Newcastle disease virus vectored vaccines as bivalent or antigen delivery vaccines

Choi, Kang-Seuk

BHV-1 is a major cause of respiratory tract disease in cattle. A major problem with the current modified live BHV-1 vaccines is their ability to cause latent infection, with the associated risk of subsequent reactivation [19] . As an alternative strategy, Khattar et al. [19] developed a rNDV vaccine (rLaSota/gDFL) expressing the gD of BHV-1. A single intranasal/intratracheal immunization with rLaSota/gDFL (1.5×10 7 PFU/ dose) induced marked mucosal and systemic antibody responses in calves. Also, intranasal challenge with a high dose of virulent BHV-1 strain Cooper (2×10 7 PFU) led to a marked reduction in viral shedding and more rapid clearance of chal- lenge virus when compared with mock-infected and challenged controls. These results suggest that NDV may have utility as a vaccine vector that can be used to develop a mucosal vaccine against BHV-1 infection of cattle. RVFV, a mosquito-borne bunyavirus that infects ruminants (cattle and sheep), causes severe economic losses to the livestock industry and has a high impact on public health in Africa and the Arabian Peninsula [27] . Currently, a live attenuated vaccine (Smithburn strain) and inactivated RVFV vaccines are available; however, although live attenuated vaccines are highly immunogenic, they are not safe for use in livestock [28, 29] . Inactivated vaccines are safer, but less effective, than live attenuated vaccines and require repeated vaccination [21] . To improve efficacy and safety, Kortekaas et al. [21] developed a NDV-vectored vaccine (NDFL-GnGc) expressing the Gn and Gc glycoproteins of RVFV. Repeat vaccination (two times) of lambs with the NDFL-GnGc vaccine (10 7.3 TCID50/dose) elicited a high titer of neutralizing antibodies specific for RVFV. These results indicate that NDV has potential as a vaccine vector in sheep.