Study On Molecular Genetic Variation Of N,M And S1 Genes Of 8 Nephrotropic IBV Isolates From Shannxi Province

Infectious bronchitis (IB) is an acute, highly contagious viral respiratory disease of chickens characterized by tracheal rales, coughing, and sneezing. Initially, IB was recognized primarily as a disease of young chicks; however, it was observed to be common in semimature and laying flocks. Infectious bronchitis is of major economic importance because it causes poor weight gain and feed efficiency with often being a component of mixed infections that produce airsacculitis that may result in condemnations at processing of broiler, and being a cause of egg-production and egg-quality declines. The highly transmissible nature of the disease, and the occurrence of multiple serotypes of infectious bronchitis virus(IBV) have sophisticated and increased the cost of attempts to prevent the disease by immunization. Avian infectious bronchitis virus (IBV) is a member of the genus Coronavirus of the family Coronariyidae. IBV virion contains three major virus-specific proteins: the spike (S) glycoproteins, the membrane (M) glycoproteins and the internal nucleocapsid (N) protein. The S protein comprises two glycopolypeptides, S1 and S2. Hemagglutination-inhibiting(HI) antibodies are induced by S1. RNA genome of IBV comprises 27 600 nucleotides, the whole of which have been cloned and sequenced.In the 1960s and 1970s, several serotypes distinct from the well-known mass serotype were described in United States and Australia. Since then, extensive surveys in Asia and Europe have revealed many new serotypes of IBV. Recent year, IBV isolates exhibit tropisms for the kidneys in China, and the major IBV isolates are variant nephrotropic strains, which make it very difficult to vaccination.The study on the pathogenicity and the molecular biological character of nephrotropic field strains ,especially the study of the molecular variety mechanism of major virus-specific gene N,M and S1, will promote study on the IB immunoprevention.The following studies of nephrotropic IBV isolates were carried out:1. A systemic analysis and isolation and identification of the epidemiology of IBV in Shaanxi province within 2003--2005. 18 field virus strains were isolated from 20 sick young chick flocks where respiratory disease broke out. It was confirmed that 13 field virus strains were infectious bronchitis virus(IBV) by epidemiology and clinic symptom of infected chicks, inoculation of chicken embryos, hemagglutination test, inhibition test to NDV,electronscopic observation, animal infection test, anti-acid and anti-alkali test. The test of pathogenicity on 3-5 week-old chickens, viruse neutralizing and EID50 test with chicken embryos indicated that...