Preliminary study on the application of PspA as carrier

The aim of the study is to research the feasibility of pneumococcal surface protein A (PspA) using as carrier protein. Three recombinant pneumococcal surface proteins A (come from family1 and family 2) were expressed by prokaryotic expression system and were conjugated to group A meningococcal polysaccharide (GAMP) to make three polysaccharide-protein conjugates. The conjugates, un-conjugated proteins, GAMP and GAMP-TT vaccine bulk (used as positive control) were immunized to mice and their immune effects were evaluated by the method of ELISA, FCM and SBA. The results showed that the polysaccharide-protein conjugates can produce higher levels of anti-GAMP IgG titers (P < 0.05), higher ratios of Th1/Th2 (P < 0.05) and higher levels of serum bactericidal activity (P < 0.05) compared with the un-conjugated GAMP. The conjugation of PspAs to GAMP also enhanced the anti-PspA responses compared with un-conjugated PspAs except PspA3. In conclusion, all the results indicated that three PspAs were suitable carrier protein as demonstrated by the characteristics of a T-cell dependent response to the GAMP, and would protect against group A of epidemic cerebrospinal meningitis and also have the potential to provide broad protection from Streptococcus pneumonia.