforms evaluate epithelial barrier repair in IBD.

With these advances, rhAITRL-based therapies may emerge as versatile immunomodulators for autoimmunity, cancer, and infections. Critical clinical readouts over 5-10 years will define their therapeutic niche.

Related Product:  AITRL Protein, Human

Alias:
TNF18, Tumor necrosis factor ligand superfamily member 18, Activation-inducible TNF-related ligand, AITRL, Glucocorticoid-induced TNF-related ligand, hGITRL, TNFSF18, GITRL, TL6, rHuActivation-inducible TNF-related Ligand/AITRL, TL-6, rHuAITRL

Species: Human

Accession: Q9UNG2

Expression Sequence: Glu52-Ser177

Bioactivity JSON:

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