Study of immunogenicity of PspA, Ply and PsaA in adults with invasive pneumococcal disease

MA Qianli; ZHANG Qiao; LI Qi; YAO Wei; XIE Xiaozheng; WANG Changzheng

Abstract：To investigate antibody responses to three Streptococeus pneumoniae surface proteins, PspA, Ply, and PsaA, in adults with invasive pneumococcal disease (IPD), in consideration of taking the three proteins as candidate antigens of Streptococcus pneumoniae vaccine. We characterized antibody responses to PspA, Ply and PsaA, in 36 adults hospitalized with IPD, and in two groups of age-matched controls (group 1: 36 patients with invasive disease due to other microorganisms and group 2:36 patients hospitalized for non infectious con-ditions). All pneumococcal isolates were typed for the PspA family. Acute serum samples[(0+3) days]and convalescent samples[(21 ± 3)days later]were obtained from IPD subjects and control group 1, while single serum samples were obtained from control group2. Antibody levels to PspA-Fam1, PspA-Fam2, Ply and PsaA were measured by ELISA. All antibody concentrations in acute samples from IPD subjects were similar to those from patients of group 1 and group 2 (P> 0.05). The antibody levels to three antigens were similar in acute and conva-lescent sera from group 1 (P> 0.05), in contrast, the geometric mean antibody concentrations to the three proteins in the convalescent sera of IPD patients were 8 and 30 times higher than those in the corresponding acute sera (P < 0.01), especially, the raise of anti-PspA and an-ti-Ply levels in convalescent sera of IPD patients were more significant than that of anti-PsaA level. Antibody levels to PspA-Fam1 were higher than antibody levels to PspA-Fam2 (P < 0.01). The results above showed that PsaA, PspA, and Ply all have immunogenicity as the components of Streptococcus pneumonia. And antibodies to PspA and Ply have significant protective effects against IPD, which suggest the two proteins could be considered as important candidate antigens for novel vaccine design for the treatment.