Antibacterial immunity in teleost fish: Integrating innate and adaptive responses for sustainable aquaculture

Bacterial infections are currently the most significant hindrance to the worldwide adoption of sustainable aquaculture, causing unprecedented economical losses and challenges to food security. Teleosts have an extremely well-developed innate and adaptive immune system, but the functional integrity of these immune systems is adversely affected under universal aquaculture-related stress factors. The current review critically and comprehensively synthesizes the two most important challenges, addressing immune resilience, which include: (1) the complex functional interactions between innate and adaptive immune mechanisms, and (2) the combined modulation of these immune mechanisms under environmental factors mentioned above. Our focus primarily centers on the role of major stressors such as temperature change, water quality measures, (physiological) chronic stressing, and microbiome diversity on innate host immunity and resistance to bacterially infected diseases. Finally, we not only conclude the current state regarding the latest research progress on the role and mechanisms utilized in the transition phase from the latent to chronic infection phase based on autophagy-related responses but also emphasize the need to adopt an integrated research area named 'Eco-Immunology' to measure and develop effective interventions against fish diseases. It is the prime requirement to improve the host's resistance to diverse farming conditions to develop sustainable and effective aquaculture. This review uniquely integrates innate-adaptive immune crosstalk with environmentally driven immune reprogramming and autophagy-mediated control of chronic bacterial infections, framing teleost antibacterial immunity within an eco-immunological perspective relevant to sustainable aquaculture.