CONICET | Buscador de Institutos y Recursos Humanos

Bovine Viral diarrhoea virus (BVDV), a member of the Pestivirus genus of the Flaviviridae family, is an important worldwide cause of economic loss in cattle. The virus causes a variety of syndromes, including diarrhea, acute and chronic mucosal disease, immunosuppression, reproductive failures and subclinical or persistent infection. BVDV has been divided into two genotypes, designated type 1 and 2, on the basis of genome and antigenic differences. In Argentina, the prevalence of antibodies against the virus is around 70% and inactive vaccines are used to control de disease. These vaccines are generally based on some reference strains from genotype 1a, a few of them have genotype 2 but none of them contain 1b genotype. In this study, we investigated the genetic and antigenic variability of BVDV in recent Argentinean field isolates from Buenos Aires and other near states, which constitute the most important breeding area of the country. In order to determine the genetic diversity of the isolates, a phylogenetic analysis was performed. For that purpose, E2 protein was chosen for sequencing since it has been shown to be the main target of neutralising antibodies; and 5´Untranslated Region (UTR) was also sequenced because it is highly conserved amongst pestivirus and it is often used for genotyping. Briefly, viral RNA was extracted from 39 isolates by using Trizol Reagent and RT PCR was performed using random hexamers. Several primers were designed to amplify each E2 gene and 5´UTR region was amplified by using a set of primers described by Rossmanith et al, 2001. The sequences were aligned using ClustalX and boostraping values were calculated in the modules SEQBOOT, DNADIST, NEIGHBOUR and CONSENSE of the Phylip package. With the purpose of studying the antigenic variability among the isolates, several seroneutralization (SN) assays were performed with the isolates and reference sera. Results of the phylogenetic and SN analysis showed that there exist an important antigenic variability of BVDV in the geographic region studied and the topology of the phylogenetic trees constructed with E2 and 5´UTR were similar. Besides, it was determined that most of the isolates belonged to 1b genotype, which showed to be monophyletic but with too much antigenic variability. The circulation of type 1b and type 2 BVDV and the existence of viral populations which differ from the reference strains commonly used in vaccine elaboration should be considered by manufacturers of vaccines.

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