Fig. 4
K57-Dpo8 enhances serum susceptibility, promotes phagocytosis, and confers therapeutic protection of K. pneumoniae infection. A Serum-killing assay of K. pneumoniae strain 8665 following K57-Dpo8 treatment. Bacteria were preincubated with K57-Dpo8 or K64-ORF41 at 37 °C for 1 h, followed by exposure to 75% rabbit serum or heat-inactivated rabbit serum for an additional 3 h at 37 °C. Surviving bacteria were counted by a dilution plating method. B Phagocytosis assay evaluating macrophage-mediated uptake of K. pneumoniae. Strain 8665 was pretreated with K57-Dpo8, K64-ORF41, or 0.01 M phosphate-buffered saline (pH 7.4) at 37 °C for 1 h before co-incubation with RAW264.7 macrophages for 2 h. Data are presented as the mean ± SEM from three independent experiments. Statistical significance was determined using a two-tailed unpaired Student’s t-test. C Therapeutic efficacy of K57-Dpo8 in a murine infection model. C57BL/6 J mice were intraperitoneally infected with 2 × 108 colony-forming units (CFU) of K. pneumoniae strain 8665. After 30 min, mice were administered either PBS or 50 μg K57-Dpo8 intraperitoneally. Each group (n = 5) was monitored over 8 days, and survival rates were analyzed using the Kaplan–Meier method with a log-rank test. * p < 0.05; **** p < 0.0001