Long Term Correction of Bilirubin-UDP-glucuronosyltransferase Deficiency in Gunn Rats by Administration of a Recombinant Adenovirus during the Neonatal Period

Abstract

Injection of a recombinant adenovirus expressing human bilirubin-UGT 1 (Ad-hBUGT 1 ) (3 ؋ 10 9 plaque-forming units (pfu) intravenously) in adult bilirubin-UDPglucuronosyltransferase-1 (BUGT 1 )-deficient Gunn rats resulted in biliary excretion of bilirubin glucuronides and a 70% reduction of serum bilirubin levels. However, the effect was transient, and host humoral and cellular immune response prevented transgene expression after subsequent injections. To determine whether injection during the neonatal period would tolerize the host to the recombinant virus, we injected 1 ؋ 10 8 pfu of AdhBUGT 1 or Ad-LacZ (a recombinant adenovirus expressing Escherichia coli ␤-galactosidase) into 1-3-day-old Gunn rats. Two subsequent injections (3 ؋ 10 9 pfu) were given 56 and 112 days after the initial injection. Injection of Ad-BUGT 1 , but not Ad-LacZ, reduced serum bilirubin by 70 -76% of the levels in untreated pups (9 ؎ 1.3 mg/dl), followed by a gradual increase to 3.25 ؎ 0.3 mg/dl in 56 days; similar or greater reductions occurred after the second and third injection. Serum neutralizing antibody titer and cytotoxic lymphocyte activity against adenovirus-infected hepatocytes were low or undetectable. Thus, tolerization by injection of the virus during the neonatal period permits long term gene therapy by repeated injection of the virus.

Pulmonary inflammation associated with repeated, prenatal exposure to an E1, E3-deleted adenoviral vector in sheep

“…Administration of adenovirus vectors into the trachea, skeletal muscle, thoracic cavity or vasculature of neonatal mice or rats results in transgene expression for several weeks or months. 12,13,[18][19][20][21][22] Subsequent administration of the adenovirus vectors were tolerated and resulted in robust gene expression in some studies 19,20,23 but not others. 18 The relative success of this approach in rodents has been attributed to the relative immaturity of the immune system in the rodent at birth.…”

“…Studies in neonatal mice and rats have demonstrated that priming with an initial intravenous dose of adenovirus vector resulted in tolerance to subsequent administration of the same vector. 19,23 The intravenous route, which delivers …”

“…12,21,22 Injection of similar amounts of adenovirus into the thoracic cavity or abdomen or vasculature of newborn rats or mice is sufficient to induce tolerance, prolong gene expression and reduce inflammatory and immune responses to subsequent exposure. 19,20,23 Interestingly, injection of a higher dose (1 × 10 10 p.f.u.) into the trachea of newborn cotton rats resulted in prolonged gene expression that was extinguished when a second vector was injected 8-10 weeks later.…”

Fetal and neonatal gene therapy: benefits and pitfalls

“…These include glycogen storage disease type Ia, 1 mucopolysaccharidosis type VII, [2][3][4][5][6] bilirubin-UDP-glucuronosyltransferase deficiency (Crigler-Najjar syndrome), 7,8 haemophilias A 9 and B [10][11][12] and congenital blindness (Leber congenital amaurosis). 13 To fully understand the basis of these successful experiments in order to move towards clinical application, several key factors concerning early gene transfer must be closely examined.…”

Gene therapy as an alternative to liver transplantation

“…On systemic administration, they localize predominantly to the liver 16,17 and transduce both dividing and nondividing cells. In sufficient doses, these agents can transduce over 90% of all hepatocytes of the liver and so have been used extensively for in vivo hepatic gene transfer.…”