Single Amino Acid Modification of Adeno-Associated Virus Capsid Changes Transduction and Humoral Immune Profiles

BK polyomavirus (BKV) causes significant urinary tract pathogenesis in immunosuppressed individuals, including kidney and bone marrow transplant recipients. It is currently unclear whether BKV-neutralizing antibodies can moderate or prevent BKV disease. We developed reporter pseudoviruses based on seven divergent BKV isolates and performed neutralization assays on sera from healthy human subjects. The results demonstrate that BKV genotypes I, II, III, and IV are fully distinct serotypes. While nearly all healthy subjects had BKV genotype I-neutralizing antibodies, a majority of subjects did not detectably neutralize genotype III or IV. Surprisingly, BKV subgenotypes Ib1 and Ib2 can behave as fully distinct serotypes. This difference is governed by as few as two residues adjacent to the cellular glycan receptor-binding site on the virion surface. Serological analysis of mice given virus-like particle (VLP)-based BKV vaccines confirmed these findings. Mice administered a multivalent VLP vaccine showed high-titer serum antibody responses that potently cross-neutralized all tested BKV genotypes. Interestingly, each of the neutralization serotypes bound a distinct spectrum of cell surface receptors, suggesting a possible connection between escape from recognition by neutralizing antibodies and cellular attachment mechanisms. The finding implies that different BKV genotypes have different cellular tropisms and pathogenic potentials in vivo. Individuals who are infected with one BKV serotype may remain humorally vulnerable to other BKV serotypes after implementation of T cell immunosuppression. Thus, prevaccinating organ transplant recipients with a multivalent BKV VLP vaccine might reduce the risk of developing posttransplant BKV disease. BK polyomaviruses (BKVs or BKPyVs) are a species of icosahedral, nonenveloped, double-stranded DNA viruses. The genomes of all known full-length isolates of BKV can be categorized into four discrete genotypes based on analyses of nucleotide sequences (1). The prevalence and sequence characteristics of each genotype are thought to vary within different human populations worldwide (2).Studies indicate that 83 to 98% of individuals show serum antibody responses to the BKV genotype I (BKV-I) major capsid protein, VP1, by the time they are 21 years of age (3). The virus is thought to establish a lifelong chronic infection in the urinary epithelium, and virions are periodically shed at low levels in the urine of 5 to 27% of healthy adults (4, 5). Although BKV-I can cause malignancy in animal model systems, conclusive evidence showing a causal connection between BKVs and human cancer is still lacking (reviewed in reference 6). While it remains uncertain whether BKVs cause pathology in healthy individuals, it is clear that certain T cell-immunosuppressed individuals, such as recipients of kidney or bone marrow transplants, are at risk of developing uncontrolled BKV replication that leads to nephropathy or hemorrhagic cystitis, respectively (reviewed in reference 7). Currently available antiv...

Section: Discussionmentioning

confidence: 99%

“…For other viral families, mutations that drive escape from antibody-mediated neutralization are sometimes accompanied by a shift in the use of cellular receptors for infectious entry (10,11). To address this possibility, we performed an additional set of analyses examining the binding characteristics and cellular entry tropism of each of the BKV serotypes.…”

mentioning

confidence: 99%

BK Polyomavirus Genotypes Represent Distinct Serotypes with Distinct Entry Tropism

Pastrana

Ray

Magaldi

et al. 2013

“…On the third day of treatment, mice were transduced with the indicated dose of AAV vector in PBS by retro-orbital injection. Live imaging of luciferase expression from AAV vectors has been previously described (44). Briefly, mice were given 150 mg/kg D-luciferin (Caliper LifeSciences) by i.p.…”

Section: Methodsmentioning

confidence: 99%

Arsenic Trioxide Stabilizes Accumulations of Adeno-Associated Virus Virions at the Perinuclear Region, Increasing Transduction In Vitro and In Vivo

Mitchell

Samulski

2013

Self Cite

Interactions with cellular stress pathways are central to the life cycle of many latent viruses. Here, we utilize adeno-associated virus (AAV) as a model to study these interactions, as previous studies have demonstrated that cellular stressors frequently increase transduction of recombinant AAV (rAAV) vectors and may even substitute for helper virus functions. Since several chemotherapeutic drugs are known to increase rAAV transduction, we investigated the effect of arsenic trioxide (As 2 O 3 ), an FDAapproved chemotherapeutic agent with known effects on several other virus life cycles, on the transduction of rAAV. In vitro, As 2 O 3 caused a dose-dependent increase in rAAV2 transduction over a broad range of cell lines from various cell types and species (e.g., HEK-293, HeLa, HFF hTERT, C-12, and Cos-1). Mechanistically, As 2 O 3 treatment acted to prevent loss of virions from the perinuclear region, which correlated with increased cellular vector genome retention, and was distinguishable from proteasome inhibition. To extend our investigation of the cellular mechanism, we inhibited reactive oxygen species formation and determined that the As 2 O 3 -mediated increase in rAAV2 transduction was dependent upon production of reactive oxygen species. To further validate our in vitro data, we tested the effect of As 2 O 3 on rAAV transduction in vivo and determined that treatment initiated transgene expression as early as 2 days posttransduction and increased reporter expression by up to 10-fold. Moreover, the transduction of several other serotypes of rAAV was also enhanced in vivo, suggesting that As 2 O 3 affects a pathway used by several AAV serotypes. In summary, our data support a model wherein As 2 O 3 increases rAAV transduction both in vitro and in vivo and maintains perinuclear accumulations of capsids, facilitating productive nuclear trafficking.

“…IHC of these eyes did not reveal any major tropism differences compared to rAAV2, in that RGC, Müller glia, and other cells of the INL were transduced by the chimeric capsid. A more recent paper has shown the amino acid at position 265 on the rAAV2.5 capsid to be solely responsible (42). Therefore, we tested an rAAV2-265D mutant capsid intravitreally, which revealed expression similar to that of the rAAV2.5 parent (see Fig.…”

Section: Hs Binding Increases the Ivit Transduction Of Other Raav Sermentioning

confidence: 96%

Heparan Sulfate Binding Promotes Accumulation of Intravitreally Delivered Adeno-associated Viral Vectors at the Retina for Enhanced Transduction but Weakly Influences Tropism

Woodard

Liang

Bennett

et al. 2016

Self Cite

Many adeno-associated virus (AAV) serotypes efficiently transduce the retina when delivered to the subretinal space but show limited success when delivered to the vitreous due to the inner limiting membrane (ILM). Subretinal delivery of AAV serotype 2 (AAV2) and its heparan sulfate (HS)-binding-deficient capsid led to similar expression, indicating transduction of the outer retina occurred by HS-independent mechanisms. However, intravitreal delivery of HS-ablated recombinant AAV2 (rAAV2) led to a 300-fold decrease in transduction compared to AAV2. Fluorescence in situ hybridization of AAV transgenes was used to identify differences in retinal trafficking and revealed that HS binding was responsible for AAV2 accumulation at the ILM. This mechanism was tested on human ex vivo retinas and showed similar accumulation with HS-binding AAV2 capsid only. To evaluate if HS binding could be applied to other AAV serotypes to enhance their transduction, AAV1 and AAV8 were modified to bind HS with a single-amino-acid mutation and tested in mice. Both HS-binding mutants of AAV1 and AAV8 had higher intravitreal transduction than their non-HS-binding parent capsid due to increased retinal accumulation. To understand the influence that HS binding has on tropism, chimeric AAV2 capsids with dual-glycan usage were tested intravitreally in mice. Compared to HS binding alone, these chimeric capsids displayed enhanced transduction that was correlated with a change in tropism. Taken together, these data indicate that HS binding serves to sequester AAV capsids from the vitreous to the ILM but does not influence retinal tropism. The enhanced retinal transduction of HS-binding capsids provides a rational design strategy for engineering capsids for intravitreal delivery. A deno-associated virus (AAV) is a small (25-nm), nonpathogenic virus that has been extensively studied as a vector for gene transfer applications (1-3). The virus consists of two parts: the viral genome and the protein capsid. The viral genome can be largely replaced with a desired transgene to create recombinant AAV (rAAV) vectors used for gene delivery. The protein capsid is responsible for cell attachment and entry via a variety of glycans and cell surface receptors. There are 11 naturally occurring serotypes of AAV, denoted AAV1 to AAV11. Glycans and receptors have been elucidated for several AAV serotypes. Heparan sulfate proteoglycan (HSPG) has been shown to be used for both rAAV2 and rAAV3 cell entry (4). rAAV6 displays dual-glycan interaction with HSPG and sialic acid; however, HSPG binding alone is insufficient for cellular entry (5). Various linkages of sialic acid are important for the transduction of the rAAV1, rAAV4, and rAAV5 serotypes (6,7). N-linked galactose is used for the transduction of the rAAV9 serotype (8). Glycans expressed on the cell surface dictate the tissue and cellular tropism observed with the various AAV capsids. In addition to attachment to these glycans, AAV serotypes interact with cell receptors, including human growth factor rec...