Correction of Feline Lipoprotein Lipase Deficiency with Adeno-Associated Virus Serotype 1-Mediated Gene Transfer of the Lipoprotein Lipase S447X Beneficial Mutation

Human lipoprotein lipase (hLPL) deficiency, for which there currently exists no adequate treatment, leads to excessive plasma triglycerides (TGs), recurrent abdominal pain, and life-threatening pancreatitis. We have shown that a single intramuscular administration of adeno-associated virus (AAV) serotype 1 vector, encoding the human LPL^S447X variant, results in complete, long-term normalization of dyslipidemia in LPL^–/– mice. As a prelude to gene therapy for human LPL deficiency, we tested the efficacy of AAV1-LPL^S447X in LPL^–/– cats, which demonstrate hypertriglyceridemia (plasma TGs, >10,000 mg/dl) and clinical symptoms similar to LPL deficiency in humans, including pancreatitis. Male LPL^–/– cats were injected intramuscularly with saline or AAV1-LPL^S447X (1 × 10¹¹–1.7 × 10¹² genome copies [GC]/kg), combined with oral doses of cyclophosphamide(0–200 mg/m² per week) to inhibit an immune response against hLPL. Within 3–7 days after administration of ≥5 × 1011 GC of AAV1-LPL^S447X per kilogram, the visible plasma lipemia was completely resolved and plasma TG levels were reduced by >99% to normal levels (10–20 mg/dl); intermediate efficacy (95% reduction) was achieved with 1 × 10¹¹ GC/kg. Injection in two sites, greatly limiting the amount of transduced muscle, was sufficient to completely correct the dyslipidemia. By varying the dose per site, linear LPL expression was demonstrated over a wide range of local doses (4 × 10¹⁰–1 × 10¹² GC/site). However, efficacy was transient, because of an anti-hLPL immune response blunting LPL expression. The level and duration of efficacy were significantly improved with cyclophosphamide immunosuppression. We conclude that AAV1-mediated delivery of LPL^S447X in muscle is an effective means to correct the hypertriglyceridemia associated with feline LPL deficiency.