Enhanced vaccine efficacy against Streptococcus agalactiae by molecular adjuvants for tilapia aquaculture in Low and Middle-Income Countries (LMICs)

Summary 

Aquaculture is the fastest growing animal food production sector globally and very important to food security. Tilapia is a fast growing fish and a very important aquaculture species for many low to middle income countries (LIMCs), since they provide an important source of protein and essential revenue for many low-income families. Intensification of tilapia farming has promoted severe disease outbreaks, resulting in high mortalities and economic hardship for tilapia farmers. Animal husbandry in LMICs is threatened by the increase in AMA resistance and if not properly managed would drive the increase in zoonotic infections.

Streptococcosis is one of the major bacterial diseases resulting in severe economic losses for tilapia farmers.  There is no commercial vaccine against Streptococcus infection till date, and farmers resort to using antibiotics to control this disease. To solve this problem, a novel bacterin vaccine, using molecular adjuvants flagellin and tilapia interferon-γ, will be developed and tested in this research project, using tilapia streptococcosis as a disease model.  Flagellin is a potent immune activator in fish. It induces the expression of the Th17 cytokine IL-17A/F1 and Th2 cytokine IL-4/13, but not the Th1 cytokine interferon-γ in fish. IFN-γ is a pleiotropic cytokine with immunostimulatory and immunomodulatory effects. A balanced Th1/Th2 and Th17 immune response is important for promoting protective immunity and eliminating tissue injury (pathological inflammation).

Therefore, novel injection vaccine formulation by incorporation of flagellin and interferon-γ as molecular adjuvants may enhance the immune response to the vaccine leading to long-lasting protection. This work will lead to the development of a cost-effective, easily administered vaccine for use in a large scale tilapia-production in Low and Middle-Income Countries (LMICs).