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A positive feedback-loop regulates transcriptional response to murine pandemic influenza infection

ABSTRACT: The biological basis for the increased severity of influenza A viruses during the 2009 influenza pandemic remains unclear. Intra-host evolution of quasispecies and strong inflammation were identified as important hallmarks of severe pandemic H1N1 influenza A virus 2009 (A(H1N1)pdm09) infection. HA-222D/G quasispecies of A(H1N1)pdm09 were shown to undergo fast evolution and to cause severe influenza in human and mice. Here, we analysed the whole genome transcriptional response of mice infected with the A/Jena/5258/09 (mpJena/5258) virus over a period of 12 days to gain insights into the pathogenesis of A(H1N1)pdm09 HA-222D/G quasispecies on a molecular level. Remarkably, the transcriptional response to severe mpJena/5258 showed biphasic expression profile for the majority of genes which was never shown before. The gene expression analysis shows first peak with 968 differentially expressed genes at day 2 post infection (p.i.), followed by a stagnant recovery phase with 359 differentially expressed genes at day 4 p.i., and a second peak with 1001 differentially expressed genes at day 7 p.i., finally followed by a recovery phase. Using a reverse engineering strategy, a regulatory network was inferred to identify key interactions leading to severe pathogenesis of mpJena/5258. Known regulatory interactions were extracted by Pathway Studio 9.0 and softly integrated during network inference. The results demonstrate a hyper-responsive action and a positive feedback loop of IFN gamma (Ifng), Stat1 and Tlr3 signalling during mpJena/5258 infection. In conclusion, mpJena/5258 infection is associated with biphasic gene expression profile and a positive feedback mechanism of Ifng which correlates with the evolution of HA-222D/G quasispecies and leads to overwhelming immune response. A significant correlation were found between the co-expression action of three genes (Ifng, Stat1 and Tlr3) with a phenomenological clinical symptom score.

ORGANISM(S): Mus musculus

PROVIDER: GSE67241 | GEO | 2017/02/10

SECONDARY ACCESSION(S): PRJNA279311

REPOSITORIES: GEO

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Project description:Background: Pandemic H1N1 influenza A is a newly emerging strain of human influenza that is easily transmitted between people and has spread globally to over 116 countries. Human infection leads to symptoms ranging from mild to severe with lower respiratory complications observed in a small but significant number of infected individuals. Little is currently known about host immunity and Pandemic H1N1 influenza infections. Methods: We examined the pathogenic potential of the pandemic influenza A vaccine strain, A/California/07/2009 (H1N1), in ferrets, and characterized the host immune responses using microarray analysis. Gene expression profiles in lung tissue were compared with those from ferrets infected with A/Brisbane/59/2007. Results: Chemokines CCL2, CCL8, CXCL7 and CXCL10 along with the majority of ISGs were expressed early, correlated to lung pathology, and abruptly decreased expression in 5 days. Interestingly, the drop in innate immune gene expression was replaced by a significant increase in the expression of the adaptive immune genes for granzymes and immunoglobulins. Serum anti-pandemic influenza H1N1 antibodies were also observed on day 7, commensurate with the elimination of viral load. Conclusions: We propose that the innate phase of host immunity causes lung pathology and a delay or failure to effectively switch to the adaptive phase contributes to morbidity and mortality during severe human pandemic H1N1 influenza A infections. Keywords: influenza, immune response, cytokines, chemokines, lung infection, time course In the experiment with influenza A/California/07/2009 (H1N1),15 ferrets were randomly allocated to 5 groups: Day 0 (before infection), and Day 3, 5, 7 and 14 (post infection) with 3 biological replicates for each group. Likewise, a second experiment with A/Brisbane/59/2007 (H1N1) was carried out using the same experimental groups, except for a group in Day 2, instead Day 3. Ferrets were euthanized and lung tissue was excised for RNA purification on the scheduled date. The subsequent gene expression analysis was performed with Affymetrix GeneChip Canine Genome 2.0 Array. Day 0 groups were used as control.

Project description:Introduction: Diagnosis of severe influenza pneumonia remains challenging because of the lack of correlation between presence of influenza virus and patient’s clinical status. We conducted gene expression profiling in the whole blood of critically ill patients to identify a gene signature that would allow clinicians to distinguish influenza infection from other causes of severe respiratory failure (e.g. bacterial pneumonia, non-infective systemic inflammatory response syndrome). Methods: Whole blood samples were collected from critically ill individuals and assayed on Illumina HT-12 gene expression beadarrays. Differentially expressed genes were determined by linear mixed model analysis and over-represented biological pathways determined using GeneGo MetaCore. Results: The gene expression profile of H1N1 influenza A pneumonia was distinctly different from bacterial pneumonia and systemic inflammatory response syndrome. The influenza gene expression profile is characterized by up-regulation of genes from cell cycle regulation, apoptosis and DNA-damage response pathways. In contrast, no distinctive gene-expression signature was found in patients with bacterial pneumonia or systemic inflammatory response syndrome. The gene expression profile of influenza infection persisted through five days of follow-up. Furthermore, in patients with primary H1N1 influenza A infection who subsequently developed bacterial co-infection, the influenza gene-expression signature remained unaltered, despite the presence of a super-imposed bacterial infection. Conclusions: The whole blood expression profiling data indicates that the host response to influenza pneumonia is distinctly different from that caused by bacterial pathogens. This information may speed up identification of the cause of infection in patients presenting with severe respiratory failure, allowing appropriate patient care to be undertaken more rapidly. Daily PAXgene samples for up to 5 days for; influenza A pneumonia patients (n=8), bacterial pneumonia patients (n=16), mixed bacterial and influenza A pneumonia patients (n=3), systemic inflammatory response patients (SIRS, n=13). Days 1 and 5 PAXgene samples for healthy control individuals

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A positive feedback-loop regulates transcriptional response to murine pandemic influenza infection

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