Proteomic analysis of Neobenedenia sp. and Rhabdosynochus viridisi (Monogenea, Monopisthocotylea): Insights into potential vaccine targets and diagnostic markers for finfish aquaculture.

Monogeneans are parasitic flatworms that represent a significant threat to the aquaculture industry. Species like Neobenedenia melleni (Capsalidae) and Rhabdosynochus viridisi (Diplectanidae) have been identified as causing diseases in farmed fish. In the past years, molecular research on monogeneans of the subclass Monopisthocotylea has focused on the generation of genomic and transcriptomic information and the identification in silico of some protein families of veterinary interest. Proteomic analysis has been suggested as a powerful tool to investigate proteins in parasites and identify potential targets for vaccine development and diagnosis. To date, the proteomic dataset for monogeneans has been restricted to a species of the subclass Polyopisthocotylea, while in monopisthocotyleans there is no proteomic data. In this study, we present the first proteomic data on two monopisthocotylean species, Neobenedenia sp. and R. viridisi, obtained from three distinct sample types: tissue, excretory-secretory products (ESPs), and eggs. A total of 1691 and 1846 expressed proteins were identified in Neobenedenia sp. and R. viridisi, respectively. The actin family was the largest protein family, followed by the tubulin family and the heat shock protein 70 (HSP70) family. We focused mainly on ESPs because they are important to modulate the host immune system. We identified proteins of the actin, tubulin, HSP70 and HSP90 families in both tissue and ESPs, which have been recognized for their antigenic activities in parasitic flatworms. Furthermore, our study uncovered the presence of proteins within ESPs, such as annexin, calcium-binding protein, fructose bisphosphate aldolase, glutamate dehydrogenase, myoferlin, and paramyosin, that are targets for immunodiagnostic and vaccine development and hold paramount relevance in veterinary medicine. This study expands our knowledge of monogeneans and identified proteins that, in other platyhelminths are potential targets for vaccines and drug discovery.