THE EFFECTS OF YEAST B-GLUCAN DERIVATIVES ON THE IMMUNE RESPONSES OF THE HAEMOCYTES OF WHITE SHRIMP LITOPENAEUS VANNAMEI

Yeast -glucan is a widely-used immunostimulant in aquaculture. However, the insolubility of -glucan reduces its efficiency as an immunostimulant. In our study, carboxymethylglucan (CMG) and sulfoethylglcuan (SEG) were generated to increase the solubility of -glucan. Both CMG-type and SEG-type of glucans had four derivatives with different degree of substitution (DS), so in total eight kinds of immunostimulants and -glucan as the control were tested in our study. Each immunostimulant was added to the primary culture of the haemocytes of white shrimp Litopenaeus vannamei at different concentrations of 5, 25 and 100 g/mL. With each concentration of every immunostimulant the primary culture was incubated for 6, 12 and 24 hours, before the haemocytes were sampled and their phenoloxidase (PO) activity and respiratory burst (RB) were assayed. After 6 hours, the PO activity of the haemoctyes incubated with all the eight -glucan derivatives was significantly higher than those incubated with -glucan control at the same concentration (P0.05). The RB of the haemocytes incubated with 25 g/mL of all the -glucan derivatives was significantly higher than those incubated with 25 g/mL of -glucan (P0.05). After 12 hours, PO activity and RB of the haemoctyes incubated with all the -glucan derivatives were significantly higher than those with -glucan (P0.05). However, the eight -glucan derivatives showed no significant difference among each other in their effects on the PO activity or RB of the haemoctyes (P0.05). Our study revealed that the immune-enhancing effects of -glucan derivatives were higher than -glucan. However, there was no significant difference in immune-enhancing effects between CMG and SEG. The concentration of -glucan derivatives could significantly influence their immune-enhancing effects, but DS did not affect the immune-enhancing effects of -glucan derivatives.