Progress 02/15/11 to 02/14/14
Outputs
Target Audience:Poultry producers are the primary target audience for this project. Improved control of infectious laryngotracheitis, a severe avian repiratory disease, will improve animal health, food safety, and productivity. Changes/Problems:The initial step to be used in this project was to identify naturally occuring field isolates of ILTV that had reduced pathogenicity. Although several ILTV field isolates were identified for study, none of them proved to be reduced in pathogenicity when compared to currently used ILTV vaccines. However, researchers have reported that ILTV vaccines may be composed of virus mixtures (as determined by PCR-RFLP). As an alternative method to identify novel vaccine strains, attempts were made to identify less pathogenic strains of ILTV from currently used vaccines. This process was successful. Two promising vaccine ILTV candidates have been identified from a commercially available ILTV vaccine. Although the vaccine is moderately pathogenic, these two strains are significantly less pathogenic, while still retaining the ability to provide protection from a virulant challenge. What opportunities for training and professional development has the project provided?This project has been instrumental in the training of both undergarduate students and graduate students. Emily Taylor received her training support for her M.S. degree from this grant. Natalie Fogarty was an undergarduate student who obtained summer funding during her pursuit of a Degree with Distrinction through this grant. Both individuals are now attending veterinary school. How have the results been disseminated to communities of interest?Results from this project have been disseminated at three scientific meetings: the 23rd Annual Convention of the AVMA (Chicago, IL) in 2013, the 2014 Annual Convention of the AVMA (new orleans, LA) in 2014, and the 10th International Symposium on Marek's Disease and Avian herpesviruses (East Lansing, MI) in 2014. Keeler, C.L., Jr. and C.M. Boettger (2014) Characterizing chicken-embryo-origin (CEO) strains of infectious laryngotracheitis virus exhibiting reduced pathogenicity. 2014 Annual Convention of the AVMA, Denver, CO C.M. Boettger and C. L. Keeler, Jr. (2014) A commercial ILTV CEO vaccine is composed of a mixed population of viruses exhibiting differences in pathogenicity and sequence. 10th International Symposium on Marek's Disease and Avian Herpesviruses, East Lansing, MI, p. 64 2nd Lohman & K. A. Schat Scientific Award - 3rd place C.L. Keeler, Jr. and C.M. Boettger (2014) Rapid sequencing of infectious laryngotracheitis virus. 10th International Symposium on Marek's Disease and Avian Herpesviruses, East Lansing, MI, p. 82 Keeler, C.L., Jr., R. White, J.K. Rosenberger and C.M. Boettger (2013) Rapid sequencing of a field isolate of infectious laryngotracheitis virus. 2013 Annual Convention of the AVMA, Chicago, IL What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Objective 1: Identify and evaluate strains of infectious laryngotracheitis virus (ILTV) for use in broilers as attenuated live vaccines. Criteria were developed for screening potential strains of ILTV as vaccine candidates. The criteria require that the strain be isolated from a field case where ILT has been confirmed by histopathology, where the flock was not vaccinated for ILT, and that flock mortality be less than 1 per 1000. Several ILTV vaccine candidate strains were identified. However, all strains tested were as pathogenic as currently used live attenuate vaccines. Previous work (PCR-RFLP analysis) has shown that currently used chicken-embryo-origin (CEO) vaccines may be composed of different virus subpopulations that differ in their genotype (sequence). A modified limit dilution procedure was utilized to partially purify 5 independent "pock-purified" CEO vaccine derivatives. Two of these derivatives are significantly less pathogenic than the parent CEO vaccine and still protect birds from a virulent challenge, making them potential vaccine candidates. All five isolates differ in sequence from the published CEO vaccine sequence. However, they still are composed of virus mixtures. Objective 2: Develop the next generation of recombinant live-attenuated infectious laryngotracheitis vaccines. Using DNA from a vaccine strain of ILTV approximately half of the clones required for an ILTV cosmid library have been identified LMH cell lines expressing the ILTV VP16 and ICP4 proteins have been created. These cell lines will be used in the reconstitution of ILTV virus from a pool of cosmid clones.
Publications
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Progress 02/15/11 to 02/14/12
Outputs
OUTPUTS: Infectious laryngotracheitis (ILT) is an infectious disease with severe consequences for the poultry industry. Growers typically vaccinate for this disease only in the face of an acute outbreak because a) current chicken-embryo-origin (CEO) vaccines are considered too pathogenic and cannot be easily distinguished from field strains of the virus b) CEO vaccines are thought to become more virulent upon use in the field and c) tissue-culture-origin (TCO) vaccines do not provide adequate protection. Objective 1: Identify and evaluate strains of infectious laryngotracheitis virus (ILTV) for use in broilers. Evaluate these strains under field conditions and make them available to the boiler industry by the completion of this project. We are using a combination of traditional (virus isolation, purification, and characterization) and contemporary (next generation sequencing) methods to identify, characterize, and evaluate new ILTV strains that are less pathogenic than current CEO vaccines and that can be used by the broiler industry. Objective 2: Develop the next generation of recombinant live-attenuated infectious laryngotracheitis vaccines. The handful of currently available ILTV mutants have been created using in vivo recombination methods. This method of generating recombinants is challenging since ILTV grows only in primary avian embryonic hepatocytes, an avian hepatocyte cell line (LMH) or primary avian kidney cells. The use of BACs (bacterial artificial chromosomes) and cosmids to create mutants has proven successful with other herpesviruses such as human cytomegalovirus. We are developing BAC and fosmid technologies for the rapid construction of recombinant ILTV viruses. PARTICIPANTS: Individuals - Cynthia Boettger, Research Associate, University of Delaware TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Objective 1: Identify and evaluate strains of infectious laryngotracheitis virus (ILTV) for use in broilers. Evaluate these strains under field conditions and make them available to the boiler industry by the completion of this project. We have developed criteria for screening potential strains of ILTV as vaccine candidates. This includes field cases where ILT has been confirmed by histopathology, the flock was not vaccinated for ILT, and flock mortality was less than 1 per 1000. Several candidate strains have been identified. One strain (627) has been successfully grown in eggs. This isolate will be tested for pathogenicity. Objective 2: Develop the next generation of recombinant live-attenuated infectious laryngotracheitis vaccines. Using DNA from a vaccine strain of ILTV approximately half of the required cosmid clones have been constructed. Experiments are underway to create LMH cell lines expressing the ILTV VP16 and ICP4 proteins. These cell lines will be used in the reconstitution of ILTV virus from a pool of cosmid clones.
Publications
- No publications reported this period
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