Fig. 6: Evaluating the efficacy of the KE-VAC-adjuvanted SFTSV vaccine in ferrets.

a Timeline detailing the immunisation schedule, blood collection intervals, and SFTSV challenge protocol. Ferrets were administered a mock-PBS, an inactivated SFTSV vaccine alone, or an inactivated SFTSV with Alum/nanoliposome (KE-VAC). The components were intramuscularly injected into ferret twice, with a 2-week interval. The doses were as follows: Inactivated SFTSV, 30 µg; Alum, 100 µg; and m-TLR7/8a in nanoliposome, 20 µg. b Changes in the serum neutralizing titers against live virus of ferrets were tracked at 2-week intervals for 30 weeks after immunisation (n = 5). c and d IFN-γ production in PBMCs immediately before the challenge was confirmed by an ELISPOT assay (c), with a representative image shown in (d) (n = 2). e On days 2, 4 and 6 after the SFTSV challenge, organ tissues from three ferrets per group were collected, and the viral load was quantified via qRT‒PCR (n = 3). f-h Health monitoring of ferrets after challenge included measuring changes in body weight (f), body temperature (g), and platelet count (h) until 6 dpi (n = 6). i Serum neutralizing titers were measured at various time points after the challenge (n = 6). Data presented as mean ± SD. Statistical significance was analysed via unpaired two-tailed t test in (e and g). p values: ns not significant; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001).