PNNL

Abstract

Adeno-Associated Virus (AAV) has a single-stranded DNA genome encapsidated in a small 16 icosahedrally symmetric protein shell with 60 subunits. AAV is the leading delivery vector in 17 emerging gene therapy treatments for inherited disorders, so its structure and molecular 18 interactions with human hosts are of intense interest. A wide array of electron microscopic 19 approaches have been used to visualize the virus and its complexes, depending on the scientific 20 question, technology available and amenability of the sample. Approaches range from sub-21 volume tomographic analyses of complexes with large and flexible host proteins to detailed 22 analysis of atomic interactions within the virus and with small ligands at resolutions as high as 23 1.6 Å. Analyses have led to the reclassification of glycan receptors as attachment factors, to 24 structures with a new-found receptor protein, to identification of the epitopes of antibodies and a 25 new understanding of possible neutralization mechanisms. AAV is now well-enough 26 characterized that it has also become a model system for EM methods development. Heralding 27 a new era, cryo-EM is now also being deployed as an analytic tool in the process development 28 and production quality control of high value pharmaceutical biologics, namely AAV vectors.