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1.
An inactivated, aluminum hydroxide adjuvant equine influenza vaccine was tested in horses and guinea pigs to determine the levels of antigen that would elicit maximum serological responses. Vaccine containing serial twofold increments of A/Equi-1/Prague and A/Equi-2/Miami strains of equine influenza virus was administered to random groupings of both types of test animals. The hemagglutination inhibition antibody response for each group was then measured. Results in horses and guinea pigs were compared to determine if the equine serological values could be related to a potency test in laboratory animals. The highest mean hemagglutination inhibition antibody response in horses occurred in groups vaccinated, respectively, with 128 or 256 hemagglutination units of A/Equi-1 and 512 or 1024 hemagglutination units of A/Equi-2 antigen. Groups vaccinated with further two- or fourfold increases in these antigens had mean hemagglutination inhibition titers that were somewhat lower than the maximum levels. When graded doses of vaccine were given to guinea pigs, their hemagglutination inhibition antibody titers reached a plateau of maximum values, similar to the serological response in vaccinated horses. Test horses remained clinically free from signs of equine influenza during the year following vaccination and no untoward post-vaccination reactions were observed.  相似文献   

2.
In Italy epizootics of equine influenza often occur, but no virus isolation has been reported since 1971. This paper describes the antigenic and biochemical characterization of two equine influenza viruses isolated in Italy from 1985 to 1989. The virus isolates were shown to differ antigenically from earlier strains of the same subtype, A/equine/Miami/1/63 (H3N8). Monoclonal antibody analysis showed that the haemagglutinins of these strains were serologically indistinguishable from A/equine/Fontainebleau/1/79, a variant of A/equine/Miami, never isolated in Italy before. One of the two virus isolates was obtained from a horse immunized with a bivalent inactivated influenza vaccine, not containing A/equine/Fontainebleau/79 antigens.

The vaccine failure underlines the importance of antigenic relatedness between currently circulating viruses and vaccine strains. Therefore, to improve the protection afforded by equine immunization, the vaccine composition should be decided according to the results of a virological surveillance activity, systematically conducted among horses.  相似文献   


3.
Antigenic variation among equine H 3 N 8 influenza virus hemagglutinins   总被引：1，自引：0，他引：1  
To provide information on the antigenic variation of the hemagglutinins (HA) among equine H 3 influenza viruses, 26 strains isolated from horses in different areas in the world during the 1963-1996 period were analyzed using a panel of monoclonal antibodies recognizing at least 7 distinct epitopes on the H 3 HA molecule of the prototype strain A/equine/Miami/1/63 (H 3 N 8). The reactivity patterns of the virus strains with the panel indicate that antigenic drift of the HA has occurred with the year of isolation, but less extensively than that of human H 3 N 2 influenza virus isolates, and different antigenic variants co-circulate. To assess immunogenicity of the viruses, antisera from mice vaccinated with each of the 7 representative inactivated viruses were examined by neutralization and hemagglutination-inhibition tests. These results emphasize the importance of monitoring the antigenic drift in equine influenza virus strains and to introduce current isolates into vaccine. On the basis of the present results, equine influenza vaccine strain A/equine/Tokyo/2/71 (H 3 N 8) was replaced with A/equine/La Plata/1/93 (H 3 N 8) in 1996 in Japan. The present results of the antigenic analysis of the 26 strains supported the results of a phylogenetic analysis, that viruses belonging to each of the Eurasian and American equine influenza lineages have independently evolved. However, the current vaccine in Japan consists of two American H 3 N 8 strains; A/equine/Kentucky/1/81 and A/equine/La Plata/1/93. It is also therefore recommended that a representative Eurasian strain should be included as a replacement of A/equine/Kentucky/1/81.  相似文献   

4.
The antibody responses to equine influenza viruses were investigated during a postepizootic period of the disease. Serum samples were collected from a total of 128 horses on three occasions during the years 1967-77. No significant increase of hemagglutination-inhibition antibody titers to subtypes 1 and 2 of equine influenza virus were detected in any of the sera tested. The maternal hemagglutination-inhibition antibody titers of foals decreased over a four month interval. A marked increase of the titers was recognized in only the equine influenza virus vaccinated horses. These findings suggest that equine influenza virus was not prevalent in the horse populations during the observation period. In such conditions, the dissemination of equine influenza viruses in the horses is discussed in relation to introduction of the disease from abroad. We also examined whether the doctrine of original antigenic sin, an immunological phenomenon recognized in human influenza, was applicable for equine influenza. However, no marked increase of hemagglutination-inhibition antibody titer to the primary infecting subtype in the 44 horses was observed after administration of the heterologous subtype vaccine.  相似文献   

5.
Peripheral blood leucocytes from a pony previously exposed to equine influenza virus (H3, N8) and vaccinated with killed virus (H3, N8 and H7, N7 subtypes) were cultured in vitro with live A/equine/Prague/56 (H7, N7). On the sixth day of culture, cells were harvested and fused with mouse myeloma cells (X63-Ag8.653). From this fusion, one hemagglutinin specific, equine IgG monoclonal antibody secreting hybridoma was identified and cloned twice by limiting dilution. The antibody inhibited hemagglutination by nine H7 equine influenza virus isolates obtained over a 21-year period, but did not inhibit A/equine/Miami/63 (H3, N8), or A/PR/8/34 (H1, N1). The neutralizing titer of hybridoma induced, nude mouse ascitic fluid was 10(-4.5) when tested in eggs against 100 egg infective doses (EID50) A/equine/Prague/1/56. The hybridoma continued to synthesize antibody during more than 4 months in continuous culture.  相似文献   

6.
During the epidemic of equine influenza which occurred in India in 1987, serum samples were collected at late acute/early convalescent phase (7–9 days), at 5 weeks and at 18–23 weeks after onset of illness, from six affected horses from the Union Territory of Changigarh, and Nawanshahr, Punjab State, India, and were examined for antibodies to A/eq-1 and A/eq-2 influenza viruses by hemagglutination inhibition (HI) tests. It was found that the antibody response to A/eq-1 virus strains, Ludhiana/87 and Prague/56, was stronger and antibodies persisted at high levels in four animals. The fifth animal showed a diagnostic decrease in HI titers while the sixth animal seroconverted. The corresponding HI titers to A/eq-2/Ludhiana virus showed a 4-fold decrease in all six animals.Another nine equine animals in the single convalescent serum samples had detectable or high HI titers against A/eq-1 and A/eq-2 viruses.In serum samples from horses and ponies, taken 5 weeks to 9 months after onset of illness, little or no difference in antibody titers to A/eq-2/Miami/63 and A/eq-2/Fontainebleau/79 strains was found.It seems clear that the antibody titers that ensued were indicative of recent influenza infections. Apparently, two distinct equine influenza viruses, A/eq-1 and A/eq-2, were involved during the epidemic, infecting the equine animals simultaneously in the region.  相似文献   

7.
Equine influenza type 2 infections occurred in the Newmarket areas in January 1976. The disease did not spread to any extent and while this may have been due to recent vaccination it was found that not all vaccinated horses were fully protected. The virus involved showed some antigenic drift from the prototype strain A/equine/Miami/1/63 (Heq 2 Neq 2).  相似文献   

8.
Influenza A viruses of the H3N8 subtype are a major cause of respiratory disease in horses. Subclinical infection with virus shedding can occur in vaccinated horses, particularly where there is a mismatch between the vaccine strains and the virus strains circulating in the field. Such infections contribute to the spread of the disease. Rapid diagnostic techniques are available for detection of virus antigen and can be used as an aid in control programmes. Improvements have been made to methods of standardising inactivated virus vaccines, and a direct relationship between vaccine potency measured by single radial diffusion and vaccine-induced antibody measured by single radial haemolysis has been demonstrated. Improved adjuvants and antigenic presentation systems extend the duration of immunity induced by inactivated virus vaccines, but high levels of antibody are required for protection against field infection. In addition to circulating antibody, infection with influenza virus stimulates mucosal and cellular immunity; unlike immunity to inactivated virus vaccines, infection-induced immunity is not dependent on the presence of circulating antibody to HA. Live attenuated or vectored equine influenza vaccines, which may better mimic the immunity generated by influenza infection than inactivated virus vaccines, are now available. Mathematical modelling based upon experimental and field data has been applied to examine issues relating to vaccine efficacy at the population level. A vaccine strain selection system has been implemented and a more global approach to the surveillance of equine influenza is being developed.  相似文献   

9.
The objective of this project was to develop and implement an active surveillance program for the early and rapid detection of equine influenza viruses in Ontario. For this purpose, from October 2003 to October 2005, nasopharyngeal swabs and acute and convalescent serum samples were collected from 115 client-owned horses in 23 outbreaks of respiratory disease in Ontario. Sera were paired and tested for antibody to equine influenza 1 (AE1-H7N7), equine influenza 2 (AE2-H3N8), equine herpesvirus 1 and 4 (EHV1 and EHV4), and equine rhinitis A and B (ERAV and ERBV). Overall, the cause-specific morbidity rate of equine influenza virus in the respiratory outbreaks was 56.5% as determined by the single radial hemolysis (SRH) test. The AE2-H3N8 was isolated from 15 horses in 5 outbreaks. A 4-fold increase in antibody levels or the presence of a high titer against ERAV or ERBV was observed in 10 out of 13 outbreaks in which AE2-H3N8 was diagnosed as the primary cause of disease. In conclusion, AE2-H3N8 was found to be an important contributor to equine respiratory viral disease. Equine rhinitis A and B (ERAV and ERBV) represented an important component in the equine respiratory disease of performing horses.  相似文献   

10.
Flu Avert IN vaccine is a new, live attenuated virus vaccine for equine influenza. We tested this vaccine in vivo to ascertain 1) its safety and stability when subjected to serial horse to horse passage, 2) whether it spread spontaneously from horse to horse and 3) its ability to protect against heterologous equine influenza challenge viruses of epidemiological relevance. For the stability study, the vaccine was administered to 5 ponies. Nasal swabs were collected and pooled fluids administered directly to 4 successive groups of na?ve ponies by intranasal inoculation. Viruses isolated from the last group retained the vaccine's full attenuation phenotype, with no reversion to the wild-type virus phenotype or production of clinical influenza disease. The vaccine virus spread spontaneously to only 1 of 13 nonvaccinated horses/ponies when these were comingled with 39 vaccinates in the same field. For the heterologous protection study, a challenge model system was utilised in which vaccinated or na?ve control horses and ponies were exposed to the challenge virus by inhalation of virus-containing aerosols. Challenge viruses included influenza A/equine-2/Kentucky/98, a recent representative of the 'American' lineage of equine-2 influenza viruses; and A/equine-2/Saskatoon/90, representative of the 'Eurasian' lineage. Clinical signs among challenged animals were recorded daily using a standardised scoring protocol. With both challenge viruses, control animals reliably contracted clinical signs of influenza, whereas vaccinated animals were reliably protected from clinical disease. These results demonstrate that Flu Avert IN vaccine is safe and phenotypically stable, has low spontaneous transmissibility and is effective in protecting horses against challenge viruses representative of those in circulation worldwide.  相似文献   

11.
In April 2004 an outbreak of equine influenza occurred at the Zagreb hippodrome, Croatia. Clinical respiratory disease of the same intensity was recorded in vaccinated and non-vaccinated horses. The equine influenza vaccine used in Croatia at the time of the outbreak contained the strains A/equine/Miami/63 (H3N8), A/equine/Fontainebleau/79 (H3N8) and A/equine/Prague/56 (H7N7). At the same time, the usual strains in vaccines used in Europe were, in accordance with the recommendation of the World Organisation for Animal Health (OIE) Expert Surveillance Panel on equine influenza, A/equine/Newmarket/1/93 (H3N8) and A/equine/Newmarket/2/93 (H3N8). At the same time, some current vaccines in the USA contained A/equine/Kentucky/97 (H3N8). Genetic characterization of the HA1 portion of the haemagglutinin (HA) gene of virus isolated from the outbreak indicated that the isolate (A/equine/Zagreb/04) was an H3N8 strain closely related to recent representative viruses of the American lineage Florida sub-lineage. In comparison with both H3N8 vaccine strains used in horses at the Zagreb hippodrome, A/equine/Zagreb/04 displayed amino acids changes localised to 4 of the 5 described antigenic sites (A-D) of subunit protein HA1. Comparison of the amino acid sequence of the HA1 subunit protein of the outbreak strain with that of A/equine/Newmarket/1/93 displayed three amino acids changes localised in antigenic sites B and C, while antigenic sites A, D and E were unchanged. The Zagreb 2004 outbreak strain had the same amino acids at antigenic sites of the HA1 subunit protein as the strain A/equine/Kentucky/97. Amino acid changes in antigenic sites between HA1 subunit of the outbreak strain and the strains used in the vaccines likely accounted for the vaccine failure and the same clinical signs in vaccinated and unvaccinated horses. Use of a recent strain in vaccines should limit future outbreaks.  相似文献   

12.
Six outbreaks of equine influenza virus A2 (EIVA2) were diagnosed serologically at five different racetracks during 1983–84. EIVA2 was isolated from horses at four outbreaks. Of the horses sampled, only horses which had not been vaccinated within six months became clinically ill. Clinically normal stablemates sampled during theseoutbreaks showed no serological evidence of subclinical infection. Thereappeared to be a correlation between hemagglutination inhibition (HI) titerand susceptibility to disease. Horses vaccinated biweekly appeared to have a statistically significantly higher EIVA2 HI titer than those vaccinated tri-annually. Empirically, it was concluded that there had been no significant change in the antigenic components of EIVA2.  相似文献   

13.
It has been recommended that modern equine influenza vaccines should contain an A/equi-1 strain and A/equi-2 strains of the American and European-like subtype. We describe here the efficacy of a modern updated inactivated equine influenza-herpesvirus combination vaccine against challenge with a recent American-like isolate of equine influenza (A/equine-2/Kentucky/95 (H3N8). The vaccine contains inactivated Influenza strains A-equine-1/Prague'56, A-equine-2/Newmarket-1/'93 (American lineage) and A-equine-2/ Newmarket-2/93 (Eurasian lineage) and inactivated EHV-1 strain RacH and EHV-4 strain V2252. It is adjuvanted with alhydrogel and an immunostim. Horses were vaccinated at the start of the study and 4 weeks later. Four, six and eight weeks after the first vaccination high anti-influenza antibody titres were found in vaccinated horses, whereas at the start of the study all horses were seronegative. After the challenge, carried out at 8 weeks after the first vaccination, nasal swabs were taken, rectal temperatures were measured and clinical signs were monitored for 14 days. In contrast to unvaccinated control horses, vaccinated animals shed hardly any virus after challenge, and the appearance of clinical signs of influenza such as nasal discharge, coughing and fever were reduced in the vaccinated animals. Based on these observations, it was concluded that the vaccine protected against clinical signs of influenza and, more importantly, against virus excretion induced by an American-like challenge virus strain. In a second experiment the duration of the immunity induced by this vaccine was assessed serologically. Horses were vaccinated at the start of the study and 6 and 32 weeks later. Anti-influenza antibody titres were determined in bloodsamples taken at the first vaccination, and 2, 6, 8, 14, 19, 28, 32, 37, 41, 45 and 58 weeks after the first vaccination. Vaccinated horses had high anti-influenza antibody titres, above the level for clinical protection against influenza, against all strains present in the vaccine until 26 weeks after the third vaccination.  相似文献   

14.
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15.
An outbreak of an influenza-like illness affected approximately 1/3 of the 1050 race horses stabled at a standardbred racetrack and resulted in a 3-day suspension of racing. A/Equi-2 influenza virus was isolated from 1 affected horse and 8 of 10 horses sampled seroconverted. Threshold protective levels of HI antibody against A/Equi-2 influenza virus were not demonstrated in unaffected horses. Resistance in unaffected horses was assumed to result from other factors following previous exposure. Few of the horses had been vaccinated against equine influenza. It was felt that an outbreak of this magnitude might have been prevented if a vaccination program had been followed.  相似文献   

16.
We compared the efficacy of 3 commercial vaccines against swine influenza A virus (SIV) and an experimental homologous vaccine in young pigs that were subsequently challenged with a variant H3N2 SIV, A/Swine/Colorado/00294/2004, selected from a repository of serologically and genetically characterized H3N2 SIV isolates obtained from recent cases of swine respiratory disease. The experimental vaccine was prepared from the challenge virus. Four groups of 8 pigs each were vaccinated intramuscularly at both 4 and 6 wk of age with commercial or homologous vaccine. Two weeks after the 2nd vaccination, those 32 pigs and 8 nonvaccinated pigs were inoculated with the challenge virus by the deep intranasal route. Another 4 pigs served as nonvaccinated, nonchallenged controls. The serum antibody responses differed markedly between groups. After the 1st vaccination, the recipients of the homologous vaccine had hemagglutination inhibition (HI) titers of 1:640 to 1:2560 against the challenge (homologous) virus. In contrast, even after 2nd vaccination, the commercial-vaccine recipients had low titers or no detectable antibody against the challenge (heterologous) virus. After the 2nd vaccination, all the groups had high titers of antibody to the reference H3N2 virus A/Swine/Texas/4199-2/98. Vaccination reduced clinical signs and lung lesion scores; however, virus was isolated 1 to 5 d after challenge from the nasal swabs of most of the pigs vaccinated with a commercial product but from none of the pigs vaccinated with the experimental product. The efficacy of the commercial vaccines may need to be improved to provide sufficient protection against emerging H3N2 variants.  相似文献   

17.
In this study, antibody responses after equine influenza vaccination were investigated among 1,098 horses in Korea using the hemagglutination inhibition (HI) assay. The equine influenza viruses, A/equine/South Africa/4/03 (H3N8) and A/equine/Wildeshausen/1/08 (H3N8), were used as antigens in the HI assay. The mean seropositive rates were 91.7% (geometric mean antibody levels (GMT), 56.8) and 93.6% (GMT, 105.2) for A/equine/South Africa/4/03 and A/equine/Wildeshausen/1/08, respectively. Yearlings and two-year-olds in training exhibited lower positive rates (68.1% (GMT, 14) and 61.7% (GMT, 11.9), respectively, with different antigens) than average. Horses two years old or younger may require more attention in vaccination against equine influenza according to the vaccination regime, because they could be a target of the equine influenza virus.  相似文献   

18.
Previous studies have shown that protection against equine influenza virus (EIV) is partially mediated by virus-specific IgGa and IgGb. In this study we tested whether addition of a CpG ODN formulation to a commercial killed virus vaccine would enhance EIV-specific IgGa and IgGb antibody responses, and improve protection against an experimental EIV challenge. Thirty na?ve horses were assigned to one of three groups and vaccinated as follows: 10 were given vaccine (Encevac TC4, Intervet Inc.) alone, 10 were given vaccine plus 0.25 mg CpG ODN 2007 formulated with 30% Emulsigen (CpG/Em), and 10 controls were given saline. All horses were challenged with live virus 12 weeks after the final vaccination. Antibody responses were tested by single radial hemolysis (SRH) and ELISA, and protection was evaluated by determination of temperature, coughing, and clinical scores. Killed virus vaccine combined with CpG/Em induced significantly greater serologic responses than did the vaccine alone. All antibody isotypes tested increased after the addition of CpG/Em, although no shift in relative antibody isotypes concentrations was detected. Vaccination significantly improved protection against challenge but the differences between the two vaccine groups were not statistically significant. This study is the first demonstration that CpG/Em enhances antigen-specific antibody responses in horses and supports its potential to be used as an adjuvant for vaccines against equine infections.  相似文献   

19.
Processing of nasal materials from clinical cases during the 1987 influenza epidemic in Northern and Central India resulted in the isolation of two haemagglutinating agents; one each from donkeys and horses at Bhiwani in Haryana State and Ludhiana in Punjab State, respectively. These were typed as Influenza A/Equi-2 viruses by haemagglutination inhibition test. The two isolates were designated as A/Equi-2/Bhiwani/1/87 and A/Equi-2/Ludhiana/1/87. The Bhiwani/87 isolate was confirmed to have H3N8 antigenic structure and was indistinguishable from the Miami/63 strain of A/Equi-2 virus. However, the A/Equi-2 Ludhiana/87 isolate was closely related to the Fontainebleau/79 strain of A/equi-2 virus.  相似文献   

20.
Between March and May 2003, equine influenza virus infection was confirmed as the cause of clinical respiratory disease among both vaccinated and unvaccinated horses of different breeds and types in at least 12 locations in the UK. In the largest outbreak, 21 thoroughbred training yards in Newmarket, with more than 1300 racehorses, were affected, with the horses showing signs of coughing and nasal discharge during a period of nine weeks. Many of the infected horses had been vaccinated during the previous three months with a vaccine that contained representatives from both the European (A/eq/Newmarket/2/93) and American (A/eq/Newmarket/1/93) H3NN8 influenza virus lineages. Antigenic and genetic characterisation of the viruses from Newmarket and elsewhere indicated that they were all closely related to representatives of a sublineage of American viruses, for example, Kentucky/5/02, the first time that this sublineage had been isolated in the uk. In the recently vaccinated racehorses in Newmarket the single radial haemolysis antibody levels in acute sera appeared to be adequate, and there did not appear to be significant antigenic differences between the infecting virus and A/eq/Newmarket/1/93, the representative of the American lineage virus present in the most widely used vaccine, to explain the vaccine failure. However, there was evidence for significantly fewer infections among two-year-old horses than older animals, despite their having similar high levels of antibody, consistent with a qualitative rather than a quantitative difference in the immunity conveyed by the vaccination.  相似文献   

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