Clin Exp Vaccine Res.  2016 Jul;5(2):169-174. 10.7774/cevr.2016.5.2.169.

A recombinant rabies virus (ERAGS) for use in a bait vaccine for swine

• Yang DK
• Kim HH
• Choi SS
• Lee SH
• Cho IS

• KMID: 2421564
• DOI: http://doi.org/10.7774/cevr.2016.5.2.169

Abstract

PURPOSE
Rabies viruses (RABV) circulating worldwide in various carnivores occasionally cause fatal encephalitis in swine. In this study, the safety and immunogenicity of a recombinant rabies virus, the ERAGS strain constructed with a reverse genetics system, was evaluated in domestic pigs.
MATERIALS AND METHODS
Growing pigs were administered 1 mL (108.0 FAID50/mL) of the ERAGS strain via intramuscular (IM) or oral routes and were observed for 4 weeks' post-inoculation. Three sows were also inoculated with 1 mL of the ERAGS strain via the IM route. The safety and immunogenicity in swine were evaluated using daily observation and a virus-neutralizing assay (VNA). Fluorescent antibody tests (FAT) for the RABV antigen and reverse transcriptase-polymerase chain reaction (RT-PCR) assays for the detection of the nucleocapsid (N) gene of RABV were conducted with brain tissues from the sows after necropsy.
RESULTS
The growing pigs and sows administered the ERAGS strain did not exhibit any clinical sign of rabies during the test period test and did develop VNA titers. The growing pigs inoculated with the ERAGS strain via the IM route showed higher VNA titers than did those receiving oral administration. FAT and RT-PCR assays were unable to detect RABV in several tissues, including brain samples from the sows.
CONCLUSION
Our results suggest that the ERAGS strain was safe in growing pigs and sows and induced moderate VNA titers in pigs.

Keyword

Rabies; Vaccines; Swine

MeSH Terms

Administration, Oral
Brain
Encephalitis
Nucleocapsid
Rabies virus*
Rabies*
Reverse Genetics
Sus scrofa
Swine*
Vaccines
Vaccines

Figure

• 

  Fig. 1 Protective effect of antibody elicited by administration of the ERAGS in pigs. At 2 and 4 weeks after administration, high levels of neutralizing antibody titers were induced in growing pigs and sows inoculated via intramuscular (IM) and oral routes versus the control group that received no treatment. No pig inoculated with the ERAGS strain showed any clinical sign related to rabies. Each bar represents the mean±standard error of the mean of six or three independent samples. Different lower-case letters indicate significant differences (*p<0.05, Tukey's post hoc test). FAVN, fluorescent assay virus-neutralizing.

• 

  Fig. 2 Identification of the rabies viruses (RABV) antigen using fluorescent antibody tests in brain samples obtained from sows inoculated with the ERAGS strain. There were no positive reactions to the RABV in the sow brain samples (A), and specific fluorescence was shown in the positive control sample (B).

• 

  Fig. 3 Identification of the rabies viruses (RABV) using reverse transcriptase-polymerase chain reaction in tissue samples obtained from sows inoculated with ERAGS strain. There were no positive reactions to the RABV in the seven tissue samples. M, 1-kb ladder; lanes 1 to 7, cerebrum, cerebellum, midbrain, spleen, liver, kidney, and lymphoid node, respectively; P, positive sample; N, negative sample.

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