Purified protein derivative (PPD) as an immunogen carrier elicits high antigen specificity to haptens

The effectiveness of the carrier protein in eliciting antigen-specific anti bodies was investigated. The effect of the carrier protein was independent of the conjugation chemistry involved. Keyhole limpet hemocyanin (KLH), pur ified protein derivative (PPD), and ovalbumin (OVA) were used as carrier pr oteins in the immunization of mice. Three antigens were studied: LY170881 ( a small drug molecule), 4-[1'-cyanobenz(f)isoindolyl]butyric acid (CBI-buty ric acid), and a seven residue peptide GPGRGPG (KLE1). The serum antibody r esponse to the antigen or antigen:BSA conjugate was superior in the case wh ere the PPD:antigen conjugates were used as the immunogen when compared to KLH and OVA. The specificity of the antibodies to the respective antigens v s cross-reactivity with the carrier protein was investigated. PPD-coupled a ntigen immunized mice generated a higher percentage of antigen-specific hyb ridomas compared to the other carrier proteins. These findings confirmed PP D as the best carrier molecule for the production of both polyclonal and mo noclonal antibodies.