Recombinant fowlpox virus elicits transient cytotoxic T cell responses due to suboptimal innate recognition and recruitment of T cell help.

Recombinant fowlpox viruses (FPVs) have been used in a variety of vaccine strategies; however strong data clearly demonstrating the characteristics of the strength and nature of the resultant immune response elicited by these vectors are lacking. By utilising a recombinant variant of FPV which expresses the nominal antigen chicken ovalbumin (OVA), and assessing innate FPV- and OVA-specific adaptive immune responses, we show that recombinant FPV induces a rapid type I interferon (IFN) response, mediated primarily by plasmacytoid dendritic cells (pDCs). These cells are necessary for the development of a strong but transient CD8(+) T cell effector response directed against OVA-expressing target cells.

The potential role of fowlpox virus in rational vaccine design.

The design of optimal vaccines requires detailed knowledge of how protective immune responses are generated in vivo under normal circumstances. This approach to vaccine development, where the immune correlates of protection are defined and vaccines are designed to elicit the same response, is called rational vaccine design. Poxviruses are attractive candidates for inclusion in such design strategies owing to their large genome, which allows for the inclusion of multiple heterologous genes, including those encoding antigens, co-stimulatory molecules and cytokines.