Jin-Ju Nah

Serosurveillance for Japanese encephalitis, Akabane, and Aino viruses for Thoroughbred horses in Korea.

Recent global warming trends may have a significant impact on vector-borne viral diseases, possibly affecting vector population dynamics and disease transmission. This study measured levels of hemagglutination-inhibition (HI) antibodies against Japanese encephalitis virus (JEV) and neutralizing antibodies against Akabane virus (AKAV) and Aino virus (AINV) for Thoroughbred horses in Korea. Blood samples were collected from 989 racehorses in several provinces, between October 2005 and March 2007. Sera were tested using either an HI assay or a virus neutralization test. Approximately half (49.7%; 492/989) of the horses tested were antibody-positive for JEV. The HI titer against JEV was significantly correlated with racehorse age (p < 0.05). Horses with an HI antibody titer of 1:160 or higher accounted for 3.9% of the animals tested, indicating that vectors transmitting arthropod-borne viruses bit relatively few horses. In contrast, 3.8% (19/497) and 19.5% (97/497) of horse sera collected in March 2007 were positive against AKAV and AINV, respectively. The presence of antibodies against AKAV and AINV may indicate the multiplication of AKAV and AINV in these horses.

The present and future of veterinary vaccines for Japanese encephalitis in Korea

Japanese encephalitis (JE) is a mosquito-borne zoonotic disease that affects approximately 50,000 people annually in Asia, causing 10,000 deaths. Considering the role of pigs as the virus-amplifying host and the economic loss in the swine industry, JE is an important disease for both public and animal health. A nationwide JE virus (JEV) vaccination program has been conducted annually for more than 30 years to prevent severe reproductive disorders in the Korean sow population. Remarkable progress in molecular biology has made it possible to analyze the genome of the vaccine strain at the nucleotide and amino acid levels. However, the scientific record of the current JEV veterinary vaccine has not been reported. Therefore, this article outlines the current JEV vaccine strain used in animals and discusses future directions for developing new veterinary JEV vaccines.

Inactivated genotype 1 Japanese encephalitis vaccine for swine.

Purpose Japanese encephalitis is a reproductive disorder caused by Japanese encephalitis virus (JEV) in swine. Recent genotype (G) shift phenomenon (G3 to G1) in the Asia-wide has posed a challenge for proper prevention by the current vaccine strain. Thus, new kinds of JEV G1 vaccines with enhanced immunogenicity have been required for pigs. Materials and Methods Recombinant porcine granulocyte monocyte-colony stimulating factor (reporGM-CSF) protein was expressed in Spodoptera frugiperda (Sf-9) cells using baculovirus expression system. Two kinds of trials with inactivated JEV vaccines containing IMS1313 adjuvant (Seppic, France) were prepared with or without reporGM-CSF protein. Safety and immunogenicity of the pigs inoculated with the JEV vaccines via intramuscular route was evaluated for 28 days after inoculation. Results Mice, guinea pigs, and fattening pigs inoculated with the inactivated vaccine showed no signs for 14 and 21 days. Both hemagglutination inhibition and plaque reduction neutralizing antibody titers were significantly higher in pigs immunized with the vaccine containing reporGM-CSF protein after boosting. However, on the side of vaccine efficacy, most mice (87%) immunized with the inactivated JEV vaccine survived after virulent JEV challenge. Whereas the group with the vaccine containing reporGM-CSF protein showed lower protective effects than the vaccine alone for the biological activity of the GM-CSF depending on species specific. Conclusion Our data indicate that animals inoculated with the JEV vaccines was safe and pigs inoculated with inactivated JEV vaccine containing reporGM-CSF protein showed higher humoral immune responses than that of inactivated JEV vaccine without reporGM-CSF protein.

A single immunization with recombinant rabies virus (ERAG3G) confers complete protection against rabies in mice

Purpose New alternative bait rabies vaccines applicable to pet dogs and wild animals are needed to eradicate rabies in Korea. In this study, recombinant rabies virus, ERAG3G strain was constructed using reverse genetic system and the safety, efficacy and immunogenicity of the ERAG3G strain was evaluated in mice and dogs. Materials and Methods Using the full-length genome mutated amino acid at position 333 of glycoprotein of rabies virus (RABV) and helper plasmids, the ERAG3G strain was rescued in BHK/T7-9 cells successfully. Mice were inoculated with the ERAG3G strain for safety and efficacy. Safety and immunogenicity of the dog inoculated with the ERAG3G strain (1 mL, 108.0 FAID50/mL) via intramuscular route was evaluated for 28 days after inoculation. Results The ERAG3G strain rescued by reverse genetic system was propagated well in the mouse neuroblastoma cells revealing titer of 108.5 FAID50/mL and was not pathogenic to 4- or 6-week-old mice that received by intramuscular or intracranical route. Immunization with the ERAG3G strain conferred complete protection from lethal RABV in mice. Dogs inoculated with the vaccine candidate via intramuscular route showed high neutralizing antibody titer ranging from 2.62 to 23.9 IU/mL at 28 days postinoculation. Conclusion Our findings suggest that the ERAG3G strain plays an important role in inducing protective efficacy in mice and causes to arise anti-rabies neutralizing antibody in dogs.

Rabbit Hemorrhagic Disease Virus Variant Recombinant VP60 Protein Induces Protective Immunogenicity

Rabbit hemorrhagic disease virus (RHDV) is highly contagious and often causes fatal disease that affects both wild and domestic rabbits of the species Oryctolagus cuniculus. A highly pathogenic RHDV variant (RHDVa) has been circulation in the Korean rabbit population since 2007 and has a devastating effect on the rabbit industry in Korea. A highly pathogenic RHDVa was isolated from naturally infected rabbits, and the gene encoding the VP60 protein was cloned into a baculovirus transfer vector and expressed in insect cells. The hemagglutination titer of the Sf-9 cell lysate infected with recombinant VP60 baculovirus was 131,072 units/50 μl and of the supernatant 4,096 units/50 μl. Guinea pigs immunized twice intramuscularly with a trial inactivated RHDVa vaccine containing recombinant VP60 contained 2,152 hemagglutination inhibition (HI) geometric mean titers. The 8-week-old white rabbits inoculated with one vaccine dose were challenged with a lethal RHDVa 21 days later and showed 100% survival rates. The recombinant VP60 protein expressed in a baculovirus system induced high HI titers in guinea pigs and rendered complete protection, which led to the development of a novel inactivated RHDVa vaccine.