The complete genome sequence of a Chinese very virulent infectious bursal disease virus (vvIBDV) strain, Harbin-1, was determined. Based on the sequence analysis, the molecular characteristics and potential virulence determinants and origin of vvIBDV strains were identified. Phylogenetic analysis indicated that a reassortment and/or recombination event may have occurred in the emergence of Chinese vvIBDV strains.
"The phylogenies recovered by maximum likelihood and Bayesian analysis were congruent for all data sets analysed. When recombination is disregarded and all data included in analysis (Fig. 1) the phylogeny supports , in part, the findings of previous studies (Bais et al., 2003; Sun et al., 2003; Xia et al., 2008 "
[Show abstract][Hide abstract] ABSTRACT: Infectious bursal disease virus (IBDV) causes Gumboro disease, which is highly contagious and immunosuppressive in young chickens. A virulent form of IBDV reached South Africa in 1989 and to date there has been little molecular information available for this strain. In this study, the polyprotein coding region of the South African strain SA-KZN95 was sequenced and analysed along with 52 representative sequences of other serotype I and II strains. We explored the relative impact of recombination on phylogenetic reconstruction using a multidimensional scaling approach. Phylogenetic analyses consistently placed the South African isolate within the very virulent IBDV clade. Selection analyses were also conducted to identify evolutionarily relevant amino acid residues. Previously, 19 residues in the polyprotein were shown to be potentially diagnostic for the different IBDV pathotypes. This study identified an additional two unique residues in the polyprotein which may be used as genetic signatures in future viral identifications. Better strain identification would aid in the development and application of vaccines.
Infection, genetics and evolution: journal of molecular epidemiology and evolutionary genetics in infectious diseases 11/2013; 21. DOI:10.1016/j.meegid.2013.11.017 · 3.02 Impact Factor
"This is in accordance with the pathology and clinical signs of two distinctly virulent IBDV. Infection with vvIBDV results in lymphoid depletion, marked atrophy of the bursal tissues and high rates of mortality [33,34], but Ts strain infection does not cause obviously clinical signs . "
[Show abstract][Hide abstract] ABSTRACT: Cytokines are important mediators and regulators of host responses against foreign antigen, with their main function to orchestrate the functional activities of the cells of the immune system. However little is known about the role of cytokines in pathogenesis and immune responses caused by infectious bursa disease virus (IBDV). The aim of this study was to examine the transcripts of cell-mediated immune response-related cytokine genes in the bursal tissues of chickens infected with IBDVs of varying virulence to gain an understanding of pathological changes and mechanisms of immunosuppression caused by IBDV infection and the immune responses evoked.
Real-time quantitative PCR analysis revealed that the expression levels of both Th1 [interferon (IFN)-γ, interleukins (IL)-2 and IL-12p40] and Th2 (IL-4, IL-5, IL-13 and IL-10) cytokines were significantly up-regulated following challenge with the H strain (vvIBDV) and up to 2- and 30-fold, respectively (P < 0.05). Following infection with the Ts strain (cell-adapted virus) these cytokine transcripts were up-regulated at 5 days post-infection (dpi), 2- and 13-fold respectively (P < 0.05), while the expression levels of IL-2 and IL-4 were not significantly different (P > 0.05). A higher degree of cytokine expression was induced by the H strain compared with the Ts strain.
The results indicate that the expression of cell-mediated immune-related cytokine genes is strongly induced by IBDV, especially by the vvIBDV, H strain and reveal that these cytokines could play a crucial role in driving cellular immune responses during the acute phase of IBDV infection, and the cellular immune responses caused by IBDV of varying virulence are through different signaling pathways.
[Show abstract][Hide abstract] ABSTRACT: The complete genome sequence of infectious bursal disease virus (IBDV) YS07 strain with low mortality isolated from Guangdong province of China in 2007 was reported in this study. The genome sequences and deduced amino acid (aa) sequences of YS07 were compared with that of previously reported IBDV strains. Phylogenetic analyses based on the deduced aa sequences of VP5, polyprotein, and VP1 protein revealed that YS07 bears its origin from European very virulent (vv) IBDV strains. Multiple aa sequences alignment revealed that YS07 contained a diversified genetic composition being characteristic to vv, variant, classical, and attenuated IBDV strains as well as its own unique ones. Our findings suggest that IBDV strains in China may gradually experience adaptive evolution due to immune pressure from intensive vaccination and demonstrate that the determination and analysis of full genome sequences is a valuable tool for studying the relationship between genetic composition and pathogenicity of IBDV strains.
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