Preclinical evaluation of a BinJ/ZIKV-prME chimeric virus vaccine

IFNAR^−/− mice on a C57BL/6 J background (63) were vaccinated intramuscularly (50 μl into each quadriceps femoris) (34). Mice were aged 5 to 27 weeks; for each group within each experiment, the same age distribution of mice ±1 week was used. Where indicated, chimeric virions were formulated (1:1) with AddaVax adjuvant (InvivoGen). Antibody responses to ZIKV were determined as previously described (34), except that ZIKV_PRVABC59 was used in the neutralization assays and goat anti-mouse IgG1 and IgG2 secondary antibodies (Invitrogen) were also used.

Mice were challenged subcutaneously in the base of the tail with 100 μl of 10³ CCID₅₀ ZIKV_PRVABC59 with viremia assessed by CCID₅₀ assay as described previously (34). Virus preparations were tested for mycoplasma contamination, and FBS used for propagation was tested for endotoxin. Histology and IHC were performed as described previously (34, 64), with the latter undertaken using the mAb 4G4 (anti-NS1) and the Warp Red Chromogen kit (Biocare Medical). Quantitative RT-PCR analyses (to detect ZIKV_PRVABC59 E) were undertaken as previously described (34) but using ZIKV E primers (forward, 5′-CCGCTGCCCAACACAAG-3′; reverse, 5′-CCACTAACGTTCTTTTGCAGACAT-3′).