Objective        To evaluate the safety and efficacy of a novel pneumococcal attenuated vaccine strain D39△CPS-TA when delivered intra-nasally with adjuvant Pam2CSK4 in a infant mice model of pneumococcal infection.       Methods        C57/BL6 infant mice were intra-nasally administrated on days 0

7

14 and 28 with 1 dose of D39△CPS-TA+ cholera toxin (CT) or Pam2CSK4

with D39△CPS-TA alone or with one of selected adjuvant alone. In 1 week after the last immunization

antibodies and cytokines levels were measured by enzyme-linked immunosorbent assay (ELISA). In 2 weeks after the last immunization

mice were challenged with pneumococcal serotype 19F or 2 and protective effects were observed. Furthermore

the safety of D39△CPS-TA was measured by a survival experiment and the safety of Pam2CSK4 was evaluated by monitoring body weight and pathological analysis.       Results       Intranasal immunization with D39△CPS-TA+Pam2CSK4 in infant mice induced IgG1-based rise in antigen-specific IgG

increase of IFN-γ

IL-4

IL-10 and IL-17A

clearance of nasal colonization of pneumococcal serotype 19F and protective effects against lethal infection of pneumococcal serotype 2. High dose of D39△CPS-TA was tolerated by infant mice and Pam2CSK4 was safer than CT.       Conclusion       Intra-nasal immunization with D39△CPS-TA+Pam2CSK4 in infant mice stimulates humeral and cellular immune responses safely and effectively

and protects mice against pneumococcal infection.