INDUCTION OF POLYCLONAL ANTIBODIES TO THE S1 SUBUNIT OF PERTUSSIS TOXIN BY SYNTHETIC PEPTIDES COUPLED TO PPD - EFFECT OF CONJUGATION METHOD, ADJUVANT, PRIMING AND ANIMAL SPECIES

Two peptides, designated L and K, covering a sequence near the NH-term inal end of the S1 subunit of pertussis toxin (PT) were conjugated to the PPD (purified protein derivative) of M. tuberculosis by either glu taraldehyde (GLUT) or succinimidyl 4-(N-maleimidomethyl) cyclohexane-1 -carboxylate (SMCC) and N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) and injected into groups of mice and guinea pigs. Initially, th e effect of priming the animals with BCG vaccine and the use of alumin ium hydroxide as adjuvant for the anti-peptide antibody response was s tudied. The group of BCG-primed mice immunized with adsorbed peptide c onjugates showed the highest anti-peptide conjugate antibody response. Based on this finding, groups of BCG-primed mice were immunized four times with either adsorbed peptide L-GLUT, peptide L-SMCC/SPDP or pept ide K-SMCC/SPDP conjugates and the fine peptide specificity as well as the PT and S1 cross-reactivity was investigated in ELISA. Mice immuni zed with peptide L-GLUT showed a significant antibody response to the homologous conjugate, only, whereas the group injected with the peptid e L-SMCC/SPDP conjugate gave a significant response to both peptide K and L conjugated by the SMCC-SPDP method. Likewise, mice immunized wit h the peptide K-SMCC/SPDP conjugate reacted with the homologous and pe ptide L-SMCC/SPDP conjugate, although only the response to the former conjugate was significantly greater than the response to PPD. All grou ps showed a strong anti-PPD response. The anti-PT/Sl cross-reactivity of the antisera varied considerably within each group but was found to be highest in the peptide L-GLUT-immunized animals. The results of th e present study not only stress the importance of BCG priming and use of aluminium hydroxide adjuvants for the immunogenicity of the peptide s in question but also point to the specificity of the conjugation met hods employed as low cross-reactivity between the anti-peptide L-GLUT and L-SMCC/SPDP antisera was noted. Moreover, it appeared that the cho ice of conjugation method may have an effect on the ability of the pep tide conjugates to induce an antibody response cross-reacting with the native protein.