The Study Of A Recombinant Fusion Protein Composedof PsaA And PcpA As Streptococcus Pneumococcal Vaccine

Pneumonia is a disease with high morbidity and mortality in children and the elderly throughout the world, particularly in developing countries. According to the WHO, every year pneumonia is responsible for about 1.6 million people’s death. And between 700 thousand and 1 million cases of them are children. Streptococcus pneumoniae is a major pathogen of pneumonia. And it can also cause sinusitis, otitis media, bacteremia and meningitis and other diseases. Due to the abuse of antibiotic, which led to the emergence of drug-resistant pneumococcal strains, vaccination has become the primary way to prevent Streptococcus pneumonia infections. Currently, the wildly used pneumococcal vaccine is polysaccharide conjugate vaccine, whose effect has been proved, but limited by serotype-dependent and high price from wildly used in developing countries. Recently, due to the advantages like serotype-independent, relatively cheap and good immunogenicity, protein-based pneumococcal vaccine is considered as a reasonable candidate for the next generation pneumococcal vaccine.Combination of various Streptococcus pneumonia proteins as vaccine component is thought as an appropriate way to improve vaccine effectiveness. Pneumococcal surface adhesion A(Psp A) is exposed on the pneumococci surface. It has a conservative sequence and a good immunogenicity. There has also been reported that antibodies against Psa A has the effect of reducing pneumococcal colonization. Pneumococcal choline-binding protein A(Pcp A) is also a surface protein with a conservative sequence. Studies have speculated that Pcp A may play an important role in the adhesion of S. pneumoniae, while it may be not necessary in colonization. In this study, we generated a fusion protein called Psa A-Pcp A of the full-length sequence of Psa A and the N-terminal functional domain of Pcp A. With 3 times Psa A-Pcp A immunization for mice, serum antibody levels are evaluate. After lethal-dose pneumococci challenge, the survival date is obtained. The results showed that Psa A-Pcp A has a good immunogenicity to induce the immune response effectively and the protection is better than the 23-valent polysaccharide pneumococcal vaccine. In brief, Psa A-Pcp A shows its potential as a component candidate of the next generation serotype-independent protein-based pneumococcal vaccine.