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Host immunity and skin microbiome interplay: Importance for protection against sea lice infestation in Atlantic salmon

Background
Previous attempts to develop vaccines against salmon lice infection in salmon have not produced satisfactory results. Candidate antigens are difficult to identify and test for their ability to induce efficacious immune responses. Several studies have used a concealed antigen strategy (transferred from the Boophilus microplus vaccine in cattle) and while results initially were promising, results have been difficult to reproduced. NMBU/Aqua has participated in the Sea Lice Research Center (SLRC) with a focus on immunomodulation of the host, including to develop immunoprophylactic principles against infection. We have worked with vaccination modalities using DNAprime/ protein boost but again, results have not been promising. For this reason we have taken a different path with an idea that lack of protection can be related to amount of antigen used for immunization/ low corresponding antibody responses. Lice antigens have been prepared from sea lice and used for immunization of salmon at high antigen load. With this approach we have obtained 65% reduction in sea lice numbers (compared controls) and at heavy infection load.
Objectives
Main objective 
To establish a protocol for vaccination combined with skin microbiome engineering that increase the resistance towards lice infection in Atlantic salmon.
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Sub-objectives
• ​To identify protective antigens of lice preparations for subsequent use of recombinant antigen design and vaccine delivery using a “reverse vaccinology” approach.
• To characterize, quantify and detail the impact of sea lice infection on the skin microbiome in Atlantic salmon in terms of its taxon presence/absence and relative abundance.
• To test these prophylactic interventions at laboratory scale and in small scale field studies.
​Expected project impact
Obtained results can be used for prevention of sea lice infection in salmon under field conditions. The generated know how and knowledge will be available for use in the salmon farming industry  and the aim is to license the vaccination concept to pharmaceutical for commercial use in the industry.
​Project design and implementation
The project will be run through 3 scientific workpackages (WP1–3), plus a workpackage WP4 dedicated to communication and dissemination:

WP 1: Vaccination against lice infection using a reverse vaccinology approach for antigen detection
Task 1.1 Vaccination and challenge
Task 1.2 Identification of protective antigens (reverse approach)
Task 1.3 Confirmation of biological activity/immunogenicity of lice antigens

WP 2:  Profiling of microbiome and importance for lice fitness
Task 2.1 Profiling of skin microbiome - baseline studies
Task 2.2 Microbiome profiling post lice studies
Task 2.3 Modulation of microbiome pre- and post-lice challenge

WP 3: Host microbiome – importance for lice development
Task 3.1 Impact of host microbiome on sea lice development

WP 4: Communication and dissemination
​The project aims at having an open and broad communication, both nationally in Norway and internationally.
Dissemination of project results
Project results will be presented in popular science publications (online and paper), targeting the salmon farming industry (kyst.no/ilaks.no etc) and Norsk Fiskeoppdrett, plus international journals with peer review. Presentation at conferences nationally (Frisk Fisk/Havbrukskonferansen) and international (EAFP SeaLice conferences) will be part of the communication strategy.
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