MOLECULAR CHARACTERIZATION OF THE ATTENUATED DUCK HEPATITIS VIRUS STRAINS USED AS VACCINE IN VIETNAM BASED ON THE ANTIGENIC SEQUENCE OF VPl

Abstract

The entire sequence of 714 bp responsible for coding ofthe  antigenic VPl  gene from two attenuated duck hepatitis viras sttains used as vaccine in Vietnam, designated as VxXT and VxAC (from  Egypt), was obtained using RT-PCR,  then  cloned,  sequenced  and  analyzed. Nucleotide  and  amino  acid  sequences  from  these  two sttains were aligned with the VPl  sequence collected from  12 sttains (vaccine and vimlent) of China, and other countries.  As  resuhs,  the  VxAC  strain,  although  from  Egypt,  has  high  identity  (nucleotide)  and  homology (amino  acid) to  the  current  sttains  in  China;  the  VxXT  sttain  has  identity/homology  to  the  HS  (Korea)  and

DRL62 (ATCC, USA). Phylogenetic analysis revealed that all the sttains smdied fall into 4 groups: I, II, III, IV, among which 3 groups contains the Chinese sttains (groups I, III, IV); and one group (II) includes the Korean HS and the American DRL62. The VxAC used in Vietnam was clustered with those in group I of China origin (vaccine and viralent); and the VxXT is placed  into group II with the HS (Korea) and DRL62  (USA) sttains. Genetic and phylogenetic analyses confirmed that the VxAC having close genetic relation to the Chinese group I is infered  as to be originated  from  China. The VxXT belonging to the group of the Korean HS and DRL62 (USA) strains indicates that this vaccine strain used in Vietaam might be imported from  Korea, hence  before, however, the attenuated vaccine strains in Korea may be originated from the United States.