Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects

Abstract

Background: Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is a negative immune regulator. Heterozygous CTLA4 germline mutations can cause a complex immune dysregulation syndrome in human subjects.

Objective: We sought to characterize the penetrance, clinical features, and best treatment options in 133 CTLA4 mutation carriers.

Methods: Genetics, clinical features, laboratory values, and outcomes of treatment options were assessed in a worldwide cohort of CTLA4 mutation carriers.

Results: We identified 133 subjects from 54 unrelated families carrying 45 different heterozygous CTLA4 mutations, including 28 previously undescribed mutations. Ninety mutation carriers were considered affected, suggesting a clinical penetrance of at least 67%; median age of onset was 11 years, and the mortality rate within affected mutation carriers was 16% (n = 15). Main clinical manifestations included hypogammaglobulinemia (84%), lymphoproliferation (73%), autoimmune cytopenia (62%), and respiratory (68%), gastrointestinal (59%), or neurological features (29%). Eight affected mutation carriers had lymphoma, and 3 had gastric cancer. An EBV association was found in 6 patients with malignancies. CTLA4 mutations were associated with lymphopenia and decreased T-, B-, and natural killer (NK) cell counts. Successful targeted therapies included application of CTLA-4 fusion proteins, mechanistic target of rapamycin inhibitors, and hematopoietic stem cell transplantation. EBV reactivation occurred in 2 affected mutation carriers after immunosuppression.

Conclusions: Affected mutation carriers with CTLA-4 insufficiency can present in any medical specialty. Family members should be counseled because disease manifestation can occur as late as 50 years of age. EBV- and cytomegalovirus-associated complications must be closely monitored. Treatment interventions should be coordinated in clinical trials.

Keywords: Cytotoxic T-lymphocyte antigen 4; abatacept; autoimmunity; common variable immunodeficiency; hematopoietic stem cell transplantation; hypogammaglobulinemia; immune dysregulation; primary immunodeficiency; sirolimus.

Figure 1. Pedigrees of families with CTLA-4 insufficiency

Pedigrees of all families with more than one CTLA4 mutation carrier. Squares, male subjects; circles, female subjects; black filled symbols, mutation carriers classified as affected; gray filled symbols, mutation carriers classified as unaffected; slashed symbols, deceased subjects; *, sequencing of CTLA4 was performed; §, genotype inferred from clinical symptoms.

Figure 2. Age of onset and age of death in CTLA-4 insufficient subjects

A. Kaplan Meier curve of age of onset of CTLA4 mutation carriers (n=85). B. Age of death in affected (n=86) versus unaffected mutation carriers (n=39).

Figure 3. Heterozygous germline mutations within the CTLA4 gene are distributed throughout exon 1–3

Figure 3 shows the distribution of the heterozygous germline mutations throughout the CTLA4 gene. Eight mutations are located in exon 1, 31 are located in exon 2, and six are located in exon 3. §, mutation was functionally tested by transendocytosis assay.

Figure 4. Main clinical findings in CTLA-4 insufficiency

Percentage distribution of clinical manifestations within affected mutation carriers. Clinical data was available for 71 to 90 affected mutation carriers.

Figure 5. Exemplary findings upon CT and MRI in CTLA-4-insufficient subjects

Panel A: splenomegaly (17.5 cm in diameter) and lymphadenopathy in A.III.3. Panel B: large pneumatocele following necrotizing pneumonia in PP.II.1. Panel C: CT scan of ZZ.II.1 showing peripheral bronchiectasis with inflammatory nodules in all lobes of the lung. Panel D: bronchiectasis with peribronchial ground glass nodules in keeping with bronchiolitis in XX.II.1. Panel E: multiple inflammatory nodules in O.II.1. Panel F: signal change in the right temporal lobe and cerebellum consistent with inflammation in KK.II.1. Panel G: enhancement in the thoracic cord in keeping with inflammation in KK.II.1. Panel H: signal change and swelling in the cerebellum in keeping with inflammation in P.II.2.

Figure 6. Lymphocytic infiltrations and loss of EBV control define the spectrum of inflammatory and neoplastic lesions

Panel A and B: lung samples of PP.II.1 and KK.II.1 with follicular bronchitis/ bronchiolitis, respectively. Lymphoid follicles are marked by asterisks. In Panel A, the follicle contains a germinal center. Panel C: EBV-coded small RNAs (EBER) positive nuclei (dark blue staining) of an early invasive gastric adenocarcinoma of B.II.4. Panel D: autoimmune gastritis with severely atrophic mucosa of the stomach, antral metaplasia and numerous intraepithelial CD8+ T cells (brown staining) of B.II.4. Panel E: nodular T cell lymphocytosis (brown staining) in the bone marrow of Z.II.2. Panel F: perivascular lymphocytes in the brain tissue of KK.II.1 (arteriolar wall highlighted by arrowhead, lumen marked by asterisk). Panel G and H: Hodgkin lymphoma in a lymph node excision sample of MM.II.1. Reed-Sternberg cell is highlighted by an arrowhead (G) or CD30 immunohistochemistry (red staining in H). Nuclei of Hodgkin cells and Reed-Sternberg cells were positive for EBER (dark blue staining, inlet H).