
Read the
magazine
story to find out more. Scientists
Crack Code of Virus That Causes Key Chicken DiseaseBy Jan Suszkiw July 27, 2001In a step towards creating new chicken
vaccines, Agricultural Research Servicescientists have cracked the biochemical code of the herpesvirus that causes
Mareks disease. Severe cases of Mareks can cause cancerlike tumors, partial paralysis
and other disorders in afflicted birds. Although vaccines made from benign or
disabled Mareks strains are commercially available, some are failing to
immunize the birds against virulent new forms of the virus that have emerged.
Bird deaths, diminished egg laying and carcass condemnation costs at processing
plants due to Mareks cause an estimated $1 billion annually worldwide,
and up to $100 million in the United States alone. In recently published studies, ARS researchers led an effort to chart the
nucleotide sequences for two Mareks disease strains--MDV1-Md5 vv and
MDV1-GA--and a non- disease-causing variant in turkeys called serotype 3, which
is used to vaccinate chickens. Nucleotides are chemical subunits whose
arrangement spells out the DNA alphabet for the viruss 100-plus genes. Now available on the GenBank database, Mareks nucleotide coding will
help speed the identification of viral genes and mechanisms by which the
pathogen survives in nature, evades a hosts immune system and causes
disease, according to Sanjay Reddy, a medical safety officer at ARS
Avian Disease and Oncology
Laboratory, East Lansing, Mich. There, Reddy and colleagues Lucy Lee, Robert Silva and Richard Witter are
using information gleaned from Mareks nucleotide coding to study the
genes it uses to produce tumors in chickens, as well as silence them.
Theyve also begun using gene- splicing techniques to design recombinant
vaccines to better protect chickens from GA and Md5 vv, as well as other
virulent Mareks disease strains. Both are tumor-causing members of a herpesvirus family that researchers
around the world have been studying for more than 20 years and--until now--only
partially decoded, notes Lee, a research chemist. A more detailed story about the work appears in this months issue of
Agricultural Researchmagazine. ARS is the U.S. Department of
Agricultures chief scientific research agency. U.S. Department of Agriculture |