Fig. 2: Constant serum concentration (CSC) assay provides more consistent subject stratification than the variable serum concentration (VSC) assay format.
From: Overcoming matrix effects in AAV neutralization assays with a constant serum concentration approach
Throughout the figure, Constant refers to the CSC method, where total serum remains fixed at 10%, while Variable refers to the VSC method, where total serum concentration increases with less dilution. A–C Identification of putative seronegative samples from a pool of 46 sera using CSC and VSC assays tested against AAV1 (A), AAV5 (B), and AAV9 (C). Sera yielding above 90% transduction at a 1/4 serum dilution are labeled as seronegative (teal dots), while sera below this threshold are labeled as ineligible for inclusion in a hypothetical reference serum pool (red dots). The black dashed line represents the 90% transduction threshold. The CSC approach assigns more samples as ineligible than the VSC format, reducing misclassification of borderline neutralizers. D–F Classification of the same sera into non-neutralizing (teal dots) or neutralizing (red dots) categories using 50% transduction at a 1/4 dilution as a criterion. Samples above the black dashed line (50% transduction threshold) are classified as non-neutralizing, whereas those below it are classified as neutralizing. Discordant samples—those classified differently under CSC vs. VSC—are connected by gray lines. The proportion of discordant samples is indicated above each plot, with p-values from McNemar tests reflecting the significance of classification differences across AAV serotypes.
