Fig. 9. Results heterologous challenge trial.

Average rectal temperatures (mean) with s.d. of vRVFV-4s vaccinated and mock-vaccinated lambs post heterologous RVFV challenge (a). Monitoring of viremia in vaccinated and mock-vaccinated lambs by RT-qPCR and virus isolation (b). Samples that tested negative are depicted at the detection limit of the PCR (1.3 log₁₀ RNA copies/ml) or virus isolation (1.55 log₁₀ TCID₅₀/ml). Detection of viral RNA in liver and spleen samples (c). The detection limit of the PCR was 2.3 log₁₀ RNA copies/g. Open symbols represent animals that died or were euthanised during the study because they reached a humane endpoint. Neutralizing antibody responses in time as determined by virus-neutralizing test (d). Challenge (red arrow) of both groups was on study day 21. Detection of anti-N antibodies by ELISA (e) in weekly obtained sera. Titres are expressed as percentage competition ratio of the optical densities (OD) of the sample and the OD of the negative control (% S/N). All values lower than 40% are considered positive, between 40 and 50% are considered doubtful and above 50% are considered negative. Challenge (red arrow) of both groups was on DPV 21. Measurements were taken from distinct samples.