This study has three primary purposes: to assess parathyroid function after parathyroid
transplantation in infants with Complete DiGeorge syndrome; to assess immune function
development after transplantation; and, to assess safety and tolerability of the procedures.
This is a Phase 1, single site, open, non-randomized clinical protocol. Enrollment is closed
and study intervention is complete for all enrolled subjects; but subjects continue for
observation and follow-up. Subjects under 2 years old with complete DiGeorge syndrome
(atypical or typical) received thymus transplantation. Subjects received pre-transplant
immune suppression with rabbit anti-human-thymocyte-globulin. Subjects with
hypoparathyroidism and an eligible parental donor received thymus and parental parathyroid
transplantation. A primary hypothesis: Thymus/Parathyroid transplant subjects will need less
calcium and/or calcitriol supplementation at 1 year post-transplant as compared to
Detailed: DiGeorge Syndrome is a complex of three problems, 1) cardiac defects, 2)
parathyroid deficiency, and 3) absence of the thymus, resulting in profound T-cell
deficiency. There is a spectrum of disease in DiGeorge syndrome with respect to all three
defects. There is no safe and effective treatment for DiGeorge Syndrome and most patients
die by the age of two. For patients with a severe T cell defect, the PI has shown that
thymus transplantation is safe and efficacious under other clinical protocols. Research
subjects with complete typical and atypical DiGeorge syndrome were eligible for this study.
Subjects with athymia and profound hypoparathyroidism were eligible for parental parathyroid
transplantation in this protocol. DiGeorge syndrome infants, who have successful thymus
transplants but have hypoparathyroidism, must go to the clinic for frequent calcium levels
and to the hospital for calcium infusions; infants with hypoparathyroidism are at risk for
seizures from low calcium. Approximately ½ of infants with profound hypoparathyroidism will
develop nephrocalcinosis. Depending on T cell phenotype and function, subjects were given
one of two different immunosuppression regimens. Typical complete DiGeorge subjects (with
proliferative T cell function < 50,000 cpm) received Thymoglobulin pre-transplantation.
Typical complete DiGeorge subjects (with proliferative cell response to PHA > 50,000 cpm)
and atypical DiGeorge subjects (with proliferative T cell response to PHA < 75,000 cpm)
received Thymoglobulin (pre-transplantation) and cyclosporine (pre-transplantation and
post-transplantation). Thymoglobulin was used in part to prevent graft rejection and also to
deplete any T cells in the donor parathyroid. Cyclosporine was used to deplete activated T
cells in the recipient. For all subjects, acetaminophen, diphenhydramine, and
methylprednisolone were given concurrently with the rabbit anti-human thymocyte globulin.
The thymus was cultured in standard medium for 10-21 days to deplete mature thymocytes which
could cause GVHD. In the operating room, thymus tissue was placed in the quadriceps muscle
in one or both legs. The parathyroid donation was preferably done at the same time as the
thymus transplantation. Parathyroid tissue was placed in the quadriceps muscle in only one
leg, using the same incision as the thymus transplantation. Depending on post-transplant
immune status, subjects may have received cyclosporine and steroids.
For 3 months after thymus transplantation, T cells were monitored by flow cytometry
approximately every 2-4 weeks. Alternatively, absolute lymphocyte count was used as the
maximum possible T cell number. At 2-3 months post-transplant, the subject had a thymus
allograft biopsy, done under general anesthesia in the operating room. The biopsy was
approximately 4 pea-sized (3x3mm) portions of muscle tissue where the thymus transplant had
been inserted. Using immunohistochemistry, the biopsy determined thymopoiesis and any graft
rejection. The parathyroid was not biopsied because it is very small; doing a biopsy could
remove all of the parathyroid tissue. A research skin biopsy (at site of skin incision at
the time of transplantation) was done to determine whether T cells were present
pre-transplantation. A skin biopsy was also done at the time of thymus graft biopsy to look
for clonal T cell populations. For all subjects who developed T cells, post-transplantation
pneumocystis prophylaxis was used for approximately 1 year and IV immunoglobulin for
approximately 2 years.
- Complete DiGeorge syndrome (typical or atypical) - may have DiGeorge as part of 22q11
hemizygosity, CHARGE association, or diabetic embryopathy or they may have no
- Must have 1 of following:
- Circulating CD3+ T cells < 50/mm3; or
- Circulating CD3+ T cells that also positive for CD45RA and CD62L must be <50/mm3
or must be < 5% of total T cells.
- Must be <24 months old
- Laboratory studies must be done w/in 1 month of treatment:
- Thyroid studies - if abnormal must be on therapy, if recommended by
- PT and PTT must be <2x upper limits of normal (ULN)
- Absolute neutrophil count must be >500/mm3
- Platelet count must be >50,000/mm3
- AST and ALT must be <5x ULN
- Creatinine must be <1.5 mg/dl
- Parents must agree to have infant stay in Durham until thymus biopsy is done 2-3
- Typical subjects must not have a rash with T cells on biopsy nor lymphadenopathy.
- Atypical subjects have rash with T cells on biopsy; may have lymphadenopathy.
- PHA proliferative responses must be tested 2x • Atypical: PHA response must be
<75,000cpm on 2 tests; test can be done while on immunosuppression.
Additional Criteria for Parathyroid Treatment Inclusion
- At least 1 parent must agree to be parathyroid donor
- Must require calcium supplementation to maintain ionized calcium >1.0 mmol/L.
Alternatively, intact PTH must be <lower limit of normal when ionized calcium is <1.2
mmol/L. (Intact PTH measured 2x pre-treatment.)
DiGeorge Treatment Exclusion:
- Heart surgery conducted <4 weeks pre-treatment
- Heart surgery anticipated w/in 3 months of treatment
- Rejection by surgeon or anesthesiologist as surgical candidate
- Lack of sufficient muscle tissue to accept 0.2gms/kg treatment
- Prior attempts at immune reconstitution, such as bone marrow treatment or previous
- Doesn't commit to remaining at Duke until thymus allograft biopsy
Parathyroid Donor Inclusion:
- Serum calcium in normal range
- Normal parathyroid hormone function
- HLA typing must be consistent with parentage.
- Must not be on anticoagulation or can come off
- Parent chosen for donation will be the 1 sharing most HLA alleles with thymus donor
- HLA-DR matching preferred over HLA class I matching. If there no HLA matching at all,
then either parent will be acceptable if meets other criteria.
- Negative for EBV; CMV; HIV-1; Syphilis; West Nile virus; Hepatitis B; Hepatitis C;
pregnancy; & evidence of head/neck infection
- Fiberoptic nasolaryngoscopy shows vocal cords functioning normally.
- Normal thyroid function
- No history of cancer
- The infant-recipient has 2 living involved parents.
Parathyroid Donor Exclusion:
- Infant recipient doesn't have 2 living involved parents
- Animal tissue/organ recipient
- West Nile virus
- Hepatitis B
- Hepatitis C
- Evidence of head/neck infection
- Vocal cords not functioning normally.
- Thyroid abnormalities
- History of cancer
- Mad cow disease (positive)
- SARS(and exposure)
- Smallpox exposure
Biological Mother of DiGeorge Subjects Inclusions:
Mother must be competent to consent or assent to study participation and willing to
provide blood sample. No other inclusion/exclusion.
M. Louise Markert, MD, PhD
Duke University Medical Center, Pediatrics, Allergy & Immunology