ABSTRACT
Porcine circovirus-2 (PCV2) is the etiologic agent of several diseases in pigs, including multi-systemic wasting syndrome (PMWS). In this work, a new mutant PCV2b was isolated from PMWS-affected pigs on a Brazilian farm. Its genome showed high sequence similarity (>99% identity) to those from a group of emerging mutants isolated from cases of PMWS outbreaks in vaccinated pigs in China, the USA and South Korea. Here, we show that these isolates share a combination of low-frequency substitutions (single amino acid polymorphisms with a frequency of ≤25%) in the viral capsid protein, mainly in regions of immunoprotective epitopes, and an additional lysine residue at position 234. These isolates were phylogenetically grouped in the PCV2b clade, reinforcing the idea of the emergence of a new group of mutants PCV2b associated with outbreaks worldwide. The identification of these polymorphisms in the viral capsid highlights the importance of considering these isolates for the development of more-effective vaccines.
Subject(s)
Amino Acid Substitution , Capsid Proteins/genetics , Circoviridae Infections/veterinary , Circovirus/genetics , Epitopes/genetics , Porcine Postweaning Multisystemic Wasting Syndrome/virology , Amino Acid Sequence , Animals , Brazil , Capsid Proteins/chemistry , Capsid Proteins/immunology , Circoviridae Infections/virology , Circovirus/classification , Circovirus/immunology , Circovirus/isolation & purification , Epitopes/chemistry , Epitopes/immunology , Molecular Sequence Data , Phylogeny , Polymorphism, Single Nucleotide , SwineABSTRACT
Three porcine circovirus-2 strains were isolated from pigs on a Brazilian farm during an outbreak, indicating a vaccine failure. They present identical genomic sequences, with high identities to other isolates that were also related to vaccination failures, supporting the recent theory about an antigen drift being associated with vaccine failures throughout the world.
