Preexisting Immunity and Low Expression in Primates Highlight Translational Challenges for Liver-directed AAV8-mediated Gene Therapy

Hurlbut, Gregory D.; Ziegler, Robin J.; Nietupski, Jennifer B.; Foley, Joseph W.; Woodworth, Lisa; Meyers, Elizabeth; Bercury, Scott D.; Pande, Nilesh; Souza, David W.; Bree, Mark P.; Lukason, Michael; Marshall, John; Cheng, Seng H.; Scheule, Ronald K.

doi:10.1038/mt.2010.175

Cited by 118 publications

(134 citation statements)

References 38 publications

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“…The prevalence of preexisting antibodies against AAV vectors limits their therapeutic efficacy (70,71). To overcome this challenge, capsid modification based on capsid antigenic epitopes can generate variants with the ability to escape from antibody recognition (25,72).…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Adeno-Associated Virus 1 and 6 Sialic Acid Binding Site

Huang

Patel

et al. 2016

J Virol

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The adeno-associated viruses (AAVs), which are being developed as gene delivery vectors, display differential cell surface glycan binding and subsequent tissue tropisms. For AAV serotype 1 (AAV1), the first viral vector approved as a gene therapy treatment, and its closely related AAV6, sialic acid (SIA) serves as their primary cellular surface receptor. Toward characterizing the SIA binding site(s), the structure of the AAV1-SIA complex was determined by X-ray crystallography to 3.0 Å. Density consistent with SIA was observed in a pocket located at the base of capsid protrusions surrounding icosahedral 3-fold axes. Site-directed mutagenesis substitution of the amino acids forming this pocket with structurally equivalent residues from AAV2, a heparan sulfate binding serotype, followed by cell binding and transduction assays, further mapped the critical residues conferring SIA binding to AAV1 and AAV6. For both viruses five of the six binding pocket residues mutated (N447S, V473D, N500E, T502S, and W503A) abolished SIA binding, whereas S472R increased binding. All six mutations abolished or decreased transduction by at least 50% in AAV1. Surprisingly, the T502S substitution did not affect transduction efficiency of wildtype AAV6. Furthermore, three of the AAV1 SIA binding site mutants-S472R, V473D, and N500E-escaped recognition by the anti-AAV1 capsid antibody ADK1a. These observations demonstrate that common key capsid surface residues dictate both virus binding and entry processes, as well as antigenic reactivity. This study identifies an important functional capsid surface "hot spot" dictating receptor attachment, transduction efficiency, and antigenicity which could prove useful for vector engineering. IMPORTANCEThe adeno-associated virus (AAV) vector gene delivery system has shown promise in several clinical trials and an AAV1-based vector has been approved as the first gene therapy treatment. However, limitations still exist with respect to transduction efficiency and the detrimental effects of preexisting host antibodies. This study aimed to identify key capsid regions which can be engineered to overcome these limitations. A sialic glycan receptor recognition pocket was identified in AAV1 and its closely related AAV6, using X-ray crystallography. The site was confirmed by mutagenesis followed by cell binding and transduction assays. Significantly, residues controlling gene expression efficiency, as well as antibody escape variants, were also identified. This study thus provides, at the amino acid level, information for rational structural engineering of AAV vectors with improved therapeutic efficacy.

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Section: Discussionmentioning

confidence: 99%

Characterization of the Adeno-Associated Virus 1 and 6 Sialic Acid Binding Site

Huang

Patel

et al. 2016

J Virol

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“…Individuals with preexisting immunity to the virus may require higher doses, which may evoke safety concerns as illustrated in hemophilia trials ( 92 ). Additionally, due to differences in biology, anatomy, and size, the encouraging results in mice may not translate to larger animal models with the latter providing less salutary outcomes ( 93,94 ). Nevertheless, there is a planned clinical study in galactosialidosis using a systemically delivered recombinant scAAV8 vector encoding protective protein cathepsin A ( Table 1 ).…”

Section: Recombinant Aav Vectorsmentioning

confidence: 99%

Gene therapy for the neurological manifestations in lysosomal storage disorders

Cheng¹

2014

Journal of Lipid Research

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precise mechanistic links between these altered biochemical and cellular states and disease pathophysiology and pathogenesis remain unclear. Typically, disease severity is correlated with the level of residual activity, with individuals harboring lower levels presenting with more aggressive and severe disease manifestations. A large percentage of individuals, particularly those with signifi cantly diminished lysosomal function, also exhibit CNS involvement, the extent of which is dependent on the nature of the specifi c storage metabolites and the differential sensitivity of the resident cell types to the accumulated substrates. Although individually each LSD may be relatively rare, as a group, these disorders have an incidence of approximately 1 per 5,000 live births ( 4, 5 ).Of the approximately 50 LSDs that have been identifi ed thus far, the majority (greater than 70%) exhibit significant CNS involvement ( 6 ). This fi nding is not surprising given that lysosomes and related organelles are ubiquitously present in most cell types and are involved not only in recycling cellular debris but also in maintaining cellular homeostasis ( 7-9 ). Irrespective of the LSD, these CNS diseases are typically characterized by generalized infl ammation and neurodegeneration in multiple brain regions. In a subset of the diseases, altered calcium homeostasis and oxidative stress may also contribute to the overall pathology ( 10 ). Moreover, each specifi c disease may initially present with a unique temporal and spatial alteration that is dictated by the nature of the storage metabolites prior to the development of a more generalized global derangement ( 11 ). In some diseases, the symptoms are evident in neonates, whereas in others, they become apparent only in early childhood. Consequently, some LSDs may require early therapeutic intervention to affect broad and potentially all regions of the CNS. The lysosomal storage disorders (LSDs) are a heterogeneous group of inherited metabolic diseases that result from a defi ciency in one or more of the 80 enzymes or transporters that normally reside within the lysosomal compartment ( 1-3 ). A reduction or loss of one or more of these activities results in the progressive and relentless accumulation of undegraded macromolecules, a consequent derangement of proper lysosomal and autophagosomal functions, and ultimately, cellular demise. However, the

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“…Serologic studies show that ϳ40 to 70% of the human population has been exposed to AAVs (14)(15)(16)(17). Neutralization by preexisting antibodies decreases AAV transduction efficiency, even at low antibody titers (18)(19)(20). For this reason, individuals with evidence of preexisting AAV antibodies were excluded from participation in a hemophilia B trial with the rAAV8 vector (4).…”

mentioning

confidence: 99%

Adeno-Associated Virus Serotype 1 (AAV1)- and AAV5-Antibody Complex Structures Reveal Evolutionary Commonalities in Parvovirus Antigenic Reactivity

Tseng

Gurda

Chipman

et al. 2015

J Virol

114

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The clinical utility of the adeno-associated virus (AAV) gene delivery system has been validated by the regulatory approval of an AAV serotype 1 (AAV1) vector for the treatment of lipoprotein lipase deficiency. However, neutralization from preexisting antibodies is detrimental to AAV transduction efficiency. Hence, mapping of AAV antigenic sites and engineering of neutralization-escaping vectors are important for improving clinical efficacy. We report the structures of four AAV-monoclonal antibody fragment complexes, AAV1-ADK1a, AAV1-ADK1b, AAV5-ADK5a, and AAV5-ADK5b, determined by cryo-electron microscopy and image reconstruction to a resolution of ϳ11 to 12 Å. Pseudoatomic modeling mapped the ADK1a epitope to the protrusions surrounding the icosahedral 3-fold axis and the ADK1b and ADK5a epitopes, which overlap, to the wall between depressions at the 2-and 5-fold axes (2/5-fold wall), and the ADK5b epitope spans both the 5-fold axis-facing wall of the 3-fold protrusion and portions of the 2/5-fold wall of the capsid. Combined with the six antigenic sites previously elucidated for different AAV serotypes through structural approaches, including AAV1 and AAV5, this study identified two common AAV epitopes: one on the 3-fold protrusions and one on the 2/5-fold wall. These epitopes coincide with regions with the highest sequence and structure diversity between AAV serotypes and correspond to regions determining receptor recognition and transduction phenotypes. Significantly, these locations overlap the two dominant epitopes reported for autonomous parvoviruses. Thus, rather than the amino acid sequence alone, the antigenic sites of parvoviruses appear to be dictated by structural features evolved to enable specific infectious functions. IMPORTANCEThe adeno-associated viruses (AAVs) are promising vectors for in vivo therapeutic gene delivery, with more than 20 years of intense research now realized in a number of successful human clinical trials that report therapeutic efficacy. However, a large percentage of the population has preexisting AAV capsid antibodies and therefore must be excluded from clinical trials or vector readministration. This report represents our continuing efforts to understand the antigenic structure of the AAVs, specifically, to obtain a picture of "polyclonal" reactivity as is the situation in humans. It describes the structures of four AAV-antibody complexes determined by cryoelectron microscopy and image reconstruction, increasing the number of mapped epitopes to four and three, respectively, for AAV1 and AAV5, two vectors currently in clinical trials. The results presented provide information essential for generating antigenic escape vectors to overcome a critical challenge remaining in the optimization of this highly promising vector delivery system. T he adeno-associated viruses (AAVs), single-stranded DNA packaging viruses belonging to the Parvoviridae family, are promising vectors for gene delivery. There are over 100 AAV genomic isolates, and 13 human and nonhuman serotypes h...

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Preexisting Immunity and Low Expression in Primates Highlight Translational Challenges for Liver-directed AAV8-mediated Gene Therapy

Cited by 118 publications

References 38 publications

Characterization of the Adeno-Associated Virus 1 and 6 Sialic Acid Binding Site

Characterization of the Adeno-Associated Virus 1 and 6 Sialic Acid Binding Site

Gene therapy for the neurological manifestations in lysosomal storage disorders

Adeno-Associated Virus Serotype 1 (AAV1)- and AAV5-Antibody Complex Structures Reveal Evolutionary Commonalities in Parvovirus Antigenic Reactivity

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