1a. Objectives (from AD-416):
1. Determine the impact of variant and emerging viruses on the development and control of Newcastle disease by developing means to detect and survey variant and emerging Newcastle disease viruses and by determining the presence of variant and emerging Newcastle disease viruses in wild birds and live poultry markets. 1.A. Determine the impact of variant and emerging viruses on the evolution and control of Newcastle disease by determining the presence of variant and emerging Newcastle disease viruses in wild birds and live poultry markets. 1.B. Develop means to detect and survey variant and emerging Newcastle disease viruses. 2. Elucidate the host-pathogen interactions of Newcastle disease virus infections that impact vaccine efficacy by defining host pathways modulated by Newcastle disease viral infections and by identifying genetic and biological viral determinants that affect the safety and efficacy of Newcastle disease vaccine virus strains. 2.A. Define host response pathways modulated by Newcastle disease viral infections. 2.B. Identify viral determinants that affect the safety and efficacy of Newcastle disease vaccine virus strains. 3. Develop vaccine strategies to effectively control Newcastle disease and stop disease outbreaks by developing vaccine platforms specifically designed to control low virulent and virulent Newcastle disease outbreaks.
1b. Approach (from AD-416):
Field samples of Newcastle disease virus (NDV) collected from poultry, cormorants, pigeons, wild birds, and live bird markets from the U.S. and abroad will be characterized by genomic nucleotide sequencing and by performing virulence testing. Sequence variants or genetically diverse isolates will be biologically evaluated by determining the mean death time in eggs (MDT) and the intra-cerebral pathogenicity index (ICPI) in one day old chicks. Viruses of novel lineages that display evidence of increased virulence will be further characterized in specific pathogen free chickens by conducting standard pathogenesis experiments. Field samples from exotic viruses and viruses circulating in U.S. wild bids, and live bird market will be evaluated using available real time rapid detection assays (fusion, matrix and polymerases gene based) and those samples that fail detection with any of the U.S. Department of Agriculture (USDA) real time polymerase chain reaction rapid tests will be further analyzed using classical virological techniques or random sequencing. We will construct chimeric vaccine viruses by replacing the surface fusion and hemagglutinin-neuraminidase proteins from current circulating virulent field strains onto a tested vaccine backbone (LaSota). The effect of replacing these genes on virulence, clinical signs, tissue tropism, viral shedding, and induction of antigenic and protective response will be evaluated in animals experiments using immunologically mature chickens. Vaccination-challenge experiments will be performed to evaluate how well new circulating Asian, African and South American virulent viruses perform during current commercial vaccination schemes. Current vaccines such as LaSota or B1 will be used to vaccinate birds and clinical signs, pathological outcomes, viral replication and shedding will be compared after challenges with emerging strains of NDV. Live vaccines viruses expressing genes of NDV from viruses of recent outbreaks will be evaluated with the expectation that improved protection will result. This increased protection after virulent challenge should effectively reduce transmission from vaccinated animals and provide better clinical protection. Additionally, utilizing recombinant technology live vaccines expressing chicken cytokines will be developed.
3. Progress Report:
The Newcastle Disease Virus research project has remained active nationally and internationally to meet the objectives and milestones of this project. For objectives 1 milestone 1.1 the group evaluated the sequence of 57 exotic virulent Newcastle Disease Viruses (NDV), and continued studying the evolution of the viruses through phylogenetic analysis. Part of this research will be published in a recently accepted manuscript entitled,” Genetic diversity of avian paramyxovirus type 1: proposal for a unified nomenclature and classification system of Newcastle disease virus genotype. This work has led to the discovery of additional genetic diversity for NDV with fifteen genotypes identified. Another manuscript entitled, “Characteristics of Pigeon Paramyxovirus Serotype-1 Isolates (PPMV-1) from the Russian Federation from 2001 to 2009” revealed that a relatively poorly documented subgroup is circulating in the Russian Federation. For subjective 1.b, “Develop means to detect and survey variant and emerging Newcastle disease viruses,” we have characterized recent Newcastle disease isolates from Peru and the Dominican Republic and described the genetic characteristics of those unique viruses in two recently accepted publications. For sub-objective 2a “To study the host response pathways modulated by Newcastle disease virus,” we have studied the role of the interferon gene on the immune response and determined that high levels of interferon expressed early during an infection effectively attenuates a virulent Newcastle disease virus. In addition, we performed clinical and pathological studies with highly virulent viruses from Burkina Faso, Nigeria, Niger, South Africa, Peru, Venezuela, and the Dominican Republic. The milestones of sub objective 2b, “Construction of recombinant viruses with F and HN replacements,” were fully met and four different vaccine viruses containing the surface proteins F and HN from viruses of different genotypes were constructed and MTA to transfer those vaccines to a company are in place. The milestone of sub-objective 3a, “Evaluation of classical vaccines against genotypes V and VIId,” were fully met and the protective effects of classical vaccines against new circulating viruses of Mexico, Peru, South Africa, West Africa, and Venezuela were evaluated. A publication is in preparation. Collaborative work continues with a number of national and international partners and additional funding has been obtained from NIFA to study the stability and evolution of recombinant vaccines viruses, from the Gates Foundation to develop Newcastle disease resistant viruses, with the Bio-security Engagement program from The Department of State to support collaborations with Indonesia, Pakistan, Ukraine and Russia. Isolates from most of the above-mentioned countries have been incorporated in our repositories and are being characterized.
1. Genetic characterization of new exotic viruses. Virulent Newcastle disease viruses (NDV) are found in most countries of the world and the United States (U.S.) has strict rules to prevent their entry. However, it is important for the U.S. to monitor and characterize viruses that are a potential threat to the U.S. poultry industry. Strains of NDV obtained recently from Mexico, Indonesia, Malaysia, Venezuela, Pakistan, Vietnam, Belize, Dominican Republic, South Africa, Peru and from wild birds from the U.S. have been sequenced and characterized genetically. The sequences of key genes have been obtained and allowed the prediction of the virulence of those viruses. This characterization has led to the identification of viruses of Asian lineages for the first time in the American continent (in Peru and in Venezuela) and to the identification of the expansion of the host range of North American virulent Newcastle disease from cormorants to other wild birds and the discovery of this type of viruses on the east cost of the U.S. (Massachusetts, Maine, New Hampshire, and Maryland).
2. Construction of recombinant viruses with surface proteins that resemble circulating viruses. Current vaccines are not effective in preventing viral replication. Vaccines that are homologous to circulating viruses are more likely to prevent virus replication and to reduce viral presence in the environment. To reduce viral load in the environment we have constructed four vaccine candidates that will likely be more effective in preventing viral replication in vaccinated birds and help prevent the introduction of highly virulent exotic NDV into the U.S. These vaccine candidates are currently being evaluated by a vaccine company as candidates for distribution worldwide.
3. Pathogenic characterization of exotic viruses. Newcastle disease viruses with different genomic characteristics behave differently in poultry and the clinical signs and lesions seen can vary greatly. Pathogenesis experiments were used to ensure that we can identify the disease if it entered into our poultry. As part of Objective 3 we initiated the pathotyping of new viral isolates that have the potential to be introduced in the U.S. Pathogenic characterization of viruses from China, Peru, Dominican Republic, Belize, Vietnam and U.S. waterfowl were done in chickens. These data, again, allow for the identification of the disease signs which are crucial to quickly preventing the spread NDV. Publication of that material is planned.
Harrison, L., Brown, C.C., Afonso, C.L., Zhang, J., Susta, L. 2011. Early occurrence of apoptosis in lymphoid tissues from chickens infected with strains of Newcastle disease virus of varying virulence. Journal of Comparative Pathology. 145:327-335.