ln the present work to determine effect of a Streptococcus pneumoniae conjugate vaccine, S.pneumoniae capsule attached to the surface protein (JY-Pol) was ex amined. This JY-Pol contained approximately 92% and 6% carbohydrate and protein, respectively. Gel electrophoresis revealed the presence of the surface protein in the JY-Pol. By the double immunodiffusion and isotyping ELISA analyses, administration of JY-Pol that was adsorbed to alum adjuvant (JY-Pol/Alum) into mice induced IgM, IgG, and IgA specific for the S.pneumoniae capsule. The ATCC capsular polysaccharide adsorbed to alum (ATCC-Pol/Alum) provoked only IgM in mice. In survival tests, mice that were immunized with the JY-Pol/Alum before intravenous challenge with live S.pneumoniae survived entire period of 46 day-observation, whereas all mice that received ATCC-Pol/Alum or only diluent instead of the vaccination died within 5 and 12 days, respectively. Results from footpad-edema test showed that JY-Pol/Alum formula provoked the cellular immunity as determined by swelling of the mouse footpad. These data indicate that the naturally conjugated JY- Pol enhances resistance of mice against disseminated pneumococcal disease due to S.pneumoniae by both humoral and cellular immune responses.