Fig. 5. Avidity index as a correlate of protection in Qβ-(NANP)6-vaccinated mice.
BALB/c mice (n = 24) were vaccinated with Qβ-(NANP)6 by intramuscular injection, using 1 µg per dose, two shots, a 3-week prime-boost interval, and Matrix-M™ adjuvant. A Serum was collected from mice 2 weeks post-boost and standard curve ELISA performed against (NANP)6. B Mice were challenged intravenously with 1000 PfCSP transgenic P. berghei sporozoites 3 weeks post-boost. Daily thin blood smears were used to determine the time to reach 1% blood-stage parasitaemia by linear regression. Mice with sterile protection are coloured blue, and those with a delay in time to reach 1% blood-stage parasitaemia coloured red, where “delay” is defined as time-to-1% greater than the mean of naïve challenged mice plus two standard deviations. C Associations with protection were obtained by categorising mice into two or three groups following challenge: protected or delayed (p/d) vs. no delay (nd), or protection (p) vs. delay (d) vs. no delay (nd). Numbers represent p values t tests (comparing two groups) or ANOVA with Bonferroni’s multiple comparisons test (comparing three groups). Means are shown ± SD.