Fifty Sprague Dawley rats were randomly classified into control, α-MMC, PEGylated α-MMC, MAP30, and PEGylated MAP30 groups of ten each. The rats in the control group were subcutaneously injected with saline solution, and the RIP and PEGylated RIP groups were emulsified in Freund's complete adjuvant at a dose of 1.42 mg/kg at the infection frequency of 3 days for 17 days. Blood samples were collected from the capillary vessel in rats' eyes and separated sera were stored at -20°C. Antigen-specific serum IgG levels were measured by ELISA. Briefly, 96-well plates were coated with 100 µL of 30 µg/mL purified antigen (RIPs and PEG-RIPs) in 0.05 M carbonate-coating buffer, 