Rift Valley Fever (RVF) virus belonged to genus Phlebovirus, family Bunyaviridae cause an acute, febrile disease in ruminants. In Egypt, a locally prepared inactivated RVF virus vaccine with
aluminum hydroxide gel adjuvant has long been used for immunization of susceptible animals against the disease. The choice of an adjuvant which gives high and long standing immune response assume a critical part in immunization. The present study aimed to develop a new RVF virus vaccine with Montanide oil IMS 1313 nanoparticles as adjuvant and evaluate its impact on cellular
and humeral immune response in sheep. The prepared vaccine was sterile and safe. SNT results demonstrated that the prepared vaccine induced protective neutralizing serum antibody titer from
the 2nd week post vaccination (PV), reached the highest level at the 3rd month PV and persisted in protective level until the 9th month PV. These results were confirmed using ELISA. Evaluation of RVF virus-specific cell-mediated immunity in vaccinated sheep using XTT assay showed significant lymphocyte proliferation expressed by optical density in vaccinated sheep group that
increased to reach a maximum 10th day PV. Results indicated that the Montanide IMS 1313 VG NPR oil based vaccine induced high immunological enhancement without toxicity and with long
duration of immunity that extended for 9 months.