Update of inactivated equine influenza vaccine strain in Japan.

Japan established a vaccine selection system, in which a committee evaluates veterinary influenza vaccines to determine if the vaccine should be updated. In 2013, it was concluded that the present equine influenza vaccine strains did not have to be updated, but clade 2 (Fc2) viruses of the Florida sublineage should be included. We collected three Fc2 viruses as candidates and conducted comparative tests. Results indicated that A/equine/Carlow/2011 (H3N8) is not suitable, because of its unstable antigenic characteristics. A comparison between A/equine/Richmond/1/2007 (H3N8) (Richmond/07) and A/equine/Yokohama/aq13/2010 (H3N8) (Yokohama/10) in eggs showed that they shared equal growth properties. Immunogenicity test in mice showed that Yokohama/10 induced higher HI antibody titers than Richmond/07. Therefore, we concluded that Yokohama/10 was the most suitable strain.

Protective efficacy of stockpiled vaccine against H5N8 highly pathogenic avian influenza virus isolated from a chicken in Kumamoto prefecture, Japan, in 2014.

H5 highly pathogenic avian influenza (HPAI) viruses have spread worldwide, and antigenic variants of different clades have been selected. In this study, the national stockpiled vaccine prepared from A/duck/Hokkaido/Vac-1/2004 (H5N1) strain was evaluated for the protective efficacy against H5N8 HPAI virus isolated in Kumamoto prefecture, Japan, in April 2014. In the challenge test, all of the vaccinated chickens survived without showing any clinical signs and reduced virus shedding. It was concluded that the present stockpiled vaccine was effective against the H5N8 HPAI virus.

Introduction of an update system for vaccine strains of veterinary influenza vaccines in Japan.

The basic countermeasures used to control highly pathogenic avian influenza (HPAI) are early detection procedures and the culling of affected chickens. However, if successive HPAI outbreaks occur, the vaccination may be an option for controlling HPAI. Therefore, avian influenza (AI) vaccines are stocked by the Japanese government. By contrast, equine influenza (EI) vaccine is an effective tool for preventing or controlling EI. Because antigenic drifts affect the efficacy of AI and EI vaccines, the vaccine strains should be updated rapidly. However, the development and registration of veterinary vaccines usually takes several years. In response to this issue, the Ministry of Agriculture, Forestry, and Fisheries (MAFF) established a system that allows AI and EI vaccine strains to be updated rapidly. National Veterinary Assay Laboratory, MAFF, established a vaccine strains selection committee for veterinary influenza vaccine. The main agendas involve determining whether the current vaccine strains need to be updated and selecting the most appropriate vaccine strains. The committee concluded that A/duck/Hokkaido/Vac-3/2007(H5N1) was added to the strains of stockpiled AI vaccines and that the EI vaccine strains did not need to be changed, but that the clade 2 viruses of the Florida sub-lineage strain, A/equine/Yokohama/aq13/2010(H3N8) was added to the EI vaccine strain.

Report on the international workshop on alternative methods for human and veterinary rabies vaccine testing: state of the science and planning the way forward.

Potency testing of most human and veterinary rabies vaccines requires vaccination of mice followed by a challenge test using an intracerebral injection of live rabies virus. NICEATM, ICCVAM, and their international partners organized a workshop to review the availability and validation status of alternative methods that might reduce, refine, or replace the use of animals for rabies vaccine potency testing, and to identify research and development efforts to further advance alternative methods. Workshop participants agreed that general anesthesia should be used for intracerebral virus injections and that humane endpoints should be used routinely as the basis for euthanizing animals when conducting the mouse rabies challenge test. Workshop participants recommended as a near-term priority replacement of the mouse challenge with a test validated to ensure potency, such as the mouse antibody serum neutralization test for adjuvanted veterinary rabies vaccines for which an international collaborative study was recently completed. The workshop recommended that an in vitro antigen quantification test should be a high priority for product-specific validation of human and non-adjuvanted veterinary rabies vaccines. Finally, workshop participants recommended greater international cooperation to expedite development, validation, regulatory acceptance, and implementation of alternative test methods for rabies vaccine potency testing.

Rabies immune status of dogs brought into the Hyogo Prefecture Animal Well-being Center, Japan.

Stray dogs are a public health risk factor when canine rabies is endemic. The Rabies Prevention Law has introduced measures to control stray dogs, but many dogs are still captured in Japan. In order to estimate the immune status of stray dogs for the purposes of risk management, we conducted a serological survey at the Hyogo Prefecture Animal Well-being Center. Only 27.7% of dogs brought into the Center (n=166) had protective immune status. This result suggests that there is the potential for reintroduction of canine rabies into stray dogs, leading to endemic rabies and its transmission to humans. Continued removal of stray dogs, education on rabies prevention and vaccination of dogs therefore remain important public health issues.

The pathogenicity of canine parvovirus type-2b, FP84 strain isolated from a domestic cat, in domestic cats.

Canine parvovirus type-2a (CPV-2a) and type-2b (CPV-2b) have recently been isolated from domestic cats. The pathogenicity of CPV-2b in domestic cats is still unclear. In this study, we performed infection tests to examine the pathogenicity of CPV-2b, FP84 strain, isolated from a domestic cat. The results demonstrated that the CPV strain FP84 is able to infect and replicate well in domestic cats. Two of the 3 cats used in the test died. They showed loss of appetite, diarrhea, leukopenia and dehydration. Since FP84 was found to be virulent to domestic cats, it is necessary to examine the efficacy of inactivated feline panleukopenia virus vaccines against CPV infection in domestic cats.

Establishment of a potency test by ELISA for a rabies vaccine for animal use in Japan.

The ELISA we developed was able to determine the antigen content and was suitable for a potency test, and we described a relative potency assay method which determines the potency of test vaccines by comparing the ELISA value of a test vaccine to that of a reference vaccine. In the present study, we standardized the reference vaccine used for determining the potencies of test vaccines, and established a potency test by ELISA. We evaluated the proposed reference vaccine by the neutralizing antibody responses in dogs after vaccination, by the challenge protection test in guinea pigs (GP potency test), which is the earlier official potency test used in Japan, and by the NIH potency test, which is widely used throughout the world. The results showed that a 4-fold dilution of the proposed reference vaccine induced sufficient immunity in dogs. A 3-fold dilution of the proposed reference vaccine passed the GP potency test. The international units (IU) calibrated by the NIH potency test were 3.7 IU/dose. From the results and the WHO recommendation that veterinary rabies vaccines should have a potency of at least 1.0 IU/dose, we determined to dilute the proposed reference vaccine by 3 fold and regarded it as the reference vaccine. Finally, we confirmed that there is a good agreement between the results of the potency test by ELISA and the results of the GP potency test. The establishment of the potency test by ELISA has made it possible to monitor the potency in the production process and has contributed to the stable production of the vaccine.