Quantitative adenovirus neutralization assays based on the secreted alkaline phosphatase reporter gene: application in epidemiologic studies and in the design of adenovector vaccines.

Replication-defective recombinant adenoviruses (rAd) are used as vectors for vaccines as well as for gene therapy. To determine type-specific antibodies to adenovirus (Ad) serotypes 2, 5, 24, 34, and 35, we developed quantitative neutralization assays using recombinant adenoviruses with the secreted alkaline phosphatase (SEAP) reporter gene. Among the standardized parameters, the concentration of infectious and noninfectious adenoviral particles used in the assay is critical for a reliable comparison of data from different studies. The usefulness of this assay was demonstrated in a pilot epidemiologic study of 40 healthy individuals. In this study, the highest prevalence of antiadenovirus antibodies was found for the Ad2 serotype (82.5%), followed by Ad5 (35%). The prevalence of antiadenovirus antibodies for the serotypes 24, 34, and 35 was low (7.5%, 2.5%, and 0%, respectively). In addition, epidemiologic parameters such as gender and age were statistically evaluated. A positive association was found between age and the presence of anti-Ad5 antibodies. The assay was also useful for evaluating the presence of antiadenovirus antibodies in the design of vaccines using a rhesus monkey model. In this animal model, it was possible to determine differential dose and time responses, and the specificity for the detection of neutralizing antibodies was assessed. The evaluation of serotype-specific neutralizing antibodies can be of both clinical and epidemiologic importance as a means of selecting the appropriate serotype adenovector(s).

Development of an adenovirus-shedding assay for the detection of adenoviral vector-based vaccine and gene therapy products in clinical specimens.

Adenoviral vectors are used widely as gene therapy and vaccine delivery systems. An adenovirus-shedding assay may be performed in clinical trials to monitor the safety of the vector and to investigate the potential relation between clinical symptoms and shed vector virus. This report describes the development and statistical performance of the shedding assay. Live adenovirus was recovered from throat swab and urine samples spiked with E1-deleted adenovirus type 5 vector expressing HIV-1 gag [Ad5HIVgag], in the presence or absence of wild-type adenovirus (WT Ad5). Samples were cultured in 293 and A549 cells, and the DNA extracted from virus culture was tested by polymerase chain reaction (PCR) for sequence identity. The results showed that the frequency of Ad5HIVgag infectivity in 293 cells by cytopathic effect (CPE) or an immunofluorescence assay (IFA) was concentration-dependent (53% for 10(2), 94% for 10(4), and 100% for 10(6) viral particles). WT Ad5 virus did not interfere with Ad5HIVgag. PCR amplisets could specifically amplify target sequences in the background of nonspecific DNA matrices and could distinguish Ad5HIVgag from wild-type adenoviruses. This assay may be used for clinical trials using adenovirus vectors as vehicles for vaccines.