SGER: Preliminary characterization of sodium channel toxins in Gambierdiscus spp. from the Pacific and Atlantic Oceans

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Ciguatera is the most common seafood intoxication in the world. Humans acquire ciguatoxin by eating reef fish that have accumulated the toxins via the marine food web. Lipid-soluble ciguatoxins produced by the dinoflagellate Gamberiduscus toxicus are consumed by herbivorous fish, beginning the processes of foodweb biomagnification and biotransformation that ultimately leads to humans. The frequency of ciguatera is variously estimated to be 500,000 cases per year, and records from various Pacific locals suggest that over 90% of human fish poisonings are due to ciguatera. A serious public health threat in the U.S., ciguatera is estimated to account for 95% of medical costs associated with harmful algal blooms. Because these toxins may also affect fish directly, altering behavior and possibly compromising immune responses, ciguatera impacts both human and ecosystem health.Despite its long history and decades of research, the factors controlling ciguatera outbreaks are poorly understood. This is due in no small part to the complex molecular structure of ciguatoxin, the minute doses that produce clinical symptomology, and the robust analytical chemistry required for definitive analyses. Proliferation of high-potency strains of G. toxicus, human and/or naturally-induced oceanographic perturbations, have all been hypothesized as causative factors explanations for geographic variability in ciguatera frequency and symptomology. Exceptionally little is known about differences in the source toxins from Gambierdiscus spp. and their influence on the subsequent biotransformation of ciguatoxin congeners; this is the focus of this collaborative research. With funding through this Small Grant for Exploratory Research, researchers at four U.S. institutions will undertake exploratory research addressing a basic question: Are the ciguatoxins produced by Gambierdiscus the same across species and strains from the Atlantic (Gulf of Mexico and Caribbean) and the Pacific Ocean basins? Despite the severity, impact, and global distribution of the illness, this question has never been answered, although there is abundant information on other, less severe HAB toxins. The results should provide foundation information for future studies examining epidemiology, toxin transfer and modification, and dynamics of ciguatera. The problem will be addressed by a collaborative effort between The University of Texas at Austin, the University of Hawaii?s Center for Oceans and Human Health (Pacific Marine Biomedical Research Center), the FDA Seafood Safety laboratory (Dauphin Island, Alabama) and NOAA Natural Products Center (Charleston, SC). The primary goal of the research is to determine if the mass of the sodium channel toxin (ciguatoxin) is the same or different in Gambierdiscus strains isolated from these different areas. The secondary goal is to determine if the profile of dominant and secondary sodium channel toxins differ across species or strains. The project will have an unprecedented degree of analytical confirmation in this difficult field and will provide a solid foundation for future work involving these toxins. Besides the obvious broader impacts for public health, the project will support two M.S. graduate students (UTexas and UHawaii), one of whom will train at the FDA laboratory in the techniques of the toxin bioassay. Results will be presented at national meetings and disseminated to the scientific community via peer-reviewed publications. The techniques used will provide a standard and tested protocol for future researchers in this area and will be of interest to HAB toxin researchers in general.