A real-time PCR assay for quantification of canine adenoviral vectors

The pre-existing humoral and cellular immunity found in the great majority of the population raises concerns about the clinical efficacy and safety of vectors derived from ubiquitous human adenovirus serotypes. To alleviate these concerns, canine adenovirus type 2 vectors (CAV-2) were developed. Owing to their extraordinary neuronal tropism and efficient axonal retrograde transport, CAV-2 vectors hold great promise for the treatment of neurodegenerative diseases. The development and validation of a SYBR Green qPCR assay for determination of CAV-2 titers is reported in the present study. This method uses specific primers designed to amplify a small genomic fragment of CAV-2 structural genes (pVI-hexon). The method was accurate and reproducible as determined by the low intra- and inter-assay variability (<15% R.S.E.). It is sensitive and useful over a 5-log range (1 × 103 to 1 × 107 genome copies/reaction). The assay can be used to quantify purified vector samples as well as crude viral lysates. The titers obtained by qPCR correlated well with both, those obtained by OD260 and TCID50 as indicated by the high coefficients of determination obtained by regression analysis (r2 > 0.83). The development of this simple and rapid CAV-2 quantitation method should be helpful for process development and monitoring.