Effectiveness of fusion peptide-based vaccine TT-P0 on the dynamics of salmon lice (Lepeophtheirus salmonis) infection in Atlantic salmon (Salmo salar L.)

Infection with parasitic copepod salmon louse Lepeophtheirus salmonis , represents one of the most important limitations to sustainable Atlantic salmon ( Salmo salar L.) farming today in the North Atlantic region. The parasite exerts negative impact on health, growth and welfare of farmed fish as well as impact on wild salmonid populations. It is therefore central to ensure continuous low level of salmon lice with the least possible handling of the salmon and drug use. This necessitates development of an alternative preventive strategy that can document both effect on lice and that fish welfare is maintained in a satisfactory manner with high economic impact. To address this, vaccination is a cost-effective and environmentally free control approach avoiding the disadvantages of chemical and mechanical treatments. In this study, efficacy of a vaccine candidate (TT-P0), encompassing a peptide derived from ribosomal protein P0 and promiscuous T cell epitopes from tetanus toxin and measles virus, was validated post infestation with L. salmonis, at the lab-scale. The sampling results showed good potential of the TT-P0 vaccine in limiting the ectoparasite load, when administered intraperitoneal in the host, by affecting the total adult lice female counts and fecundity, with greater presumptive effect in F1 lice generation. This consequently speculate vaccine9s potential to reduce the amount and frequency of chemical drug, mechanical treatment and handling stress, currently used in salmon farming practices, thus improving the fish welfare, environment and economy. On the other hand, the vaccine showed minimal secondary effects and differential modulation of pro-inflammatory, Th1, Th2 and T regulatory mediators at the transcript level with respect to different lice stages in the vaccinated groups as compared to control. Overall, the results indicated potential effectiveness of TT-P0 antigen as a good and safe vaccine candidate against salmon lice. This is a very important preliminary documentation of the TT-P0 vaccine, as a preventive measure, for sustainable and profitable growth of the salmon industry. However, further validation is necessary under field conditions.