Objective To obtain the pneumococcal autolysin(LytA)and choline binding protein A(CbpA)by prokaryotic expression system and investigate their diagnosis for infection caused by Streptococcus pneumoniae.Methods The specific primers were designed according to lytA and cbpA of Streptococcus pneumoniae gene sequence.lytA and cbpA were amplified by PCR form the pneumococcus genome.After IPTG inducing,the recombinant proteins were purified by electroeluting of bag filter,detected by SDS-PAGE and Western blot.Serum lgG and IgM antibodies accordingly of BALB/c mice infected with Streptococcus pneurnoniae were detected by ELISA.Results The recombinant plasmid pET-32a(+)/lytA and pET-32a (+)/cbpA were constructed successfully.Fusion proteins LytA and CbpA were expressed and displayed expected antigenicity.IgM and IgG antibodies level anti LytA were significantly higher than the control group (infections with B Streptococcus group and healthy mice),(P<0.05),but antibodies level anti CbpA did not increase as compared with group infected with B Streptococcus(P>0.05).Diagnostic sensitivity of CbpA was 83.3%(IgG)and 75.0%(IgM).Diagnostic specificity of LytA was 100%(IgG and IgM).Conclusion The synergistic use of specificity of LytA and sensitivity of CbpA may be worthy of serological diagnosis for Streptococcus pneumoniae infection,and may be used for further clinical test.