Objective:To evaluate the ability of the cooperative protection of the Strep to coccus pneumoniae multivalent DNA vaccine containing lytA gene(N-acetylmuramoyl-L-alanine amidase

LytA)and pspA’gene(N fragment of pneumococcal surface protein A

PspA)against intraperitoneal Streptococcus pneumoniae D39 infection.Methods The genomic DNA of the standard Streptococcus pneumoniae strain D39 was isolated.LytA gene fragment was amplified by polymerase chain reaction(PCR)and cloned into the eukaryotic expression vector pcDNA3.1(+)

which was transfected into BHK-21 cells using Lipofectamine TM2000

and then the expression of LytA protein was detected with Western-blot.Furthermore

three formats of recombinant plasmid DNA vaccines(pcDNA3.1-LytA+pcDNA3.1-PspA’

pcDNA3.1-PspA’

pcDNA3.1-LytA)were used to inject intramuscularly BALB/c mice

with pcDNA3.1(+)plasmid and PBS as controls.The levels of antibodies against PspA’and LytA proteins were checked.Live times of intraperitoneal infection mice by Streptococcus pneumoniae D39 in BALB/c models were analysis.Results:The three DNA vaccines all producted high levels serum special IgG antibodies.The anti-LytA antibodies level elicited by the DNA vaccine pcDNA3.1-LytA + pcDNA3.1-PspA’was higher than the DNA vaccine pcDNA3.1-LytA(P<0.01)

but the anti-PspA’antibodies level elicited by the DNA vaccine pcDNA3.1-LytA + pcDNA3.1-PspA’had no significant statistics deviation(P>0.05).The result of the effect on intraperitoneal infection by Streptococcus pneumoniae D39 in BALB/c mice models showed the median live times in pcDNA3.1-LytA + pcDNA3.1-PspA’group was longer than pcDNA3.1-LytA group and the control groups(P<0.01)

but no significant statistics deviation was found between pcDNA3.1-LytA + pcDNA3.1-PspA’group with pcDNA3.1-PspA’group(P >0.05).Conclusion:The multivalent DNA vaccine of Streptococcus pneumoniae containing LytA gene and pspA gene had no the higher performance protection than the DNA vaccine only containing pspA gene against Streptococcus pneumoniae.It is should be further evaluated that LytA gene is concluded as the one of advantages candidate antigens of the Streptococcus pneumoniae multivalent DNA vaccine.