ABSTRACT
Epidemiological studies have shown that a single-nucleotide polymorphism in the equid herpesvirus type 1 DNA polymerase gene is associated with outbreaks of highly lethal neurological disease in horses. Reverse genetics experiments further demonstrated that a G(2254) A(2254) nucleotide mutation introduced in neurovirulent strain Ab4, which resulted in an asparagine for aspartic acid substitution (D(752) N(752)), rendered the virus nonneurovirulent in the equine. Here, we report that the nonneurovirulent strain equid herpesvirus type 1 strain NY03 caused lethal neurological disease in horses after mutation of A(2254) G(2254) (N(752) D(752)), thereby providing final proof that the D(752) allele in the viral DNA polymerase is necessary and sufficient for expression of the lethal neurovirulent phenotype in the natural host. Although virus shedding was comparable between the N(752) and D(752) variants, infection with the latter was accompanied by efficient establishment of prolonged cell-associated viremia in peripheral blood mononuclear cells and neurological disease in 2 of 6 animals.
Subject(s)
DNA-Directed DNA Polymerase/genetics , Herpesvirus 1, Equid/genetics , Horse Diseases/mortality , Horse Diseases/virology , Polymorphism, Single Nucleotide , Animals , Antiviral Agents/therapeutic use , Aphidicolin/therapeutic use , DNA, Viral/blood , DNA, Viral/genetics , Genetic Variation , Herpesviridae Infections/drug therapy , Herpesviridae Infections/mortality , Herpesvirus 1, Equid/pathogenicity , Horses , Microbial Sensitivity Tests , Virus SheddingABSTRACT
BACKGROUND: Cichlid fishes, particularly tilapias, are an important source of animal protein in tropical countries around the world. To support selective breeding of these species we are constructing genetic and physical maps of the tilapia genome. Physical maps linking collections of BAC clones are a critical resource for both positional cloning and assembly of whole genome sequences. RESULTS: We constructed a genome-wide physical map of the tilapia genome by restriction fingerprinting 35,245 bacterial artificial chromosome (BAC) clones using high-resolution capillary polyacrylamide gel electrophoresis. The map consists of 3,621 contigs and is estimated to span 1.752 Gb in physical length. An independent analysis of the marker content of four contigs demonstrates the reliability of the assembly. CONCLUSION: This physical map is a powerful tool for accelerating genomic studies in cichlid fishes, including comparative mapping among fish species, long-range assembly of genomic shotgun sequences, and the positional cloning of genes underlying important phenotypic traits. The tilapia BAC fingerprint database is freely available at http://hcgs.unh.edu/fpc/image.php.
