The product generated at the end of the project is a vaccine candidate against Piscirickettsiosi, which consists of a chimera type protein, called SRS-Q1, which is formed by highly antigenic and immunogenic regions of different proteins related to the pathogenicity of P. salmonis. SRS-Q1 has been validated in in vivo assays in Atlantic salmon specimens, showing the ability to induce the expression of different markers of immune response, such as IL-12, INF-γ and the ability to induce a protective immune response, superior to vaccines and/or bacterins currently available for the control of the disease.

In order to obtain the molecule, the reverse vaccinology strategy has been used, which consists of the identification of possible immunogenic molecules from the genome sequence of the microorganism, using different predictive bioinformatics tools. After the in silico identification of the target molecules and epitopes, their chemical synthesis is performed to evaluate their immunogenic capacity. The immunodominant epitopes were selected to form part of the chimeric protein, which was designed bioinformatically, for its subsequent expression in a heterologous system (Escherichia coli) and final evaluation of its immunomodulatory capacity in vivo.

The use of a chimeric protein as a vaccine, such as SRS-Q1, avoids possible antagonistic effects that may arise when different proteins or antigens are mixed, facilitating the incorporation of several molecules with antigenic capacity.
The design of a chimeric protein allows for the addition of
kers or peptide spacers between each epitope, which have adjuvant capacity, thus increasing the immunogenic capacity of the molecule.
It allows the molecule to be tested in different tors and expression
tors and expression systems, including as a DNA vaccine, so that different formulations containing the same molecule can be evaluated.
As SRS-Q1 is a single molecule containing different epitopes of P. salmonis antigenic proteins, it is more stable, easier to handle and its production at industrial level is faster and more efficient.
SRS-Q1 is highly immunogenic, as it is able to activate different immune markers associated with the elimination of intracellular pathogens, as well as inducing the production of a high rate of specific antibodies, indicating that it is activating the adaptive immune response.

Among the bacterial agents with the greatest sanitary, productive and economic impact on the salmon industry is Piscirickettsia salmonis, etiological agent of Piscirickettsiosis, a disease that is responsible, on average, for 90% of the losses in Coho salmon, 85% in rainbow trout and 75% in Atlantic salmon. These numbers represent 55.6% of the annual mortalities in the sector, which is equivalent to around US$ 800 million per year for the industry.

To date, there is still no effective treatment for the control of Piscirickettsiosis, since the existing vaccines on the market, based on bacteria inactivated by chemical or physical agents (bacterins), do not generate significant protection against the disease. Vaccines based on recombinant antigens have also been developed, which have shown high levels of efficacy in the laboratory, but have not had the expected results in field trials. This has led to the use of large quantities of antibiotics to control the disease, therapies that have also been inconsistent without achieving the expected results. According to SERNAPESCA data, 96% of the antibiotics used in salmon farming are aimed at controlling Piscirickettsiosis.