Hepatic Gene Transfer in Neonatal Mice by Adeno-Associated Virus Serotype 8 Vector

Abstract

For genetic diseases that manifest at a young age with irreversible consequences, early treatment is critical and essential. Neonatal gene therapy has the advantages of achieving therapeutic effects before disease manifestation, a low vector requirement and high vector-to-cell ratio, and a relatively immature immune system. Therapeutic effects or long-term rescue of neonatal lethality have been demonstrated in several animal models. However, vigorous cell proliferation in the newborn stage is a significant challenge for nonintegrating vectors, such as adeno-associated viral (AAV) vector. Slightly delaying the injection age, and readministration at a later time, are two of the alternative strategies to solve this problem. In this study, we demonstrated robust and efficient hepatic gene transfer by self-complementary AAV8 vector in neonatal mice. However, transduction quickly decreased over a few weeks because of vector dilution caused by fast proliferation. Delaying the injection age improved sustained expression, although it also increased neutralizing antibody (NAb) responses to AAV capsid. This approach can be used to treat genetic diseases with slow progression. For genetic diseases with early onset and severe consequences, early treatment is essential. A second injection of vector of a different serotype at a later time may overcome preexisting NAb and achieve sustained therapeutic effects.

Immunological Ignorance Allows Long-Term Gene Expression After Perinatal Recombinant Adeno-Associated Virus-Mediated Gene Transfer to Murine Airways

“…This is supported by the fact that contrary to the strong decrease in lung signal 3 months after perinatal treatment ( Figs. 1 and 2), the same dose administered to adult mice resulted in stable gene expression (our unpublished observations), in line with data published by Wilson and colleagues (Wang et al, 2012).…”

“…Transduction with a nonintegrating rAAV vector results in transient gene expression in actively dividing cells and remains a challenge in many gene therapy studies (Flageul et al, 2009;Wang et al, 2012). At present, many methods are being evaluated for rAAV readministration, for example, by serotype switching (Weinstein et al, 2010;Wang et al, 2012), capsid engineering , or immune modulation and tolerance induction to prevent immune responses to the vector and/or transgene (Goudy et al, 2011;Wang et al, 2011).…”

“…At present, many methods are being evaluated for rAAV readministration, for example, by serotype switching (Weinstein et al, 2010;Wang et al, 2012), capsid engineering , or immune modulation and tolerance induction to prevent immune responses to the vector and/or transgene (Goudy et al, 2011;Wang et al, 2011). Alternatively, the viral vector can be administered to an immature immune system by perinatal gene therapy (Sabatino et al, 2007;Sinn et al, 2008;Hu et al, 2011).…”

In vivo genome editing of the albumin locus as a platform for protein replacement therapy

“…However, long-term expression after conventional, predominantly nonintegrating AAV administration in young patients may be compromised because of episomal dilution as hepatocytes divide. 22 Integration of a donor transgene into the albumin locus could potentially address this limitation. We treated adult wild-type mice with AAV8-ZFN and 4 donors that encoded human a-galactosidase A, acid b-glucosidase, iduronate-2 sulfatase, or a-L-iduronidase (ie, the genes that are deficient in patients with Fabry and Gaucher diseases and Hunter or Hurler's syndromes, respectively).…”

Versatile and robust genome editing with Streptococcus thermophilus CRISPR1-Cas9

“…However, a limitation in the therapeutic use of rAAV is the loss of episomal vector genomes from actively dividing cells resulting in transient expression of therapeutic transgenes [46][47][48] . Hence, the combination of genome editing technology with rAAV-mediated delivery could lead to permanent genome modification and positive therapeutic outcome in young patients when tissues, such as the liver and retina, are still growing 19,49 .…”