Table 3.
Effect of AAV8 Neutralizing Antibodies on In Vivo Transduction by scAAV8.FIXR338L and Failure of Excess Empty AAV8 Capsids to Affect Transduction
| Factor IX expression (% factor IX activity) | |||||||
|---|---|---|---|---|---|---|---|
| Condition | AAV8 NAb | scAAV8.FIXR338L (VG/kg) | Empty capsid (EC) (VG/kg) | Week 1 | Week 2 | Week 4 | Week 8 |
| Vector alone | None | 1×1011 | None | 5.6±0.8 | 8.2±2.9 | 7.5±2.1 | 7.9±2.0 |
| Moderate-titer NAb | 1:16 | 1×1011 | None | <1 | <1 | <1 | <1 |
| Moderate-titer NAb+50% EC | 1:16 | 1×1011 | 1×1011 | <1 | <1 | <1 | <1 |
| Moderate-titer NAb+80% EC | 1:16 | 1×1011 | 4×1011 | <1 | <1 | <1 | <1 |
| Week 1 | Week 2 | Week 4 | Week 8 | ||||
|---|---|---|---|---|---|---|---|
| Vector alone | None | 1×1011 | None | 5.0±1.0 | 6.6±1.0 | 5.9±0.6 | No sample |
| Low-titer NAb | 1:2 | 1×1011 | None | <1 | <1 | <1 | No sample |
| Low-titer NAb+50% EC | 1:2 | 1×1011 | 1×1011 | <1 | <1 | <1 | No sample |
| Low-titer NAb+80% EC | 1:2 | 1×1011 | 4×1011 | <1 | <1 | <1 | No sample |
| Week 1 | Week 2 | Week 4 | Week 8 | ||||
|---|---|---|---|---|---|---|---|
| Vector alone | None | 1×1011 | None | 7.0±3.1 | 11.5±3.2 | 12.8±5.5 | 12.8±4.7 |
| 95% EC | None | 1×1011 | 1.8×1012 | 7.9±2.7 | 10.5±3.5 | 13.0±4.5 | 12.5±3.5 |
AAV8, adeno-associated virus serotype 8; EC, empty capsids; NAb, neutralizing antibody; VG, vector genomes.
Note: Serum from syngeneic (C57BL/6) mice, previously vaccinated with AAV8.A1AT vector, was used to passively transfer titratable AAV8 neutralizing antibodies (NAbs) into previously untreated C57BL/6 FIX–/– mice. Mice received either no AAV8 NAb, or NAb adequate to achieve low neutralizing titers (1:2), or to achieve moderate NAb titer (1:16). Subsequently, all mice were treated with the same dose of FIXR338L expression vector. Various cohorts of mice received the scAAV8.FIXR338L GLP vector alone (∼5–10% empty capsid contamination) or the GLP vector mixed at a 1:1 ratio with AAV8 empty capsids or the GLP vector.