Evaluation of Adeno-Associated Viral Vectors for Liver-Directed Gene Transfer in Dogs

Abstract

This study evaluated six adeno-associated viral (AAV) vectors expressing green fluorescent protein (GFP) from the liver-specific thyroid hormone-binding globulin (TBG) promoter made with novel capsids in canine liverdirected gene transfer. Studies in 1.5-month-old dogs, which were administered vector through a peripheral vein, showed that AAV8 capsid vectors had the most favorable performance profiles. Interestingly, the absolute levels of hepatocyte transduction achieved with AAV8 were lower in dogs compared with what had been achieved in mice and nonhuman primates. Additional studies were performed with AAV8 delivered into the hepatic artery in adult dogs, with higher doses of vector used to assess potential dose-limiting toxicities. These studies showed good transduction on day 7 in one dog that apparently was lost by day 28 in another dog through the generation of GFP-specific T cells. Each adult dog was carefully monitored for any hemodynamic changes associated with vector infusion. Both animals demonstrated mild to moderate hypotension and bradycardia, which appeared to be anesthesia-related, making it difficult to evaluate contributions of the vector.

Long-Term Systemic Myostatin Inhibition via Liver-Targeted Gene Transfer in Golden Retriever Muscular Dystrophy

“…The scAAV8-TBG-dnMSTAT construct was designed to express the secreted canine myostatin Belgian Blue inhibitory peptide (Kambadur et al, 1997) containing a D76A mutation that confers protease resistance (Wolfman et al, 2003) under control of the liver-specific thryroid-hormone binding globulin (TBG) promoter (Bell et al, 2011).…”

“…The scAAV8-TBG-dnMSTAT vector was tested in two normal canines prior to its use in GRMD canines. One normal canine received 10 12 genome copies (gc)/kg vector via hepatic artery infusion as previously described (Bell et al, 2011), and one normal canine received 10 12 gc/kg vector via peripheral intravenous (IV) infusion (cephalic vein). The remaining dogs used in the study were GRMD canines, which received either 1.7 · 10 12 gc/kg vector (n = 4) via IV infusion or no treatment (n = 3).…”

“…The scAAV8-dnMSTAT vector was tested in two normal canines prior to its use in GRMD canines. One normal canine received 10 12 gc/kg vector via hepatic artery infusion as previously described (Bell et al, 2011), and one normal canine received 10 12 gc/kg vector via peripheral IV infusion (cephalic vein). Expression levels of dnMSTAT in canine serum are demonstrated up to 20 weeks post injection (Fig.…”

CpG-depleted adeno-associated virus vectors evade immune detection

“…The apparent immune evasion of AAV8 to antigenic transgene products in mouse models is not relevant to larger animals such as primates and dogs (23)(24)(25), in which vibrant and destructive CTLs are elicited. In fact, the study of AAVrh32.33 in mice may better reflect the anticipated biology of other AAV capsids in large animals and humans.…”

Mapping a Neutralizing Epitope onto the Capsid of Adeno-Associated Virus Serotype 8

“…However, such high levels of hepatic cell transduction by AAV8-based vectors observed in mice have yet to be repeated in larger animal models. Levels of gene transfer similar to those found in mice have been demonstrated in studies of infant rhesus macaques (73), and recent data suggest lower efficiency in dog models (7). Despite these results, studies in dogs with hemophilia have demonstrated AAV8-mediated continuous expression of canine factor VIIa at levels above normal values (46).…”