Caracterização molecular do vírus Melao cepas BE AR 633512 e BE AR 8033 (Bunyaviridae, Orthobunyavirus) e infecção experimental em hamsters dourados (Mesocricetus auratus)

Abstract

The Melao Virus (MELV) strains, BE AR 8033 e BE AR 633512 were isolated from lots of Ochlerotatus (Ochlerotatus) scapularis mosquitoes, in Belém- PA (1955) and Alta Floresta do Oeste- RO (2000), Brazil, respectively. The aim of this study was to carry out molecular characterization of the MELV strains BE AR 633512 and BE AR 8033 and to describe the histopathologic, biochemistry and immunological changes in golden hamsters (Mesocricetus auratus). Hamsters showed susceptibility to these MELV strains. The viremia produced in hamsters by BE AR 633512 strain occurred between 3 and 6 days post-infection (dpi.), and for the BE AR 8033 occurred only in the 2nd dpi. Neutralizing antibodies for both strains were initially detected on the 5th dpi. and remained up to the 30 dpi. The biochemistry markers AST, ALT and blood urea nitrogen showed values statistically significants among inoculated animals with both VMEL strains, while creatinine value it was only altered by BE AR 633512 strain. Histopathologic changes were observed in the central nervous system, liver, kidney, and spleen of the hamsters, and infection was confirmed by immunohistochemical assay in all them. Strain BE AR 633512 caused more intense tissue damage showing increases virulence and pathogenicity than BE AR 8033 strain. The genetic analysis of the N, Gn and Gc genes revealed that for N and Gn genes, the BE AR 8033 and prototype strain (TRVL 9375) are genetically more closed related, and for the Gc gene, the BE AR 8033 and BE AR 633512 strains are more related. BE AR 633512 strain showed increased genetic variability, mainly in the Gn gene, were several aminoacid changes were observed, but the Gc mutations should be responsible for the increased virulence for hamsters.