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Ohta M, Kambayashi Y, Mita H, Kuroda T, Bannai H, Tsujimura K, Yamanaka T, Garvey M, Cullinane A, Yamayoshi S, Kawaoka Y, Nemoto M. Protective efficacy of a reverse genetics-derived inactivated vaccine against equine influenza virus in horses. Vaccine 2022; 40:6362-6366. [PMID: 36175213 DOI: 10.1016/j.vaccine.2022.09.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/09/2022] [Accepted: 09/15/2022] [Indexed: 01/27/2023]
Abstract
Updating vaccine strains is essential to control equine influenza. We evaluated the protective efficacy of an inactivated equine influenza vaccine derived from viruses generated by reverse genetics (RG) in horses in an experimental viral challenge study. Wild-type (WT) virus (A/equine/Tipperary/1/2019) and virus generated by RG (consisting of hemagglutinin and neuraminidase genes from A/equine/Tipperary/1/2019 and six other genes from high-growth A/Puerto Rico/8/34) were inactivated by formalin for vaccine use. Twelve 1-year-old naïve horses with no antibodies against equine influenza virus were assigned to three groups (each n = 4): control, WT, and RG. They were vaccinated twice, 4 weeks apart, and were challenged with A/equine/Tipperary/1/2019 2 weeks after the second vaccination. All four horses in the control group and one horse in the WT group had pyrexia for multiple days and respiratory illness, and one horse in the RG group had pyrexia for 2 days without respiratory illness. The mean rectal temperatures and the mean concentrations of serum amyloid A in the WT and RG groups were significantly lower than those in the control group, with no significant differences between them. The WT and RG vaccines significantly reduced viral shedding relative to the control. The protective efficacy of the RG-derived inactivated vaccine against equine influenza virus is comparable to that of the vaccine derived from WT viruses in horses. The RG technique can make it easy to update equine influenza vaccine strains.
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Affiliation(s)
- Minoru Ohta
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | | | - Hiroshi Mita
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Taisuke Kuroda
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Hiroshi Bannai
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Koji Tsujimura
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Takashi Yamanaka
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Marie Garvey
- Virology Unit, Irish Equine Centre, Kildare, Ireland
| | - Ann Cullinane
- Virology Unit, Irish Equine Centre, Kildare, Ireland
| | - Seiya Yamayoshi
- Division of Virology, Institute of Medical Science, University of Tokyo, Tokyo, Japan; The Research Center for Global Viral Diseases, National Center for Global Health and Medicine Research Institute, Tokyo, Japan
| | - Yoshihiro Kawaoka
- Division of Virology, Institute of Medical Science, University of Tokyo, Tokyo, Japan; The Research Center for Global Viral Diseases, National Center for Global Health and Medicine Research Institute, Tokyo, Japan; Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Manabu Nemoto
- Equine Research Institute, Japan Racing Association, Tochigi, Japan.
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Ohta M, Bannai H, Kambayashi Y, Tsujimura K, Tamura N, Iwamoto Y, Wakuno A, Yamayoshi S, Kawaoka Y, Nemoto M. Antibody Responses to a Reverse Genetics-Derived Bivalent Inactivated Equine Influenza Vaccine in Thoroughbred Horses. J Equine Vet Sci 2021; 109:103860. [PMID: 34973368 DOI: 10.1016/j.jevs.2021.103860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 12/20/2021] [Accepted: 12/24/2021] [Indexed: 11/27/2022]
Abstract
Updating vaccine strains is important to control equine influenza (EI). Previously, we reported that a monovalent inactivated EI vaccine derived from a virus generated by reverse genetics (RG) elicited immunogenicity in horses. In the present study, we compared antibody responses to a bivalent inactivated EI vaccine generated by RG and a commercially available bivalent inactivated EI (CO) vaccine derived from wild-type equine influenza viruses in Thoroughbred horses. The CO vaccine contained A/equine/Ibaraki/1/2007 (Florida sub-lineage clade 1) and A/equine/Yokohama/aq13/2010 (Florida sub-lineage clade 2) as vaccine strains. We generated two RG viruses possessing the hemagglutinin and neuraminidase genes from A/equine/Ibaraki/1/2007 or A/equine/Yokohama/aq13/2010. These viruses were inactivated by formalin, and the hemagglutinin titer of the RG vaccine was adjusted to be the same as that of the CO vaccine. Sixteen unvaccinated yearlings (7 for the RG vaccine group and 9 for the CO vaccine group) received two doses of a primary vaccination course four weeks apart. Thirty-two vaccinated adult horses (18 in the RG-vaccinated group and 14 in the CO vaccine group) received a single dose of a booster vaccination. The patterns of hemagglutination inhibition antibody response to the primary and booster vaccinations were similar for the RG and CO groups in unvaccinated yearlings and vaccinated adult horses. These results suggest that a bivalent vaccine derived from RG viruses elicits equivalent immunogenicity to that elicited by a CO vaccine derived from wild-type viruses. RG viruses can, therefore, be used in multivalent as well as monovalent vaccines for horses.
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Affiliation(s)
- Minoru Ohta
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Hiroshi Bannai
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | | | - Koji Tsujimura
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Norihisa Tamura
- Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Yohei Iwamoto
- Hidaka Training and Research Center, Japan Racing Association, Hokkaido, Japan
| | - Ai Wakuno
- The Horse Racing School, Japan Racing Association, Chiba, Japan
| | - Seiya Yamayoshi
- Division of Virology, Institute of Medical Science, University of Tokyo, Tokyo, Japan; The Research Center for Global Viral Diseases, National Center for Global Health and Medicine Research Institute, Tokyo, Japan
| | - Yoshihiro Kawaoka
- Division of Virology, Institute of Medical Science, University of Tokyo, Tokyo, Japan; The Research Center for Global Viral Diseases, National Center for Global Health and Medicine Research Institute, Tokyo, Japan; Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI
| | - Manabu Nemoto
- Equine Research Institute, Japan Racing Association, Tochigi, Japan.
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Ohta M, Bannai H, Kambayashi Y, Tamura N, Tsujimura K, Yamayoshi S, Kawaoka Y, Nemoto M. Growth properties and immunogenicity of a virus generated by reverse genetics for an inactivated equine influenza vaccine. Equine Vet J 2021; 54:139-144. [PMID: 33527477 DOI: 10.1111/evj.13431] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 01/09/2021] [Accepted: 01/22/2021] [Indexed: 12/01/2022]
Abstract
BACKGROUND Keeping vaccine strains up to date is the key to controlling equine influenza (EI). Viruses generated by reverse genetics (RG) are likely to be effective for quickly updating a vaccine strain. OBJECTIVES To evaluate the growth properties of an RG virus in embryonated chicken eggs, and to evaluate antibody responses to a formalin-inactivated vaccine derived from the RG virus in Thoroughbred horses. STUDY DESIGN In vitro and in vivo experiments. METHODS Wild-type (WT) viruses (A/equine/Ibaraki/1/2007) or RG viruses (consisting of haemagglutinin [HA] and neuraminidase genes derived from A/equine/Ibaraki/1/2007 and the six other genes derived from high-growth A/Puerto Rico/8/34) were inoculated into embryonated chicken eggs, and the allantoic fluids were harvested at every 24 hours after inoculation. WT and RG viruses were inactivated by formalin for vaccine use. Ten unvaccinated yearlings (five each for WT or RG vaccine) received the first two doses of a primary vaccination course 4 weeks apart followed by their third dose 12 weeks later. Twenty vaccinated adult horses (10 each for WT or RG vaccine) received a single dose of a booster vaccination. RESULTS The RG virus had high growth properties in embryonated chicken eggs. Unvaccinated yearlings responded poorly to the first vaccination, especially those that received the RG vaccine, but mounted better responses to the second and the third vaccinations, and maintained relatively high haemagglutination inhibition (HI) titres up to 28 weeks after the first vaccination. Vaccinated adult horses did not respond remarkably to the booster vaccination, but no horses showed titres below their pre-booster values even at 12 weeks after vaccination. The RG virus elicited immunogenicity in horses adequate for vaccine use. MAIN LIMITATIONS No virus challenge study was performed. CONCLUSIONS The RG viruses are useful as an EI vaccine strain, and quick updates of an EI vaccine strain can be achieved by using RG techniques.
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Affiliation(s)
- Minoru Ohta
- Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Hiroshi Bannai
- Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Yoshinori Kambayashi
- Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Norihisa Tamura
- Clinical Veterinary Medicine Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Koji Tsujimura
- Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan
| | - Seiya Yamayoshi
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan
| | - Yoshihiro Kawaoka
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.,Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Manabu Nemoto
- Molecular Biology Division, Equine Research Institute, Japan Racing Association, Tochigi, Japan
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Nemoto M, Yamayoshi S, Bannai H, Tsujimura K, Kokado H, Kawaoka Y, Yamanaka T. A single amino acid change in hemagglutinin reduces the cross-reactivity of antiserum against an equine influenza vaccine strain. Arch Virol 2019; 164:2355-2358. [PMID: 31227892 DOI: 10.1007/s00705-019-04328-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Accepted: 05/27/2019] [Indexed: 12/22/2022]
Abstract
Equine influenza virus is an important pathogen for the horse industry because of its economic impact, and vaccination is a key control measure. Our previous work suggested that a mutation at position 144 in the hemagglutinin of Florida sublineage clade 2 viruses reduces the cross-neutralizing activity of antiserum against a former vaccine strain. To confirm this suggestion, here, we generated viruses by reverse genetics. Antibody titers against the mutated viruses were one-tenth to one-sixteenth of those against the former vaccine strain. Our findings confirm that this single amino acid substitution reduces the cross-reactivity of antiserum against this former Japanese vaccine.
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Affiliation(s)
- Manabu Nemoto
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan.
| | - Seiya Yamayoshi
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan
| | - Hiroshi Bannai
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
| | - Koji Tsujimura
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
| | - Hiroshi Kokado
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
| | - Yoshihiro Kawaoka
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.,Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin Madison, Madison, WI, USA
| | - Takashi Yamanaka
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
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Yamanaka T, Nemoto M, Bannai H, Tsujimura K, Matsumura T, Kokado H, Gildea S, Cullinane A. Neutralization antibody response to booster/priming immunization with new equine influenza vaccine in Japan. J Vet Med Sci 2017; 80:382-386. [PMID: 29237998 PMCID: PMC5836781 DOI: 10.1292/jvms.17-0538] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Equine influenza (EI) vaccine has been widely used. However, the causative EI virus
(H3N8) undergoes continuous antigenic drift, and the vaccine strains must be periodically
reviewed and if necessary, updated to maintain vaccine efficacy against circulating
viruses. In 2016, the Japanese vaccine was updated by replacing the old viruses with the
Florida sub-lineage Clade (Fc) 2 virus, A/equine/Yokohama/aq13/2010 (Y10). We investigated
the virus neutralization (VN) antibody response to Fc2 viruses currently circulating in
Europe, after booster or primary immunization with the new vaccine. These European viruses
have the amino acid substitution A144V or I179V of the hemagglutinin. In horses that had
previously received a primary course and bi-annual boosters with the old vaccine booster,
immunization with the updated vaccine increased the VN antibody levels against the
European Fc2 viruses as well as Y10. There were no significant differences in the VN
titers against Y10 and the Fc2 viruses with A144V or I179V substitution in horses that had
received a primary course of the updated vaccine. However, a mixed primary course where
the first dose was the old vaccine and the second dose was the updated vaccine, reduced VN
titers against the European viruses compared to that against Y10. In summary, the new
vaccine affords horses protective level of VN titers against the Fc2 viruses carrying
A144V or I179V substitution, but our results suggest that the combination of the old and
new vaccines for primary immunization would not be optimum.
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Affiliation(s)
- Takashi Yamanaka
- Equine Research Institute, the Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi 329-0412, Japan
| | - Manabu Nemoto
- Equine Research Institute, the Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi 329-0412, Japan
| | - Hiroshi Bannai
- Equine Research Institute, the Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi 329-0412, Japan
| | - Koji Tsujimura
- Equine Research Institute, the Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi 329-0412, Japan
| | - Tomio Matsumura
- Equine Research Institute, the Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi 329-0412, Japan
| | - Hiroshi Kokado
- Equine Research Institute, the Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi 329-0412, Japan
| | - Sarah Gildea
- Irish Equine Centre, Johnstown, Naas, Co., Kildare, W91 RH93, Ireland
| | - Ann Cullinane
- Irish Equine Centre, Johnstown, Naas, Co., Kildare, W91 RH93, Ireland
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Abstract
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.
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Affiliation(s)
- Koichiro Gamoh
- National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan
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Yamanaka T, Nemoto M, Bannai H, Tsujimura K, Kondo T, Matsumura T, Gildea S, Cullinane A. Assessment of antigenic difference of equine influenza virus strains by challenge study in horses. Influenza Other Respir Viruses 2016; 10:536-539. [PMID: 27465864 PMCID: PMC5059955 DOI: 10.1111/irv.12418] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2016] [Indexed: 12/02/2022] Open
Abstract
We previously reported that horse antiserum against the Japanese equine influenza vaccine virus, A/equine/La Plata/1993 (LP93) exhibited reduced cross-neutralization against some Florida sublineage Clade (Fc) 2 viruses, for example, A/equine/Carlow/2011 (CL11). As a result, Japanese vaccine manufacturers will replace LP93 with A/equine/Yokohama/aq13/2010 (Y10, Fc2). To assess the benefit of updating the vaccine, five horses vaccinated with inactivated Y10 vaccine and five vaccinated with inactivated LP93 were challenged by exposure to a nebulized aerosol of CL11. The durations of pyrexia (≥38.5°C) and other adverse clinical symptoms experienced by the Y10 group were significantly shorter than those of the LP93 group.
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Affiliation(s)
- Takashi Yamanaka
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan.
| | - Manabu Nemoto
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
- Virology Unit, Irish Equine Centre, Johnstown, Naas, Co. Kildare, Ireland
| | - Hiroshi Bannai
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
| | - Koji Tsujimura
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
| | - Takashi Kondo
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
| | - Tomio Matsumura
- Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
| | - Sarah Gildea
- Virology Unit, Irish Equine Centre, Johnstown, Naas, Co. Kildare, Ireland
| | - Ann Cullinane
- Virology Unit, Irish Equine Centre, Johnstown, Naas, Co. Kildare, Ireland
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Introduction of an update system for vaccine strains of veterinary influenza vaccines in Japan. Biologicals 2015; 43:150-2. [PMID: 25614371 DOI: 10.1016/j.biologicals.2014.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 12/20/2014] [Indexed: 11/22/2022] Open
Abstract
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.
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A Systematic Review of Recent Advances in Equine Influenza Vaccination. Vaccines (Basel) 2014; 2:797-831. [PMID: 26344892 PMCID: PMC4494246 DOI: 10.3390/vaccines2040797] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Revised: 09/19/2014] [Accepted: 09/24/2014] [Indexed: 01/28/2023] Open
Abstract
Equine influenza (EI) is a major respiratory disease of horses, which is still causing substantial outbreaks worldwide despite several decades of surveillance and prevention. Alongside quarantine procedures, vaccination is widely used to prevent or limit spread of the disease. The panel of EI vaccines commercially available is probably one of the most varied, including whole inactivated virus vaccines, Immuno-Stimulating Complex adjuvanted vaccines (ISCOM and ISCOM-Matrix), a live attenuated equine influenza virus (EIV) vaccine and a recombinant poxvirus-vectored vaccine. Several other strategies of vaccination are also evaluated. This systematic review reports the advances of EI vaccines during the last few years as well as some of the mechanisms behind the inefficient or sub-optimal response of horses to vaccination.
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Yamanaka T, Cullinane A, Gildea S, Bannai H, Nemoto M, Tsujimura K, Kondo T, Matsumura T. The potential impact of a single amino-acid substitution on the efficacy of equine influenza vaccines. Equine Vet J 2014; 47:456-62. [DOI: 10.1111/evj.12290] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Accepted: 04/09/2014] [Indexed: 11/29/2022]
Affiliation(s)
- T. Yamanaka
- Epizootic Research Center; Equine Research Institute; Japan Racing Association; Shimotsuke Japan
| | - A. Cullinane
- Virology Unit; Irish Equine Centre; Johnstown Naas Co.; Kildare Ireland
| | - S. Gildea
- Virology Unit; Irish Equine Centre; Johnstown Naas Co.; Kildare Ireland
| | - H. Bannai
- Epizootic Research Center; Equine Research Institute; Japan Racing Association; Shimotsuke Japan
| | - M. Nemoto
- Epizootic Research Center; Equine Research Institute; Japan Racing Association; Shimotsuke Japan
| | - K. Tsujimura
- Epizootic Research Center; Equine Research Institute; Japan Racing Association; Shimotsuke Japan
| | - T. Kondo
- Epizootic Research Center; Equine Research Institute; Japan Racing Association; Shimotsuke Japan
| | - T. Matsumura
- Epizootic Research Center; Equine Research Institute; Japan Racing Association; Shimotsuke Japan
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Efficacy of a single intravenous dose of the neuraminidase inhibitor peramivir in the treatment of equine influenza. Vet J 2012; 193:358-62. [DOI: 10.1016/j.tvjl.2012.01.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 12/26/2011] [Accepted: 01/04/2012] [Indexed: 11/20/2022]
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No evidence of horizontal infection in horses kept in close contact with dogs experimentally infected with canine influenza A virus (H3N8). Acta Vet Scand 2012; 54:25. [PMID: 22506984 PMCID: PMC3416777 DOI: 10.1186/1751-0147-54-25] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 04/16/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Since equine influenza A virus (H3N8) was transmitted to dogs in the United States in 2004, the causative virus, which is called canine influenza A virus (CIV), has become widespread in dogs. To date, it has remained unclear whether or not CIV-infected dogs could transmit CIV to horses. To address this, we tested whether or not close contact between horses and dogs experimentally infected with CIV would result in its interspecies transmission. METHODS Three pairs of animals consisting of a dog inoculated with CIV (10(8.3) egg infectious dose 50/dog) and a healthy horse were kept together in individual stalls for 15 consecutive days. During the study, all the dogs and horses were clinically observed. Virus titres in nasal swab extracts and serological responses were also evaluated. In addition, all the animals were subjected to a gross pathological examination after euthanasia. RESULTS All three dogs inoculated with CIV exhibited clinical signs including, pyrexia, cough, nasal discharge, virus shedding and seroconversion. Gross pathology revealed lung consolidations in all the dogs, and Streptococcus equi subsp. zooepidemicus was isolated from the lesions. Meanwhile, none of the paired horses showed any clinical signs, virus shedding or seroconversion. Moreover, gross pathology revealed no lesions in the respiratory tracts including the lungs of the horses. CONCLUSIONS These findings may indicate that a single dog infected with CIV is not sufficient to constitute a source of CIV infection in horses.
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