Comparison of Serum rAAV Serotype-Specific Antibodies in Patients with Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, Inclusion Body Myositis, or GNE Myopathy

Abstract

Recombinant adeno-associated virus (rAAV) is a commonly used gene therapy vector for the delivery of therapeutic transgenes in a variety of human diseases, but pre-existing serum antibodies to viral capsid proteins can greatly inhibit rAAV transduction of tissues. Serum was assayed from patients with Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), inclusion body myositis (IBM), and GNE myopathy (GNE). These were compared to serum from otherwise normal human subjects to determine the extent of pre-existing serum antibodies to rAAVrh74, rAAV1, rAAV2, rAAV6, rAAV8, and rAAV9. In almost all cases, patients with measurable titers to one rAAV serotype showed titers to all other serotypes tested, with average titers to rAAV2 being highest in all instances. Twenty-six percent of all young normal subjects (<18 years old) had measurable rAAV titers to all serotypes tested, and this percentage increased to almost 50% in adult normal subjects (>18 years old). Fifty percent of all IBM and GNE patients also had antibody titers to all rAAV serotypes, while only 18% of DMD and 0% of BMD patients did. In addition, serum-naïve macaques treated systemically with rAAVrh74 could develop cross-reactive antibodies to all other serotypes tested at 24 weeks post treatment. These data demonstrate that most DMD and BMD patients should be amenable to vascular rAAV-mediated treatment without the concern of treatment blockage by pre-existing serum rAAV antibodies, and that serum antibodies to rAAVrh74 are no more common than those for rAAV6, rAAV8, or rAAV9.

Keywords: adeno-associated virus; gene therapy; muscular dystrophy; myopathy.

Figure 1.

Average reciprocal dilution factor for positive signal and propensity of positive signals in young and adult normal patients compared to Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), inclusion body myositis (IBM), and GNE myopathy (GNE) patients. Average reciprocal dilution factor required for a positive serum antibody signal to rAAVrh74, rAAV8, rAAV1, rAAV2, rAAV6, or rAAV9 (A) and the percentage of patients with positive signal at a 1:50 or 1:800 serum dilution (B) are shown. Errors in (A) are standard error of the mean for 19 (<18 normal), 21 (>18 normal), 22 (DMD), 16 (BMD), 18 (IBM) or 4 (GNE) patients.

Figure 2.

Induction of cross-reactive macaque serum rAAV antibodies after systemic treatment with rAAVrh74.MCK.GALGT2. Highest reciprocal dilutions required for positive signal of serum antibodies to rAAVrh74, rAAV8, rAAV1, rAAV2, rAAV6, or rAAV9 are shown in patients in macaques treated for 12 weeks (A) or 24 weeks (B and C) with 2 × 10¹²vg/kg rAAVrh74.MCK.GALGT2 with (C) or without (A and B) prednisone pre- and co-treatment.