Evaluation of rAAVrh74 gene therapy vector seroprevalence by measurement of total binding antibodies in patients with Duchenne muscular dystrophy.

Background: Adeno-associated virus (AAV) vectors are a promising platform for in vivo transfer of transgenes designed to treat diseases. Pre-existing humoral immunity to these vectors can potentially impact the safety and efficacy of gene therapies. Consequently, individuals with pre-existing antibodies to the specific AAV serotypes used may be excluded from clinical trials and treatments. Recombinant AAV serotype rh74 (rAAVrh74), a vector originally isolated from rhesus monkeys and potentially less immunogenic than other serotypes isolated from humans (e.g. AAV2, AAV5, and AAV9), efficiently transduces muscle and is being investigated for use in gene therapy for Duchenne muscular dystrophy (DMD). Objective: To evaluate prevalence of total binding antibodies (neutralizing and non-neutralizing) against rAAVrh74 in patients with DMD. Methods: Eligible individuals (N = 107) were ⩾ 4 to < 18 years old with genetically confirmed DMD and were excluded from the study if they lived with a person who had known exposure to rAAVrh74 or other gene transfer therapy, or if they received prior treatment with gene transfer therapy. A single blood sample was obtained from each participant, and anti-rAAVrh74 total binding antibodies were measured by enzyme-linked immunosorbent assay. Total binding antibody level < 1:400 was defined as not elevated or seronegative. Primary endpoint was the percentage of subjects with elevated total antibody titers to rAAVrh74. Results: A large preponderance (86.1%) of patients with DMD in this data set was seronegative for anti-rAAVrh74 total binding antibodies. These patients would potentially meet the antibody status eligibility criterion for entry into rAAVrh74-based gene therapy clinical trials. Conclusion: Measuring total binding antibodies is a more comprehensive approach to assess pre-existing immune response versus measuring neutralizing antibodies alone. The low seroprevalence of total binding antibodies against rAAVrh74 shown here supports the broad applicability of rAAVrh74-based gene transfer therapy for patients with DMD and potentially other neuromuscular diseases.

Racial and ethnic disparities in diagnostic efficacy of comprehensive genetic testing for sensorineural hearing loss.

Understanding racial and ethnic disparities in diagnostic rates of genetic testing is critical for health equity. We sought to understand the extent and cause of racial and ethnic disparities in diagnostic efficacy of comprehensive genetic testing (CGT) for sensorineural hearing loss (SNHL). We performed a retrospective cohort study at two tertiary children's hospitals on a diverse cohort of 240 consecutive pediatric patients (76% publicly insured, 82% non-White) with SNHL of unknown etiology who underwent CGT. Definite and possible genetic diagnoses were assigned for each patient, representing the likelihood of a genetic cause of hearing loss. Associations between diagnostic rates were examined. 3.8 ± 2.1 variants were detected per patient; this frequency did not vary between White/Asian and Hispanic/Black cohorts. Overall, 82% of variants were variants of uncertain significance (VUS). Compared with White and Asian subjects, variants identified among Hispanic and Black children were less likely to be classified as pathogenic/likely pathogenic (15% vs. 24%, p < 0.001), and Hispanic and Black children were less likely to have a definite genetic diagnosis (10% vs. 37%, p < 0.001). The adjusted odds ratio for definite genetic diagnosis in Black and Hispanic children compared with White and Asian children was 0.19. Expanding genetic diagnostic criteria to include predicted deleterious VUSs reduced these disparities between White/Asian and Hispanic/Black children, with comparable molecular diagnostic rates (41% vs. 38%, p = 0.72). However, in silico predictions are insufficiently valid for clinical use. Increased inclusion of underrepresented groups in genetic hearing-loss studies to clinically validate these variants is necessary to reduce racial and ethnic disparities in diagnostic efficacy of comprehensive genetic testing.

Quantitative attenuation accuracy of virtual non-enhanced imaging compared to that of true non-enhanced imaging on dual-source dual-energy CT.

PURPOSE: To evaluate the quantitative attenuation and reliability of virtual non-contrast (VNC) images of the abdomen acquired from multiphasic scans with a dual-energy computed tomography (DECT) system and compare it with that of true non-enhanced images (TNC) on second- (Flash) and third- (Force) generation DECT scanners. METHODS: This retrospective study was approved by the institutional review board and included 123 patients with pancreatic cancer who had undergone routine clinical multiphasic DECT examinations at our institution using Flash and Force scanners between March and August 2017. VNC images of the abdomen were reconstructed from late arterial phase images. For every patient, regions-of-interest were defined in the aorta, fluid-containing structures (gallbladder, pleural effusion, and renal cysts > 10 mm), paravertebral muscles, subcutaneous fat, spleen, pancreas, renal cortex, and liver (eight locations) on TNC and VNC images. The mean attenuation of VNC was compared with TNC by organ for each CT scanner using an equivalence test and the Bland-Altman plot. The mean attenuations for TNC or VNC were compared between the Force and Flash CT scanners using a two-sample t test. RESULTS: The VNC attenuation of organs on the Force scanner was lower than was that on the Flash, and the mean attenuation difference in different organs on the Force was closer to 0. The estimated means of TNC and VNC were equivalent for an equivalence margin of 10 on the Force scanner. CONCLUSION: VNC images in DECT are a promising alternative to TNC images. In clinical scenarios in which non-enhanced CT images are required but are not available for accurate diagnosis, VNC images can potentially serve as an alternative to TNC images without the radiation exposure risks.