Microglia-specific targeting by novel capsid-modified AAV6 vectors.
Recombinant adeno-associated viruses (rAAV) have been widely used in gene therapy applications for central nervous system diseases. Though rAAV can efficiently target neurons and astrocytes in mouse brains, microglia, the immune cells of the brain, are refractile to rAAV. To identify AAV capsids with microglia-specific transduction properties, we initially screened the most commonly used serotypes, AAV1-9 and rh10, on primary mouse microglia cultures. While these capsids were not permissive, we then tested the microglial targeting properties of a newly characterized set of modified rAAV6 capsid variants with high tropism for monocytes. Indeed, these newly characterized rAAV6 capsid variants, specially a triply mutated Y731F/Y705F/T492V form, carrying a self-complementary genome and microglia-specific promoters (F4/80 or CD68) could efficiently and selectively transduce microglia in vitro. Delivery of these constructs in mice brains resulted in microglia-specific expression of green fluorescent protein, albeit at modest levels. We further show that CD68 promoter-driven expression of the inflammatory cytokine, interleukin-6, using this capsid variant leads to increased astrogliosis in the brains of wild-type mice. Our study describes the first instance of AAV-targeted microglial gene expression leading to functional modulation of the innate immune system in mice brains. This provides the rationale for utilizing these unique capsid/promoter combinations for microglia-specific gene targeting for modeling or functional studies.
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Awilda M
AM
Rosario
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Pedro E
PE
Cruz
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Carolina
C
Ceballos-Diaz
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Michael R
MR
Strickland
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Zoe
Z
Siemienski
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Meghan
M
Pardo
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Keri-Lyn
KL
Schob
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Andrew
A
Li
Department of Pediatrics, University of Florida , Gainesville, Florida, USA.
George V
GV
Aslanidi
Department of Pediatrics, University of Florida , Gainesville, Florida, USA.
Arun
A
Srivastava
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Todd E
TE
Golde
Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, University of Florida , Gainesville, Florida, USA.
Paramita
P
Chakrabarty