Progress 06/04/10 to 09/30/13
Outputs
Progress Report Objectives (from AD-416): Characterize avian influenza viruses circulating in Vietnam, select representative isolates, and perform vaccine efficacy studies with these isolates. The goal is to provide scientific data to allow the determination of the best vaccine and vaccination protocols to be used as part of the vaccine program to be used in the country. The specific objectives are: 1) Sequence analysis of recent avian influenza (AI) viruses from Vietnam to identify what is circulating in the country; 2) Antigenic analysis of selected viruses to provide information for vaccine selection; 3) Vaccine efficacy studies using available commercial vaccines with representative strains to identify vaccines that provide clinical protection and reduce viral shedding to the greatest degree in chickens and ducks.; 4) Studies evaluating the effects of maternal immunity on vaccination. This is an important issue, especially in ducks, since vaccination at the hatchery would be an ideal solution for increasing vaccination of all birds, as opposed to the twice yearly campaigns that leave large gaps in coverage. Approach (from AD-416): Representative isolates will be sent from the National Center of Veterinary Diagnosis in Hanoi. The viruses will be fully sequenced and based on the phylogenetic analysis, isolates will be selected for biological and antigenic comparison. The hemagglutinin gene will be cloned and placed in either deoxyribonucleic acid (DNA) vaccine vectors or in a reverse genetics constructed virus and inoculated in chickens to get immune serum that will be compared with H5 standards by hemagglutination inhibition analysis. This information will provide a prediction of antigenic differences among the Vietnamese isolates. Additionally, selected isolates will be used for biological assessment in ducks for pathogenic potential. Using the sequence, antigenic and biological information, two or more isolates will be selected as challenge strains for vaccine efficacy studies. Available commercial vaccines and autogenous vaccines made from the challenge viruses will be used to vaccinate both chickens and ducks. After 3 weeks the antibody response will be measured and the birds challenged with the Vietnamese highly pathogenic avian influenza viruses. The vaccine efficacy will be evaluated by measuring morbidity, mortality, and virus shedding. The serologic response before and after challenge will also be evaluated using both homologous and heterologous antigen to evaluate the immune response in conjunction with the challenge data. The effect of maternal immunity on the response to vaccination in chickens and ducks will be evaluated by passive antibody transfer studies. This research is directly related to inhouse objective 1 - Characterize variant and emerging avian influenza viruses in live poultry markets and commercial production systems; inhouse objective 4 - Improve existing diagnostic tests and testing strategies for avian influenza virus surveillance, detection, and recovery from disease outbreaks; and inhouse objective 5 - Develop new vaccine platforms designed to control and prevent avian influenza virus outbreaks. Studies were conducted demonstrating the suboptimal protection conferred by the Re-1 and Re-5 commercial vaccines in ducks against H5N1 HPAI clade 2.3.2.1 viruses, underscoring the importance of monitoring vaccine efficacy in the control of H5N1 HPAI in ducks. The protective efficacy in ducks of the two commercial H5N1 vaccines widely used in Vietnam; Re-1 and Re-5 was examined. Vaccinated ducks were challenged with H5N1 HPAI viruses belonging to the HA clades 1.1, 2.3.4.3, 2.3.2.1.A and 2.3.2.1.B isolated between 2008 and 2011 in Vietnam. Progressively less protection was observed with the more recent isolates. The HA proteins of the 2011 challenge viruses had the greatest number of amino acid differences from the two vaccines as compared to the viruses from 2008 and 2009, which correlates with the lesser protection observed with these viruses. This is a serious concern for the control of H5N1 HPAI in Vietnam considering the important role of domestic ducks in the epidemiology of H5N1 HPAI. A manuscript with the latest results has been submitted for publication.
Impacts
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Publications
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Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): Characterize avian influenza viruses circulating in Vietnam, select representative isolates, and perform vaccine efficacy studies with these isolates. The goal is to provide scientific data to allow the determination of the best vaccine and vaccination protocols to be used as part of the vaccine program to be used in the country. The specific objectives are: 1) Sequence analysis of recent avian influenza (AI) viruses from Vietnam to identify what is circulating in the country; 2) Antigenic analysis of selected viruses to provide information for vaccine selection; 3) Vaccine efficacy studies using available commercial vaccines with representative strains to identify vaccines that provide clinical protection and reduce viral shedding to the greatest degree in chickens and ducks.; 4) Studies evaluating the effects of maternal immunity on vaccination. This is an important issue, especially in ducks, since vaccination at the hatchery would be an ideal solution for increasing vaccination of all birds, as opposed to the twice yearly campaigns that leave large gaps in coverage. Approach (from AD-416): Representative isolates will be sent from the National Center of Veterinary Diagnosis in Hanoi. The viruses will be fully sequenced and based on the phylogenetic analysis, isolates will be selected for biological and antigenic comparison. The hemagglutinin gene will be cloned and placed in either deoxyribonucleic acid (DNA) vaccine vectors or in a reverse genetics constructed virus and inoculated in chickens to get immune serum that will be compared with H5 standards by hemagglutination inhibition analysis. This information will provide a prediction of antigenic differences among the Vietnamese isolates. Additionally, selected isolates will be used for biological assessment in ducks for pathogenic potential. Using the sequence, antigenic and biological information, two or more isolates will be selected as challenge strains for vaccine efficacy studies. Available commercial vaccines and autogenous vaccines made from the challenge viruses will be used to vaccinate both chickens and ducks. After 3 weeks the antibody response will be measured and the birds challenged with the Vietnamese highly pathogenic avian influenza viruses. The vaccine efficacy will be evaluated by measuring morbidity, mortality, and virus shedding. The serologic response before and after challenge will also be evaluated using both homologous and heterologous antigen to evaluate the immune response in conjunction with the challenge data. The effect of maternal immunity on the response to vaccination in chickens and ducks will be evaluated by passive antibody transfer studies. This project is related to objective 1 and 5 of the in-house project: Characterize variant and emerging avian influenza viruses in lilve poultry markets and commercial production systems; 5. develop new vaccine platforms designed to control and prevent avian influenza virus outbreaks. The pathogenicity of two recent H5N1 highly pathogenic avian influenza (HPAI) viruses circulating in Vietnam was evaluated in domestic ducks. One of the viruses, A/duck/Vietnam/NCVD-672/2011 (clade 2.3.2B), was highly virulent for ducks but the other virus, A/chicken/Vietnam/NCVD- 675/2011 (clade 2.3.2A) was moderately pathogenic, with some ducks surviving infection. Vaccine failures have been reported in Vietnam when attempting to protect poultry against infection with these HA clade 2.3.2 viruses. The protection conferred by two commercial inactivated vaccines currently used in Vietnam (Re-1 and Re-5) to protect ducks against the HA clade 2.3.2 viruses was also evaluated. Both vaccines protected ducks against mortality for one of the viruses (HA clade 2.3.2A), but the Re-1 vaccine did not protect ducks against the HA clade 2.3.2B virus. All ducks vaccinated with either one of the vaccines shed virus for more than eight days after infection, indicating that the vaccines are not protecting ducks adequately against the HA clade 2.3.2 H5N1 viruses. This is a serious concern for the control of H5N1 in Vietnam considering the important role of domestic ducks in the epidemiology of H5N1 HPAI.
Impacts
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Publications
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) Characterize avian influenza viruses circulating in Vietnam, select representative isolates, and perform vaccine efficacy studies with these isolates. The goal is to provide scientific data to allow the determination of the best vaccine and vaccination protocols to be used as part of the vaccine program to be used in the country. The specific objectives are: 1) Sequence analysis of recent avian influenza (AI) viruses from Vietnam to identify what is circulating in the country; 2) Antigenic analysis of selected viruses to provide information for vaccine selection; 3) Vaccine efficacy studies using available commercial vaccines with representative strains to identify vaccines that provide clinical protection and reduce viral shedding to the greatest degree in chickens and ducks.; 4) Studies evaluating the effects of maternal immunity on vaccination. This is an important issue, especially in ducks, since vaccination at the hatchery would be an ideal solution for increasing vaccination of all birds, as opposed to the twice yearly campaigns that leave large gaps in coverage. Approach (from AD-416) Representative isolates will be sent from the National Center of Veterinary Diagnosis in Hanoi. The viruses will be fully sequenced and based on the phylogenetic analysis, isolates will be selected for biological and antigenic comparison. The hemagglutinin gene will be cloned and placed in either deoxyribonucleic acid (DNA) vaccine vectors or in a reverse genetics constructed virus and inoculated in chickens to get immune serum that will be compared with H5 standards by hemagglutination inhibition analysis. This information will provide a prediction of antigenic differences among the Vietnamese isolates. Additionally, selected isolates will be used for biological assessment in ducks for pathogenic potential. Using the sequence, antigenic and biological information, two or more isolates will be selected as challenge strains for vaccine efficacy studies. Available commercial vaccines and autogenous vaccines made from the challenge viruses will be used to vaccinate both chickens and ducks. After 3 weeks the antibody response will be measured and the birds challenged with the Vietnamese highly pathogenic avian influenza viruses. The vaccine efficacy will be evaluated by measuring morbidity, mortality, and virus shedding. The serologic response before and after challenge will also be evaluated using both homologous and heterologous antigen to evaluate the immune response in conjunction with the challenge data. The effect of maternal immunity on the response to vaccination in chickens and ducks will be evaluated by passive antibody transfer studies. This research is related to inhousoe objective 2: Develop vaccines that effectively stop outbreaks, allow differentiation from natural infection, and can be administered in a cost effective manner. The pathogenicity of H5N1 highly pathogenic avian influenza (HPAI) Vietnam viruses from three different hemagglutinin (HA) clades (1, 2.3.4, and 7) was evaluated in chickens and ducks. HA clade 7 viruses have been reported to be less pathogenic in birds in Vietnam, and was in fact less pathogenic in our studies than the other two viruses from clades 1 and 2. 3.4, which were very virulent for both chickens and ducks, as previously studied viruses from Vietnam. The HA clade 7 virus did not produce disease in ducks, however did produce disease in chickens, which could be a concern because the ducks could be healthy carriers and spread these viruses among other poultry species. Vaccine efficacy studies using available commercial vaccines with representative strains help identify vaccines that provide clinical protection and reduce viral shedding to the greatest degree in chickens and ducks. The protection conferred by two commercial inactivated vaccines currently used in Vietnam (Re-1 and Re-5) to protected ducks against H5N1 HPAI was also evaluated. Both vaccines conferred good protection against mortality to ducks challenged with two recent H5N1 HPAI viruses from 2010.
Impacts
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Publications
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