Virus and Vector Shedding

As part of clinical trial studies of virus gene therapy products or other live virus products there is a requirement to understand if and by how much the body sheds virus. Today virus products are being used at higher titres than in the past and there is a greater potential for virus to be shed into the environment.

Guideline on ‘Good Pharmacovigilance Practices (GVP) Product- or Population-Specific Considerations I: Vaccines for Prophylaxis Against Infectious Diseases’ is a draft guidance that discusses several aspects of clinical studies for vaccines. For live vaccines, consideration should be made of shedding and transmission from vaccinated individuals to unvaccinated close contacts and the risk for pregnant women and the foetus. Reversion to virulence should also be considered. The presence of adventitious agents from raw biological material or agents introduced during the production process should also be evaluated. Reversion to virulence after multiplication or recombination with wild type virus in the vaccine recipients may be a consideration for some types of viral vaccines. Tests to distinguish between wild and vaccine strains should be considered.

Virus can be shed from the body via a number of different routes, each route being required to be qualified and validated for robustness prior to being used during the clinical trials. There are relatively few methods of detecting virus in biological samples which are suitable for these studies. BioOutsource primarly offers the Polymerase Chain Reaction (PCR) technology to detect virus in biological samples. Each study has specific assays to detect and quantitate the amount of virus present in each sample. In addition, BioOutsource can also offer in vitro methods to quantitate the level of infectious virus in biological samples using plaque assays for example.

BioOutsource has experience with Adenovirus, Vaccinia, Herpesvirus, Adeno-associated virus and many other virus types.