RESUMO
The widespread perception of the effectiveness of applying tests based on the detection of antibodies against foot-and-mouth disease (FMD) viral non-capsid proteins (NCPs) to assess virus circulation irrespective of vaccination triggered the demand for international standards to evaluate the comparative performance of the upcoming assays against the OIE Index test developed at the Pan American Foot-and-Mouth Disease Center, PAHO/WHO. To this end, a panel was developed composed of 34 cattle sera from animals with an unambiguous exposed/infected status, covering serotypes O, A and C, obtained either under experimental conditions or from the field in regions with different epidemiological situations. Reference values in the Index test and their reproducibility in other laboratories, data on stability as well as results in four other commercial kits and one in house test were obtained. The characteristics of the panel which comprise adequate preparation following international guidelines, a broad range of antibody reactivity, proper stability and the ability to assess comparative diagnostic sensitivity, make it suitable as a reference standard to evaluate if tests equivalent to the OIE Index method are used in support of FMD control programs and by trading partners, and also whether they maintain their standards of diagnostic performance.
Assuntos
Anticorpos Antivirais/sangue , Doenças dos Bovinos/imunologia , Vírus da Febre Aftosa/imunologia , Febre Aftosa/imunologia , Imunoensaio/normas , Imunoensaio/veterinária , Proteínas não Estruturais Virais/imunologia , Animais , Bovinos , Doenças dos Bovinos/diagnóstico , Doenças dos Bovinos/virologia , Febre Aftosa/diagnóstico , Febre Aftosa/virologia , Vírus da Febre Aftosa/classificação , Kit de Reagentes para Diagnóstico , Padrões de Referência , Reprodutibilidade dos Testes , VacinaçãoRESUMO
Foot-and-mouth disease virus (FMDV), by nature of its RNA genome, possesses a high rate of mutation during replication. This results in extensive genetic polymorphism of virus populations in nature. The emergence of FMDV variants during replication has been reported. Genetic changes in the viral capsid protein (VP1) gene can result in amino acid changes affecting the immunodominant epitopes of FMDV. The genetic heterogeneity of FMDV in the field and the antigenic variants observed after cell culture isolation has been investigated by PCR sequencing and reactivity with monoclonal antibodies. These methods were applied to viruses causing two different outbreaks of FMD before and after replication in cell culture and in the animal host. The VP1 region of the genome was amplified by PCR and sequenced to reveal variant sequences identified after passage and to determine their presence in the original field tissue. In one case, reactivity with monoclonal antibodies was lost after passage as a result of an amino acid change in the subpopulation. These findings suggest that host cells can select specific virus genetic and antigenic subpopulations during virus isolation and propagation.
Assuntos
Antígenos Virais/genética , Aphthovirus/genética , Capsídeo/genética , Febre Aftosa/microbiologia , Variação Genética/genética , Sequência de Aminoácidos , Animais , Antígenos Virais/análise , Aphthovirus/isolamento & purificação , Aphthovirus/fisiologia , Sequência de Bases , Brasil/epidemiologia , Capsídeo/análise , Proteínas do Capsídeo , Bovinos , Surtos de Doenças/veterinária , Epitélio/microbiologia , Febre Aftosa/epidemiologia , Itália/epidemiologia , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , RNA Viral/análise , Análise de Sequência de DNA , Suínos , Cultura de Vírus , Replicação Viral/genéticaRESUMO
The antigenic sites A and C (the G-H loop and the C terminus, respectively) in VP1 of foot-and-mouth disease virus (FMDV) have been considered the immunodominant regions of the virus involved in the induction of protection. Other antigenic sites have been described but their involvement in protection has not been established. Here we report that two closely related but serologically different FMDVs (the field isolate C3 Argentina/84 and the vaccine strain C3 Resende Br/55) have identical A and C sites but differ as other antigenic sites. Such differences have been documented by reactivity with a panel of 28 monoclonal antibodies (MAbs). The two viruses reacted to the same extent with each of 13 MAbs which recognized epitopes within sites A or C, but reacted differently with six out of 15 MAbs that recognized other sites. Accordingly, sequencing of the entire region coding for the capsid proteins, for both viruses, revealed four amino acid substitutions at three antigenic sites other than A and C. The results suggest that identity of sites A and C may not be sufficient to induce cross-protection, and provide the first evidence of significant antigenic diversification of FMDV in the field mediated by amino acid substitutions outside sites A or C.