Beyond Live Cells: Postbiotics, Parabiotics, and Trained Innate Immunity in Aquatic Animal Health

The global aquaculture industry faces an urgent need to eliminate antibiotic dependency while sustaining productivity against increasingly complex disease challenges. Live probiotics have been extensively studied and well-documented; however, a transformative frontier has emerged that remains scientifically underexplored: postbiotics and parabiotics—preparations of inanimate microorganisms, their structural constituents, or their fermentation-derived metabolites—and their capacity to reprogram the host’s innate immune system through the phenomenon of trained innate immunity.Trained immunity refers to the long-lasting functional and epigenetic reprogramming of innate immune cells following an initial microbial stimulus, enabling enhanced responsiveness to subsequent heterologous pathogen encounters. While well characterized in mammalian systems, its mechanistic basis in ectothermic aquatic animals—including teleost fish, penaeid shrimp, and mollusks—remains poorly understood, representing a critical knowledge gap. Emerging evidence suggests that heat-killed bacteria, cell-wall fragments, bacteriocins, short-chain fatty acids, and exopolysaccharides derived from aquaculture-relevant microorganisms can activate conserved innate immune pathways such as NF-κB, MAPK, TLR signaling, and Nrf2/antioxidant cascades, potentially inducing durable immune priming through epigenetic modifications including histone methylation and acetylation.This Research Topic invites original research articles, systematic reviews, and hypothesis-driven papers addressing the following themes:• Isolation and characterization of novel postbiotic/parabiotic candidates; • Molecular and epigenetic mechanisms of trained immunity in aquatic animals; • Comparative efficacy of live versus inactivated microbial preparations in pathogen challenge models; • Multi-omics approaches (transcriptomics, metabolomics, genomics) to decode immune training signatures; • Delivery systems and feed-based formulation strategies.By uniting microbiology, immunology, and aquaculture biotechnology, this collection aims to define the scientific foundation for a next-generation, antibiotic-free disease management paradigm grounded in sustainable immune priming strategies. Topic editors: Linh Nguyen Vu, Nguyen Dinh-Hung, Patima Permpoonpattana Source: https://www.frontiersin.org/research-topics/80844/beyond-live-cells-postbiotics-parabiotics-and-trained-innate-immunity-in-aquatic-animal-health