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Vaccination of domestic ruminants is considered to be an effective strategy for protecting
these animals against Rift Valley fever (RVF), but available vaccines have limitations.
Therefore, the aim of this study was to determine the safety and immunogenicity of RVF virus
(RVFV) mutagenesis passage 12 (MP-12) and arMP-12ΔNSm21/384 vaccine candidates in
goats (Capra aegagrus hircus) in Tanzania. Goats were vaccinated intramuscularly with RVFV
MP-12 or arMP-12ΔNSm21/384, and then on Day 87 post-vaccination (PV) all animals were
revaccinated using the RVFV MP-12 vaccine candidate. Serum samples were collected from
the animals before and after vaccination at various intervals to test for RVFV using a Vero cell
culture assay and reverse transcription polymerase chain reaction and for RVFV-neutralising
antibody using a plaque reduction neutralisation assay. Serum samples collected before
vaccination on Days -14 and 0, and on Days 3, 4 and 5 PV were negative for RVFV and
neutralising antibody. All animals remained healthy, and viremia was not detected in any of
the animals. Rift Valley fever virus antibody was first detected on Day 5 PV at a 1:10 dilution
in five of five animals vaccinated with the MP-12 vaccine and in five of eight animals
vaccinated with arMP-12ΔNSm21/384. Titres then increased and were sustained at 1:40 to
1:640 through to Day 87 PV. All animals that were revaccinated on Day 87 PV with MP-12
developed antibody titres ranging from 1:160 to as high as 1:10 240 on Days 14 and 21 PV.
Although the antibody titres for goats vaccinated with RVF MP-12 were slightly higher than
titres elicited by the arMP-12ΔNSm21/384 vaccine, these findings demonstrated that both
vaccines are promising candidates for the prevention of RVF among Tansanian goats. |
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