Immunological properties of conjugates of ragweed pollen antigen E with methoxypolyethylene glycol or a copolymer of D-glutamic acid and D-lysine.

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Abstract
The major allergen of ragweed pollen, antigen [Ag] E, was modified by coupling its amino acid groups with methanol, methoxypolyethylene glycol (MPEG) of 5000 daltons or a synthetic copolymer of D-glutamic acid and D-lysine (DGL) of 34,000 daltons, all appropriately activated. These conjugates were characterized chemically and immunologically. Compared to the native Ag, the methoxy conjugate showed little reduction in allergenic activity, but the other 2 conjugates showed strong reductions, as measured by heterologous passive cutaneous anaphylaxis in rats sensitized with murine anti-Ag E reaginic sera. The MPEG conjugate was apparently nonimmunogenic in mice known to be high responders to the native Ag. MPEG and DGL conjugates retained the immunosuppressive property of the native Ag as s.c. treatment of Ag E sensitized mice with these 2 conjugates led to significant long-lasting depression of their Ag E-specific Ig[immunoblobulin]E and IgG antibody levels. These immunological changes may result from reduction of antigenic valency and specificity upon coupling the bulky molecules to the protein Ag.