Effect of Polyvalent Pneumococcal Capsular Polysaccharide Conjugates on Immune Response in Mice

Objective To investigate the effect of polyvalent pneumococcal capsular polysaccharide conjugates on immune response in mice.Methods Five-to nine-valent pneumococcal capsular polysaccharide conjugates were prepared using tetanus toxoid (TT)and TT+diphtheria toxoid(DT)as carrier proteins separately,and used for immunization of NIH mice.The specific IgG levels against pneumococcal capsular polysaccharide in sera of immunized mice were determined by indirect ELISA.Results The immune effect of polyvalent pneumococcal capsular polysaccharide conjugates was superior to that of the corresponding monovalent conjugates. The immune response level of mice showed a decreasing tendency with the increasing number of valence of conjugates,which was relived by using TT+DT as carriers.However,excessive carrier dosage still inhibited the immune response.Conclusion After immunization of mice with polyvalent pneumococcal capsular polysaccharide conjugates,epitope suppression induced by carrier proteins was observed with the increasing carrier dosage,resulting in decreased immune response level,which was relived by using two kinds of carrier proteins at the same time.