M E S '9 8 - University of Georgia College of Veterinary Medicine

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PoultryGeorgia’s poultry industry dominated the state’s animal agricultural dollars withmore than $2.5 billion in annual revenue in 1996. The state’s poultry industry iscontinuing to expand as broiler production in Georgia increased from 20.6million per week in 1995 to 22.2 million per week in 1996. The urbanization ofnorthern Georgia is causing the broiler expansion to occur primarily in the state’ssouthern section. Because of the intensive management system, poultryproducers emphasize disease prevention. VMES scientists have responded toindustry demands by developing vaccines to prevent infectious diseases. Theyare also helping to improve poultry health by developing inexpensive, rapid, andaccurate methods for disease diagnosis. Although the primary poultry healthconcerns are respiratory diseases, recent efforts have been initiated to controltype J avian leukosis virus, a major cause of the tumor, myeloblastosis.Researchers are also focusing on the reduction of potential human pathogens onpoultry products nationwide.Increasing Resistance to Marek’s Diseasevia Immune ModulationDiagnostics for Avian Enteric CoronavirusInfections in Commercial Poultry6The overall objectives of this project are toestablish the importance of natural killer (NK)cell-like activity in the innate ability of chickensto resist Marek’s disease virus (MDV)infection and to then determine whether modulationof this natural immunity (NK cell activity)could be used as part of Marek’s diseaseprevention programs.We have assessed NK-like activity ofchickens having haplotypes reported to confereither resistance, N-2a chickens (B13), or sensitivity,P-2a chickens (B21), to MDV. Theresults from cytotoxicity assays indicate N-2achickens have greater killing capabilities byNK cells than the P-2a chickens. The N-2achickens displayed greater killing at one, two,and three weeks of age, with the increasebecoming significant by the third week. Wehave also compared NK activities in two commerciallines of broilers: Arbor Acres line andPerdue line. Between these two broiler lineswe found the Perdue birds to have significantlyhigher natural cytotoxic ability. Studies wereperformed to assess the efficacy of possibleimmune modulators on susceptibility toMarek’s disease. NK cell activity was assayedat day 7 postvirus challenge (day 14 postmodulation).Surviving birds were euthanized, andnecropsy with histopathology was performedat six weeks for determination of disease susceptibility,organ involvement, and severity ofdisease. In the broiler line (Arbor Acres), theimmunomodulator significantly increased theNK-like cytotoxic activity. Comparison ofimmunomodulated birds with birds thatreceived only virus suggests that theimmunomodulator may be a protective factoragainst Marek’s disease in this broiler line.Denise I. Bounous, Steven E. Poet, William L.Ragland, Mark A. Goodwindbounous@calc.vet.uga.eduVirus neutralizing polyclonal antibodieswere developed in rabbits using multipleimmunizations of adjuvant plus purified cellculture-origin sucrose gradient purified avianenteric coronavirus (AEC). The antibodieswere used to develop 1) an indirect immunofluorescentantibody detection system (IFA)for either AEC or anti-AEC antibody afterinfection; 2) fluorescent detection of AEC infrozen tissue sections; and 3) immunohistochemicaldetection of AEC in formalin-fixedtissue sections. The IFA system was adapted to96 well microtiter plates to increase throughput.The latter antibody technique is currentlybeing used as part of the eradication plan todetect flocks naturally infected with AEC, sothey can be eliminated to prevent spread toother poultry farms. Bovine enteric coronaviruswas found to infect commercial turkeys.Infection of poultry with this virus leads toconfusion in AEC eradication programs. Wehave developed seven monoclonal antibodies(Mabs) against AEC surface proteins. TheseMabs are being used in the IFA test to differentiateAEC infection from bovine coronavirus(BCV) infection in cell cultures and birds.Genes coding for the S surface viral proteinof multiple AEC isolates have beensequenced and primer sets constructed to identifythese genes. Polymerase chain reaction(PCR) assays have been developed based onthese primers. These PCR primers and additionalprimer sets are currently being investigatedfor in situ use as probes for AEC. Inaddition, sequences coding for AEC viral proteinS are being cloned into vectors for productionof vaccinal quantities of this viral proteinfor test immunization.Thomas P. Brown, Doris D’Souza, Laura Kelly,AnaPatricia Garciatbrown@arches.uga.edu
Differential Diagnosis of InfectiousLaryngotracheitis Viruses by PCRInfectious Laryngotracheitis is a severeacute respiratory disease of chickens caused byInfectious Laryngotracheitis Virus (ILTV), amember of the family Alphaherpesviridiae.During 1994-1995, ILT outbreaks were reportedin Georgia, Alabama, Arkansas, andDelaware. These outbreaks caused severefinancial losses to the poultry industry. Themajor obstacle against the effective control andprevention of the disease is the inability toclearly and easily determine the source of outbreaks.Therefore, discrimination of ILTVstrains of different pathogenicity, and particularlyof field isolates from vaccine strains, is amajor necessity. The main objective of thisproject is to develop a polymerase chain reaction(PCR) test capable of distinguishingamong ILTV strains circulating in the field.We have identified restriction enzyme site differencesin the gE gene, and the upstreamregion of the ICP4 gene. Digestion of PCRproducts with specific enzymes, deduced fromthe sequence data obtained during this year’sproject, has allowed us to characterize fieldisolates as either “chicken embryo origin(CEO) like,” or “tissue culture origin (TCO)like” vaccine strains. Most importantly, wehave identified restriction enzymes that producerestriction fragment length polymorphism(RFLP) patterns unique to some of the fieldisolates analyzed. These indicate that specificmutations are acquired by field isolates atthese particular areas of the genome, for example,digestion of PCR products of the sevenfield isolates with enzymes DdeI, MnLI,and Ple.Maricarmen Garcíamcgarcia@arches.uga.eduprocess of producing a recombinant chickenbeta-defensin.Recombinant peptides will be used tocharacterize the complete spectrum of antimicrobialactivity against avian pathogens.Moreover, development of resistance to theseendogenous antibiotics by pathogenic bacteriacan be studied using recombinant defensins.Ultimately, it may be possible to manipulatethis endogenous defense system to enhancedisease resistance in poultry.Barry G. Harmon and Mark W. Jackwoodharmonb@calc.vet.uga.eduRecombinant Vaccines for InfectiousBronchitis VirusThe main objective of this proposal is todevelop a recombinant vaccine for infectiousbronchitis virus (IBV). A plasmid expressionvector that works in an avian cell line is beingused to express the immunogenic spike glycoproteinof IBV. The expressed protein is beingcharacterized and tested for its suitability as asubunit vaccine in chickens. In addition, anewly redesigned nucleic acid vaccine for IBV,which provides higher expression of the IBVspike glycoprotein, was tested and found to beefficacious when given to young chickens byintramuscular injection at 1 and 14 days ofage. We are currently examining the immuneresponse generated by that vaccine, as well astesting for its suitability when given in ovo.Mark W. Jackwoodmjackwoo@arches.uga.eduAntimicrobial Peptides in Broiler ChickensAntimicrobial peptides are important componentsof innate disease resistance in vertebrateand invertebrate animals. These peptidesarm phagocytic leukocytes and mucosalepithelial cells of the gastrointestinal and respiratorytract with a broad spectrum of antimicrobialactivity and serve as the first line ofdefense against microbial pathogens. Recently,we discovered the cDNA sequences for twochicken and two turkey heterophil antimicrobialpeptides, referred to as betadefensins.We will now attempt to sequencethe genes that encode the avian defensins andthen study the regulation and expression ofthese genes. We have cloned the cDNAsequences for a chicken peptide and are in theVictoria Leiting works on DNA fingerprinting of Mycoplasma organisms.7
Page 3 and 4: VM E S ‘98Veterinary Medical Expe
Page 7: DNA VaccinesEver since Dr. Edward J
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Page 15 and 16: Cattle and Other RuminantsCattle, s
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Page 21 and 22: WildlifeGeorgia’s wildlife habita
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Page 33 and 34: Selected PublicationsAllen, S.W., C
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Page 37 and 38: Quist, C.F., Howerth, E.W., Bounous

M E S '9 8 - University of Georgia College of Veterinary Medicine

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