Experience with cultured thymus tissue in 105 children.

BACKGROUND: Currently, there are no approved therapies to treat congenital athymia, a condition of immune deficiency resulting in high early mortality due to infection and immune dysregulation. Multiple syndromic conditions, such as complete DiGeorge syndrome, 22q11.2 deletion syndrome, CHARGE (coloboma, heart defects, choanal atresia, growth or mental retardation, genital hypoplasia, and ear anomalies and/or deafness) syndrome, diabetic embryopathy, other genetic variants, and FOXN1 deficiency, are associated with congenital athymia. OBJECTIVE: Our aims were to study 105 patients treated with cultured thymus tissue (CTT), and in this report, to focus on the outcomes of 95 patients with treatment-naive congenital athymia. METHODS: A total of 10 prospective, single-arm open-label studies with patient enrollment from 1993 to 2020 form the basis of this data set. Patients were tested after administration of CTT for T-cell development; all adverse events and infections were recorded. RESULTS: A total of 105 patients were enrolled and received CTT (the full analysis set). Of those patients, 10 had diagnoses other than congenital athymia and/or received prior treatments. Of those 105 patients, 95 patients with treatment-naive congenital athymia were included in the efficacy analysis set (EAS). The Kaplan-Meier estimated survival rates at year 1 and year 2 after administration of CTT in the EAS were 77% (95% CI = 0.670-0.844) and 76% (95% CI = 0.657-0.834), respectively. In all, 21 patients died in the first year before developing naive T cells and 1 died in the second year after receipt of CTT; 3 subsequent deaths were not related to immunodeficiency. A few patients developed alopecia, autoimmune hepatitis, psoriasis, and psoriatic arthritis after year 1. The rates of infections, autologous graft-versus-host-disease manifestations, and autoimmune cytopenias all decreased approximately 1 year after administration of CTT. CONCLUSION: Treatment with CTT led to development of naive T cells with a 1-year survival rate of 77% and a median follow-up time of 7.6 years. Immune reconstitution sufficient to prevent infections and support survival typically develops 6 to12 months after administration of CTT.

Care of Children with DiGeorge Before and After Cultured Thymus Tissue Implantation.

BACKGROUND: Children with complete DiGeorge anomaly (cDGA) have congenital athymia plus a myriad of other challenging clinical conditions. The term cDGA encompasses children with congenital athymia secondary to 22q11.2DS, CHARGE syndrome (coloboma, heart defects, choanal atresia, growth or mental retardation, genital abnormalities, and ear abnormalities and/or deafness), and other genetic abnormalities. Some children have no known genetic defects. Since 1993, more than 100 children with congenital athymia have been treated with cultured thymus tissue implantation (CTTI). Naïve T cells develop approximately 6 to 12 months after CTTI. Most of the children had significant comorbidities such as heart disease, hypoparathyroidism, and infections requiring complex clinical care post cultured thymus tissue implantation (CTTI). OBJECTIVE: The purpose of this guidance is to assist multidisciplinary teams in caring for children with cDGA both before and after CTTI. METHODS: Thirty-one specialists, in addition to the authors, were asked to share their experience in caring for children with cDGA at Duke University Health System, before and after CTTI. These specialists included physicians, nurses, dentists, therapists, and dieticians. RESULTS: The goal of a multidisciplinary approach is to have children in the best possible condition for receiving CTTI and provide optimal care post CTTI through development of naïve T cells and beyond. The CTT (cultured thymus tissue) must be protected from high doses of steroids which can damage CTT. Organs must be protected from adverse effects of immunosuppression. CONCLUSION: Creating a multidisciplinary team and a detailed plan of care for children with cDGA is important for optimal outcomes.

Clinical course and outcome predictors of critically ill infants with complete DiGeorge anomaly following thymus transplantation.

OBJECTIVES: To identify risk factors for PICU admission and mortality of infants with complete DiGeorge anomaly treated with thymus transplantation. We hypothesized that age at transplantation and the presence of congenital heart disease would be risk factors for emergent PICU admission, and these factors plus development of septicemia would increase morbidity and mortality. DESIGN: Retrospective review. SETTING: Academic medical-surgical PICU. PATIENTS: All infants with complete DiGeorge anomaly treated with thymus transplantation between January 1, 1993, and July 1, 2010. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Consent was obtained from 71 infants with complete DiGeorge anomaly for thymus transplantation, and 59 infants were transplanted. Median age at transplantation was 5.0 months (range, 1.1-22.1 mo). After transplantation, 12 of 59 infants (20%) required 25 emergent PICU admissions. Seven of 12 infants (58%) survived to PICU discharge with six surviving 6 months posttransplantation. Forty-two of 59 infants (71%) transplanted had congenital heart disease, and 9 of 12 (75%) who were admitted to the PICU had congenital heart disease. In 15 of 25 admissions (60%), intubation and mechanical ventilation were necessary. There was no difference between median ventilation-free days between infants with and without congenital heart disease (33 d vs 23 d, p = 0.544). There was also no correlation between ventilation-free days and age of transplantation (R, 0.17; p = 0.423). Age at transplantation and the presence of congenital heart disease were not associated with risk for PICU admission (odds ratio, 0.95; 95% CI, 0.78-1.15 and odds ratio, 1.27; 95% CI, 0.30-5.49, respectively) or PICU mortality (odds ratio, 0.98; 95% CI, 0.73-1.31 and odds ratio, 0.40; 95% CI, 0.15-1.07, respectively). CONCLUSIONS: Most transplanted infants did not require emergent PICU admission. Age at transplantation and the presence of congenital heart disease were not associated with PICU admission or mortality.

Mechanisms of tolerance to parental parathyroid tissue when combined with human allogeneic thymus transplantation.

BACKGROUND: The induction of tolerance toward third-party solid organ grafts with allogeneic thymus tissue transplantation has not been previously demonstrated in human subjects. OBJECTIVE: Infants with complete DiGeorge anomaly (having neither thymus nor parathyroid function) were studied for conditions and mechanisms required for the development of tolerance to third-party solid organ tissues. METHODS: Four infants who met the criteria received parental parathyroid with allogeneic thymus transplantation and were studied. RESULTS: Two of 3 survivors showed function of both grafts but subsequently lost parathyroid function. They demonstrated alloreactivity against the parathyroid donor in mixed lymphocyte cultures. For these 2 recipients, parathyroid donor HLA class II alleles were mismatched with the recipient and thymus. MHC class II tetramers confirmed the presence of recipient CD4(+) T cells with specificity toward a mismatched parathyroid donor class II allele. The third survivor has persistent graft function and lacks alloreactivity toward the parathyroid donor. All parathyroid donor class II alleles were shared with either the recipient or the thymus graft, with minor differences between the parathyroid (HLA-DRB1∗1104) and thymus (HLA-DRB1∗1101). Tetramer analyses detected recipient T cells specific for the parathyroid HLA-DRB1∗1104 allele. Alloreactivity toward the parathyroid donor was restored with low doses of IL-2. CONCLUSION: Tolerance toward parathyroid grafts in combined parental parathyroid and allogeneic thymus transplantation requires matching of thymus tissue to parathyroid HLA class II alleles to promote negative selection and suppression of recipient T cells that have alloreactivity toward the parathyroid grafts. This matching strategy may be applied toward tolerance induction in future combined thymus and solid organ transplantation efforts.

Review of 54 patients with complete DiGeorge anomaly enrolled in protocols for thymus transplantation: outcome of 44 consecutive transplants.

The purpose of this study was to characterize a large group of infants with complete DiGeorge anomaly and to evaluate the ability of thymus transplantation to reconstitute immune function in these infants. DiGeorge anomaly is characterized by varying defects of the heart, thymus, and parathyroid glands. Complete DiGeorge anomaly refers to the subgroup that is athymic (< 1%). The characteristics of 54 subjects at presentation and results from 44 consecutive thymus transplantations are reported. Remarkably, only 52% had 22q11 hemizygosity and only 57% had congenital heart disease requiring surgery. Thirty-one percent developed an atypical phenotype with rash and lymphadenopathy. To date, 33 of 44 subjects who received a transplant survive (75%) with post-transplantation follow-up as long as 13 years. All deaths occurred within 12 months of transplantation. All 25 subjects who were tested 1 year after transplantation had developed polyclonal T-cell repertoires and proliferative responses to mitogens. Adverse events developing after transplantation included hypothyroidism in 5 subjects and enteritis in 1 subject. In summary, diagnosis of complete DiGeorge anomaly is challenging because of the variability of presentation. Thymus transplantation was well tolerated and resulted in stable immunoreconstitution in these infants.