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Algal vaccines for aquaculture. Evaluation of an algal-based oral vaccine against salmonid alphavirus.

The Challenge 

Viral diseases are responsible for severe economic losses in global salmonid aquaculture. Current vaccination methods involve injection of anaesthetized fish which is expensive, labour-intensive and stressful to the fish. An oral delivery route therefore represents an attractive low-tech, low-stress alternative to injection or immersion vaccination. To date, there have been few examples of successful oral vaccines for aquaculture. This project will investigate the use of the microalga Chlamydomonas reinhardtii as a host for scalable production of a recombinant oral salmonid alphavirus (SAV) vaccine and increase understanding of fish immunisation efficiency via an oral route.


The aim of this proof-of-concept project is to generate a transgenic line of C. reinhardtii expressing the structural proteins of salmonid alphavirus and determine whether the dried algal biomass can serve as an effective oral vaccine against the virus when formulated into fish feed.

1. Design & construct the transgenic alga, and determine yield of the SAV antigen
2. Optimise algal biomass production and the drying process
3. Carry out fish vaccination and challenge trials
4. Carry out virological, histopathological and immunological analysis
5. Undertake a techno-economic analysis of fish vaccination using algal oral vaccines

Industry relevant outputs

• Oral vaccines have the potential to reduce costs, simplify vaccine delivery and storage, as well as provide animal welfare benefits. Tackling this disease will save money and protect livelihoods and food sources.
• Strains expressing the SAV antigen will be produced at UCL using established techniques for genetically engineering the alga. In order to enhance the process economics, we will investigate the influences of cultivation, harvesting and drying strategies.
• The algal vaccine will then be tested in animal trials to establish how effective this may be in comparison to the established injection method of vaccination. The effectiveness of the oral vaccine will depend on the digestion and immune response elicited by the microalgae within the gut of the fish. Following the scale up of cultivation and the resulting animal trials, we will perform an economic assessment to understand the commercial viability of algal-based oral vaccines.

Basic methodology and work packages (WP)


Design & construction of transgenic algae, and determination of antigen yield
Construction of the transgenic algal cell lines, and determination of antigen yield
Report on different cultivation methods (e.g. growth media, dosing regimes) on growth rates and yields of recombinant protein expression using lab-scale photobioreactors
Optimised cultivation protocol for ‘hanging bag’ scale-up system.


Optimisation of algal harvesting and drying processes
A comparison of flocculation vs centrifugation for the harvest of algal biomass
Comparison of spray-dried vs freeze drying as a method of vaccine preparation
Production of material for laboratory trials


Fish vaccination and challenge trials
Vaccination of Atlantic salmon with candidate test vaccines followed by viral challenge


Virological, histopathological and immunological analysis
Assessment of fate of orally delivered antigen, immunogenicity (mucosal, humoral and innate), and relative protection (RPS) after viral challenge


Techno-economic analysis of fish vaccination using algal oral vaccines
Flowsheet design for vaccine production
Cost modelling and techno economic evaluation using bioprocess model

Joint Call in Aquaculture: Collaborative Research & Innovation

18 months: Jan 2019 – June 2020


Dr Brenda Parker
Dept. Biochemical Eng.


Prof Saul Purton (UCL)


Gateway to Research

UCL Biochemical Engineering


1. University College London
2. Cefas

Project outline made in collaboration with ARCH-UK

More project outlines can be found at www.aquaculturehub-uk.com

Reproduced courtesy of ARCH-UK and the associated project partners.