Search

To assess the effects of A3α-peptidoglycan (A3α-PG) extracted from Bifidobacterium sp. on the immune response and disease resistance of sea cucumber, different concentrations (0, 0.5, 5 and 50 mg mL−1) of A3α-PG suspensions were used to perform hypodermic injection on Apostichopus japonicus, followed by a Vibrio splendidus challenge. Total coelomocyte count ( TCC), phagocytosis activity and activities of four immunological enzymes in both cell-free coelomic fluid (extra-cellular, EC) and coelomocyte lysate supernatant (intracellular, IC), including acid phosphatase ( ACP), alkaline phosphatase ( ALP), superoxide dismutase ( SOD) and peroxidase ( POD), were measured at 2, 6, 14 and 24 h post injection (hpi). The TCC was not significantly affected ( P > 0.05) by A3α-PG, ranging from 1.84 × 106 to 3.53 × 106 cells mL−1. The coelomocyte phagocytosis activity was significantly activated ( P < 0.05) in all the A3α-PG treatments, whereas no significant difference was observed between them except 24 hpi ( P > 0.05). The EC-ACP activity in the 5.0 mg mL−1 treatment increased significantly ( P < 0.05) at all sampling times, while the IC-ACP activity in the 50 mg mL−1 treatment increased significantly ( P < 0.05) at 2 hpi. Also, the 5.0 mg mL−1 treatment had significant ( P < 0.05) increase in the EC-ALP activity within 14 hpi and the EC-POD activity at 2 hpi, respectively, while significantly ( P < 0.05) enhanced IC-ALP and IC-POD activities were observed in the 50 mg mL−1 treatment within 6 hpi and at 2 hpi, respectively. Only the 5.0 mg mL−1 treatment showed significant ( P < 0.05) increase in the EC-SOD activity at 2 hpi and IC-SOD activity within 14 hpi, respectively. The challenge test showed that the animals treated with 50 mg mL−1 of A3α-PG had notably lower cumulative mortality after 14 days following V. splendidus exposure. All together, these results suggest that A3α-PG could positively enhance immune response that effectively promotes the health status of A. japonicus against V. splendidus infection. [ABSTRACT FROM AUTHOR]

To determine the effects of A3α-peptidoglycan (A3α-PG) extracted from Bifidobacterium sp. on the growth, immune response and disease resistance of sea cucumber Apostichopus japonicus, a 70-day feeding trial was conducted in this study. A total of 216 sea cucumbers were fed with four practical diets prepared from a commercial feed with different contents (0, 1.5, 2.5 and 4.0 g kg−1) of A3α-PG. The specific growth rate (SGR), total coelomocyte count (TCC), phagocytotic activity and activities of four immunological enzymes in both cell-free coelomic fluid (extracellular, EC) and coelomocyte lysate supernatant (intracellular, IC), including acid phosphatase (ACP), alkaline phosphatase (ALP), peroxidase (POD) and superoxide dismutase (SOD), were measured at the end of the feeding trial. Finally, the animals were administered a 16-day Vibrio splendidus challenge via intraperitoneal injection to test the potency of A3α-PG on disease resistance. Compared with the control (0 g kg−1 A3α-PG), a significant increase ( P < 0.05) in SGR was observed in the groups fed with 1.5 and 2.5 g kg−1 A3a-PG. The TCC, ranging from 7.25 × 106 to 1.05 × 107 cells mL−1, was not significantly affected ( P > 0.05) by A3α-PG,. Coelomocyte phagocytotic activities in all of the A3α-PG-supplemented groups were significantly activated ( P < 0.05), but no significant difference ( P > 0.05) was observed. Sea cucumbers fed with 1.5 and 2.5 g kg−1 A3α-PG exhibited significant activation ( P < 0.05) of EC/IC-ACP, EC/IC-ALP, and EC/IC-POD activities. A significant increase in EC-SOD activities ( P < 0.05) was exhibited by all groups with A3α-PG supplementation. The challenge test showed that animals fed with diets containing 2.5 and 4.0 g kg−1 A3α-PG had significantly lower cumulative mortalities compared with the control 16 days after exposure. All of the results presented here show that A3α-PG can positively enhance the growth, immune response and disease resistance of sea cucumber, suggesting that dietary supplementation of A3α-PG has potential applications in the health management of economic species of sea cucumber. [ABSTRACT FROM AUTHOR]