Induced autoimmunity against gonadal proteins affects gonadal development in juvenile zebrafish

A method to mitigate or possibly eliminate reproduction in farmed fish is highly demanded. The existing approaches have certain applicative limitations. So far, no immunization strategies affecting gonadal development in juvenile animals have been developed. We hypothesized that autoimmune mechanisms, occurring spontaneously in a number of diseases, could be induced by targeted immunization. We have asked whether the immunization against specific targets in a juvenile zebrafish gonad will produce an autoimmune response, and, consequently, disturbance in gonadal development. Gonadal soma-derived factor (Gsdf), growth differentiation factor (Gdf9), and lymphocyte antigen 75 (Cd205/Ly75), all essential for early gonad development, were targeted with 5 immunization tests. Zebrafish (n=329) were injected at 6 weeks post fertilization, a booster injection was applied 15 days later, and fish were sampled at 30 days. We localized transcripts encoding targeted proteins by in situ hybridization, quantified expression of immune-, apoptosis-, and gonad-related genes with quantitative real-time PCR, and performed gonadal histology and whole-mount immunohistochemistry for Bcl2-interacting-killer (Bik) pro-apoptotic protein. The treatments resulted in an autoimmune reaction, gonad developmental retardation, intensive apoptosis, cell atresia, and disturbed transcript production. Testes were remarkably underdeveloped after anti-Gsdf treatments. Anti-Gdf9 treatments promoted apoptosis in testes and abnormal development of ovaries. Anti-Cd205 treatment stimulated a strong immune response in both sexes, resulting in oocyte atresia and strong apoptosis in supporting somatic cells. The effect of immunization was FSH-independent. Furthermore, immunization against germ cell proteins disturbed somatic supporting cell development. This is the first report to demonstrate that targeted autoimmunity can disturb gonadal development in a juvenile fish. It shows a straightforward potential to develop auto-immunization-based technologies to mitigate fish reproduction before they reach maturation. However, the highly variable results between treatments and individuals suggest significant optimization should be performed to achieve the full potential of this technology.