Optimization of Enhanced Expression of Interferon-γ and Interleukin-2 in Chicken Peripheral Blood Mononuclear Cells by Polysaccharide Immunomodulators Using Historical-Data Response Surface Methodology

Abstract

Background: Natural polysaccharides have been found to act as potent immunomodulatory agents. Objectives: The present study aimed to assess and optimize the concentration of polysaccharides driven from Chlorella by-product (CBP) for interferon-γ (IFN-γ) and interleukin-2 (IL-2) gene expression by chicken peripheral blood mononuclear cells (PBMCs). Methods: In this study, a crude polysaccharide (CP) was extracted from CBP and fractionated to F1 and F2 using anion-exchange chromatography. Extracted polysaccharides were used at the concentrations of 200 to 1000 μg/mL in the culture medium for PBMCs. The data were analyzed by historical-data response surface methodology (RSM) approach. The analysis of variance test was applied to check the significance of RSM results. Results: The effects of immunomodulator type and concentration were statistically significant (P < 0.0001) on both cytokines. In addition, the interaction effect was also significant for IFN-γ expression (P = 0.03). The regression models of IFN-γ and IL-2 expression were confirmed by the non-significant lack of fit (P = 0.056 and P = 0.066, respectively), the determination coefficient (R2 = 0.98 and R2 = 0.96, respectively), and adjusted determination coefficient (Adj. R2 = 0.97 and Adj. R2 = 0.94, respectively). The predicted determination coefficients (Pred. R2 = 0.96 and Pred. R2 = 0.92 for IFN-γ and IL-2 expression, respectively) were in reasonable agreement with the adjusted R2 values and confirmed that the models had a good predictive ability. The adequate precision values of above 4 (37.51 and 24.45 for IFN-γ and IL-2, respectively) also proved the established models could navigate the design space. Furthermore, the optimization results by the historical-data design of RSM revealed that F1 at 786.68 μg/mL with the desirability of 0.87 could be selected to maximize the gene expression of IFN-γ and IL-2 by chicken PBMCs. Conclusions: It is concluded that the immunostimulatory effect was more prominent for F1 than for CP or F2 polysaccharides. In addition, historical-data RSM showed to be a valuable technique to optimize the factors and reach maximum gene expression in chicken PBMCs. Further investigations are now in progress to determine the interrelationship between the molecular structure and bioactivities of CP and fractionated polysaccharides.