1. Species Choice for Animal Modeling Cystic Fibrosis and Gene Therapy to the Airway
Authors: Xiaoming Liu, Ziying Yan, Meihui Luo, Liang N. Zhang, Cyndi Trygg, Carolina Smith, Keith Munson, William Guggino, Bruce Bunnell, John F. Engelhardt
Journal: Molecular Therapy (2006)

The development of gene therapies for cystic fibrosis (CF) lung disease requires animal models that can appropriately reproduce the human disease phenotype and human vector biology of gene transfer to the airway. However, the efficacy of certain viral vector systems for gene delivery to the airways in CF mice has been notably different than that in humanized systems. We systematically analyzed gene transfer properties of in vitro polarized airway epithelia from a number of species including human, mouse, pig, ferret, and non-human primates using air-liquid interface (ALI) models. In this context, recombinant AAV (rAAV) transduction of mouse airway epithelia, demonstrated a significant mouse-specific tropism for transduction (rAAV5>>rAAV2) that was not seen in human ALI cultures (rAAV5≅rAAV2). Transduction of pig and ferret ALI cultures with these two rAAV serotypes was more similar to human, although species-specific differences in the polarity of transduction between apical and basolateral membranes were observed. Interestingly, when an expanded serotype profile for rAAV1, rAAV2, and rAAV5 was compared between human and non-human primates (Indian and Cynomolgus Monkeys) ALI cultures, species-specific transduction was also observed for rAAV1(human>>non-human primate), while rAAV2 and rAAV5 serotypes transduced both human and non-human primate ALI cultures with equal efficiency. These findings suggest that substantial differences exist in the ability of various rAAV serotypes to transduce the proximal airway of different species, even at the level of non-human primates. Additionally, we analyzed the bioelectric properties of ALI epithelia including amiloride-sensitive Na+ transport, DIDS- sensitive Cl− transport, and cAMP-sensitive ClCl− transport, as a functional basis for comparing ion channel properties in the airways of these species. The bioelectric properties of ALI epithelia were most similar between human and non-human primates, while pig and ferret epithelia demonstrated enhanced amiloride-sensitive Na+ transport or reduced DIDS-sensitive Cl− transport, respectively, in comparison to human epithelia. Comparison of ALI cultures generated from deltaF508CFTR and wtCFTR mice demonstrated substantial cAMP-inducible Cl− currents that were not associated with CFTR, pointing out the limitation of the mouse model to study CFTR-associated abnormalities in the airway. These studies suggest that the species-specific differences in the tropism of rAAV transduction to the airway may complicate preclinical testing of gene therapies with this vector for CF lung disease in humans. Additionally, differences in the biology of electrolyte transport of airway epithelia between various species may influence which of these species is most appropriate for developing new CF animal models by which to assess CFTR functional complementation. The development of gene therapies for cystic fibrosis (CF) lung disease requires animal models that can appropriately reproduce the human disease phenotype and human vector biology of gene transfer to the airway. However, the efficacy of certain viral vector systems for gene delivery to the airways in CF mice has been notably different than that in humanized systems. We systematically analyzed gene transfer properties of in vitro polarized airway epithelia from a number of species including human, mouse, pig, ferret, and non-human primates using air-liquid interface (ALI) models. In this context, recombinant AAV (rAAV) transduction of mouse airway epithelia, demonstrated a significant mouse-specific tropism for transduction (rAAV5>>rAAV2) that was not seen in human ALI cultures (rAAV5≅rAAV2). Transduction of pig and ferret ALI cultures with these two rAAV serotypes was more similar to human, although species-specific differences in the polarity of transduction between apical and basolateral membranes were observed. Interestingly, when an expanded serotype profile for rAAV1, rAAV2, and rAAV5 was compared between human and non-human primates (Indian and Cynomolgus Monkeys) ALI cultures, species-specific transduction was also observed for rAAV1(human>>non-human primate), while rAAV2 and rAAV5 serotypes transduced both human and non-human primate ALI cultures with equal efficiency. These findings suggest that substantial differences exist in the ability of various rAAV serotypes to transduce the proximal airway of different species, even at the level of non-human primates. Additionally, we analyzed the bioelectric properties of ALI epithelia including amiloride-sensitive Na+ transport, DIDS- sensitive Cl− transport, and cAMP-sensitive ClCl− transport, as a functional basis for comparing ion channel properties in the airways of these species. The bioelectric properties of ALI epithelia were most similar between human and non-human primates, while pig and ferret epithelia demonstrated enhanced amiloride-sensitive Na+ transport or reduced DIDS-sensitive Cl− transport, respectively, in comparison to human epithelia. Comparison of ALI cultures generated from deltaF508CFTR and wtCFTR mice demonstrated substantial cAMP-inducible Cl− currents that were not associated with CFTR, pointing out the limitation of the mouse model to study CFTR-associated abnormalities in the airway. These studies suggest that the species-specific differences in the tropism of rAAV transduction to the airway may complicate preclinical testing of gene therapies with this vector for CF lung disease in humans. Additionally, differences in the biology of electrolyte transport of airway epithelia between various species may influence which of these species is most appropriate for developing new CF animal models by which to assess CFTR functional complementation.