Detection of Clade 2.3.4.4b Avian Influenza A(H5N8) Virus in Cambodia, 2021.

In late 2021, highly pathogenic avian influenza A(H5N8) clade 2.3.4.4b viruses were detected in domestic ducks in poultry markets in Cambodia. Surveillance, biosafety, and biosecurity efforts should be bolstered along the poultry value chain to limit spread and infection risk at the animal-human interface.

Correction: ADAMTS5 Is a Critical Regulator of Virus-Specific T Cell Immunity.

[This corrects the article DOI: 10.1371/journal.pbio.1002580.].

ADAMTS5 Is a Critical Regulator of Virus-Specific T Cell Immunity.

The extracellular matrix (ECM) provides physical scaffolding for cellular constituents and initiates biochemical and biomechanical cues that are required for physiological activity of living tissues. The ECM enzyme ADAMTS5, a member of the ADAMTS (A Disintegrin-like and Metalloproteinase with Thrombospondin-1 motifs) protein family, cleaves large proteoglycans such as aggrecan, leading to the destruction of cartilage and osteoarthritis. However, its contribution to viral pathogenesis and immunity is currently undefined. Here, we use a combination of in vitro and in vivo models to show that ADAMTS5 enzymatic activity plays a key role in the development of influenza-specific immunity. Influenza virus infection of Adamts5-/- mice resulted in delayed virus clearance, compromised T cell migration and immunity and accumulation of versican, an ADAMTS5 proteoglycan substrate. Our research emphasises the importance of ADAMTS5 expression in the control of influenza virus infection and highlights the potential for development of ADAMTS5-based therapeutic strategies to reduce morbidity and mortality.

miRNA modulation of SOCS1 using an influenza A virus delivery system.

Difficulties associated with efficient delivery and targeting of miRNAs to cells is hampering the real world application of miRNA technology. This study utilized an influenza A-based delivery system to express miR-155 in order to knockdown SOCS1 mRNA. Using qPCR and dual luciferase technology we show that miR-155 delivery resulted in a significant increase in cellular miR-155 which facilitated a downregulation of SOCS1 gene expression and a functional increase in IL-6 and IFN-ß cytokines.

Promotion of Hendra virus replication by microRNA 146a.

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-κB-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-κB 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-κB activity aids Hendra virus replication. Furthermore, overexpression of the IκB 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.

Analysis of acidified feed components containing African swine fever virus.

Mitigation of African swine fever (ASF) virus in contaminated feed materials would assist control activities. Various finely-ground pig feed ingredients (5 cereals, 4 plant proteins, 2 animal proteins, 1 oil, 1 compound) were sprayed and mixed thoroughly with a buffered formic acid formulation (0, 1 or 2% vol/vol) to produce a consistent and durable level of formate (1% or 2%) with consistent acidification of cereal ingredients to less than pH 4. No such acidification was noted in other ingredients. Selected representative feed ingredients were further mixed with infectious ASF virus (106 TCID50) or media alone and incubated for 0, 6, 12, 24, 48, 72 or 168 h. The residual ASF virus at each timepoint was quantified using qPCR and a cell culture based TCID50 assay to determine survivability. Maize, rice bran and compound feed (with or without formate) all reduced infectious ASF virus to levels below the detection threshold of the cell culture assay (101.3 TCID50/mL). A consistent reduction in ASF virus DNA levels was observed by qPCR assay when maize containing ASF virus was mixed with 1% or 2% buffered formic acid. This reduction in viral DNA corresponded to the acidifying pH effect measured. No such reduction in ASF virus DNA levels was noted in non-cereal ingredients containing ASF virus, in which the pH had not been lowered below pH 4 following treatment. Interestingly, residual ASF virus levels in spiked meat/bone meal were greater than control levels, suggesting a buffering effect of that feed ingredient.

In vitro characterisation of SARS-CoV-2 and susceptibility of domestic ferrets (Mustela putorius furo).

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is an emerging virus that has caused significant human morbidity and mortality since its detection in late 2019. With the rapid emergence has come an unprecedented programme of vaccine development with at least 300 candidates under development. Ferrets have proven to be an appropriate animal model for testing safety and efficacy of SARS-CoV-2 vaccines due to quantifiable virus shedding in nasal washes and oral swabs. Here, we outline our efforts early in the SARS-CoV-2 outbreak to propagate and characterize an Australian isolate of the virus in vitro and in an ex vivo model of human airway epithelium, as well as to demonstrate the susceptibility of domestic ferrets (Mustela putorius furo) to SARS-CoV-2 infection following intranasal challenge.

First probable Australian cases of human infection with Rickettsia felis (cat-flea typhus).

Human infection with Rickettsia felis has been reported in most parts of the world, and R. felis has recently been confirmed in cat fleas in Western Australia. The clinical presentations of R. typhi and R. felis are similar, and in the past, the incidence of R. felis infection may have been underestimated. We describe the first reported cases of probable human R. felis infection in Australia. Two adults and three children in Victoria contracted a rickettsial disease after exposure to fleas from kittens. Molecular testing of fleas demonstrated the presence of R. felis but not R. typhi.

Isolation of a novel Orientia species (O. chuto sp. nov.) from a patient infected in Dubai.

In July 2006, an Australian tourist returning from Dubai, in the United Arab Emirates (UAE), developed acute scrub typhus. Her signs and symptoms included fever, myalgia, headache, rash, and eschar. Orientia tsutsugamushi serology demonstrated a 4-fold rise in antibody titers in paired serum collections (1:512 to 1:8,192), with the sera reacting strongest against the Gilliam strain antigen. An Orientia species was isolated by the in vitro culture of the patient's acute blood taken prior to antibiotic treatment. The gene sequencing of the 16S rRNA gene (rrs), partial 56-kDa gene, and the full open reading frame 47-kDa gene was performed, and comparisons of this new Orientia sp. isolate to previously characterized strains demonstrated significant sequence diversity. The closest homology to the rrs sequence of the new Orientia sp. isolate was with three strains of O. tsutsugamushi (Ikeda, Kato, and Karp), with a nucleotide sequence similarity of 98.5%. The closest homology to the 47-kDa gene sequence was with O. tsutsugamushi strain Gilliam, with a nucleotide similarity of 82.3%, while the closest homology to the 56-kDa gene sequence was with O. tsutsugamushi strain TA686, with a nucleotide similarity of 53.1%. The molecular divergence and geographically unique origin lead us to believe that this organism should be considered a novel species. Therefore, we have proposed the name "Orientia chuto," and the prototype strain of this species is strain Dubai, named after the location in which the patient was infected.

Novel rickettsia in ticks, Tasmania, Australia.

A novel rickettsia was detected in Ixodes tasmani ticks collected from Tasmanian devils. A total of 55% were positive for the citrate synthase gene by quantitative PCR. According to current criteria for rickettsia speciation, this new rickettsia qualifies as Candidatus Rickettsia tasmanensis, named after the location of its detection.