KIR2DS1-HLA-C status as a predictive marker for benefit from rituximab: a post-hoc analysis of the RICOVER-60 and CLL8 trials.

BACKGROUND: The addition of rituximab to chemotherapy has substantially improved outcomes for patients with B-cell malignancies. The mechanisms of action of rituximab include activation of natural killer cells. Killer-cell immunoglobulin-like receptors (KIRs) mediate natural killer cell function through interaction with HLA. We evaluated the clinical impact of KIR-HLA genotypes on rituximab-containing therapy. METHODS: For this post-hoc analysis, we used data from the RICOVER-60 trial (NCT00052936) as the discovery cohort and the CLL8 trial (NCT00281918) as the validation cohort. RICOVER-60 included patients aged 61-80 years with aggressive B-cell lymphoma treated with CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) with or without rituximab. CLL8 included patients aged 30-81 years with chronic lymphocytic leukaemia treated with chemotherapy (fludarabine and cyclophosphamide; FC) with or without rituximab. We evaluated the KIR and HLA-C status of 519 patients with available blood samples in the RICOVER-60 trial and the KIR2DS1 and HLA-C status of 549 patients with available blood samples in the CLL8 trial, and evaluated their associations with event-free survival (RICOVER-60), progression-free survival, and overall survival (RICOVER-60 and CLL8). FINDINGS: In the RICOVER-60 trial, 201 (39%) patients were positive for KIR2DS1, 79 (15%) were homozygous for HLA-C2, and 36 (7%) were positive for KIR2DS1 and homozygous for HLA-C2. In the CLL8 trial, 206 (38%) patients were positive for KIR2DS1, 75 (14%) were homozygous for HLA-C2, and 26 (5%) were positive for KIR2DS1 and homozygous for HLA-C2. In the RICOVER-60 trial, both KIR2DS1 and HLA-C status were identified as independent risk factors for survival. KIR2DS1 positivity, homozygosity for HLA-C2, and subsequent KIR2DS1-HLA-C status were associated with adverse clinical outcome in patients receiving rituximab-containing therapy (event-free survival for patients with KIR2DS1-HLA-C2/C2 vs all other patients, HR 2·6 [95% CI 1·4-4·7], p=0·0015; progression-free survival, 2·7 [1·5-5·1], p=0·0013; overall survival, 2·8 [1·5-5·4], p=0·0016) but not in patients receiving CHOP chemotherapy only (event-free survival, 0·9 [0·5-1·7], p=0·85; progression-free survival, 1·1 [0·6-2·0], p=0·81; overall survival, 1·2 [0·6-2·4], p=0·53). A significant interaction between KIR2DS1-HLA-C status and rituximab was observed (p=0·018 for event-free survival and p=0·034 for progression-free survival). In contrast to all other patients, those positive for KIR2DS1 and homozygous for HLA-C2 did not benefit from adding rituximab to CHOP chemotherapy (event-free survival, 1·9 [0·8-4·6], p=0·16; progression-free survival, 1·4 [0·6-3·4], p=0·48; overall survival, 1·6 [0·6-4·3], p=0·33). In the CLL8 trial, KIR2DS1-HLA-C status was confirmed as a predictive marker for benefit from rituximab therapy (p=0·024 for the interaction of KIR2DS1-HLA-C status and rituximab regarding progression-free survival). In contrast to all other patients, those positive for KIR2DS1 and homozygous for HLA-C2 did not benefit from adding rituximab to FC chemotherapy (progression-free survival, 2·1 [0·9-4·9], p=0·094; overall survival, 2·6 [0·5-12·7], p=0·21). INTERPRETATION: Assessment of KIR2DS1 and HLA-C genotype might identify patients who would not benefit from rituximab, thereby allowing alternative therapies to be given. Further validation of these findings in prospective clinical trials is needed. FUNDING: F Hoffman La Roche.

Autoantibodies against SUMO1-DHX35 in long-COVID.

Long COVID is a collection of symptoms as a late sequelae of SARS-CoV-2 infection. It often includes mental symptoms such as cognitive symptoms, persisting loss of smell and taste, in addition to exertional dyspnea. A role of various autoantibodies (autoAbs) has been postulated in long-COVID and is being further investigated. With the goal of identifying potentially unknown autoAbs, we screened plasma of patients with long COVID on in-house post-translationally modified protein macroarrays including citrullinated, SUMOylated and acetylated membranes. SUMO1ylated isoform DEAD/H (Asp-Glu-Ala-Asp/His) box helicase 35 (SUMO1-DHX35) was identified as only candidate antigen. In adult patients with long COVID, IgG autoAbs against SUMO1-DHX35 of IgG class were found in seven of 71 (9.8%) plasma samples, of IgM and IgG class in one of 69 (1.4%) samples, not in 200 healthy adult controls, not in 442 healthy children, and 146 children after SARS-CoV-2 infection. All autoAb-positive seven patients were female. AutoAb titers ranged between 200 to up to 400 By point mutagenesis and expression of FLAG-tagged mutants of DHX35 in HEK293 cells, and subsequent SUMOylation of purified constructs, lysine 53 was identified as a unique, never yet identified, SUMOylation site. The autoAbs had no reactivity against the non-SUMO1ylated mutant (K53R) of DHX35. To summarize, autoAbs against SUMO1-DHX35 were identified in adult female patients with long-COVID. Further studies are needed to verify the frequency of occurrence. The function of DHX35 has not yet been determined and there is no available information in relation to disease implication. The molecular mechanism causing the SUMOylation, the potential functional consequences of this post-translational modification on DHX35, and a potential pathogenicity of the autoAbs against SUMO1-DHX35 in COVID-19 and other possible contexts remain to be elucidated.