The tree shrew is a promising model for the study of influenza B virus infection

Identification and characterization of the tumor necrosis factor receptor superfamily in the Chinese tree shrew (Tupaia belangeri chinensis)

The tumor necrosis factor receptor superfamily (TNFRSF) plays a vital role in eliciting immune responses against infections. The tree shrew, closely related to primates, is often utilized in human disease models. Here, we analyzed TNFRSF members from 11 different animal species, including the Chinese tree shrew, and identified 24 tree shrew TNFRSF (tTNFRSF) genes, which were grouped into seven subcategories with similar motifs, sequences, and gene structures. As expected, the multi-species collinearity analysis revealed that tTNFRSF genome bears a greater resemblance to humans than to mice. Transcriptome data from 28 samples across ten organ types showed high TNFRSF expression predominantly in immune organs. It was seen that TNFRSF13C co-expresses consistently with the B cell surface marker CD79A, which is consistent with its characteristics in humans. The tissue distribution and co-expression were confirmed via RT-qPCR and immunofluorescence. Evaluation of transcriptome data from 70 samples infected with six types of viruses showed that most TNFRSF genes were upregulated in tree shrew post-viral infection. TNFRSF exerts antiviral function most probably through the activation of the NF-κB pathway, subsequently causing apoptosis of infected cells. Our findings provide evolutionary and functional insights into tTNFRSF, indicating its potential utility in human viral infection models.

Environmental stressors and zoonoses in the Arctic: Learning from the past to prepare for the future

The risk of zoonotic disease transmission from animals to humans is elevated for people in close contact with domestic and wild animals. About three-quarters of all known human infectious diseases are zoonotic, and potential health impacts of these diseases are higher where infectious disease surveillance and access to health care and public health services are limited. This is especially the case for remote circumarctic regions, where drivers for endemic, emerging, and re-emerging zoonotic diseases include anthropogenic influences, such as pollution by long-range transport of industrial chemicals, climate change, loss of biodiversity and ecosystem alterations. In addition to these, indirect effects including natural changes in food web dynamics, appearance of invasive species and thawing permafrost also affect the risk of zoonotic disease spill-over. In other words, the Arctic represents a changing world where pollution, loss of biodiversity and habitat, and maritime activity are likely driving forward occurrence of infectious diseases. As a broad international consortium with a wide range of expertise, we here describe a selection of case studies highlighting the importance of a One Health approach to zoonoses in the circumarctic, encompassing human health, animal health, and environmental health aspects. The cases highlight critical gaps in monitoring and current knowledge, focusing on environmental stressors and lifestyle factors, and they are examples of current occurrences in the Arctic that inform on critically needed actions to prepare us for the future. Through these presentations, we recommend measures to enhance awareness and management of existing and emerging zoonoses with epidemic and pandemic potential while also focusing on the impacts of various environmental stressors and lifestyle factors on zoonoses in the Arctic.

Study of tree shrew biology and models: A booming and prosperous field for biomedical research

The tree shrew ( Tupaia belangeri) has long been proposed as a suitable alternative to non-human primates (NHPs) in biomedical and laboratory research due to its close evolutionary relationship with primates. In recent years, significant advances have facilitated tree shrew studies, including the determination of the tree shrew genome, genetic manipulation using spermatogonial stem cells, viral vector-mediated gene delivery, and mapping of the tree shrew brain atlas. However, the limited availability of tree shrews globally remains a substantial challenge in the field. Additionally, determining the key questions best answered using tree shrews constitutes another difficulty. Tree shrew models have historically been used to study hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, myopia, and psychosocial stress-induced depression, with more recent studies focusing on developing animal models for infectious and neurodegenerative diseases. Despite these efforts, the impact of tree shrew models has not yet matched that of rodent or NHP models in biomedical research. This review summarizes the prominent advancements in tree shrew research and reflects on the key biological questions addressed using this model. We emphasize that intensive dedication and robust international collaboration are essential for achieving breakthroughs in tree shrew studies. The use of tree shrews as a unique resource is expected to gain considerable attention with the application of advanced techniques and the development of viable animal models, meeting the increasing demands of life science and biomedical research.

Integrated analysis of miRNA-mRNA expression of newly emerging swine H3N2 influenza virus cross-species infection with tree shrews

BACKGROUND

Cross-species transmission of zoonotic IAVs to humans is potentially widespread and lethal, posing a great threat to human health, and their cross-species transmission mechanism has attracted much attention. miRNAs have been shown to be involved in the regulation of IAVs infection and immunity, however, few studies have focused on the molecular mechanisms underlying miRNAs and mRNAs expression after IAVs cross-species infection.

METHODS

We used tree shrews, a close relative of primates, as a model and used RNA-Seq and bioinformatics tools to analyze the expression profiles of DEMs and DEGs in the nasal turbinate tissue at different time points after the newly emerged swine influenza A virus SW2783 cross-species infection with tree shrews, and miRNA-mRNA interaction maps were constructed and verified by RT-qPCR, miRNA transfection and luciferase reporter assay.

RESULTS

14 DEMs were screened based on functional analysis and interaction map, miR-760-3p, miR-449b-2, miR-30e-3p, and miR-429 were involved in the signal transduction process of replication and proliferation after infection, miR-324-3p, miR-1301-1, miR-103-1, miR-134-5p, miR-29a, miR-31, miR-16b, miR-34a, and miR-125b participate in negative feedback regulation of genes related to the immune function of the body to activate the antiviral immune response, and miR-106b-3p may be related to the cross-species infection potential of SW2783, and the expression level of these miRNAs varies in different days after infection.

CONCLUSIONS

The miRNA regulatory networks were constructed and 14 DEMs were identified, some of them can affect the replication and proliferation of viruses by regulating signal transduction, while others can play an antiviral role by regulating the immune response. It indicates that abnormal expression of miRNAs plays a crucial role in the regulation of cross-species IAVs infection, which lays a solid foundation for further exploration of the molecular regulatory mechanism of miRNAs in IAVs cross-species infection and anti-influenza virus targets.

Impact of adjuvant: Trivalent vaccine with quadrivalent-like protection against heterologous Yamagata-lineage influenza B virus

As new vaccine technologies and platforms, such as nanoparticles and novel adjuvants, are developed to aid in the establishment of a universal influenza vaccine, studying traditional influenza split/subunit vaccines should not be overlooked. Commercially available vaccines are typically studied in terms of influenza A H1 and H3 viruses but influenza B viruses need to be examined as well. Thus, there is a need to both understand the limitations of split/subunit vaccines and develop strategies to overcome those limitations, particularly their ability to elicit cross-reactive antibodies to the co-circulating Victoria (B-V) and Yamagata (B-Y) lineages of human influenza B viruses. In this study, we compared three commercial influenza hemagglutinin (HA) split/subunit vaccines, one quadrivalent (H1, H3, B-V, B-Y HAs) and two trivalent (H1, H3, B-V HAs), to characterize potential differences in their antibody responses and protection against a B-Y challenge. We found that the trivalent adjuvanted vaccine Fluad, formulated without B-Y HA, was able to produce antibodies to B-Y (cross-lineage) on a similar level to those elicited from a quadrivalent vaccine (Flucelvax) containing both B-V and B-Y HAs. Interestingly, Fluad protected mice from a lethal cross-lineage B-Y viral challenge, while another trivalent vaccine, Fluzone HD, failed to elicit antibodies or full protection following challenge. Fluad immunization also diminished viral burden in the lungs compared to Fluzone and saline groups. The success of a trivalent vaccine to provide protection from a cross-lineage influenza B challenge, similar to a quadrivalent vaccine, suggests that further analysis of different split/subunit vaccine formulations could identify mechanisms for vaccines to target antigenically different viruses. Understanding how to increase the breadth of the immune response following immunization will be needed for universal influenza vaccine development.

Tree Shrew as an Emerging Small Animal Model for Human Viral Infection: A Recent Overview

Viral infection is a global public health threat causing millions of deaths. A suitable small animal model is essential for viral pathogenesis and host response studies that could be used in antiviral and vaccine development. The tree shrew (Tupaia belangeri or Tupaia belangeri chinenesis), a squirrel-like non-primate small mammal in the Tupaiidae family, has been reported to be susceptible to important human viral pathogens, including hepatitis viruses (e.g., HBV, HCV), respiratory viruses (influenza viruses, SARS-CoV-2, human adenovirus B), arboviruses (Zika virus and dengue virus), and other viruses (e.g., herpes simplex virus, etc.). The pathogenesis of these viruses is not fully understood due to the lack of an economically feasible suitable small animal model mimicking natural infection of human diseases. The tree shrew model significantly contributes towards a better understanding of the infection and pathogenesis of these important human pathogens, highlighting its potential to be used as a viable viral infection model of human viruses. Therefore, in this review, we summarize updates regarding human viral infection in the tree shrew model, which highlights the potential of the tree shrew to be utilized for human viral infection and pathogenesis studies.

Characteristics of Angiotensin I-converting enzyme 2, type II transmembrane serine protease 2 and 4 in tree shrew indicate it as a potential animal model for SARS-CoV-2 infection

Angiotensin I-converting enzyme 2 (ACE2), type II transmembrane serine protease 2 and 4 (TMPRSS2 and TMPRSS4) are important receptors for SARS-CoV-2 infection. In this study, the full-length tree shrewACE2 gene was cloned and sequenced, and its biological information was analyzed. The expression levels of ACE2, TMPRSS2 and TMPRSS4 in various tissues or organs of the tree shrew were detected. The results showed that the full-length ACE2 gene in tree shrews was 2,786 bp, and its CDS was 2,418 bp, encoding 805 amino acids. Phylogenetic analysis based on the CDS of ACE2 revealed that tree shrews were more similar to rabbits (85.93%) and humans (85.47%) but far from mice (82.81%) and rats (82.58%). In silico analysis according to the binding site of SARS-CoV-2 with the ACE2 receptor of different species predicted that tree shrews had potential SARS-CoV-2 infection possibility, which was similar to that of rabbits, cats and dogs but significantly higher than that of mice and rats. In addition, various tissues or organs of tree shrews expressed ACE2, TMPRSS2 and TMPRSS4. Among them, the kidney most highly expressed ACE2, followed by the lung and liver. The esophagus, lung, liver, intestine and kidney had relatively high expression levels of TMPRSS2 and TMPRSS4. In general, we reported for the first time the expression of ACE2, TMPRSS2 and TMPRSS4 in various tissues or organs in tree shrews. Our results revealed that tree shrews could be used as a potential animal model to study the mechanism underlying SARS-CoV-2 infection.

Development and Characterization of a Highly Sensitive NanoLuciferase-Based Immunoprecipitation System for the Detection of Anti-Influenza Virus HA Antibodies

Antibody detection is crucial for monitoring host immune responses to specific pathogen antigens (Ags) and evaluating vaccine efficacies. The luciferase immunoprecipitation system (LIPS) was developed for sensitive detection of Ag-specific antibodies in sera from various species. In this study, we describe NanoLIPS, an improved LIPS assay based on NanoLuciferase (NLuc), and employ the assay for monitoring antibody responses following influenza virus infection or vaccination. We generated recombinant influenza virus hemagglutinin (HA) proteins tagged with N-terminal (N-NLuc-HA) or C-terminal (C-NLuc-HA) NLuc reporters. NLuc-HA yielded an at least 20-fold higher signal-to-noise ratio than did a LIPS assay employing a recombinant HA-Gaussia princeps luciferase (GLuc) fusion protein. NanoLIPS-based detection of anti-HA antibodies yielded highly reproducible results with a broad dynamic range. The levels of antibodies against C-NLuc-HA generated by mice vaccinated with recombinant vaccinia virus DIs strain expressing an influenza virus HA protein (rDIs-HA) was significantly correlated with the protective effect elicited by the rDIs-HA vaccine. C-NLuc-HA underwent glycosylation with native conformations and assembly to form a trimeric structure and was detected by monoclonal antibodies that detect conformational epitopes present on the globular head or stalk domain of HA. Therefore, NanoLIPS is applicable for evaluating vaccine efficacy. We also showed that C-NLuc-HA is applicable for detection of HA-specific antibodies in sera from various experimental species, including mouse, cynomolgus macaque, and tree shrew. Thus, NanoLIPS-based detection of HA offers a simple and high-sensitivity method that detects native conformational epitopes and can be used in various experimental animal models.IMPORTANCE Influenza virus HA-specific antibodies can be detected via the hemagglutination inhibition (HI) assay, the neutralization (NT) assay, and the enzyme-linked immunosorbent assay (ELISA). However, these assays have some drawbacks, including narrow dynamic range and the requirement for large amounts of sera. As an alternative to an ELISA-based method, luciferase immunoprecipitation system (LIPS) was developed. We focused on NanoLuciferase (NLuc), which has a small size, higher intensity, and longer stability. In this study, we developed a technically feasible and highly sensitive method for detecting influenza virus-specific antibodies using a NLuc-tagged recombinant HA protein produced in mammalian cells. HA with a C-terminal NLuc extension (C-NLuc-HA) was glycosylated and formed trimeric complexes when expressed in mammalian cells. Furthermore, C-NLuc-HA was recognized not only by monoclonal antibodies that bind to the globular head domain but also by those that bind to the stalk domain. We also demonstrated that the data obtained by this assay correlate with the protection of an experimental vaccine in animal models.

Host Diversity and Potential Transmission Pathways of SARS-CoV-2 at the Human-Animal Interface

Emerging infectious diseases present great risks to public health. The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19), has become an urgent public health issue of global concern. It is speculated that the virus first emerged through a zoonotic spillover. Basic research studies have suggested that bats are likely the ancestral reservoir host. Nonetheless, the evolutionary history and host susceptibility of SARS-CoV-2 remains unclear as a multitude of animals has been proposed as potential intermediate or dead-end hosts. SARS-CoV-2 has been isolated from domestic animals, both companion and livestock, as well as in captive wildlife that were in close contact with human COVID-19 cases. Currently, domestic mink is the only known animal that is susceptible to a natural infection, develop severe illness, and can also transmit SARS-CoV-2 to other minks and humans. To improve foundational knowledge of SARS-CoV-2, we are conducting a synthesis review of its host diversity and transmission pathways. To mitigate this COVID-19 pandemic, we strongly advocate for a systems-oriented scientific approach that comprehensively evaluates the transmission of SARS-CoV-2 at the human and animal interface.

Lianhua-Qingwen Displays Antiviral and Anti-Inflammatory Activity and Synergistic Effects with Oseltamivir against Influenza B Virus Infection in the Mouse Model

Influenza B virus (IBV) is one of the main pathogens of the annual influenza epidemic, and the disease burden is significant, especially among children and young teenagers. In this study, the antiviral and anti-inflammatory effects of a traditional Chinese medicine prescription, the Lianhua-Qingwen capsule, were evaluated. Our results showed that Lianhua-Qingwen capsule can inhibit both Victoria and Yamagata lineages, and the 50% inhibitive concentrations ranged from 0.228 ± 0.150 to 0.754 ± 0.161 mg/mL. The time course results demonstrated that IBV yields were reduced with treatment at 0–4 h after infection, and the mechanistic research verified that Lianhua-Qingwen capsule has hemagglutination inhibition activity against B/Guangzhou/0215/2012 but not A/California/04/2009. In addition to antiviral activity, Lianhua-Qingwen capsule can also inhibit excessive expression of RANTES, IL-6, IL-8, IP-10, TNF-α, MCP-1, MIP-1β, and IFN-λ at the mRNA level and prevent a severe inflammatory response. The in vivo results confirmed that orally administered Lianhua-Qingwen capsule (100–400 mg/kg/day) does not reduce IBV-induced lung viral load and mortality in mice. However, the pathological change in lungs was alleviated, and there were fewer inflammatory cells in the lungs of Lianhua-Qingwen capsule treated mice than those in controls. Further research confirmed that the combination treatment of 200 mg/kg/day of Lianhua-Qingwen capsule with 2 mg/kg/day of oseltamivir significantly reduced IBV infection over the individual administration of either alone in vivo. Our findings prove that Lianhua-Qingwen capsule could be used as an assistant medicine to enhance the effect of oseltamivir against influenza B virus infection.

Comprehensive Glycomic Profiling of Respiratory Tract Tissues of Tree Shrews by TiO2-PGC Chip Mass Spectrometry

Due to its relatively small size, homology to humans, and susceptibility to human viruses, the tree shrew becomes an ideal alternative animal model for the study of human viral infectious diseases. However, there is still no report for the comprehensive glycan profile of the respiratory tract tissues in tree shrews. In this study, we characterized the structural diversity of N-glycans in the respiratory tract of tree shrews using our well-established TiO₂-PGC chip-Q-TOF-MS method. As a result, a total of 219 N-glycans were identified. Moreover, each identified N-glycan was quantitated by a high sensitivity and accurate MRM method, in which ¹³C-labeled internal standards were used to correct the inherent run-to-run variation in MS detection. Our results showed that the N-glycan composition in the turbinate and lung was significantly different from the soft palate, trachea, and bronchus. Meanwhile, 28 high-level N-glycans in turbinate were speculated to be correlated with the infection of H1N1 virus A/California/04/2009. This study is the first to reveal the comprehensive glycomic profile of the respiratory tract of tree shrews. Our results also help to better understand the role of glycan receptors in human influenza infection and pathogenesis.

Comparative Pathogenicity and Transmissibility of Pandemic H1N1, Avian H5N1, and Human H7N9 Influenza Viruses in Tree Shrews

Influenza A viruses (IAVs) continuously challenge the poultry industry and human health. Studies of IAVs are still hampered by the availability of suitable animal models. Chinese tree shrews (Tupaia belangeri chinensis) are closely related to primates physiologically and genetically, which make them a potential animal model for human diseases. In this study, we comprehensively evaluated infectivity and transmissibility in Chinese tree shrews by using pandemic H1N1 (A/Sichuan/1/2009, pdmH1N1), avian-origin H5N1 (A/Chicken/Gansu/2/2012, H5N1) and early human-origin H7N9 (A/Suzhou/SZ19/2014, H7N9) IAVs. We found that these viruses replicated efficiently in primary tree shrew cells and tree shrews without prior adaption. Pathological lesions in the lungs of the infected tree shrews were severe on day 3 post-inoculation, although clinic symptoms were self-limiting. The pdmH1N1 and H7N9 viruses, but not the H5N1 virus, transmitted among tree shrews by direct contact. Interestingly, we also observed that unadapted H7N9 virus could transmit from tree shrews to naïve guinea pigs. Virus-inoculated tree shrews generated a strong humoral immune response and were protected from challenge with homologous virus. Taken together, our findings suggest the Chinese tree shrew would be a useful mammalian model to study the pathogenesis and transmission of IAVs.