Evaluation of infectious titer in a candidate HSV type 2 vaccine by a quantitative molecular approach

Abstract

BackgroundOne of the critical tasks in analytical testing is to monitor and assign the infectivity or potency of viral based vaccines from process development to production of final clinical lots. In this study, a high throughput RT-qPCR based approach was developed to evaluate the infectious titre in a replication-defective HSV-2 candidate vaccine, called HSV529. This assay is a combination of viral propagation and quantitative RT-PCR which measures the amount of RNA in infected cells after incubation with test samples.ResultsThe relative infectious titre of HSV529 candidate vaccine was determined by a RT-qPCR method targeting HSV-2 gD2 gene. The data were analyzed using the parallel-line analysis as described in the European Pharmacopoeia 8th edition. The stability of HSV529 test samples were also investigated in a concordance study between RT-qPCR infectivity assay and a classical plaque assays. A suitable correlation was determined between both assays using an identical sample set in both assays. The RT-qPCR infectivity assay was further characterized by evaluating the intermediate precision and accuracy. The coefficient of variation from the six independent assays was less than 10%. The accuracy of each of the assay was also evaluated in the range of 92.91% to 120.57%.ConclusionsOur data demonstrate that the developed RT-qPCR infectivity assay is a rapid high throughput approach to quantify the infectious titer or potency of live attenuated or defective viral-based vaccines, an attribute which is associated with product quality.

Development of one-step real-time PCR assay for titrating trivalent live attenuated influenza vaccines

“…The RT-qPCR method has gained increased attention and is expected to overcome drawbacks of the conventional assays. 12,14,20 Notably, virus titration by using RT-qPCR, which is also suitable for non-cytopathic viruses, can be determined more quickly than by the CPE method. 21 In our study, the influenza vaccine titers could be estimated within 24 h using the RT-qPCR method, which was much earlier than the required 48 h for type A or 72 h for type B in the EID 50 assay.…”