ABSTRACT
Porcine circovirus type 2 (PCV2) belongs to the family Circoviridae, and is the causative agent of post-weaning multisystemic wasting syndrome (PMWS) in pigs. In this study, phylogenetic analyses of three complete PCV2 genomic sequences from Hong Kong suggest that natural recombination happened among different lineages of PCV2. A preliminary investigation of the parental strains of these potential recombinants was carried out using bootscanning. Statistical significance of this recombination event was tested and positions of the potential recombination breakpoints were estimated in a maximum-likelihood framework. The recombinant breakpoints were estimated to be located within the origin of replication (ori) and replicase (rep) gene of PCV2. Interestingly, several GenBank sequences of PCV2 in mainland China were found to have a recombination pattern similar to that of the potential PCV2 recombinants from Hong Kong, implying that this recombinant genotype might already be widespread within mainland China.
Subject(s)
Circovirus/genetics , Genome, Viral , Recombination, Genetic , Animals , Base Sequence , China , Circoviridae , Circoviridae Infections/veterinary , Circoviridae Infections/virology , Circovirus/isolation & purification , DNA, Viral/chemistry , DNA, Viral/genetics , Hong Kong , Molecular Epidemiology , Molecular Sequence Data , Phylogeny , Sequence Analysis, DNA , Sequence Homology , Swine , Swine Diseases/virologyABSTRACT
Tissue culture adaptation of infectious bursal disease virus (IBDV) results in alternation of three residues on its major capsid protein VP2 and these residues may engage in receptor binding. Although the key of successful infection of tissue culture adapted IBDV in tissue cultures was defined as the virus entering steps, mechanism of the adaptation is poorly understood. In this study, recombinant VP2s of an attenuated strain (D78) and a very virulent strain (HK46) of IBDV tagged with rabbit immunoglobulin G heavy chain were expressed in mammalian cells, generating RAVP2 and RVVP2, respectively, in high purity. Using flow cytometry, both RAVP2 and RVVP2 were demonstrated to bind with Vero cells while these bindings were blocked by D78 viral particles, implying both very virulent IBDVs (vvIBDVs) and attenuated IBDVs bind to Vero cells through the same receptor(s). Since vvIBDVs cannot be propagated directly in tissue cultures, the specific binding between RVVP2 and Vero cells suggests the barrier for tissue culture adaptation may be beyond the virus attachment process.
