Análise da diversidade genética e evolução molecular de Infectious bursal disease virus (IBDV)

• Autor(a) principal: Silva, Fernanda Miquelitto Figueira da
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/306
• topic: Diversidade genética; IBDV; Genetic diversity; IBDV; CNPQ::CIENCIAS BIOLOGICAS::BIOFISICA::BIOFISICA MOLECULAR

Infectious bursal disease virus (IBDV) is considered one of the most important pathogens for chickens of the poultry industry. Considering the differences in levels of virulence among isolates of IBDV, this paper proposes a non-arbitrary genotyping definition and a unified nomenclature for the viral isolates of IBDV. In this approach, the sets of 96 VP2 and 561 hvVP2 sequences available in GenBank are analyzed and clustered by four different methods (UPGMA, Neighbor-joining, Maximum Likelihood and Bayesian inference). A threshold value of 0.032 of pairwise distance was selected to group the IBDV isolates in three genotypes: IBDV-1, IBDV-2, and IBDV-3. In addition, the fourth group containing unclassified hvVP2 sequences was defined as genotype IBDV-4. The present work contributes to the establishment of a genotype definition for IBDV and provides clear criteria for IBDV classification below the genus level. The hvVP2 sequences are a reliable phylogenetic marker for IBDV genotypes since it were able to reconstruct the same tree as the whole VP2 sequences. In this work, an evolutionary epidemiology of viral isolates of IBDV was assessed. First, the selective forces that operated during the diversification of IBDV were tested. Then, Bayesian Markov chain Monte Carlo (MCMC) coalescent analyses and phylogeographical approaches were selected to predict IBDV dispersion. Six VP1 (RNA-dependent RNA polymerase) complete sequences and 26 VP2 (outer capsid protein) complete sequences were produced in this study. The results showed that negative selection is the main evolutionary force that affects nucleotide diversity and rates of evolution of IBDV. In addition, phylogeographic analysis of VP2 suggests that IBDV isolates were introduced in Brazil by at least three events of viral introduction.