Figure 3.

Immunogenicity of IUGT

(A) AAV8 recipients maintained low-level anti-AAV8 IgG after IUGT, which steadily increased following postnatal vector challenges in 8007 (arrows). Recipients of AAV5 mounted a more robust IgG response sustained for a year post-IUGT. (B) A single vector challenge to 5006 did not cause a substantial shift in IgG expression (arrow). (C) Expression in 8007 remained sub-therapeutic after both vector challenge (VC) (broken lines) at 30 and 46 months of age, peaking at 1.3% after the second challenge. Anti-AAV Ab levels remained subclinical. (D) NAbs were detected briefly by >50% loss of GFP expression in previously transduced cells in vitro. (E) Similar observations were made in 5006 in following VC (broken line) at 32 months; anti-AAV5 Abs remained stable. Upper dotted line in (C) and (E) indicates positive threshold for IgG response; lower dotted line indicates therapeutic minimum of 1% hFIX activity. (F) In 8007, IL-2 and TNF-α was expressed in 2% of CD8 central memory cells at week 1 and was no longer detectable by week 2 (positive ∼23.5% IL-2, TNF-α, and INF-γ; negative ∼1% expression). (G) 5006 showed intermittent increases in liver-specific ALT following VC (arrowhead), whereas minimal responses were observed in 8007 (arrows). Intermittent fluctuations in AST were observed before and after VC in both animals.