Bacterial Kidney Disease (BKD) is the most economically important disease of wild and farmed salmonids. Currently, there are no effective vaccines or treatments for BKD. Our overall objective is to develop BKD vaccines for fish. Our strategy is
to use a combinatorial phage display library to identify novel antigens for BKD
express those antigens in microalgae
deliver microalgae expressing BKD antigens to fish via feed or by immersion, and
to determine whether the microalgal-BKD antigen delivery system provides protection against BKD (vaccination). We propose that our vaccine development strategy will have broad applications for many disease systems including those in which it is not possible to isolate or grow the pathogen.

BKD is a major disease of fresh-water and marine salmonids resulting in substantial mortality. The disease is slow to manifest symptoms and therefore is difficult to treat with antibiotics. As a result, BKD is a prime candidate for the development of an effective vaccine treatment. To date, traditional approaches to identifying and delivering vaccines to trout for BKD control have proven ineffective. We propose that a combinatorial antigen discovery strategy will lead to the rapid identification of novel vaccine immunogens. The delivery of these immunogens in microalgae will induce an immune response both in serum and in mucus, providing the best possible protection against BKD.

We will construct and screen a combinatorial phage display library for phages displaying antigens recognized by immune serum (BKD) from trout. The genes encoding these antigenic determinants will be transformed and expressed in the microalga, Chlamydomonas reinhardtii. Chlamydomonas has been shown to be an effective means to induce an immune response in the serum or mucus of fish either as a component of the feed or by immersion. We will then conduct vaccine trials to determine whether microalgal expressing BKD-immunogenic mimotopes induce protection in fish against subsequent BKD infection.

Our objectives were to screen combinatorial phage dispaly libaries for phage expressing proteins which may be used as candidate antigens for the development of recombinant vaccines for salmonids against IHNV. We have successfully identified bacteriophage which express antigenic determinants that have 30% homology to the the IHNV Gprotein antigenic determinant-1.These results are promising and further screens are under way to refine the screening process and to increase the fidelty of phage (epitope) screening.