The highest levels of IgG appear to be for AAV2, AAV3, and AAVrh74, suggesting an initial infection with AAV2 or AAV3, with the high levels of AAVrh74-IgG in some individuals attributable to the broad cross-reactivity of this serotypes, as discussed above

The highest levels of IgG appear to be for AAV2, AAV3, and AAVrh74, suggesting an initial infection with AAV2 or AAV3, with the high levels of AAVrh74-IgG in some individuals attributable to the broad cross-reactivity of this serotypes, as discussed above. 7-year-old MPS III patients than in healthy controls. Seroprevalence for the majority of tested SOCS-2 AAV serotypes appears to peak before 8 years of age in MPS III subjects, with the exception of increases in AAV8 and AAV9 Abs in 8- to 19-year-old MPS IIIA patients. In contrast, significant increases in seroprevalence were observed for virtually all tested AAV serotypes in 8- to 15-year-old healthy children compared to 2- to 7-year-olds. Co-prevalence and Ab level correlation results followed the previously established divergence-based Lasofoxifene Tartrate clade positions of AAV1C9. Interestingly, the individuals positive for AAVrh74-Abs showed the lowest co-prevalence with Abs for AAV1C9 (22C40%). However, all or nearly all (77C100%) of subjects who were seropositive for any of serotypes 1C9 were also positive for AAVrh74-IgG. Notably, the majority (78%) of AAV seropositive individuals were also Ab-positive for one to five of the tested AAV serotypes, mostly with low levels of AAV-Abs (1:50C100), while a minority (22%) were seropositive for six or more AAV serotypes, mostly with high levels of AAV-IgG for multiple serotypes. In general, the highest IgG levels were reactive to AAV2, AAV3, and AAVrh74. The data illustrate the complex seroprevalence profiles of AAV1C9 and rh74 in MPS patients and healthy children, indicating the potential association of AAV seroprevalence with age and disease conditions. The broad co-prevalence of Abs for different AAV serotypes reinforces the challenge of pre-existing AAV-Abs for translating AAV gene therapy to clinical applications, regardless of the vector serotype. Keywords:?: AAV, pre-existing Abs, MPS III, seroprevalance Introduction Mucopolysaccharidosis (MPS) III is usually a group of four (A, Lasofoxifene Tartrate B, C, and D) neuropathic lysosomal storage diseases, each caused by the autosomal recessive defect in a specific lysosomal enzyme that is essential for the stepwise degradation of heparan sulfate (HS) glycosaminoglycans (GAGs).1 The lack of the specific enzyme activity results in the accumulation of HS-GAGs in cells in virtually all organs. Patients with MPS III appear normal at birth, but progress to multisystem manifestations, with severe profound neurological disorders, leading to high mortality and premature death. No effective treatment is currently available for MPS III. However, recombinant adeno-associated virus (rAAV) mediated gene therapy has shown promise for the treatment of MPS IIIA and IIIB.2C6 The AAV vectors are promising as effective gene delivery tools for long-term transduction in a broad range Lasofoxifene Tartrate of tissues. They have displayed efficacy and safety after systemic delivery in numerous preclinical disease models and in clinical trials, particularly for monogenic diseases.2,4,7C10 The recognition of the trans-bloodCbrain barrier (BBB) neurotropic properties of rAAV9 vector11,12 have led to significant advancements in AAV gene delivery for diseases with global or broad neuropathies in the central nervous system (CNS), demonstrating promising clinical potential.2C4,10,13 These studies have led to the translation of systemic rAAV9 gene delivery to a Phase I clinical trial in patients with type 1 spinal muscular atrophy (SMA1; NCT02122952) and Phase I/II trials in patients with MPS IIIA (NCT02716246, ongoing) and MPS IIIB (to be initiated), and intrathecal gene delivery clinical trials in patients with giant axonal neuropathy (NCT02362438) and Batten disease (CLN6; NCT02725580). As effective rAAV gene therapy approaches become available for clinical application, pre-existing host humoral immunity against AAV poses critical challenges. While having no known pathogenesis, AAV is usually widespread in humans, and >90% of the adult population is usually naturally infected, with a high prevalence of antibodies (Abs) to various AAV serotypes.14,15 Although AAV2 is the most prevalent in humans, cross-reactivity among different serotypes reduces the potential utility of rAAV vectors packaged into alternative serotypes.14C16 While the presence of neutralizing Abs against specific AAV serotypes has been demonstrated to block the type-specific AAV vector,17 non-neutralizing anti-AAV Abs can also trigger vector clearance.18 For rAAV gene therapy clinical trials, the absence of anti-AAV (AAV) neutralizing Abs is often used as a critical exclusion criteria, though Lasofoxifene Tartrate a serum AAV total immunoglobulin G (IgG) titer <1:50 has also been accepted by the Food and Drug Administration as negative for allowing subject enrollment (NCT02122952, NCT02716246, NCT02725580, NCT02376816, NCT02354781, and NCT01976091). In support of an ongoing rAAV gene therapy program, serum samples from patients with MPS IIIA or IIIB were compared to healthy children for total IgG against AAV1C9 and rh74 in order to determine the profiles of pre-existing AAV-Abs in these pediatric populations, and the potential utility of different AAV serotypes as vectors for future gene therapy design. Materials and Methods Serum Lasofoxifene Tartrate samples Serum samples were obtained from patients with MPS IIIA (or genes, or undetectable or significantly reduced and value. Values shown in bold have no significant correlation (p?>?0.05). +, correlation was determined based on data from all individuals who were IgG-positive against each AAV serotype (n). Discussion This study demonstrates the complex humoral immunity profiles to AAVs among 2- to 18-year-old healthy individuals and patients with MPS IIIA.