My research interests include engineering viral membrane glycoproteins.

Long-Term Research Aims

Develop injectable gene therapy vectors for the treatment of disseminated malignancies (particularly multiple myeloma) and demonstrate their efficacy in clinical trials.

Mid-Term Research Aims

• Understand membrane fusion.
• Learn how to regulate the specificity of membrane fusion.
• Learn how to target gene delivery in vivo.
• Test the cytoreductive potency of fusogenic glycoproteins in cancer gene therapy trials.

Approach

One of the aims of the lab is to target viral vectors. To this end we developed a versatile strategy for the display of different polypeptides on retroviruses as N-terminal extensions of their surface (SU) glycoproteins. Using this approach, we demonstrated that the specificity of virus attachment could be easily modified, and virus tropism restricted by receptor-mediated or steric mechanisms. Protease cleavage signals were introduced into the linker between the SU glycoprotein and its N-terminal extension such that the infectivity of an engineered vector for a specified target cell population became wholly or partially conditional upon its exposure to a specific protease (protease targeting). Current protease targets include proteases that are known to be involved in cancer invasion and angiogenesis. To derive novel protease-activatable vectors we made a library of replication competent 'substrate' retroviruses presenting a diverse array of potential protease substrates whose cleavage would result in their activation. By propagating the library on selector cells we isolated viruses that were activatable by endogenous cellular proteases. We are now testing the in vivo potential of these targeting strategies and we are developing new retroviral display libraries for in vivo selection.

A second aim of the lab is to destroy tumor cells by transducing them with genes coding for targeted fusogenic membrane glycoproteins that are potent inducers of cell-cell fusion. To this end we have restricted the specificity of cell-cell fusion by displaying tropism-modifying polypeptides on a hyperfusogenic gibbon ape leukemia virus (GALV) envelope glycoprotein and on the measles virus H glycoprotein. We are now constructing gene therapy vectors to test the therapeutic potential of these toxic transgenes after delivery to tumor xenografts in vivo.