Detection of Genetic Variation in the VP2 Gene of Vaccine and Field Strains of Infectious Bursal Disease Viruses

Abstract

Reverse transcription - polymerase chain reaction of the VP2 gene followed by restriction endonuclease analysis was used to detect genetic variation among 25 strains of both field and vaccine strains of infectious bursal disease virus (IBDV) in Taiwan. Restriction fragment profiles generated by Taql, Sspl, Sacl, Nael, Hinfl, BstEII and Maelll showed variation between strains. The IBDV strains were placed into four molecular groups. Group 1 consisted of 3 subgroups. Subgroup 1A (6 strains) consisted of serotype II strains, classic serotype I strains, variant strains and one vaccine strain. Subgroups 1B and 1C consisted of 2 and 5 vaccine strains, respectively. Group 2 contained 2 vaccine strains. Group 3A contained 7 Taiwanese strains of very virulent IBDV (vvIBDV), while a Japanese vvlBDV strain was assigned to group 3B. Group 4 contained a Taiwanese vvlBDV strain and an Israeli vaccine strain (MB). A phylogenetic study indicated that Taiwanese vvlBDV strains are very similar to French and Japanese vvlBDV strains. It is concluded that hypervariable region of the VP2 of vvlBDVs and an attenuated derivative are different from classic strains, variant strains , and attenuated strains derived from classic strains.