Development of herpes simplex virus 1 vectors for dendritic cell based immunotherapy of malaria
Herpes simplex virus 1 (HSV-1) naturally infects dendritic cells but this prevents the cell from undergoing maturation. Removal of the virus host shutoff protein (vhs) has been shown to improve the ability of both human dendritic cells and mouse bone marrow dendritic cells to mature following virus infection. An HSV-1 vhs" backbone was further modified by deletion of the ICP47 gene and mutation of the VP 16 gene resulting in a vector that does not interfere at all with the ability of mouse dendritic cells to mature. This virus therefore, provided a good candidate for use as vector for antigen delivery in immunotherapy. A recombinant vhs"ICP47"VP16" virus expressing the full length influenza nucleoprotein (NP) was constructed and used to determine the ability of this virus to induce immune responses upon immunisation with virus alone or upon immunisation with infected DCs. Both cellular and humoral responses were investigated and a CD8+ CTL response to both the NP gene and to the virus was obtained after different immunisation regimes confirming the potential of the virus to be used for immunotherapy. In the attempt to further improve the vector, mGMCSF was added to the viral constructs and viruses expressing both mGMCSF and NP or full length Plasmodium yoelii sporozoite surface protein 2 (PySSP2) or circumsporozoite protein (PyCS) were constructed. The effect of co-expressing mGMCSF from the virus was investigated. A convincing CD8+ CTL response was obtained against - the antigen upon direct virus injection though co-expression of mGMCSF did not seem to confer a significant advantage. Overall an HSV-1 vector has been developed and optimised for the infection of dendritic cells and then successfully used for induction of specific CTL and antibody response to full length NP, PySSP or PyCS.