Species-specific immune response to immunization with human versus rodent A beta peptide

Amyloid beta (A beta) immunization of amyloid precursor protein (APP)-transgenic (tg) mice with human A beta induces humoral immunity, however, the immune response to endogenous rodent A beta is unknown. Fourteen-month J20 APP-tg mice and non-tg littermates were immunized subcutaneously followed by chronic intranasal boosting with human or rodent A beta peptide and adjuvant LT(R192G). Rodent A beta-immunized APP-tg mice had anti-rodent A beta antibody levels of 257.8 micrograms/ml and those immunized with human A beta had anti-human A beta antibodies of 120.8 micrograms/ml. Non-tg littermates had anti-rodent and anti-human A beta antibody concentrations of 98.8 and 231.1 microgram/ml, respectively. Inter-species cross-reactivity was minimal. Anti-human A beta antibodies were predominately IgG1 and IgG2b, while anti-rodent A beta antibodies were equally IgG1, IgG2a, and IgG2b. Anti-human A beta antibodies recognized an epitope within human A beta1-9. Anti-rodent A beta antibodies did not stain Alzheimer's disease (AD) plaques but bound some plaques in APP-tg mice. Splenocytes proliferated modestly to their respective antigen and secreted low levels of IL-2 and IFN-gamma. Therefore, immunizing APP-tg and non-tg mice with rodent A beta resulted in a species-specific humoral response with modest T cell reactivity.