Pneumococcal conjugate vaccination in adults: circulating antibody secreting cell response and humoral antibody responses in saliva and in serum.

The results from our previous study showed IgA dominated ASC responses to pneumococcal polysaccharide vaccine and to pneumococcal polysaccharide meningococcal outer membrane protein conjugate vaccine (PncOMPC) in adult volunteers. The results indicated that a high IgA ASC response is a useful indicator of a secretory IgA response in saliva. We believe that the mucosal immune responses is potentially an important characteristic of the pneumococcal vaccines and should thus be measured when the new pneumococcal conjugate vaccines are evaluated. In the present study, we studied two new tetravalent pneumococcal conjugate vaccines: the diphtheria toxoid and tetanus toxoid conjugates. In contrast to PncOMPC, these conjugates induced higher responses than the polysaccharide vaccine. Furthermore, the different structure of the two conjugate vaccines might affect the nature of the response. Thus a different vaccine may be optimal for induction of a mucosal response than is of systemic responses.