Fig. 4. LipA induction by serum.

(A, B) S. pneumoniae strains were cultured until log phase. Goat serum was added to a final concentration of 10% and then incubated for 5 min, followed by lipA mRNA quantitation by qPCR (A), or incubated for 10min, followed by western blot analysis (B). SDS-PAGE results following Coomasie Blue staining was displayed and served as a loading control. The experiment was performed three times independently. Statistical analyses were performed using one-way ANOVA (*p ≤ 0.05). (C) Mice (n = 3) were infected with 1.5 × 10⁴ CFU of S. pneumoniae D39 or ΔlipA intraperitoneally (i.p.). At the severely morbid stage, mouse blood was collected, and lipA mRNA expression was determined by qPCR. (D) Pneumococci at log phase in THY broth were incubated with whole mouse blood for 15min, and lipA mRNA expression was determined by qPCR. (C, D) Each mouse sample was analyzed in triplicate, and the Mann-Whitney rank sum test was used for statistical analysis. N.D: not detected. (*p ≤ 0.05). (A, C and D) Control bar (Ctrl) was displayed one fold value (control/ control).