Chile: USACh scientists suggest that the design of vaccination protocols based on the photoperiod could enhance protection against diseases and optimize the immune response of fish.
In a recent study, Chilean scientists discovered that the immune response of fish is influenced by the photoperiod regime, which can modify the magnitude, quality, and effectiveness of immune memory generation.
Historically, photoperiod has been used as a tool to enhance fish growth and prevent early maturity, among other applications, but little research has addressed its effect on immunity.
That was precisely the unknown that arose for Drs. Mónica Imarai and Merari Goldstein from the Aquaculture Biotechnology Center of the University of Santiago de Chile, and for this reason they decided to investigate the subject further.
regulation of immunity
Regarding the influence of the photoperiod on the T lymphocyte cell line, the scientists explained to Salmonexpert that a particular and unique expression profile of the components involved in the differentiation of CD4 T cells was observed according to the photoperiod in which the fish were kept. .
“This is remarkable, because it implies that the type of immunity (more humoral, or cellular, or regulatory) and its effects on potential protective effects against pathogenic microorganisms will depend on the time of year or light condition to which the fish are subjected. It is likely that melatonin, a hormone produced and regulated by the length of the day, may have some role in this response. In fact, there are melatonin receptors on lymphocytes, which could explain how the photoperiod would be specifically influenced by T lymphocytes”, both experts detail.
Additionally, the experiment also indicated that photoperiod also influences the expression of cytokine genes produced by different subpopulations of T cells, such as the cytokines encoded by the il-4/13a, il-10a, and il-17a/f genes, which regulate different immune processes such as humoral immunity, homeostasis, antimicrobial activity, production of proinflammatory cytokines and oxygen and nitrogen radicals, among others.
Therefore, by exposing the fish to different light regimes and injecting them with the IPNV VP1 viral protein, known for its immunogenic property, the researchers observed different responses.
For example, in fish maintained under 24L:0D, the photoperiod used in fish farms, a significant decrease in the master regulators of T cell differentiation (Th1: t-bet; Th17: ror-ƴt and Treg: foxp3α) was observed, only light/dark condition that reduces the expression of T-cell master transcription factors, meaning that Th1, Th17, and Treg cell development could be reduced.
Photoperiod and vaccination
Put into practice, according to what was stated by the authors of the study, the fact that each photoperiod produces a unique and known immune response profile makes it possible to design vaccination protocols that consider doing this treatment in a photoperiod that induces a type of immunity protective.
“For example, for viral infections, a vaccine could be applied to fish kept for at least 30 days in the photoperiod that favors a cellular immune response (Th1 type), which is generally an antiviral response. In this sense, it will be important to carry out the necessary studies to corroborate the expected results”, declared Mónica Imarai and Merari Goldstein.
Finally, according to the researchers, this study would be the first to report that photoperiod modifies the magnitude and quality of the T helper or cooperative response in rainbow trout, this response being “one of the critical mechanisms for the generation of immune memory and protection against pathogenic microorganisms.
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