Conjugation of polysaccharide to a carrier protein has enhanced immunogenicity and efficacy of the vaccine. Carrier proteins, such as TT, DT and CRM197, are most commonly used. Co-administration of a conjugate vaccine and its corresponding carrier protein antigen may induce carrier enhancement or suppression on vaccine immunogenicity, referred as immune interference. In this study, we investigated the effect of preexistence of anticarrier immunity or co-administration of pneumococcal polysaccharide conjugate vaccine and carrier protein on anti-polysaccharide immunity.
In-house 13-valent pneumococcal polysaccharide conjugate vaccine (PCV13) with TT as carried protein and in-house DTaP vaccine were used in this study. Prevnar 13 from Pfizer® was used as positive control. Group of New Zealand white rabbits were immunized intramuscularly with DTaP and followed by in-house PCV13. A second group were given DTaP and in-house PCV13 simultaneously. Geometric mean IgG anti-TT and anti-polysaccharide concentrations were analyzed by indirect ELISA.
Anti-polysaccharide concentration of groups of preexistence of anti-TT or co-administration of PCV13 and DTaP was not statistically significant different from that of control, although anti-TT concentration was significantly increased in both these two groups.
Neither preexistence of anti-TT immunity, nor co-administration of conjugate vaccine and its corresponding carrier protein, has immune interreference on anti-polysaccharide immune response.