Novel pectin isolated from Spirulina maxima enhances the disease resistance and immune responses in zebrafish against Edwardsiella piscicida and Aeromonas hydrophila

In this study, we demonstrate the enhanced disease resistance and positive immunomodulation of novel pectin isolated from Spirulina maxima (SmP) in zebrafish model. Zebrafish larvae exposed to SmP had significantly (p < 0.05) higher cumulative percent survival (CPS) at 25 (44.0%) and 50 mu g/mL (67.0%) against Edwardsieila piscicida compared to the control. However, upon Aeromonas hydrophila challenge, SmP exposed larvae at 50 mu g/mL had slightly higher CPS (33.3%) compared to control group (26.7%). SmP supplemented zebrafish exhibited the higher CPS against E. piscicida (93.3%) and A. hydrophila (60.0%) during the early stage of post-infection (< 18 hpi). qRT-PCR results demonstrated that exposing (larvae) and feeding (adults) of SmP, drive the modulation of a wide array of immune response genes. In SmP exposed larvae, up-regulation of the antimicrobial enzyme (lyz: 3.5-fold), mucin (muc5.1: 2.84, muc5.2: 2.11 and muc5.3: 2.40-fold), pro-inflammatory cytokines (il1 beta: 1.79-fold) and anti-oxidants (cat 2.87 and sod1: 1.82-fold) were identified. In SmP fed adult zebrafish (gut) showed > 2-fold induced pro-inflammatory cytokine (il1 beta) and chemokines (cxcl18b, ccl34a.4 and ccl34b.4). Overall results confirmed the positive modulation of innate immune responses in larval stage and it could be the main reason for developing disease resistance against E. piscicida and A. hydrophila. Thus, non-toxic, natural and biodegradable SmP could be considered as the potential immunomodulatory agent for sustainable aquaculture.