FIG 4.

Induction of cross-protection against colonization with heterologous N. meningitidis strains in CEACAM1-humanized mice. (a) Schematic representation of experiment. Mice were intranasally infected at day 0 and day 21 with 10⁵ CFU of strain 90/18311, inoculated at day 47 with either the homologous strain (90/18311) or heterologous strains (H44/76, 38VI, or 196/87, respectively), and then sacrificed 3 days later to monitor colonization. (b) Typing characteristics of the four strains used for terminal intranasal challenge. (c) Results of CFU enumeration of viable N. meningitidis in nasal samples of mouse cohorts 3 days after infection of naive mice (left in each panel) or mice that were previously infected with strain 90/18311 (right in each panel) as indicated above each graph. Each circle (wild-type mice, white circles; CEACAM1-humanized mice, gray circles) represents viable CFU recovered from one mouse. Group sizes, percentages of mice colonized in each cohort, and the N. meningitidis strain used for terminal intranasal mouse challenge are indicated below each graph. Statistical analysis to compare colonization frequencies in naive mice and previously with strain 90/18311-infected mice was performed using GraphPad Prism. ** indicates a P value of <0.005, applying Fisher's exact test.