B cells are responsible for antibody production in vertebrate immune systems. Recent studies in Dr. Sunyer's laboratory have produced the unexpected finding that unlike mammalian B cells, B cells in bony fish have potent phagocytic and bactericidal capacities. His lab has also found a novel B cell lineage expressing exclusively surface IgT immunoglobins. Importantly, the IgT system has been found to be specialized in mucosal immune responses. The overarching goal of this new project is to use two complementary trout-pathogen models (Yersinia ruckeri and Ceratomyxa shasta) to test whether IgT and IgM responses are compartmentalized into mucosal and systemic sites, respectively, and to analyze the specific contributions of IgT+ and IgM+ B cell subsets in the development of an innate inflammatory response during the course of infection. Rainbow trout will be infected with these two pathogens and innate and adaptive immune B cell responses will be measured during the course of infection. The responses will include the capacity of these B cells to internalize and kill the pathogens, and their ability to produce a range of pro-inflammatory and anti-inflammatory cytokines. It is expected that IgT+ B cells will play an important role in mucosal responses whereas IgM+ B cell will play a key role in systemic responses. It is expected that both B cell subsets will play a significant role in the development of pro- and anti-inflammatory responses. This project will continue the training of underrepresented minorities in this laboratory as well as the training of one postdoctoral fellow. On a broader level, the studies proposed here will benefit society by contributing to the aquaculture industry since better knowledge of the fish immune system is essential to develop new therapeutic agents and vaccines to prevent fish diseases.
The intellectual merit of this NSF project is based on several important findings that have significantly contributed to understanding the immune system of fish and its evolution. A major finding has been the the discovery of a new B cell subset uniquely expressing IgT, a fish immunoglobulin that was subsequently found by our group to play a key role in gut mucosal immunity. This finding led to the hypothesis that IgT could also be a key immunoglobulin protecting fish in other fish mucosal sites, including the skin. Suporting the aforementioned hypothesis, we have recently reported that IgT is also the most important fish immunoglobulin in the skin mucosa of rainbow trout. These findings represent a paradigm shift in the field of fish immunology since IgM had been considered the only functional immunoglobulin in teleost fish both in systemic and mucosal sites. Our findings challenge this current view, thus indicating that teleost fish contain not one, but two functional immunoglobulins, IgT and IgM, that respond to pathogenic challenge. Moreover our discoveries indicate that while IgM is an immunoglobulin involved in systemic immunity, IgT appears to have specialized in mucosal immunity. These findings have important implications for the development of fish vaccines and other immunotherapeutics, since mucosal areas in fish, including those of the skin and gut, represent major surfaces through which pathogens infect fish. Up until recently, cells of myeloid origin (i.e, granulocytes and macrophages) were thought to be the main pro-inflammatory cells of mammals and fish. Contrary to this belief, studies carried out in our laboratory during the last few years have led to the unexpected finding that teleost fish IgM+ B cells have potent phagocytic and bactericidal abilities. We have found that these innate immune capacities are also present in the IgT+ B cell subset. Moreover, we have discovered that both IgM+ and IgT+ B cell subsets a have a potent capacity to produce pro- and anti-inflammatory cytokines, a role that in mammals is more prominent in cells of myeloid origin. For example, we have found that IgT+ B cells are the leukocytes expressing the hightest levels of IL-10, a key anti-inflammatory cytokine. This finding represents the first identification of regulatory B cells in a non-mammalian species. Overall, our findings have greatly contributed to the understanding of unique functions of fish lymphocytes in host-pathogen interactions, as well as their evolution in the context of innate and inflammatory reactions. The broader impacts of our research findings are multiple. Dr. Sunyer, the Principal Investigator (PI) of this project is currently the only faculty in his school (Veterinary School of the University of Pennsylvania) teaching different aspects of fish immunology and fish diseases. The new findings in his lab have been incorporated in the teaching materials that are used in his fish immunology lectures. Moreover, Dr. Sunyer teaches also Fish Immunology in the nationally recognized aquatic veterinary medical program AquaVet I. where his findings are also disseminated and taught every year. It should be emphasized that the PI’s laboratory environment encourages the participation of underrepresented groups. Thus, the current NSF award has supported directly two postdoctoral Hispanic females, and one of them Dr. Irene Salinas, has recently obtained an Assistant Professor position at the University of New Mexico, while the other, Dr. Daniela Gomez, is now a postdoctoral researcher in another laboratory at the University of Pennsylvani. Both Dr. Salinas and Gomez are first authors of works funded by this NSF award, including studies published in reputed journals such as Nature Immunology and Proceedings of the National Academy of Sciences. Reagents generated with the use of NSF funds have been disseminated and used by more than 10 different national and international fish research groups and, have thus contributed to a beffer understanding of the fish immune system. On a broader level, our studies on the fish immune system are benefiting society by contributing to the aquaculture industry in the short and long-term. A better knowledge of the fish immune system in the context of host-pathogen interactions is essential to the development of new therapeutic agents and vaccines to prevent fish diseases. The results obtained from this current award have been reported in several prestigious international journals, and have been presented orally in various national and international conferences. Moreover, several of the findings generated by this NSF award, have been highlighted in the form of press releases and news in numerous highlights and news sections from scientific journals (i.e., www.nature.com/nri/journal/v13/n9/full/nri3522.html) and research agencies (i.e., www.nsf.gov/news/news_summ.jsp?cntn_id=129159 [see also Fig. 1, which is shown in the previous ULR]). Significantly, during the last 3 years, the PI has chaired several sessions in several scientific conferences, and postdoctoral fellows from his group have presented oral presentations in all of these conferences.
