Impact of a candidate vaccine on the dynamics of salmon lice (Lepeophtheirus salmonis) infestation and immune response in Atlantic salmon (Salmo salarL.)

Abstract

Title): Effectiveness of fusion peptide-based vaccine TT-P0 on the dynamics of salmon lice 2 (Lepeophtheirus salmonis) infection in Atlantic salmon (Salmo salar L.) 3 4 (Short title): TT-P0 vaccine and salmon lice infection 5 6 (Authors): Abstract 24 Infection with parasitic copepod salmon louse Lepeophtheirus salmonis, represents one of the most 25 important limitations to sustainable Atlantic salmon (Salmo salar L.) farming today in the North 26 Atlantic region. The parasite exerts negative impact on health, growth and welfare of farmed fish as 27 well as impact on wild salmonid populations. It is therefore central to ensure continuous low level 28 of salmon lice with the least possible handling of the salmon and drug use. This necessitates 29 development of an alternative preventive strategy that can document both effect on lice and that 30 fish welfare is maintained in a satisfactory manner with high economic impact. To address this, 31 vaccination is a cost-effective and environmentally free control approach avoiding the 32 disadvantages of chemical and mechanical treatments. In this study, efficacy of a vaccine candidate 33 (TT-P0), encompassing a peptide derived from ribosomal protein P0 and promiscuous T cell epitopes 34 from tetanus toxin and measles virus, was validated post infestation with L. salmonis, at the lab-35 scale. The sampling results showed good potential of the TT-P0 vaccine in limiting the ectoparasite 36 load, when administered intraperitoneal in the host, by affecting the total adult lice female counts 37 and fecundity, with greater presumptive effect in F1 lice generation. This consequently speculate 38 vaccine's potential to reduce the amount and frequency of chemical drug, mechanical treatment 39 and handling stress, currently used in salmon farming practices, thus improving the fish welfare, 40 environment and economy. On the other hand, the vaccine showed minimal secondary effects and 41 differential modulation of pro-inflammatory, Th1, Th2 and T regulatory mediators at the transcript 42 level with respect to different lice stages in the vaccinated groups as compared to control. Overall, 43 the results indicated potential effectiveness of TT-P0 antigen as a good and safe vaccine candidate 44 against salmon lice. This is a very important preliminary documentation of the TT-P0 vaccine, as a 45 preventive measure, for sustainable and profitable growth of the salmon industry. However, further 46 validation is necessary under field conditions. 3 47 Author summary 48Reducing the impact of salmon lice is a major concern for salmon producers around the globe. These 49 parasitic copepods feed on host mucus, skin and blood, causing a negative impact due to reduction 50 in host immune competence and making them more susceptible to other infections or by 51 transmitting pathogens to the host. Farmed salmon populations are the main reservoirs and 52 increasing numbers of salmon lice in the farms, negatively impacts' wild salmon populations. The 53 available control methods rely mainly on pestici...

Applying genetic technologies to combat infectious diseases in aquaculture

“…Sequencing of homologous or conserved genes based on proteins and vaccine targets of ticks and other arthropods has proven an effective approach in antigen mining for sea lice. [615][616][617] RNAi enables functional characterisation of vaccine candidates 624 and has been applied to characterise a number of potential sea lice vaccine candidates including biomolecules involved in egg production (e.g., yolk-associated protein;…”

“…Sequencing of homologous or conserved genes based on proteins and vaccine targets of ticks and other arthropods has proven an effective approach in antigen mining for sea lice 615–617 . RNAi enables functional characterisation of vaccine candidates 624 and has been applied to characterise a number of potential sea lice vaccine candidates including biomolecules involved in egg production (e.g., yolk‐associated protein; LsYAP, 625 ), digestion (e.g., KEDL receptor; LsKDELR and vesicular coatomer protein complex; LsCOPB2, 626 ), muscle activity (e.g., LsalMS, 627 ) and immunomodulation (e.g., prostaglandin E‐synthase 2; PGES2, 628 ) leading to impaired parasite reproductive capacity, digestion and development.…”

Immunoproteomic analysis of fish ectoparasite, Argulus siamensis antigens

“…Further, a number of proteins have also been evaluated against sea lice with varying successes, for example, a novel gene (denoted as my32) from C rogercresseyi that showed the highest identity with the L salmonis gene akirin-2; 55 putative Toll-like receptor 6 and, potassium chloride and amino acid transporter from midgut function and blood digestion of L salmonis, 10 and a peptide from ribosomal P0 protein of L salmonis fused with T-cell epitopes. 56 The new antigens reported here add to this repertoire of proteins already been suggested as vaccine candidates in fish lice/sea lice. However, further studies need to be carried out to determine the sites of expression of these proteins in A siamensis by immunolocalization.…”

Identification and characterization of two salmon louse (Lepeophtheirus salmonis, Krøyer, 1838) heme peroxidases and their potential as vaccine antigens

“…Another recombinant vaccine targeting the vitellogenin in the parasite resulted in lower number of attached female lice and less erosion or wounds on the vaccinated sh compared to the unvaccinated control (Frost et al, 2007). Furthermore, vaccines developed using a recombinant peptide from the ribosomal protein P0 resulted in reduction in attached female lice and their ability to produce eggstrings that supposedly continued into the F1 lice generation (Swain et al, 2020). A recent study showed that a recombinant lice gut protein named P33, elicited speci c antibodies after immunization and resulted in reduction of immature and adult stages of salmon lice (Tartor et al, 2021).…”