According to the Associate Researcher of the “Aquaculture Genomics” line of the INCAR Center, Dr. Diego Valenzuela Miranda, “in recent years, the genomic knowledge of Caligus has shown us that the microbiota associated with this parasite plays a vital role both for its cycle of life and in its capacity to infest farmed salmon”.
One of the most important threats for the management of caligidosis is the loss of sensitivity of Caligus to the pharmacological treatments that are currently used to control the parasite. Due to this, it is essential to explore new non-pharmacological control mechanisms that allow obtaining new sustainable solutions. Within these options, anti-microbiota vaccines correspond to a new generation of vaccines that has recently been described as a safe, specific and effective alternative for the control of parasites in animal production.
In recent years, consensus has been generated that the development of almost all living organisms is strongly influenced by the set of microorganisms they harbor (microbiota). The composition and structure of the microbiota can be decisive for the correct functioning of various biological processes such as homeostasis, metabolism and immunity, among others. For its part, it has been described that the microbiota in parasites actively participates in the interaction with its host, through the production of toxins, redirecting the host’s immune response or supporting the correct functioning and development of the parasite. Because of this, scientists have proposed that altering the microbiota of parasites may offer a new strategy for the control of these organisms.
The concept anti-microbiota vaccine has been recently coined to describe a new type of vaccine for parasite control. These are designed to alter key bacteria in the parasite’s microbiota, by immunizing the host against these bacteria. The first step in the development of this type of vaccine corresponds to the identification of key bacteria (keystone bacteria) in the parasite’s microbiota through co-occurrence analysis. Subsequently, the host is immunized with these live, attenuated bacteria or with a species-specific protein with antigenic capacity. When the parasite infests the immunized host, circulating antibodies in the host neutralize the parasite microbiota, altering its homeostasis and mitigating the disease.
Microbiota studies in Caligus have determined the existence of a diverse bacterial community associated with sea lice, which also includes a wide variety of pathogenic species for fish, including relevant genera such as Vibrio and Tenacibaculum. Additionally, studies carried out by INCAR have suggested the existence of bacteria with roles in the metabolism of Caligus, becoming interesting candidates for the development of anti-microbiota vaccines that allow an alternative for the control of caligidosis. Through reverse vaccinology, researchers at the INCAR center have designed a recombinant vaccine of a membrane protein from a key bacterium of the Caligus microbiota.
Asked about the state of progress of the first anti-microbiota vaccine for Caligus, Dr. Valenzuela explains that “the results have shown that this vaccine generates a powerful immune response in Atlantic salmon, reducing the percentage of adult Caligus fixation in immunized individuals ”. Researchers are currently in the process of confirming that the decrease in Caligus fixation is related to an alteration in the louse microbiota. However, these results reflect that anti-microbiota vaccines could become a promising alternative for the development of non-pharmacological strategies to control caligidosis.
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