Ponente
Descripción
Pneumococcal disease is one of the most common causes of morbidity and mortality in children under 2 years of age and people over 65 years of age in the world. Every year it causes the infection of more than a million children worldwide. In Cuba it is one of the invasive bacterial agents with the highest incidence in the health of these age groups. Finlay Vaccine Institute is developing an heptavalent conjugate vaccine that includes the polysaccharide of Streptococcus pneumoniae serotype 1. Conjugation methods introduce modifications that can affect the antigenic and immunological characteristics of the polysaccharides. The objective of this work is to evaluate the influence of O-acetylation of serotype 1 polysaccharide in the efficiency of chemical conjugation and the conjugate immunogenicity. Fragmented polysaccharides with different levels of acetylation were conjugated to tetanus toxoid carrier protein by reductive amination and peptide coupling with a carbodiimide. The glycoconjugates were characterized by colorimetric techniques, High Resolution Size Exclusion Chromatography and their immune response was evaluated. All glycoconjugates were immunogenic in BALB/c mice, showing comparable response. The conjugation reaction by both methods, from de-Oacetylated fragmented polysaccharides, was the most efficient. O-acetylation content of S. pneumoniae capsular polysaccharide serotype 1 interferes in the polysaccharide incorporation to carrier protein during chemical reaction, achieving less conjugation yield. Instead unconjugated capsular polysaccharide as vaccine antigen, for the conjugate antigen, the molecule O-acetylation is not essential for the specific anti bacteria immunogenicity.
