Arch Virol (2000) 145: 291–300
Relationship between serotypes and genotypes
based on the hypervariable region of the S1 gene
of infectious bronchitis virus
C.-H. Wang and Y.-C. Huang
Department of Veterinary Medicine, National Taiwan University, Taiwan
Accepted August 31, 1999
Summary. To group infectious bronchitis virus (IBV) isolates, a genetic grouping
method based on hypervariable region 1 (HVR 1, nucleotides 168 to 197) was
compared with that based on the whole S1 gene. Both methods resulted in the
same grouping data. So the grouping method based on HVR 1 could represent the
grouping method based on the whole S1 gene. Taiwan isolates could not be placed
within the existing groups. In order to test the correlation between genotype and
serotype, a one-way neutralization test was used to compare 9 Taiwan isolates
selected from different genotypes with Massachusetts (Mass) (H120) and Con-
necticut (Conn) standard strains. In addition, a two-way cross-neutralization test
was performed in embryonated eggs with the ␤ method (constant-virus, diluted-
serum) and the reciprocal neutralization titers were calculated to give the relat-
edness (r) values. The results of two kinds of neutralizing tests showed that the
serotypes of 9 isolates were different from Mass or Conn. Based on the r-values,
9 isolates were divided into two serotypes which were correlated with their geno-
types. From pathogenicity tests, IBV Taiwan isolates could be divided into high,
intermediate, and low pathogenicity according to their pathogenicity indexes.
However, no relationship exists between pathotype and genotype. In conclusion,
the genetic typing method based on HVR 1 can be used for typing IBV isolates.
Infectious bronchitis virus (IBV) causes a highly contagious disease in chickens.
Various IBV isolates have been identiﬁed in different parts of the world .
The major IBVs isolated in Taiwan are mostly nephrotropic strains . The
infected chickens show signs of depression, dehydration, polyuria and death, and
their kidneys are swollen with severe urate deposition. Outbreaks of IB occur
frequently in spite of intensive vaccination. Infection with the ﬁeld viruses was
not prevented by the available vaccines, due to the serotype differences .