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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. To address this, vaccination is a cost-effective and environmentally friendly control approach. In this study, efficacy of a vaccine candidate, containing a peptide derived from ribosomal protein P0, was validated post infestation with L. salmonis, at the lab-scale. The sampling results showed good potential of the vaccine candidate when administered intraperitoneally in the host, in reducing the ectoparasite load, through reduction of adult female lice counts and fecundity and with greater presumptive effect in F1 lice generation. The sampling results correlated well with the differential modulation of pro-inflammatory, Th1, Th2 and T regulatory mediators at the transcript level at different lice stages. Overall, the results supports approximately 56% efficacy when administered by intraperitoneal injection. However, additional validation is necessary under large-scale laboratory trial for further application under field conditions.

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...

Inflammation is a hallmark of the physiological response to aggressions. It is orchestrated by a plethora of molecules that detect the danger, signal intracellularly, and activate immune mechanisms to fight the threat. Understanding these processes at a level that allows to modulate their fate in a pathological context strongly relies on in vivo studies, as these can capture the complexity of the whole process and integrate the intricate interplay between the cellular and molecular actors of inflammation. Over the years, zebrafish has proven to be a well-recognized model to study immune responses linked to human physiopathology. We here provide a systematic review of the molecular effectors of inflammation known in this vertebrate and recapitulate their modes of action, as inferred from sterile or infection-based inflammatory models. We present a comprehensive analysis of their sequence, expression, and tissue distribution and summarize the tools that have been developed to study their function. We further highlight how these tools helped gain insights into the mechanisms of immune cell activation, induction, or resolution of inflammation, by uncovering downstream receptors and signaling pathways. These progresses pave the way for more refined models of inflammation, mimicking human diseases and enabling drug development using zebrafish models.

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Aquaculture constitutes an alternative source for food production and contributes to the reduction of indiscriminate catch of aquatic organisms from their natural environment (Diaz & Neira, 2005; Beveridge et al., 2013). However, high mortality during larval state remains a challenge in this sector, mainly because of factors like diets and diseases induced by pathogens (Helvik et al., 2009; Stentiford et al., 2017). Therefore, growth and health management is a key strategy for sustainable aquaculture (Martinez et al., 2016a).

Aquaculture constitutes an alternative source for food production and contributes to the reduction of indiscriminate catch of aquatic organisms from their natural environment (Diaz & Neira, 2005;Beveridge et al., 2013). However, high mortality during larval state remains a challenge in this sector, mainly because of factors like diets and diseases induced by pathogens (Helvik et al., 2009;Stentiford et al., 2017). Therefore, growth and health management is a key strategy for sustainable aquaculture (Martinez et al., 2016a).