Isolation and molecular characterization of Brazilian turkey reovirus from immunosuppressed young poults

Abstract

In this study, we investigated turkey reovirus (TReoV) in tissue samples from young birds, aged 15 days. RT-PCR for TReoV detected 3.3 % positive samples and TReoV was successfully isolated in Vero cells. Histological analysis of positive bursa of Fabricius (BF) revealed atrophied follicles and lymphocyte depletion. The number of CD8+, CD4+ and IgM+ cells was lower in infected BF. Phylogenetic analysis based on S3 gene showed that the Brazilian TReoV isolates clustered in a single group with 98-100 % similarity to TReoV strains circulating in the United States. This is the first indication that TReoV infection may be a contributing factor to immunosuppression in young birds.

Fig. 1

Evaluation of TReoV isolated from bursa of Fabricius (BF). A Vero cells infected with a BF suspension prepared from healthy poults (control group). B-D Cytopathic effects were observed as rounded adherent cells (B), fusion (C), and the generation of giant multinucleated and enlarged cells (D). Magnification, 40×; bar, 20 μm

Fig. 2

Phylogenetic relationship of avian and turkey reoviruses based on the δ 2 amino acid sequences detected in commercial poults with immunosuppression. The sequences names are expressed as GenBank accession numbers; sequences starting with KC are from the present study. The Brazilian strains are marked with red boxes. The tree was constructed using the neighbor-joining method with Kimura’s two-parameter correction, and bootstrap values are shown

Fig. 3

Quantification of CD4+, CD8+ and IgM+ cells using immunofluorescence assay. A CD4+ lymphocytes. B CD8+ lymphocytes (40×). C Quantification of lymphocyte subpopulations performed by AxionVision 4.8 software grid counts of positive cells in control and infected poults. Means ± standard deviations with a * superscript differ significantly (P < 0.05)