Nonsense CD247 mutations show dominant-negative features in T-cell receptor expression and function

BACKGROUND

The invariant TCR ζ/CD247 homodimer is crucial for TCR/CD3 expression and signaling through its 3 immunoreceptor tyrosine-based activation motifs (ITAMs). Homozygous null mutations in CD247 lead to immunodeficiency, while carriers exhibit 50% reduced surface CD3. It is unclear whether carriers of other CD247 variants show dominant-negative effects.

OBJECTIVE

We sought to analyze and model the potential impact on T-cell receptor (TCR) expression and function of heterozygous nonsense CD247 mutations found in patients with signs of immunodeficiency or autoimmunity.

METHODS

Jurkat T cells, either wild-type (WT) or CRISPR/Cas9-edited CD247-deficient (ZKO), were lentivirally transduced with WT CD247 or mutations ablating 1 (Q142X), 2 (Q101X), or 3 (Q70X) ITAMs.

RESULTS

Three patients from unrelated families were studied. Two heterozygous nonsense CD247 mutations were identified (p.Y152X and p.Q101X), which affected ITAM-3 and ITAM-2 and ITAM-3, respectively. Both mutations were associated with low surface CD3 expression and normal intracellular CD247 levels using a transmembrane-specific antibody, but very low intracellular CD247 levels using an ITAM-3-specific one, suggesting the presence of truncated variants in T cells. Transduction of the mutations lacking 1, 2, or 3 ITAMs into ZKO cells could not restore normal surface CD3 expression (only 60%, 22%, and 10%, respectively), whereas in WT cells, normal surface CD3 expression was reduced (to 39%, 19%, and 9% of normal levels), and both effects were dependent on ITAM number. All 6 transfectants showed reduced CD69 induction (25% to 50%), indicating that they were unable to signal downstream properly, neither isolated nor associated with WT CD247.

CONCLUSIONS

Our results suggest that CD247 variants lacking ITAMs due to nonsense, but not null, mutations are defective for normal TCR assembly and exert a dominant-negative effect on TCR expression and signaling in vitro. This, in turn, may correlate with clinical features in vivo.

Infectious outcomes of a standardized subcutaneous immunoglobulin dose reduction strategy in primary immune deficiencies amid global shortage

Introduction

Immunoglobulin replacement therapy (IgRT), either intravenous (IVIg) or subcutaneous (SCIg), is crucial for managing primary immune deficiencies (PIDs) with hypogammaglobulinemia by reducing infection rates and mortality. During the COVID-19 pandemic, a global shortage of SCIg prompted our unit to reduce SCIg doses or maintain the same dose intravenously. This study evaluates the impact of a standardized SCIg dose reduction on infection rates and clinical outcomes in patients with humoral PID and with a low burden of infections.

Methods

Adult PID patients on SCIg for at least 6 months, with IgG trough levels ≥ 700 mg/dL (or ≥ 900 mg/dL under specific conditions), and no significant infections in the past 6 months were eligible. A dose reduction of 15 mg/kg/week (60 mg/kg/month) for every 150 mg/dL above 700 mg/dL (or 900 mg/dL) was proposed. Clinical and laboratory data, and infectious events at 6- and 12-month follow-ups, were analyzed.

Results

Thirty-one patients with PID were included: common variable immunodeficiency (54.83%), IgG subclass deficiency (9.67%), and other PIDs (35.48%). The average SCIg dose was initially reduced from 7.82 g/week to 5.72 g/week and adjusted to 6.94 g/week at 12 months. There was no significant change in severe or mild infections before and at 6- and 12-months post-dose adjustment. The dose reduction saved an average of 5,550 euros per patient annually, totaling 172,050 euros annually for our cohort.

Discussion

Optimizing SCIg doses in selected well-controlled humoral PIDs is feasible without increasing infection rates, conserving this plasma-derived product during shortages. Larger prospective studies are needed to confirm this strategy's utility and its application to other Ig formulations.

Patient-centered outcomes with subcutaneous immunoglobulin use for infection control in primary and secondary immunodeficiencies: data of a GEIE Spanish Registry

Background and aim

Subcutaneous immunoglobulin (SCIg) has emerged as an alternative to intravenous administration for patients with primary (PID) and secondary immunodeficiencies (SID), offering benefits such as fewer systemic adverse reactions and greater patient autonomy. However, comprehensive real-world data on SCIg use, including clinical and patient-centered outcomes, remain scarce. This study, conducted by expert immunodeficiency nursing teams, assesses the clinical characteristics, reported adverse effects, and quality-of-life outcomes associated with SCIg therapy with different formulations in patients with PID and SID across Spain.

Methods

A multicenter, cross-sectional study was conducted across 8 immunodeficiency nursing units in Spain, involving 223 adult patients treated with SCIg from 2004 to 2024. Data on demographics, comorbidities, SCIg treatment characteristics, reported adverse events, and quality-of-life metrics (EuroQol-5D-3L, Gijón Scale) were collected and analyzed.

Results

The cohort (61.4% female, mean age: 47.1 years) included 65% PID patients, with common variable immunodeficiency being the most frequent diagnosis (39.8%). SCIg demonstrated good tolerability overall, with no significant differences in global adverse event rates between facilitated 10% (fSCIg) and 20% formulations. However, 10% fSCIg was associated with higher reported frequencies of mild local rash (58.7% vs. 36.9%, p=0.002) and fever (10.6% vs. 1.7%, p=0.01). Quality-of-life scores indicated minimal limitations in mobility and self-care, with a mean subjective health rating of 72.7/100. Patients using 20% SCIg required fewer educational sessions for self-administration compared to the 10% group.

Conclusion

The different SCIg formulations in this large, multicenter cohort was effective and generally well-tolerated, supporting its use for maintaining adequate IgG levels and promoting patient independence in PID and SID. The study's findings advocate for tailored approaches that optimize patient satisfaction and address individual needs, emphasizing the critical role of dedicated immunodeficiency nursing teams in ensuring safe, effective, and patient-centered SCIg administration.