Newcastle Disease Virus-Vectored Rabies Vaccine Is Safe, Highly Immunogenic, and Provides Long-Lasting Protection in Dogs and Cats

Abstract

Effective, safe, and affordable rabies vaccines are still being sought. Newcastle disease virus (NDV), an avian paramyxovirus, has shown promise as a vaccine vector for mammals. Here, we generated a recombinant avirulent NDV La Sota strain expressing the rabies virus glycoprotein (RVG) and evaluated its potential to serve as a vaccine against rabies. The recombinant virus, rL-RVG, retained its high-growth property in chicken eggs, with titers of up to 10 9.8 50% egg infective doses (EID 50 )/ml of allantoic fluid. RVG expression enabled rL-RVG to spread from cell to cell in a rabies virus-like manner, and RVG was incorporated on the surface of the rL-RVG viral particle. RVG incorporation did not alter the trypsin-dependent infectivity of the NDV vector in mammalian cells. rL-RVG and La Sota NDV showed similar levels of sensitivity to a neutralization antibody against NDV and similar levels of resistance to a neutralization antibody against rabies virus. Animal studies demonstrated that rL-RVG is safe in several species, including cats and dogs, when administered as multiple high doses of recombinant vaccine. Intramuscular vaccination with rL-RVG induced a substantial rabies virus neutralization antibody response and provided complete protection from challenge with circulating rabies virus strains. Most importantly, rL-RVG induced strong and long-lasting protective neutralization antibody responses to rabies virus in dogs and cats. A low vaccine dose of 10 8.3 EID 50 completely protected dogs from challenge with a circulating strain of rabies virus for more than a year. This is the first study to demonstrate that immunization with an NDV-vectored vaccine can induce long-lasting, systemic protective immunity against rabies.

A New Rabies Vaccine Based on a Recombinant Orf Virus (Parapoxvirus) Expressing the Rabies Virus Glycoprotein

“…One important demand for improved rabies vaccines is the induction of a solid protective immunity after a single vaccine inoculation, which can be achieved with 10 7 PFU of D1701-V-RabG. Dose-dependent reduction in protection rates was accompanied by a reduction of VNA titers as reported for other recombinant rabies vaccines (22,33,35,58). The presented data, however, do not allow an unambiguous correlation between protection and magnitude of VNA titers in mice.…”

“…Since ORFV-vectored vaccines can be regarded as a potent, safe alternative to other poxvirusbased recombinant vaccines (44,49,51,57), we generated the novel recombinant D1701-V-RabG containing the RABV glycoprotein known as the principal correlate of protective immunity against rabies. The RabG gene was inserted into the vegf-e gene locus of the genome of the attenuated ORFV strain D1701-V and was correctly expressed in good amounts, which did not detectably alter the growth characteristics, the plaque phenotype, or the replication of parental D1701-V, as reported after expression of RabG in a Newcastle disease virus vector (22). Immunofluorescence experiments revealed strong expression of RABV-characteristic RabG surface projections already in the early phase of D1701-V-RabG replication (Fig.…”

“…Various recombinant rabies vaccines have been generated using different viral vector systems, such as Newcastle disease virus (22), Sindbis virus (23), herpesvirus (24), adenovirus (for a review, see reference 14), or baculovirus (25). Moreover, numerous poxvirus-vectored vaccines expressing RabG have been constructed, as reviewed recently (26).…”

A Novel Rabies Vaccine Based on a Recombinant Parainfluenza Virus 5 Expressing Rabies Virus Glycoprotein

“…1A). The RABV G gene in the PIV5 genome was flanked with a gene start (GS) sequence, intergenic sequences (I), and a gene end (GE) sequence from the junction region of the NP and V/P genes, which gave rise to a high level of transcription (29). The virus was recovered, and the genome was confirmed by RT-PCR analysis and sequencing (data not shown).…”

“…During the past decade, a number of recombinant rabies vaccine candidates based on live attenuated RABV or recombinant viruses expressing RABV G (such as V-RG) have been developed as potential alternatives to current rabies vaccines (17,29,(32)(33)(34)(35). While some of the vaccine candidates generated protective immunity when administered via the i.m.…”