An O-Antigen Glycoconjugate Vaccine Produced Using Protein Glycan Coupling Technology Is Protective in an Inhalational Rat Model of Tularemia

Figure 4

GtExoA protects F344 rats against aerosol infection with F. tularensis Schu S4. Groups of F344 rats () were vaccinated three times, two weeks apart with 10 μg GtExoA coadministered with MF59, or immunised with MF59 alone, via the s.c. or i.p. route, or 5.38 × 10⁷ LVS. 5 weeks after final vaccination, rats were challenged with a calculated retained dose of 5.48 × 10²F. tularensis Schu S4 via the aerosol route. (a) Rats were monitored twice daily and mortality and survival plotted on a Kaplan-Meier survival curve. For comparison of survival curves, a log-rank Mantel-Cox test was used (). (b) Signs of disease were recorded twice daily and average cumulative signs for surviving rats in each group of 5 presented. (c) The temperature for individual rats (black circles) in each treatment group is presented at day 5 postinfection, the day on which the maximal febrile temperature was detected. The grey bar is the average response for the group. Statistical analysis of differences between the temperatures of treatment and the PBS control group was determined by one-way ANOVA with Holm-Sidak’s posttests (, , ). (d.1–d.3) Rats were weighed once daily and average weight change of surviving rats is presented. Each group is presented with its apposite control: LVS s.c. (black lines) and PBS s.c. (red lines) (d.1), GtExoA + MF59 s.c. (black lines) and MF59 s.c. (red lines) (d.2), and GtExoA + MF59 i.p. (black lines) and MF59 i.p. (red lines) (d.3). Significance in divergence of weight change between groups was found to fit the normal, Gaussian distribution using Q-Q plots (not shown). The data was analysed using a repeated measures general linear model. Validity of the data for this test was further established using Levene’s tests for unequal variance (not shown). Individual comparisons, pairwise and dependent or independent of timepoints, were performed using Bonferroni’s correction (, , and ). Due to culling of rats that reached their humane endpoint, the limit of analysis depicted by the dotted line is the timepoint up to which statistical comparisons could be performed across all groups with equivalent power.