Immunogenicity of Casein Phosphopeptides Derived from Tryptic Hydrolysis of ß-Casein

¹ Southeast Dairy Foods Research Center, Department of Food Science, North Carolina State University, Raleigh 27695-7624

The immunogenicity of phosphopeptides derived from tryptic hydrolysis of ß-casein (CN) was investigated in a rat model system. The titers of specific immunoglobulin (Ig)G and IgE antibodies made in response to intraperitoneal sensitization to ß-CN, casein phosphopeptides, and skim milk proteins were examined using indirect and amplified indirect ELISA, respectively. Serum IgG antibodies from rats injected with ß-CN were significantly more reactive to ß-CN, casein phosphopeptides, and skim milk proteins coated on microtiter plate wells than were the IgG antibodies generated in rats that had been subjected to other treatments. A significant difference in titers because of the time of sampling (14 or 21 d postinjection) was noted for IgE but not for IgG. Rats that were injected with casein phosphopeptides did not produce IgG antibodies that crossreacted with either skim milk proteins or ß-CN. Specific antibody levels for the IgE class rarely exceeded those of unimmunized controls. The findings suggest that immunogenicity of the phosphopeptides was reduced compared with that of native ß-CN and skim milk proteins.

Key Words: ßbeta;-casein • casein phosphopeptides • immunogenicity

Submitted on July 2, 1996
Accepted on March 17, 1997