Viral vectors as vaccine carriers

•Ad vectors are highly immunogenic and thus superb vaccine carriers.•Most AAVs are poorly immunogenic and thus more suited for gene replacement therapy.•Pre-existing neutralizing antibodies reduce the immunogenicity of viral vector vaccines.•Pre-existing neutralizing antibodies can be circumvented by vectors based on viruses that circulate in non-human species.

This chapter reviews the performance of viral vectors based on adenoviruses or adeno-associated virus as vaccine carriers for infectious diseases. Replication-defective adenovirus vectors based on multiple human or non-human serotypes have consistently induced potent transgene product-specific B and T cell responses and are increasingly being explored in human clinical trials. The immunogenicity of most vectors based on adeno-associated virus vectors has been poor with the exception of a recently described hybrid vector from rhesus macaques that due to its ability to induce potent responses in mice warrant further investigation.