RESUMO
Since 2001, strains of porcine parvovirus (PPV), designated 27a-like strains, were observed in Europe, suggesting a predominance of these viruses over older strains. The reasons for the obvious evolutionary advantage are unknown. Here, a series of mutants containing amino acid replacements found in the predominant field strains were generated in a PPV-NADL2 background, and their impact on replication efficiency and antibody binding activity was determined. Some amino acid substitutions observed in the 27a-like strains significantly increased viral fitness and decreased neutralization activity of serum samples raised against commercial vaccines and old virus strains (e.g., NADL2). These mutant viruses and a monoclonal antibody raised against a classical PPV strain defined a 27a-specific neutralizing epitope around amino acid 228 of the capsid protein VP2. Based on the analysis of the mutant viruses, it is hypothesized that the predominant factor for the global spread of the PPV-27a strain substitutions is an increased viral fitness of the 27a-like viruses, possibly supported by partial immune selection. This is reminiscent to the evolution of canine parvovirus and worldwide replacement of the original virus by the so-called new antigenic types. IMPORTANCE Porcine parvovirus is one of the most important causes of reproductive failure in swine. Recently, despite the continuous use of vaccines, "new" strains emerged, leading to the hypothesis that the emergence of new amino acid substitutions could be a viral adaptation to the immune response against the commercial vaccines. Our results indicate the amino acid substitutions observed in the 27a-like strains can modify viral fitness and antigenicity. However, an absolute immune escape was not evident.
Assuntos
Proteínas do Capsídeo/genética , Parvovirus Suíno/fisiologia , Substituição de Aminoácidos , Animais , Anticorpos Monoclonais/imunologia , Anticorpos Antivirais/imunologia , Proteínas do Capsídeo/química , Proteínas do Capsídeo/imunologia , Células Cultivadas , Epitopos/genética , Epitopos/imunologia , Modelos Moleculares , Testes de Neutralização , Parvovirus Suíno/genética , Parvovirus Suíno/imunologia , Suínos , Replicação ViralRESUMO
Porcine parvovirus (PPV) is a DNA virus that causes reproductive failure in gilts and sows, resulting in embryonic and fetal losses worldwide. Epitope mapping of PPV is important for developing new vaccines. In this study, we used spot synthesis analysis for epitope mapping of the capsid proteins of PPV (NADL-2 strain) and correlated the findings with predictive data from immunoinformatics. The virus was exposed to three conditions prior to inoculation in pigs: native (untreated), high hydrostatic pressure (350 MPa for 1 h) at room temperature and high hydrostatic pressure (350 MPa for 1 h) at - 18 °C, and was compared with a commercial vaccine produced using inactivated PPV. The screening of serum samples detected 44 positive spots corresponding to 20 antigenic sites. Each type of inoculated antigen elicited a distinct epitope set. In silico prediction located linear and discontinuous epitopes in B cells that coincided with several epitopes detected in spot synthesis of sera from pigs that received different preparations of inoculum. The conditions tested elicited antibodies against the VP1/VP2 antigen that differed in relation to the response time and the profile of structurally available regions that were recognized.
Assuntos
Anticorpos Antivirais/sangue , Antígenos Virais/imunologia , Proteínas do Capsídeo/imunologia , Epitopos/imunologia , Parvovirus Suíno/imunologia , Animais , Antígenos Virais/química , Mapeamento de Epitopos , Epitopos/química , Masculino , Testes de Neutralização , Peptídeos/genética , Peptídeos/imunologia , SuínosRESUMO
To estimate the impact of porcine parvovirus (PPV) vaccines on the emergence of new phenotypes, the population dynamic history of the virus was calculated using the Bayesian Markov chain Monte Carlo method with a Bayesian skyline coalescent model. Additionally, an in vitro model was performed with consecutive passages of the 'Challenge' strain (a virulent field strain) and NADL2 strain (a vaccine strain) in a PK-15 cell line supplemented with polyclonal antibodies raised against the vaccine strain. A decrease in genetic diversity was observed in the presence of antibodies in vitro or after vaccination (as estimated by the in silico model). We hypothesized that the antibodies induced a selective pressure that may reduce the incidence of neutral selection, which should play a major role in the emergence of new mutations. In this scenario, vaccine failures and non-vaccinated populations (e.g. wild boars) may have an important impact in the emergence of new phenotypes.
Assuntos
Variação Genética , Parvovirus Suíno/classificação , Parvovirus Suíno/genética , Dinâmica Populacional , Animais , Anticorpos Antivirais/imunologia , DNA Viral/química , DNA Viral/genética , Modelos Estatísticos , Dados de Sequência Molecular , Parvovirus Suíno/imunologia , Parvovirus Suíno/isolamento & purificação , Seleção Genética , Análise de Sequência de DNA , SuínosRESUMO
The aim of this study was to evaluate Porcine parvovirus (PPV) and Porcine circovirus 2 (PCV2) infection in dams and their offspring and the role of antibody protection on these infections. Sera were collected from gilts and sows by venipuncture and from umbilical cord of newborn pre-suckle piglets for the detection of PCV2 and PPV antibodies by immunoperoxidase monolayer and haemmaglutination inhibition assays, respectively. Gilts and sows sera were submitted to viral detection by PCR, as well as heart, lung, tonsil and lymph nodes samples from stillborn and mummified fetuses. High antibody titers before artificial insemination (AI) (>5.120 and >2.560 UHA for PCV2 and PPV, respectively), were found associated with viremia and fetal exposure for both PCV2 and PPV, respectively, in gilts and sows, regardless of pregnancy stage. These infections resulted in litters with mummified, stillborn, as well as seropositive and viable newborns. These findings bring new evidence about the lack of antibody protection against PCV2 and PPV infections in dams, indicating that more studies are necessary about the role of humoral response against both pathogens.