Impaired cytotoxic function and exhausted phenotype of natural killer cells in VEXAS syndrome Available to Purchase

• NK-cell phenotyping reveals impaired cytotoxicity, chronic activation, and exhaustion in VEXAS syndrome.

• Decreased circulating NK cells were independently associated with an increased risk of severe infections in VEXAS syndrome.

VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is an autoinflammatory disorder caused by acquired somatic ubiquitin like modifier activating enzyme 1 (UBA1) mutations in hematopoietic stem cells, affecting peripheral myeloid and natural killer (NK) cells. Given the high rate of severe infections in patients with VEXAS, we hypothesized that NK-cell dysfunction contributes to this susceptibility. We conducted a comprehensive immune characterization of peripheral NK cells in patients with VEXAS (n = 40), patients with autoinflammatory diseases without UBA1 mutations (n = 22), and older sex-matched healthy controls (n = 16). Multiparameter phenotyping used cytometry by time-of-flight, single-cell RNA sequencing (scRNA-seq), whole-blood stimulation assays, and in vitro NK-cell cytotoxic assay. Peripheral NK cells in VEXAS were quantitatively and qualitatively impaired. Mass cytometry revealed reduced frequencies of mature cytotoxic CD56^dim NK cells and expansion of the CD56^high CD16^dim subset. NK cells exhibited exhaustion features, including increased programmed cell death protein 1 expression, and reduced cytotoxic markers such as NKp46 and CD8α. scRNA-seq analysis showed decreased signatures of cytotoxicity and interleukin-2 (IL-2) and interferon gamma (IFN-γ) production, alongside increased inflammatory signatures. Whole-blood stimulation assays confirmed impaired IL-2, IFN-γ, and granzyme B production following Toll-like receptor 3 (TLR3), TLR4, and TLR7/TLR8 agonist stimulation. Extended NK phenotyping by flow cytometry confirmed reduced activating receptors’ expression and impaired IFN-γ production in VEXAS syndrome. Moreover, in vitro UBA1 inhibitors impaired NK-cell cytotoxic capacity and promote cell death. Finally, reduced NK-cell frequencies were independently associated with an increased risk of severe infections. These findings suggest that NK-cell dysfunction in VEXAS syndrome contributes to increased susceptibility to severe infections.