Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Dr. Stephanie DeWitte-Orr

Advisor Role

Supervisor

Abstract

Salmonids are one of the world’s most farmed fish species. These aquatic vertebrate species rely heavily on their innate immune responses to defend themselves against invading pathogens. Although commercial vaccines are available against some viral and bacterial pathogens affecting salmonids, their protective efficacy is variable. Using a prophylactic inducer of local and systemic innate immune responses could have significant implications in salmonid aquaculture. A potent inducer of the innate immune response in fish is double-stranded RNA (dsRNA), a molecule that all viruses make during their replicative cycle. Polyinosinic:polycytidylic acid (polyI:C) is a synthetic dsRNA commonly used to induce type I interferons (IFNs), interferon stimulated genes (ISGs) as well as an antiviral state in vertebrate species. Recent research has shown that by complexing it with a phytoglycogen nanoparticle, it can increase the efficacy of polyI:C and induce enhanced innate immune responses. Since this nanoparticle is naturally derived from sweet corn, it is biodegradable and non-toxic making it ideal for both in vivo and in vitro work. The nanoparticle was complexed with polyI:C to stimulate enhanced innate immune responses in rainbow trout and Atlantic salmon, as well as to prevent viral replication in Atlantic salmon infected with infectious salmon anaemia virus (ISAV). This complex was tested as both an oral gavage and incorporated into commercially available feed pellets to test both controlled dose delivery (oral gavage) and standard feeding delivery (feed pellets). The polyI:C-nanoparticles (polyI:C-NanodendrixTM; NDx) complex was effective in initiating key innate immune components such as IFN and ISGs and its induced response was greater than polyI:C alone or NDx alone. This was found to be the case both locally, in the intestine, and systemically, in the head kidney. The novel feed pellets were also able to prevent viral replication in the intestine of Atlantic salmon that were infected with ISAV via co-habitation. This research may lead to a novel approach for drug delivery, leading to the prevention of pathogen infections and healthier farmed fish species.

Convocation Year

2021

Convocation Season

Spring

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