Photodynamic therapy (PDT), also called photochemotherapy, involves three key components: photosensitizers (PS), a light source, and tissue oxygen. In the presence of tissue oxygen and appropriate wavelength of the light source, photosensitizers will generate cytolytic reactive oxygen species (ROS) to destruct PS-accumulated cells/tissues. More importantly, ROS will attack multiple cellular targets, preventing it from being selected for resistance which is a universal problem nowadays in radiotherapy and chemotherapy of all diseases. In the present study, a novel PDT is exploited by the unusual mechanism of Leishmania parasite. When these trypanosomatid protozoa infect mammalian hosts, they will find their way to specifically parasitize in macrophages and other antigen-presenting cells (APCs). Moreover, a transgenic Leishmania, which are deficient in heme biosynthesis, undergo photolysis when illuminated by specific wavelength of light. Accordingly, it is a useful drug or vaccine carrier.

To develop a new way of vaccination, we would like to build a Leishmania-compatible BioBrick encoding hemagglutinin (HA) from H1N1 influenza virus. We believe the unique properties of transgenic Leishmania will make it a useful model to produce human Influenza vaccine. In the future, we plan to establish this transgenic Leishmania as a platform to carry other antigen or biobricks.