A novel genetic locus linked to pro-inflammatory cytokines after virulent H5N1 virus infection in mice

Differential lung gene expression changes in C57BL/6 and DBA/2 mice carrying an identical functional Mx1 gene reveals crucial differences in the host response

BACKGROUND

Influenza virus infections represent a major global health problem. The dynamin-like GTPase MX1 is an interferon-dependent antiviral host protein that confers resistance to influenza virus infections. Infection models in mice are an important experimental system to understand the host response and susceptibility to developing severe disease following influenza infections. However, almost all laboratory mouse strains carry a non-functional Mx1 gene whereas humans have a functional MX1 gene. Most studies in mice have been performed with strains carrying a non-functional Mx1 gene. It is therefore very important to investigate the host response in mouse strains with a functional Mx1 gene.

RESULTS

Here, we analyzed the host response to influenza virus infections in two congenic mouse strains carrying the functional Mx1 gene from the A2G strain. B6.A2G-Mx1r/r(B6-Mx1r/r) mice are highly resistant to influenza A virus (IAV) H1N1 infections. On the other hand, D2(B6).A2G-Mx1r/r(D2-Mx1r/r) mice, although carrying a functional Mx1 gene, were highly susceptible, exhibited rapid weight loss, and died. We performed gene expression analysis using RNAseq from infected lungs at days 3 and 5 post-infection (p.i.) of both mouse strains to identify genes and pathways that were differentially expressed between the two mouse strains. The susceptible D2-Mx1r/r mice showed a high viral replication already at day 3 p.i. and exhibited a much higher number of differentially expressed genes (DEGs) and many DEGs had elevated expression levels compared to B6-Mx1r/r mice. On the other hand, some DEGs were specifically up-regulated only in B6-Mx1r/r mice at day 3 p.i., many of which were related to host immune response functions.

CONCLUSIONS

From these results, we conclude that at early times of infection, D2-Mx1r/r mice showed a very high and rapid replication of the virus, which resulted in lung damage and a hyperinflammatory response leading to death. We hypothesize that the activation of certain immune response genes was missing and that others, especially Mx1, were expressed at a time in D2-Mx1r/r mice when the virus had already massively spread in the lung and were thus not able anymore to protect them from severe disease. Our study represents an important addition to previously published studies in mouse models and contributes to a better understanding of the molecular pathways and genes that protect against severe influenza disease.

Nardosinone and aurantio-obtusin, two medicine food homology natural compounds, are anti-influenza agents as indicated by transcriptome signature reversion

BACKGROUND

Medicine food homology (MFH) refers to food that can be used as medicine, and compounds isolated from MFH materials are valuable in novel drug discovery due to their good safety. Transcriptome signature reversion (TSR) is an attractive method for discovering drugs through transcriptional reverse matching; namely, the changes in transcriptional signatures induced by compounds are matched to a certain disease. This strategy can be used to discover anti-influenza agents among MFH natural compounds.

PURPOSE

MFH natural compounds with anti-influenza activities were identified through analyses of the reversal in the expression of multiple informative genes followed by in vitro evaluation of the cytopathic effect (CPE) caused by influenza infection and relative quantification of the nucleoprotein (NP) gene in viral RNA (vRNA). The combined effect of active compounds was determined through network-based separation score prediction followed by quantification of the viral hemagglutinin (HA) level.

METHODS

The transcriptome profiles of 4 lung or airway cell lines infected with 7 influenza virus strains were analyzed by robust rank aggregation (RRA) to identify informative genes in the signature of influenza virus infection. The identified informative genes were then matched to a transcriptomic profile library of MFH natural compounds. The anti-influenza activities of MFH natural compounds with negative enrichment scores (ESs) were evaluated in vitro using a CPE assay and relative quantification of the NP gene in the vRNA in the supernatant and cytoplasm to identify anti-influenza agents. The effects of combinations of active compounds were analyzed using network-based calculations followed by confirmation through bioassays for quantifying the viral HA levels.

RESULTS

Among the 159 MFH natural compounds, 54 compounds had negative ESs, as determined through TSR, and the anti-influenza activities of nardosinone and aurantio-obtusin were confirmed by bioassays. The half-maximal effective concentrations (EC₅₀) of nardosinone and aurantio-obtusin were 4.3-84.4 μM and 31.9-113.6 μM, respectively. The separation score between the informative genes with expression that was negatively regulated by nardosinone and aurantio-obtusin in the human protein-protein interaction (PPI) network was calculated to be 0.10, which indicated that the two compounds potentially exert a synergistic effect, and this effect was confirmed by the finding that the combination indexes (CIs) were calculated to equal 0.86 at inhibition level of 50% and 0.44 at inhibition level of 90%.

CONCLUSION

The TSR analysis and in vitro evaluation identified nardosinone and aurantio-obtusin as anti-influenza agents. Their antiviral activities were exerted by reversing the expression of multiple informative genes of the host cells. The separation analysis between the informative genes that were reversely regulated by nardosinone and aurantio-obtusin indicated that their combination may exert a synergistic effect, which was confirmed in vitro.

Up-regulated SAMD9L modulated by TLR2 and HIF-1α as a promising biomarker in tuberculosis

The aim of this study was to identify potential biomarkers of TB in blood and determine their function in Mtb-infected macrophages. First of all, WGCNA was used to analyse 9451 genes with significant changes in TB patients' whole blood. The 220 interferon-γ-related genes were identified, and then 30 key genes were screened using Cytoscape. Then, the AUC values of key genes were calculated to further narrow the gene range. Finally, we identified 9 genes from GSE19444. ROC analysis showed that SAMD9L, among 9 genes, had a high diagnostic value (AUC = 0.925) and a differential diagnostic value (AUC>0.865). To further narrow down the range of DEGs, the top 10 hub-connecting genes were screened from monocytes (GSE19443). Finally, we obtained 4 genes (SAMD9L, GBP1, GBP5 and STAT1) by intersections of genes from monocytes and whole blood. Among them, it was found that the function of SAMD9L was unknown after data review, so this paper studied this gene. Our results showed that SAMD9L is up-regulated and suppresses cell necrosis, and might be regulated by TLR2 and HIF-1α during Mtb infection. In addition, miR-181b-5p is significantly up-regulated in the peripheral blood plasma of tuberculosis patients, which has a high diagnostic value (AUC = 0.969).

New Insights on Gene by Environmental Effects of Drugs of Abuse in Animal Models Using GeneNetwork

Gene-by-environment interactions are important for all facets of biology, especially behaviour. Families of isogenic strains of mice, such as the BXD strains, are excellently placed to study these interactions, as the same genome can be tested in multiple environments. BXD strains are recombinant inbred mouse strains derived from crossing two inbred strains—C57BL/6J and DBA/2J mice. Many reproducible genometypes can be leveraged, and old data can be reanalysed with new tools to produce novel insights. We obtained drug and behavioural phenotypes from Philip et al. Genes, Brain and Behaviour 2010, and reanalysed their data with new genotypes from sequencing, as well as new models (Genome-wide Efficient Mixed Model Association (GEMMA) and R/qtl2). We discovered QTLs on chromosomes 3, 5, 9, 11, and 14, not found in the original study. We reduced the candidate genes based on their ability to alter gene expression or protein function. Candidate genes included Slitrk6 and Cdk14. Slitrk6, in a Chromosome14 QTL for locomotion, was found to be part of a co-expression network involved in voluntary movement and associated with neuropsychiatric phenotypes. Cdk14, one of only three genes in a Chromosome5 QTL, is associated with handling induced convulsions after ethanol treatment, that is regulated by the anticonvulsant drug valproic acid. By using families of isogenic strains, we can reanalyse data to discover novel candidate genes involved in response to drugs of abuse.

An integrative bioinformatics analysis for identifying hub genes associated with infection of lung samples in patients infected with SARS-CoV-2

Background

At the end of 2019, the world witnessed the emergence and ravages of a viral infection induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Also known as the coronavirus disease 2019 (COVID-19), it has been identified as a public health emergency of international concern (PHEIC) by the World Health Organization (WHO) because of its severity.

Methods

The gene data of 51 samples were extracted from the GSE150316 and GSE147507 data set and then processed by means of the programming language R, through which the differentially expressed genes (DEGs) that meet the standards were screened. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed on the selected DEGs to understand the functions and approaches of DEGs. The online tool STRING was employed to construct a protein–protein interaction (PPI) network of DEGs and, in turn, to identify hub genes.

Results

A total of 52 intersection genes were obtained through DEG identification. Through the GO analysis, we realized that the biological processes (BPs) that have the deepest impact on the human body after SARS-CoV-2 infection are various immune responses. By using STRING to construct a PPI network, 10 hub genes were identified, including IFIH1, DDX58, ISG15, EGR1, OASL, SAMD9, SAMD9L, XAF1, IFITM1, and TNFSF10.

Conclusion

The results of this study will hopefully provide guidance for future studies on the pathophysiological mechanism of SARS-CoV-2 infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40001-021-00609-4.

Tissue Specific Transcriptome Changes Upon Influenza A Virus Replication in the Duck

Ducks are the natural host and reservoir of influenza A virus (IAV), and as such are permissive to viral replication while being unharmed by most strains. It is not known which mechanisms of viral control are globally regulated during infection, and which are specific to tissues during infection. Here we compare transcript expression from tissues from Pekin ducks infected with a recombinant H5N1 strain A/Vietnam 1203/04 (VN1203) or an H5N2 strain A/British Columbia 500/05 using RNA-sequencing analysis and aligning reads to the NCBI assembly ZJU1.0 of the domestic duck (Anas platyrhynchos) genome. Highly pathogenic VN1203 replicated in lungs and showed systemic dissemination, while BC500, like most low pathogenic strains, replicated in the intestines. VN1203 infection induced robust differential expression of genes all three days post infection, while BC500 induced the greatest number of differentially expressed genes on day 2 post infection. While there were many genes globally upregulated in response to either VN1203 or BC500, tissue specific gene expression differences were observed. Lungs of ducks infected with VN1203 and intestines of birds infected with BC500, tissues important in influenza replication, showed highest upregulation of pattern recognition receptors and interferon stimulated genes early in the response. These tissues also appear to have specific downregulation of inflammatory components, with downregulation of distinct sets of proinflammatory cytokines in lung, and downregulation of key components of leukocyte recruitment and complement pathways in intestine. Our results suggest that global and tissue specific regulation patterns help the duck control viral replication as well as limit some inflammatory responses in tissues involved in replication to avoid damage.

A platform for experimental precision medicine: The extended BXD mouse family

The challenge of precision medicine is to model complex interactions among DNA variants, phenotypes, development, environments, and treatments. We address this challenge by expanding the BXD family of mice to 140 fully isogenic strains, creating a uniquely powerful model for precision medicine. This family segregates for 6 million common DNA variants-a level that exceeds many human populations. Because each member can be replicated, heritable traits can be mapped with high power and precision. Current BXD phenomes are unsurpassed in coverage and include much omics data and thousands of quantitative traits. BXDs can be extended by a single-generation cross to as many as 19,460 isogenic F1 progeny, and this extended BXD family is an effective platform for testing causal modeling and for predictive validation. BXDs are a unique core resource for the field of experimental precision medicine.

MXD1 regulates the H9N2 and H1N1 influenza A virus-induced chemokine expression and their replications in human macrophage

Human infection with influenza A/Hong Kong/156/97 (H5N1) avian influenza virus is associated with a high mortality rate of 60%. This virus is originated from influenza A/Quail/Hong Kong/G1/97 (H9N2/G1) avian influenza virus. Since the 1990s, four lineages of H9N2 viruses have been circulating in poultry and cause occasional infection in humans in different countries. Due to its zoonotic and genetic reassortment potential, H9N2/G1 and H5N1 viruses are believed to be the next pandemic candidates. Previous reports, including ours, showed that the virulence of avian virus strains correlates with their ability to dysregulate cytokine expression, including TNF-α, CXCL10, and related chemokines in the virus-infected cells. However, the transcriptional factors required for this cytokine dysregulation remains undefined. In light of our previous report showing the unconventional role of MYC, an onco-transcriptional factor, for regulating the antibacterial responses, we hypothesize that the influenza virus-induced cytokine productions may be governed by MYC/MAX/MXD1 network members. Here, we demonstrated that the influenza A/Hong Kong/54/98 (H1N1)- or H9N2/G1 virus-induced CXCL10 expressions can be significantly attenuated by knocking down the MXD1 expression in primary human blood macrophages. Indeed, only the MXD1 expression was up-regulated by both H1N1 and H9N2/G1 viruses, but not other MYC/MAX/MXD1 members. The MXD1 expression and the CXCL10 hyperinduction were dependent on MEK1/2 activation. By using EMSAs, we revealed that MXD1 directly binds to the CXCL10 promoter-derived oligonucleotides upon infection of both viruses. Furthermore, silencing of MXD1 decreased the replication of H9N2 but not H1N1 viruses. Our results provide a new insight into the role of MXD1 for the pathogenicity of avian influenza viruses.

Virucidal Action Against Avian Influenza H5N1 Virus and Immunomodulatory Effects of Nanoformulations Consisting of Mesoporous Silica Nanoparticles Loaded with Natural Prodrugs

Background

Combating infectious diseases caused by influenza virus is a major challenge due to its resistance to available drugs and vaccines, side effects, and cost of treatment. Nanomedicines are being developed to allow targeted delivery of drugs to attack specific cells or viruses.

Materials and Methods

In this study, mesoporous silica nanoparticles (MSNs) functionalized with amino groups and loaded with natural prodrugs of shikimic acid (SH), quercetin (QR) or both were explored as a novel antiviral nanoformulations targeting the highly pathogenic avian influenza H5N1 virus. Also, the immunomodulatory effects were investigated in vitro tests and anti-inflammatory activity was determined in vivo using the acute carrageenan-induced paw edema rat model.

Results

Prodrugs alone or the MSNs displayed weaker antiviral effects as evidenced by virus titers and plaque formation compared to nanoformulations. The MSNs-NH₂-SH and MSNs-NH₂-SH-QR2 nanoformulations displayed a strong virucidal by inactivating the H5N1 virus. They induced also strong immunomodulatory effects: they inhibited cytokines (TNF-α, IL-1β) and nitric oxide production by approximately 50% for MSNs-NH₂-SH-QR2 (containing both SH and QR). Remarkable anti-inflammatory effects were observed during in vivo tests in an acute carrageenan-induced rat model.

Conclusion

Our preliminary findings show the potential of nanotechnology for the application of natural prodrug substances to produce a novel safe, effective, and affordable antiviral drug.

Artificial selection reveals the role of transcriptional constraints in the maintenance of life history variation

The trade-off between reproduction and self-maintenance is a cornerstone of life history theory, yet its proximate underpinnings are elusive. Here, we used an artificial selection approach to create replicated lines of Japanese quail (Coturnix japonica) that differ genetically in their reproductive investment. Whole transcriptome sequencing revealed that females from lines selected for high reproductive output show a consistent upregulation of genes associated with reproduction but a simultaneous downregulation of immune genes. Concordant phenotypic differences in immune function (i.e., specific antibody response against keyhole limpet hemocyanin) were observed between the selection lines, even in males who do not provide parental care. Our findings demonstrate the key role of obligate transcriptional constraints in the maintenance of life history variation. These constraints set fundamental limits to productivity and health in natural and domestic animal populations.

Genetic variability of T cell responses in hypersensitivity pneumonitis identified using the BXD genetic reference panel

Hypersensitivity pneumonitis (HP) is an interstitial lung disease that may progress to fibrosis and significant risk of death. HP develops following repeated exposures to inhaled environmental antigens; however, only a fraction of the exposed population develops the disease, suggesting that host genetics contribute to disease susceptibility. We used the BXD family of mice with the Saccharopolyspora rectivirgula (SR) model of HP to investigate the role of genetics in susceptibility to HP. The BXD family is derived from a B6 mother and a D2 father and has been used to map susceptibility loci to numerous diseases. B6, D2, and BXD progeny strains were exposed to SR for 3 wk, and the development of HP was monitored. The B6 and D2 strains developed alveolitis; however, the cellular composition was neutrophilic in the D2 strain and more lymphocytic in the B6 strain. Hematoxylin-eosin staining of lung sections revealed lymphoid aggregates in B6 lungs, whereas D2 lungs exhibited a neutrophilic infiltration. Twenty-eight BXD strains of mice were tested, and the results reveal significant heritable variation for numbers of CD4⁺ or CD8⁺ T cells in the air spaces. There was significant genetic variability for lymphoid aggregates and alveolar wall thickening. We mapped a significant quantitative trait locus (QTL) on chromosome 18 for CD8⁺CD69⁺ T cells that includes cadherin 2 (Cdh2), an excellent candidate gene associated with epithelial-mesenchymal transition, which is upregulated in lungs of strains with HP. These results demonstrate that the BXD family is a valuable and translationally relevant model to identify genes contributing to HP and to devise early and effective interventions.

Identifying novel biomarkers of the pediatric influenza infection by weighted co-expression network analysis

Background

Despite the high yearly prevalence of Influenza, the pathogenesis mechanism and involved genes have not been fully known. Finding the patterns and mapping the complex interactions between different genes help us to find the possible biomarkers and treatment targets.

Methods

Herein, weighted gene co-expression network analysis (WGCNA) was employed to construct a co-expression network among genes identified by microarray analysis of the pediatric influenza-infected samples.

Results

Three of the 38 modules were found as the most related modules to influenza infection. At a functional level, we found that the genes in these modules regulate the immune responses, protein targeting, and defense to virus. Moreover, the analysis of differentially expressed genes disclosed 719 DEGs between the normal and infected subjects. The comprehensive investigation of genes in the module involved in immune system and viral defense (yellow module) revealed that SP110, HERC5, SAMD9L, RTP4, C19orf66, HELZ2, EPSTI1, and PHF11 which were also identified as DEGs (except C19orf66) have the potential to be as the biomarkers and also drug targeting for the treatment of pediatric influenza.

Conclusions

The WGCN analysis revealed co-expressed genes which were involved in the innate immune system and defense to virus. The differentially expressed genes in the identified modules can be considered for designing drug targets. Moreover, modules can help to find pathogenesis routes in the future.

Influenza Pathogenesis: The Effect of Host Factors on Severity of Disease

Influenza viruses continue to be a major global health threat. Severity and clinical outcome of influenza disease is determined by both viral and host factors. Viral factors have long been the subject of intense research and many molecular determinants have been identified. However, research into the host factors that protect or predispose to severe and fatal influenza A virus infections is lagging. The goal of this review is to highlight the recent insights into host determinants of influenza pathogenesis.

C57BL/6J and C57BL/6NJ Mice Are Differentially Susceptible to Inflammation-Associated Disease Caused by Influenza A Virus

Influenza viruses cause seasonal epidemics and sporadic pandemics, and are a major burden on human health. To develop better countermeasures and improve influenza disease outcomes, a clearer understanding of influenza pathogenesis is necessary. Host genetic factors have emerged as potential regulators of human influenza disease susceptibility, and in the mouse model, genetic background has been clearly linked to influenza pathogenicity. Here, we show that C57BL/6J mice are significantly more susceptible to disease caused by a 2009 pandemic H1N1 virus, an H7N9 virus, and a highly pathogenic H5N1 influenza virus compared to the closely related substrain, C57BL/6NJ. Mechanistically, influenza virus infection in C57BL/6J mice results in earlier presentation of edema, increased immune cell infiltration, higher levels of inflammatory cytokines, greater tissue damage, and delayed activation of regenerative processes in infected lung tissues compared to C57BL/6NJ mice. These differences are not dependent on virus replication levels. Six genes with known coding region differences between C57BL/6J and C57BL/6NJ strains exhibit increased transcript levels in influenza virus-infected mouse lungs, suggesting potential contributions to regulation of disease susceptibility. This work uncovers a previously unappreciated difference in disease susceptibility between the closely related C57BL/6J and C57BL/6NJ mice, which may be exploited in future studies to identify host factors and/or specific genetic elements that regulate host-dependent inflammatory mechanisms involved in influenza virus pathogenicity.

Influenza Pathogenesis in Genetically Defined Resistant and Susceptible Murine Strains

The murine infection model is a cornerstone for influenza virus research and includes aspects such as disease pathogenesis, immunobiology, and vaccine and antiviral drug development. One compelling feature of the murine model is the availability of inbred mouse strains, each with a unique genetic makeup and potential for variable responses to influenza infection. Using highly controlled infection studies, the response to influenza virus infection is classified on a spectrum from susceptible to resistant, reflecting severe morbidity and high mortality, to limited or no morbidity and no mortality. Although there have been a variety of studies establishing disparate pathogenesis amongst various murine strains, thus far, there is no consensus regarding the determinants of the outcome of infection. The goal of this review is to explore and discuss the differences in pathogenesis, as well as the innate and adaptive immune responses to influenza infection that have been described in susceptible and resistant mouse strains. Understanding how host genetics influences the response to influenza infection provides valuable insight into the variable responses seen in vaccine or drug efficacy studies, as well as indicates possible mechanisms contributing to increased disease severity in humans infected with influenza virus with no known risk factors.

A North American H7N3 Influenza Virus Supports Reassortment with 2009 Pandemic H1N1 and Induces Disease in Mice without Prior Adaptation

Reassortment between H5 or H9 subtype avian and mammalian influenza A viruses (IAV) can generate a novel virus that causes disease and transmits between mammals. Such information is currently not available for H7 subtype viruses. We evaluated the ability of a low-pathogenicity North American avian H7N3 virus (A/shorebird/Delaware/22/2006) to reassort with mammalian or avian viruses using a plasmid-based competition assay. In addition to genome segments derived from an avian H7N9 virus, the H7N3 virus reassorted efficiently with the PB2, NA, and M segments from the 2009 pandemic H1N1 (PH1N1) virus.In vitro and in vivo evaluation of the H7N3:PH1N1 (7 + 1) reassortant viruses revealed that the PB2, NA, or M segments from PH1N1 largely do not attenuate the H7N3 virus, whereas the PB1, PA, NP, or NS genome segments from PH1N1 do. Additionally, we assessed the functionality of the H7N3:PH1N1 7 + 1 reassortant viruses by measuring the inflammatory response in vivo We found that infection with wild-type H7N3 resulted in increased inflammatory cytokine production relative to that seen with the PH1N1 strain and that the increase was further exacerbated by substitution of PH1N1 PB2 but not NA or M. Finally, we assessed if any adaptations occurred in the individually substituted segments after in vivo inoculation and found no mutations, suggesting that PH1N1 PB2, NA, and M are genetically stable in the background of this H7N3 virus. Taking the data together, we demonstrate that a North American avian H7N3 IAV is genetically and functionally compatible with multiple gene segments from the 2009 pandemic influenza virus strain without prior adaptation.

IMPORTANCE

The 2009 pandemic H1N1 virus continues to circulate and reassort with other influenza viruses, creating novel viruses with increased replication and transmission potential in humans. Previous studies have found that this virus can also reassort with H5N1 and H9N2 avian influenza viruses. We now show that several genome segments of the 2009 H1N1 virus are also highly compatible with a low-pathogenicity avian H7N3 virus and that these reassortant viruses are stable and not attenuated in an animal model. These results highlight the potential for reassortment of H1N1 viruses with avian influenza virus and emphasize the need for continued surveillance of influenza viruses in areas of cocirculation between avian, human, and swine viruses.

Host genetics of severe influenza: from mouse Mx1 to human IRF7

Influenza viruses cause mild to moderate respiratory illness in most people, and only rarely devastating or fatal infections. The virulence factors encoded by viral genes can explain seasonal or geographic differences at the population level but are unlikely to account for inter-individual clinical variability. Inherited or acquired immunodeficiencies may thus underlie severe cases of influenza. The crucial role of host genes was first demonstrated by forward genetics in inbred mice, with the identification of interferon (IFN)-α/β-inducible Mx1 as a canonical influenza susceptibility gene. Reverse genetics has subsequently characterized the in vivo role of other mouse genes involved in IFN-α/β and -λ immunity. A series of in vitro studies with mouse and human cells have also refined the cell-intrinsic mechanisms of protection against influenza viruses. Population-based human genetic studies have not yet uncovered variants with a significant impact. Interestingly, human primary immunodeficiencies affecting T and B cells were also not found to predispose to severe influenza. Recently however, human IRF7 was shown to be essential for IFN-α/β- and IFN-λ-dependent protective immunity against primary influenza in vivo, as inferred from a patient with life-threatening influenza revealed to be IRF7-deficient by whole exome sequencing. Next generation sequencing of human exomes and genomes will facilitate the analysis of the human genetic determinism of severe influenza.

Hyporeactivity of Alveolar Macrophages and Higher Respiratory Cell Permissivity Characterize DBA/2J Mice Infected by Influenza A Virus

Influenza A virus remains a major public health problem. Mouse models have been widely used to study influenza infection in mammals. DBA/2J and C57BL/6J represent extremes in terms of susceptibility to influenza A infection among inbred laboratory mouse strains. Several studies focused specifically on the factors responsible for the susceptibility of DBA/2J or the resistance of C57BL/6J and resulted in impressive lists of candidate genes or factors over- or underexpressed in one of the strains. We adopted a different phenotypical approach to identify the critical steps of the infection process accounting for the differences between DBA/2J and C57BL/6J strains. We concluded that both a dysfunction of alveolar macrophages and an increased permissivity of respiratory cells rendered DBA/2J more susceptible to influenza infection.