Combination therapy utilizing shRNA knockdown and an optimized resistant transgene for rescue of diseases caused by misfolded proteins

Proc Natl Acad Sci U S A. 2011 Aug 23;108(34):14258-63. doi: 10.1073/pnas.1109522108. Epub 2011 Aug 15.

Abstract

Molecular knockdown of disease proteins and restoration of wild-type activity represent a promising but challenging strategy for the treatment of diseases that result from the accumulation of misfolded proteins (i.e., Huntington disease, amyotrophic lateral sclerosis, and α-1 antitrypsin deficiency). In this study we used alpha-1 antitrypsin (AAT) deficiency with the piZZ mutant phenotype as a model system to evaluate the efficiency of gene-delivery approaches that both silence the piZZ transcript (e.g., shRNA) and restore circulating wild-type AAT expression from resistant codon-optimized AAT (AAT-opt) transgene cassette using adeno-associated virus (AAV) vector delivery. After systemic injection of a self-complimentary AAV serotype 8 (scAAV8) vector encoding shRNA in piZZ transgenic mice, both mutant AAT mRNA in the liver and defected serum protein level were inhibited by 95%, whereas liver pathology, as monitored by dPAS and fibrosis staining, reversed. To restore blood AAT levels in AAV8/shRNA-treated mice, several strategies to restore functional AAT levels were tested, including using AAV AAT-opt transgene cassettes targeted to muscle and liver, or combination vectors carrying piZZ shRNA and AAT-opt transgenes separately, or a single bicistronic AAV vector. With these molecular approaches, we observed over 90% knockdown of mutant AAT with a 13- to 30-fold increase of circulating wild-type AAT protein from the shRNA-resistant AAT-opt cassette. The molecular approaches applied in this study can simultaneously prevent liver pathology and restore blood AAT concentration in AAT deficiencies. Based on these observations, similar gene-therapy strategies could be considered for any diseases caused by accumulation of misfolded proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Combined Modality Therapy
  • Dependovirus / genetics
  • Gene Knockdown Techniques*
  • Gene Silencing
  • Genetic Vectors / genetics
  • Injections, Intramuscular
  • Liver / metabolism
  • Mice
  • Mice, Mutant Strains
  • Proteostasis Deficiencies / blood
  • Proteostasis Deficiencies / therapy*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / administration & dosage
  • RNA, Small Interfering / metabolism*
  • Serotyping
  • Transduction, Genetic
  • Transgenes / genetics*
  • alpha 1-Antitrypsin / blood
  • alpha 1-Antitrypsin / genetics

Substances

  • RNA, Messenger
  • RNA, Small Interfering
  • alpha 1-Antitrypsin