Caracterização de pestivírus bovinos e avaliação de vacinas comerciais

Abstract

Bovine pestiviruses are important pathogens for cattle industry that produce productive and reproductive losses in several regions of the world. The genus Pestivirus belongs to the Flaviviridae family, and has three viral species that infect cattle: bovine viral diarrhea virus 1 (BVDV-1) - Pestivirus A, BVDV-2 - Pestivirus B and HoBi-like viruses (HoBiPeV) - Pestivirus H. These species are segregated into species and subgenotypes by comparing the conserved 5' untranslated region (5’UTR) of the genome. The virus RNA genome contributes to the occurrence of diversity, which can be demonstrated by the wide genetic and antigenic variability. Currently, BVDV-1 is allocated in 21 subgenotypes (1a-u), BVDV-2 has four (2a-d) and four subgenotypes are suggested for HoBiPeV (3a-d). Variability is a constraint for diagnosis, vaccine production, and control strategies. In a first study, is described the genetic and antigenic characterization of pestiviruses isolated from fetal bovine serum and infected animals. Of these, twelve samples were isolated, 10 out 12 were identified as BVDV-1 (four BVDV-1a and six BVDV-1b); and 2 out 12 compatibles with BVDV-2 (one BVDV-2b and one BVDV-2 undetermined subgenotype). The antigenic characterization performed with a panel of monoclonal antibodies confirmed antigenic variability in the isolates and divergence with laboratorial strains. These results demonstrate that there is genetic diversity and great antigenic variability among the isolates circulating in the herds. The second study evaluated the immunogenicity, in sheep, of four Uruguayan commercial vaccines for bovine alphaherpesvirus 1, 5 and bovine pestiviruses. Vaccine evaluation demonstrated a variable serological response in which only the G4 vaccine induced considerable levels of neutralizing antibodies to BoHV-1, 5, BVDV-1 and 2. The G3 vaccine stimulated response only to alphaherpesviruses, while G1 and G2 induced the production of neutralizing antibodies at low or undetectable levels. Thus, the results of this study demonstrate that these Uruguayan vaccines tested have little or no efficiency in the induction of neutralizing antibodies. In summary, the present study presents an overview of circulating pestivirus samples and the immunogenicity of Uruguayan commercial vaccines.