Ancestral SARS-CoV-2, but not Omicron, replicates less efficiently in primary pediatric nasal epithelial cells.

Children typically experience more mild symptoms of Coronavirus Disease 2019 (COVID-19) when compared to adults. There is a strong body of evidence that children are also less susceptible to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection with the ancestral viral isolate. However, the emergence of SARS-CoV-2 variants of concern (VOCs) has been associated with an increased number of pediatric infections. Whether this is the result of widespread adult vaccination or fundamental changes in the biology of SARS-CoV-2 remain to be determined. Here, we use primary nasal epithelial cells (NECs) from children and adults, differentiated at an air-liquid interface to show that the ancestral SARS-CoV-2 replicates to significantly lower titers in the NECs of children compared to those of adults. This was associated with a heightened antiviral response to SARS-CoV-2 in the NECs of children. Importantly, the Delta variant also replicated to significantly lower titers in the NECs of children. This trend was markedly less pronounced in the case of Omicron. It is also striking to note that, at least in terms of viral RNA, Omicron replicated better in pediatric NECs compared to both Delta and the ancestral virus. Taken together, these data show that the nasal epithelium of children supports lower infection and replication of ancestral SARS-CoV-2, although this may be changing as the virus evolves.

A delicate balancing act: immunity and immunopathology in human H7N9 influenza virus infections.

PURPOSE OF REVIEW: A delicate balance exists between a protective and detrimental immune response to an invading viral pathogen. Here, we review the latest advancements in our understanding of immunity and immunopathology during H7N9 influenza A virus (IAV) infections and its relevance to disease management and diagnosis. RECENT FINDINGS: Recent studies have highlighted the role of specific leukocytes in the pathogenesis of H7N9 IAV infections and potential diagnostic role that host cytokine profiles can play in forecasting disease severity. Furthermore, alterations in diet have emerged as a possible preventive measure for severe IAV infections. SUMMARY: The recent emergence and continued evolution of H7N9 IAVs have emphasized the threat that these avian viruses pose to human health. Understanding the role of the host immune response in both disease protection and pathogenesis is an essential first step in the creation of novel therapeutic and preventive measures for H7N9 IAV infections.

Lyssavirus in Indian Flying Foxes, Sri Lanka.

A novel lyssavirus was isolated from brains of Indian flying foxes (Pteropus medius) in Sri Lanka. Phylogenetic analysis of complete virus genome sequences, and geographic location and host species, provides strong evidence that this virus is a putative new lyssavirus species, designated as Gannoruwa bat lyssavirus.

The swan genome and transcriptome, it is not all black and white.

BACKGROUND: The Australian black swan (Cygnus atratus) is an iconic species with contrasting plumage to that of the closely related northern hemisphere white swans. The relative geographic isolation of the black swan may have resulted in a limited immune repertoire and increased susceptibility to infectious diseases, notably infectious diseases from which Australia has been largely shielded. Unlike mallard ducks and the mute swan (Cygnus olor), the black swan is extremely sensitive to highly pathogenic avian influenza. Understanding this susceptibility has been impaired by the absence of any available swan genome and transcriptome information. RESULTS: Here, we generate the first chromosome-length black and mute swan genomes annotated with transcriptome data, all using long-read based pipelines generated for vertebrate species. We use these genomes and transcriptomes to show that unlike other wild waterfowl, black swans lack an expanded immune gene repertoire, lack a key viral pattern-recognition receptor in endothelial cells and mount a poorly controlled inflammatory response to highly pathogenic avian influenza. We also implicate genetic differences in SLC45A2 gene in the iconic plumage of the black swan. CONCLUSION: Together, these data suggest that the immune system of the black swan is such that should any avian viral infection become established in its native habitat, the black swan would be in a significant peril.

Limited evidence for the role of environmental factors in the unusual peak of influenza in Brisbane during the 2018-2019 Australian summer.

OBJECTIVE: To explore the contribution of environmental factors in the unusual pattern of influenza activity observed in Brisbane, Australia during the summer of 2018-2019. METHODS: Distributed lag nonlinear models (DLNMs) were used to estimate the effect of environmental factors on weekly influenza incidence in Brisbane. Next generation sequencing was then employed to analyze minor and majority variants in influenza strains isolated from Brisbane children during this period. RESULTS: There were limited marked differences in the environmental factors observed in Brisbane between the 2018-2019 summer period and the same period of the proceeding years, with the exception of significant reduction in rainfall. DLNM showed that reduced rainfall in Brisbane (at levels consistent with the 2018-2019 period) correlated with a dramatic increase in the relative risk of influenza. Sulfur dioxide (SO2) levels were also increased in the 2018-2019 period, although these levels did not correlate with an increased risk of influenza. Sequencing of a limited number of pediatric influenza virus strains isolated during the 2018-2019 showed numerous mutations within the viral HA. CONCLUSIONS: Taken together, these data suggest a limited role for key environmental factors in the influenza activity observed in Brisbane, Australia during the summer of 2018-2019. One alternative explanation may that viral factors, in addition to other factors not studied herein, contributed to the unusual influenza season. Our findings provide fundamental information that may be beneficial to a better understanding of the seasonal trends of influenza virus.

Primary Chicken and Duck Endothelial Cells Display a Differential Response to Infection with Highly Pathogenic Avian Influenza Virus.

Highly pathogenic avian influenza viruses (HPAIVs) in gallinaceous poultry are associated with viral infection of the endothelium, the induction of a 'cytokine storm, and severe disease. In contrast, in Pekin ducks, HPAIVs are rarely endothelial tropic, and a cytokine storm is not observed. To date, understanding these species-dependent differences in pathogenesis has been hampered by the absence of a pure culture of duck and chicken endothelial cells. Here, we use our recently established in vitro cultures of duck and chicken aortic endothelial cells to investigate species-dependent differences in the response of endothelial cells to HPAIV H5N1 infection. We demonstrate that chicken and duck endothelial cells display a different transcriptional response to HPAI H5N1 infection in vitro-with chickens displaying a more pro-inflammatory response to infection. As similar observations were recorded following in vitro stimulation with the viral mimetic polyI:C, these findings were not specific to an HPAIV H5N1 infection. However, similar species-dependent differences in the transcriptional response to polyI:C were not observed in avian fibroblasts. Taken together, these data demonstrate that chicken and duck endothelial cells display a different response to HPAIV H5N1 infection, and this may help account for the species-dependent differences observed in inflammation in vivo.

A paucigranulocytic asthma host environment promotes the emergence of virulent influenza viral variants.

Influenza virus has a high mutation rate, such that within one host different viral variants can emerge. Evidence suggests that influenza virus variants are more prevalent in pregnant and/or obese individuals due to their impaired interferon response. We have recently shown that the non-allergic, paucigranulocytic subtype of asthma is associated with impaired type I interferon production. Here, we seek to address if this is associated with an increased emergence of influenza virus variants. Compared to controls, mice with paucigranulocytic asthma had increased disease severity and an increased emergence of influenza virus variants. Specifically, PB1 mutations exclusively detected in asthmatic mice were associated with increased polymerase activity. Furthermore, asthmatic host-derived virus led to increased disease severity in wild-type mice. Taken together, these data suggest that at least a subset of patients with asthma may be more susceptible to severe influenza and may be a possible source of new influenza virus variants.

Toxocara pteropodis in Free-Ranging Indian Flying Foxes (Pteropus medius) in Sri Lanka.

Toxocara pteropodis, an intestinal nematode, occurs in several captive and free-ranging pteropid bat species. We report infection in free-ranging Indian flying foxes (Pteropus medius) in Sri Lanka and contribute to our understanding of parasites in free-ranging P. medius .

Calodium hepaticum in Jungle Cats ( Felis chaus ) in Sri Lanka.

Calodium hepaticum infection is rarely reported in carnivores. We describe two cases of C. hepaticum infection, causing liver lesions, in wild jungle cats ( Felis chaus ) in Sri Lanka.