Abstract
Porcine circovirus type 2 (PCV2) is the essential infectious agent for PCV2-systemic disease (PCV2-SD, formerly known as postweaning multisystemic wasting syndrome) and other pathological conditions. Recent studies indicated antigenic variability amongst different PCV2 isolates and suggested that single amino acid changes within the capsid protein determine differences in the level of neutralization by specific monoclonal antibodies. The objective of the present study was to examine the cross-reactivity of PCV2 antibodies induced in the context of a natural infection against different PCV2 isolates belonging to genotypes PCV2a and PCV2b. Sera taken from several farms from animals of varying health status (PCV2-SD and age-matched healthy pigs and a set of slaughter-aged animals) were assayed for neutralizing activity against four PCV2 isolates from both predominant genotypes (PCV2a and PCV2b) and of differing geographic origins (Europe and North-America). Results showed that most of studied pigs (79 out of 82) contained neutralizing antibodies (NA) able to neutralize all four studied viral strains. Overall, pigs had significantly higher NA titres against PCV2a than against PCV2b (P < 0.001). Accordingly, studied serums were able to better neutralize Burgos390L4 and Stoon-1010 strains (PCV2a) than L-33-Sp-10-54 and MO/S-06 strains (PCV2b) (P < 0.001). No differences between capabilities of seroneutralization of viruses from different geographic origin were observed. Present data suggests that sequence differences between PCV2 isolates translate to functional antigenic differences in viral neutralization in vivo.
Highlights
Porcine circoviruses (PCV) are small non-enveloped, single-stranded DNA viruses within the Circoviridae family
Higher identity was observed between L-33-Sp-10-54 and MO/S-06 (% nucleic acid/ amino acid identity: 99/99) followed between Burgos390L4 and Stoon-1010 (96/97), the first two belonging to genotype PCV2b and the last two to genotype PCV2a
The present study attempted to investigate the role that sequence variability amongst PCV type 2 (PCV2) isolates from different origins and genotypes may play in their ability to be neutralized, giving a further role for antigenic variation in the immune response to PCV2
Summary
Porcine circoviruses (PCV) are small non-enveloped, single-stranded DNA viruses within the Circoviridae family. Within this family, there are two types of PCV, PCV type 1 (PCV1) and PCV type 2 (PCV2). PCV1 was firstly identified as a non-cytopathic contaminant of the porcine kidney cell line PK-15, but it does not apparently cause disease in swine [1,2]. Animals suffering from PCV2-SD demonstrate clinical signs of wasting or decreased weight gain, as well as anaemia, diarrhoea and/or respiratory distress [7]. Due to increased mortality rates and the impact on weight gain, PCV2-SD has a serious economic impact on the swine production industry
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