Evaluation of Immunoprotective Activities of White Button Mushroom () Water Extract Against Major Pathogenic Bacteria ( or ) in Goldfish ().

The white button mushroom () is a widely cultivated edible and medicinal mushroom, which contains various active substances, and has application value against pathogenic bacteria in aquaculture. Firstly, water extract (AB-WE) was prepared. Through the detection kits, it was found that the polysaccharide, protein, and polyphenol components of AB-WE were 9.11%, 3.3%, and 1.5%, respectively. The 246 compounds were identified in AB-WE, and the major small-molecule components included L-Isoleucine, L-Tyrosine, L-Valine, and Linoleic acid by HPLC-Q Exactive-Orbitrap-MS. Secondly, the AB-WE was evaluated for its immunological activities through dietary administration and pathogen challenge ( and ) in goldfish (). The results showed that the levels of immune factors of acid phosphatase (ACP), alkaline phosphatase (AKP), and lysozyme (LZM) increased ( < 0.05) in goldfish, and the relative percentage survival of AB-WE against and were 80.00% ( < 0.05) and 81.82% ( < 0.05), respectively. The AB-WE reduced the bacterial content in renal tissue, enhanced the phagocytic activity of leukocytes, and exhibited antioxidant and anti-inflammatory effects by reducing the expression of antioxidant-related factors and inflammatory factors. Through histopathological and immunofluorescence techniques, it was found that AB-WE maintained the integrity of visceral tissues and reduced renal tissue apoptosis and DNA damage. Therefore, AB-WE exhibits immunoprotective activity against and infections in fish, and holds promise as an immunotherapeutic agent against major pathogenic bacteria in aquaculture.