Binding and neutralizing anti-AAV antibodies: Detection and implications for rAAV-mediated gene therapy.

Assessment of anti-adeno-associated virus (AAV) antibodies in patients prior to systemic gene therapy administration is an important consideration regarding efficacy and safety of the therapy. Approximately 30%-60% of individuals have pre-existing anti-AAV antibodies. Seroprevalence is impacted by multiple factors, including geography, age, capsid serotype, and assay type. Anti-AAV antibody assays typically measure (1) transduction inhibition by detecting the neutralizing capacity of antibodies and non-antibody neutralizing factors, or (2) total anti-capsid binding antibodies, regardless of neutralizing activity. Presently, there is a paucity of head-to-head data and standardized approaches associating assay results with clinical outcomes. In addition, establishing clinically relevant screening titer cutoffs is complex. Thus, meaningful comparisons across assays are nearly impossible. Although complex, establishing screening assays in routine clinical practice to identify patients with antibody levels that may impact favorable treatment outcomes is achievable for both transduction inhibition and total antibody assays. Formal regulatory approval of such assays as companion diagnostic tests will confirm their suitability for specific recombinant AAV gene therapies. This review covers current approaches to measure anti-AAV antibodies in patient plasma or serum, their potential impact on therapeutic safety and efficacy, and investigative strategies to mitigate the effects of pre-existing anti-AAV antibodies in patients.

Global seroprevalence of neutralizing antibodies against adeno-associated virus serotypes used for human gene therapies.

Adeno-associated virus (AAV) vectors are promising gene therapy candidates, but pre-existing anti-AAV neutralizing antibodies (NAbs) pose a significant challenge to successful gene delivery. Knowledge of NAb seroprevalence remains limited and inconsistent. We measured activity of NAbs against six clinically relevant AAV serotypes across 10 countries in adults (n = 502) and children (n = 50) using a highly sensitive transduction inhibition assay. NAb prevalence was generally highest for AAV1 and lowest for AAV5. There was considerable variability across countries and geographical regions. NAb prevalence increased with age and was higher in females, participants of Asian ethnicity, and participants in cancer trials. Co-prevalence was most frequently observed between AAV1 and AAV6 and less frequently between AAV5 and other AAVs. Machine learning analyses revealed a unique clustering of AAVs that differed from previous phylogenetic classifications. These results offer insights into the biological relationships between the immunogenicity of AAVs in humans beyond that observed previously using standard clades, which are based on linear capsid sequences. Our findings may inform improved vector design and facilitate the development of AAV vector-mediated clinical gene therapies.

Analytical and clinical performance of the Ortho-Clinical Diagnostics VITROS amino-terminal pro-B type natriuretic peptide assay.

BACKGROUND: Measurement of amino-terminal pro-B-type natriuretic peptide (NT-proBNP) is useful for evaluating patients with heart failure (HF). METHODS: We evaluated the performance of a new automated NT-proBNP assay. RESULTS: The VITROS NT-proBNP assay had mean within-run and total imprecision of 1.0% and 3.4% at NT-proBNP concentrations from 67-27,500 ng/l. Acceptable linearity, functional/analytical sensitivity were demonstrated. Anticoagulant/tube types had no effect on results. Excellent sample stability and no high-dose hook were observed. High correlation between the VITROS and Elecsys methods was demonstrated (r=0.995; P<.001), with 98.3% clinical concordance. VITROS NT-proBNP concentrations were significantly higher in HF subjects than those without (1210 versus 68 ng/l; P<.001) and associated with HF symptom severity (P<.001). The VITROS assay had AUC for HF of 0.95 (P<.001), and had excellent NPV for excluding HF. CONCLUSIONS: The automated VITROS NT-proBNP assay demonstrates excellent analytical and clinical performance for evaluating the presence and severity of HF.