A sustained vaccine-vehicle for cattle pathogens

Infectious diseases of cattle have an enormous financial and welfare impact world-wide. High incidence pathogens with importance either through cattle disease (with associated loss of productivity) or the potential for human zoonosis include salmonella, E.coli O157, tuberculosis and Campylobacter, to name but a few. With a world cattle population in excess of 1.3 billion, the potential market for bovine vaccine products is enormous (currently estimated at 1 billion US$). Most cattle harbour the non-pathogenic parasite Trypanosoma theileri. This protozoan is sustained at low-levels without affecting productivity in beef and dairy herds. By utilising the genetic tractability of trypanosomatid parasites, we have developed T. theileri as a potential delivery system for antigens in cattle. Importantly, the vehicle is expected to persist at a low-level in cattle for long periods enabling sustained antigen delivery. Our prior work has overcome the major hurdles to development of the vehicle: namely, long-term in vitro culture, production of the stably-engineered vehicle and the expression of heterologous proteins. By optimisation and validation of the delivery system, we now wish to widen the technology to a stage suitable for evaluation of its commerical viability. Significantly, the process and production costs of the proposed vaccine-vehicle are likely to be low in comparison to existing vaccine strategies. By providing prolonged release of recombinant protein, T. theileri has the potential to afford a novel and flexible expression vehicle for immunogens from cattle pathogens. Our aims in this development phase are to: -optimise expression of exogenous proteins by the engineered parasite; -develop and validate a biological containment strategy for the vaccine-vehicle, and -examine maintenance and protein expression of the vaccine-vehicle in cattle and to assay the resulting antigen-specific immune responses. This application represents a partnership between UK academics (based at the University of Edinburgh and Moredun Research Institute) and Industry (Intervet). This provides a unique skills base to maximise the potential for ultimate commericalisation. The Industrial Partner, Intervet, is among the three most prominent animal health companies in the world and the leading company for animal vaccines. As such, their involvement brings a strong focus to the industrial applications of the project providing expertise in vaccinology, disease knowledge, and reagents to prove practicality of the system. In addition to their direct financial commitment to the proposal, the Industrial Partner also will contribute to ongoing IP protection and extensive provision of specialist contained facilities for animal trials. Combined, this represents an 'in-kind' contribution in excess of £100,000, this equating to an approximately 20% financial contribution over-and above the 10% direct cash contribution required for an Industrial Partnership Application.

We have developed a potential novel vehicle for vaccinating cattle. We aim to optimise the system to assess the efficacy of protein expression, persistence and antigen-presentation in vivo. This will provide proof-of-concept data essential for commercial development. The key objectives are: 1. Optimisation of protein expression. To maximise antigen production and presentation for sustained immune stimulation we will (i) optimise the gene expression control signals in already-proven expression constructs and (ii) exploit existing knowledge of protein trafficking in the vehicle to direct antigens to different sites (internal, surface, secreted) for presentation. 2. Containment of the vehicle. We will validate a biological containment strategy to prevent dissemination of the engineered vehicle. Transmission-disabled mutants will be assayed for their viability in culture. Non-viability of the genetically disabled vehicle in a suitable arthropod vector will also be confirmed. 3. Validation of the vehicle in cattle: The vehicle will be assayed for longevity and efficacy in cattle using dedicated facilities at Moredun Research Institute and the Industrial partner. Specifically, we will monitor: (i) The persistence of the vehicle alone, or in the context of a pre-existing population. (ii) The persistence of the vehicle in cattle when antigen is routed to different locations for expression. (iii) The sustained expression of the delivered protein after vaccination. (iv) The antibody responses generated to vaccine candidates in cattle. Our expertise in molecular cell biology (KRM), immunity to cattle parasites (JBM) and the expertise of the industrial partner in animal vaccine development will allow us to develop this novel vaccine delivery system for cattle.