In Vivo Efficacy of Purified Quillaja Saponin Extracts in Protecting against Piscirickettsia salmonis Infections in Atlantic Salmon (Salmo salar)

Abstract

Piscirickettsiosis, the main infectious disease affecting salmon farming in Chile, still has no efficient control measures. Piscirickettsia salmonis is a facultative intracellular bacterium that can survive and replicate within the host macrophages, evading the immune response. Triterpenic saponins obtained from the Quillaja saponaria tree have been widely studied, and have been shown to be immunomodulatory agents, suitable for feed and vaccine applications for veterinary and human uses. The impact of the oral administration of two extracts of Quillaja saponins on the infection of P. salmonis in Salmo salar and the corresponding gene expressions of immunomarkers were studied under three in vivo models. In the intraperitoneal challenge model, the group fed with Quillaja extracts showed lower mortality (29.1% treated vs. 37.5% control). Similar results were obtained in the cohabitation model trial (36.3% vs. 60.0%). In the commercial pilot trial, the results showed a significant reduction of 71.3% in mortality caused by P. salmonis (0.51% vs. 1.78%) and antibiotic use (reduction of 66.6% compared to untreated control). Also, Quillaja extracts significantly modulated the expression of IFN-II and CD8. These results represent evidence supporting the future use of purified Quillaja extracts as a natural non-pharmacological strategy for the prevention and control of P. salmonis infections in salmon.

Blends of Organic Acids Are Weaponizing the Host iNOS and Nitric Oxide to Reduce Infection of Piscirickettsia salmonis in vitro

“…These actions stimulate innate and adaptive immune responses, encompassing cellular and humoral immunity. Mechanistically, these protective effects observed in these studies were correlated to the early activation of INF-II and effector proteins like the C3 complement factor and CD8+ T cells, creating a protective microenvironment versus P. salmonis [5]. Other mechanisms might trigger the NF-kβ pathway and initiation of a pro-inflammatory transcriptional response [11].…”

“…P. salmonis can endure and proliferate within host macrophages, monocytes, and non-lymphoid cells, effectively circumventing the immune response [3,5]. In vivo and in vitro findings indicated that P. salmonis persisted for ≥120 h or more in macrophageenriched cell cultures derived from Atlantic salmon, with a concurrent peak in identifying the 16S rDNA copy number per cell [18].…”

“…Triggered by the pathogen Piscirickettsia salmonis, this disease is responsible for annual economic damages conservatively estimated at around 700 million dollars [2,3]. Discovered in 1989 within farmed coho salmon (Oncorhynchus kisutch) in Chile, Piscirickettsia salmonis, a Gram-negative facultative intracellular bacterium, resembles a rickettsia-like organism identified as a pathogen in fish [4,5]. Phylogenetically, the pathogen shows closer similarities to species within the Legionella, Francisella, and Coxiella genera than members of the Rickettsia genus [6].…”

“…These approaches appeal because of their simple preparation processes, cost-effectiveness, reduced environmental impact, and scientific support for using combinations of organic acids with plant extracts, essential oils, phytochemicals, and probiotics. Their antimicrobial, antioxidant, and antiviral properties, alongside their capacity to support the immune system depicted in in vivo and in vitro studies, have contributed to improved fish health and welfare [5]. In addition, phytochemicals are recognized for their role in preventing viral and bacterial adhesion to cells and influencing intracellular mechanisms [5].…”

“…Their antimicrobial, antioxidant, and antiviral properties, alongside their capacity to support the immune system depicted in in vivo and in vitro studies, have contributed to improved fish health and welfare [5]. In addition, phytochemicals are recognized for their role in preventing viral and bacterial adhesion to cells and influencing intracellular mechanisms [5]. These actions stimulate innate and adaptive immune responses, encompassing cellular and humoral immunity.…”