Abstract
BackgroundPorcine circovirus type 2 (PCV2) is a small single-stranded DNA virus and a primary cause of PCV-associated diseases (PCVAD) that result insubstantial economic loss for swine farms. Between 2016 and 2018, PCV2 field viruses were isolated from PCVAD-affected swine farms in South Korea and investigated for genetic and antigenic heterogeneity.ResultsThe genetic analysis of ORF2 showed that the genotype of the Korean PCV2 field isolates has been rapidly shifted from PCV2a or 2b to mutant PCV2b known as PCV2d with 82.6 to 100% amino acid sequence similarity. PCV2-specific monoclonal antibodies (mAbs) demonstrated variable antigen-binding activity to four representative Korean PCV2 field isolates [QIA215 (PCV2a), QIA418 (PCV2b), QIA169 (PCV2d), and QIA244 (PCV2d)] without genotype specificity, and one mAb showed neutralization activity to QIA215. In a cross-virus neutralization assay using anti-PCV2 sera of pigs and guinea pigs injected with a commercial vaccine and the Korean PCV2 field isolates, the anti-porcine sera of a commercial vaccine had high neutralization activity against QIA215 and QIA418 with statistically lower activity against PCV2d viruses. Anti-guinea pig sera of QIA215, QIA418, QIA169, and a commercial vaccine had high neutralization activity against all of the viruses with significantly lower activity against QIA244. Importantly, anti-guinea pig sera of QIA244 had high neutralization activity against all of the viruses.ConclusionsThis study confirmed genetic and antigenic diversity among recent PCV2 field isolates in Korean swine farms, and the strain-based difference in virus neutralization capability should be considered for more effective control by vaccination.
Highlights
Porcine circovirus type 2 (PCV2) is a small single-stranded DNA virus and a primary cause of PCVassociated diseases (PCVAD) that result insubstantial economic loss for swine farms
PCV2 infection is associated with various diseases, including porcine circovirus-associated disease (PCVAD), postweaning multi-systemic wasting syndrome (PMWS), porcine dermatitis and nephropathy syndrome (PDNS), and reproductive failure in pigs, especially when infected with porcine reproductive respiratory syndrome (PRRS) virus, porcine parvovirus (PPV), and mycoplasma, which lead to decreased production efficiency
Regarding the phylogenetic analysis based on ORF2 sequence (n = 164), all of the Korean isolates were classified into PCV2 field isolates [QIA215 (PCV2a) (n = 4), 2b (n = 29), and 2d (n = 131), with 2.4, 17.7, and 79.9% infection rates, respectively (Fig. 1a and b)
Summary
Porcine circovirus type 2 (PCV2) is a small single-stranded DNA virus and a primary cause of PCVassociated diseases (PCVAD) that result insubstantial economic loss for swine farms. Between 2016 and 2018, PCV2 field viruses were isolated from PCVAD-affected swine farms in South Korea and investigated for genetic and antigenic heterogeneity. Porcine circovirus type 2 (PCV2) causes severe economic loss in the swine industry worldwide. PCV2 infection is associated with various diseases, including porcine circovirus-associated disease (PCVAD), postweaning multi-systemic wasting syndrome (PMWS), porcine dermatitis and nephropathy syndrome (PDNS), and reproductive failure in pigs, especially when infected with porcine reproductive respiratory syndrome (PRRS) virus, porcine parvovirus (PPV), and mycoplasma, which lead to decreased production efficiency. PCV2 is a small, non-enveloped virus with a circular, single-stranded DNA genome, and it is comprised of two major proteins, ORF1 and ORF2. Based on ORF2 nucleotide sequences, the genotypes of PCV2 have been commonly classified as PCV2a, 2b, 2c, 2d, and 2e [2,3,4,5]
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