No abstract

In mammals, Mda5 and RIG-I are members of the evolutionary conserved RIG-like helicase family that play critical roles in the outcome of RNA virus infections. Resolving influenza infection in mammals has been shown to require RIG-I; however, the apparent absence of a RIG-I homolog in chickens raises intriguing questions regarding how this species deals with influenza virus infection. Although chickens are able to resolve certain strains of influenza, they are highly susceptible to others, such as highly pathogenic avian influenza H5N1. Understanding RIG-like helicases in the chicken is of critical importance, especially for developing new therapeutics that may use these systems. With this in mind, we investigated the RIG-like helicase Mda5 in the chicken. We have identified a chicken Mda5 homolog (ChMda5) and assessed its functional activities that relate to antiviral responses. Like mammalian Mda5, ChMda5 expression is upregulated in response to dsRNA stimulation and following IFN activation of cells. Furthermore, RNA interference-mediated knockdown of ChMda5 showed that ChMda5 plays an important role in the IFN response of chicken cells to dsRNA. Intriguingly, although ChMda5 levels are highly upregulated during influenza infection, knockdown of ChMda5 expression does not appear to impact influenza proliferation. Collectively, although Mda5 is functionally active in the chicken, the absence of an apparent RIG-I–like function may contribute to the chicken’s susceptibility to highly pathogenic influenza.

In the pursuit of improved diagnostic tests for infectious diseases, several classes of molecules have been scrutinized as prospective biomarkers. Small (18-22 nucleotide), non-coding RNA transcripts called microRNAs (miRNAs) have emerged as promising candidates with extensive diagnostic potential, due to their role in numerous diseases, previously established methods for quantitation and their stability within biofluids. Despite efforts to identify, characterize and apply miRNA signatures as diagnostic markers in a range of non-infectious diseases, their application in infectious disease has advanced relatively slowly. Here, we outline the benefits that miRNA biomarkers offer to the diagnosis, management, and treatment of infectious diseases. Investigation of these novel biomarkers could advance the use of personalized medicine in infectious disease treatment, which raises important considerations for validating their use as diagnostic or prognostic markers. Finally, we discuss new and emerging miRNA detection platforms, with a focus on rapid, point-of-care testing, to evaluate the benefits and obstacles of miRNA biomarkers for infectious disease.

Hendra and Nipah viruses (genus Henipavirus, family Paramyxoviridae) are highly pathogenic bat-borne viruses. The need for high biocontainment when studying henipaviruses has hindered the development of therapeutics and knowledge of the viral infection cycle. We have performed a genome-wide siRNA screen at biosafety level 4 that identified 585 human proteins required for henipavirus infection. The host protein with the largest impact was fibrillarin, a nucleolar methyltransferase that was also required by measles, mumps and respiratory syncytial viruses for infection. While not required for cell entry, henipavirus RNA and protein syntheses were greatly impaired in cells lacking fibrillarin, indicating a crucial role in the RNA replication phase of infection. During infection, the Hendra virus matrix protein co-localized with fibrillarin in cell nucleoli, and co-associated as a complex in pulldown studies, while its nuclear import was unaffected in fibrillarin-depleted cells. Mutagenesis studies showed that the methyltransferase activity of fibrillarin was required for henipavirus infection, suggesting that this enzyme could be targeted therapeutically to combat henipavirus infections.

The recent European Union ban on the prophylactic use of in-feed antibiotics has escalated the search for alternatives for use within the poultry industry. When evaluating the efficacy of potential antibiotic alternatives on bird health and productivity, it is important to analyze the competence of the immune cells in the gut-associated lymphoid tissue (GALT), because it is routinely involved in the surveillance of colonizing microbes as well as in interacting with the ingested feed antigens. Therefore, we studied the effect of the prebiotics mannan-oligosaccharide (MOS) and fructo-oligosaccharide (FOS) on the phenotypic and functional competence of immune cells in cecal tonsil (CT), which is a major GALT. Day-old Cobb 500 male broilers were randomized to 4 groups. Control chickens were fed the basal diet only. Chickens in experimental groups received 0.05 g/kg zinc bacitracin or 5 g/kg of either FOS or MOS in addition to basal diet. At the end of 25 d, our comparison of the experimental groups with controls revealed that the addition of prebiotics to diet resulted in a significant reduction in the proportion of B cells and in mitogen responsiveness of lymphocytes in CT. Furthermore, FOS treatment significantly enhanced the IgM and IgG antibody titers in plasma. These findings emphasize the need for the analyses of the gut immune function following treatment with novel feed additives. The knowledge obtained from such analyses may aid in understanding the mechanisms underlying the immune competence of the birds, which needs consideration when selecting and optimizing new feed additives instead of antibiotics for poultry production.

No abstract

Understanding the molecular basis of drug resistance and utilising this information to overcome chemoresistance remains a key challenge in oncology. Here we report that survivin, a key protein implicated in drug resistance, is overexpressed in cancer stem cell pool of doxorubicin-resistant breast cancer cells. Moreover, by utilising an active targeting system consisting of an RNA aptamer targeted against the epithelial cell adhesion molecule and a Dicer substrate survivin siRNA, we could deliver a high dose of the siRNA to cancer stem cells in xenograft tumours. Importantly, silencing of survivin with this aptamer-siRNA chimera in cancer stem cell population led to the reversal of chemoresistance, such that combined treatment with low dose of doxorubicin inhibited stemness, eliminated cancer stem cells via apoptosis, suppressed tumour growth, and prolonged survival in mice bearing chemoresistant tumours. This strategy for in vivo cancer stem cell targeting has wide application for future effective silencing of anti-death genes and in fact any dysregulated genes involved in chemoresistance and tumour relapse.

c Hendra virus is a highly pathogenic zoonotic paramyxovirus in the genus Henipavirus. Thirty-nine outbreaks of Hendra virus have been reported since its initial identification in Queensland, Australia, resulting in seven human infections and four fatalities. Little is known about cellular host factors impacting Hendra virus replication. In this work, we demonstrate that Hendra virus makes use of a microRNA (miRNA) designated miR-146a, an NF-B-responsive miRNA upregulated by several innate immune ligands, to favor its replication. miR-146a is elevated in the blood of ferrets and horses infected with Hendra virus and is upregulated by Hendra virus in human cells in vitro. Blocking miR-146a reduces Hendra virus replication in vitro, suggesting a role for this miRNA in Hendra virus replication. In silico analysis of miR-146a targets identified ring finger protein (RNF)11, a member of the A20 ubiquitin editing complex that negatively regulates NF-B activity, as a novel component of Hendra virus replication. RNA interference-mediated silencing of RNF11 promotes Hendra virus replication in vitro, suggesting that increased NF-B activity aids Hendra virus replication. Furthermore, overexpression of the IB superrepressor inhibits Hendra virus replication. These studies are the first to demonstrate a host miRNA response to Hendra virus infection and suggest an important role for host miRNAs in Hendra virus disease.