Characterization of interleukin-1β mRNA expression in chicken macrophages in response to avian reovirus

Abstract

Inhibitors of viral disassembly or RNA and protein synthesis, viral disassembly intermediates (infectious subviral particles, ISVP), binary ethylenimine-inactivated virions, and viral particles lacking genomic double-stranded (ds) RNA (empty particles) were used to assess the expression of interleukin-1b (IL-1b) mRNA in chicken (chIL-1b) macrophages in response to avian reovirus. The results demonstrate that two distinct expression patterns of chIL-1b mRNA mediated by different steps in viral replication were found. Viral disassembly was required for the induction of a rapid, transient expression pattern of chIL-1b mRNA that was rapidly induced at 30 min, with maximal levels reached by 2 h, and fell to a low level within 6 h post-inoculation, while viral RNA synthesis rather than protein translation, which was subsequent to membrane penetration, was required to induce a stable, sustained expression pattern of chIL-1b mRNA that occurred at and after 6 h post-inoculation. In addition, the induction of chIL-1b mRNA expression by the empty particles and ISVP was extremely weak, compared with the active dsRNA + virions or binary ethylenimine-inactivated virions, suggesting that the presence of dsRNA, even if transcriptionally inactive, may be an important factor in this response. INTRODUCTIONAvian reovirus (ARV) has a genome consisting of 10 segments of double-stranded RNA (dsRNA), which is encapsidated by a double-shell capsid (Spandidos & Graham, 1976). The virus encodes at least 13 primary translation products; eight of them are structural components and the other five are non-structural proteins (Varela & Benavente, 1994;Bodelon et al., 2001;Shmulevitz et al., 2002;Touris-Otero et al., 2004). Viruses have been isolated frequently from the gastrointestinal and respiratory tracts of chickens with a variety of disease conditions (Rosenberger, 2003). Among them, viral arthritis and pale bird syndrome are the most commonly recognized diseases in poultry.It has been demonstrated that the expression and release of pro-inflammatory cytokines, such as interleukin-1 (IL-1) and type I interferons, is a primary antiviral response in virus-infected cells (Jacobs & Langland, 1996;Iordanov et al., 2001;Maggi et al., 2003). In mammals, IL-1, which exhibits a broad spectrum of activities, has been extensively studied. It is a low molecular mass protein produced by many different cell types, but with stimulated macrophages being the main producers (Dinarello, 2000). IL-1 is an important factor in the pathogenesis of many diseases and in the mediation of a host response to infections through inflammatory and immunological events (Dinarello, 2000). IL-1b is a member of the IL-1 family (Burger et al., 2006). The primary translation product of the IL-1b gene is converted into a mature protein of approximately 17 kDa by the IL-1b converting enzyme, a proteinase that belongs to the caspase family of proteases (Nicholson & Thomberry, 1997). It is not glycosylated in spite of a number of potential N-glycosylation sites being present in it...

Application of chicken microarrays for gene expression analysis in other avian species

“…These genes include IL-1β, MHC class II alpha chain and the defensin gene GAL4. These genes have been previously shown to be involved in a chicken's response to infection [16] and thus it is plausible that these genes play a similar role in ducks. Interestingly the sequence similarity of IL-1β in ducks and chicken is 99% and it has recently been shown to be structurally and functionally homologous [17-19].…”

Characterization of Host Responses against a Recombinant Fowlpox Virus-Vectored Vaccine Expressing the Hemagglutinin Antigen of an Avian Influenza Virus

“…The upregulation of these genes indicates the ability of FPV to elicit proinflammatory responses leading to the recruitment and activation of adaptive immune system cells. IL-1␤ and IL-8 both are proinflammatory cytokines whose function has been studied in the chicken (61,62). The expression of both cytokines is enhanced following infection with certain viruses, such as reovirus and infectious bursal disease virus (27,28,61).…”

Autophagy induced by avian reovirus enhances viral replication in chickens at the early stage of infection

“…Autophagy can be stimulated by ARV infection and plays a positive role in ARV replication [8, 14]; then, activated autophagy contributes to the biogenesis and secretion of IL-1β [17]. Consequently, more immune cells are recruited and can be infected [22–24] and carry ARV into the circulatory system.…”