Comparative phenotyping of susceptibility/resistance patterns to murinized H1N1 influenza A virus in two inbred mouse lines, C57BL/6 and DBA/2.

peer reviewe

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

peer reviewedInfluenza 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

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

peer reviewedInfluenza 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

Higher mortality rate in PVM-infected P2Y₂-deficient mice.

<p>Following intranasal inoculation of PVM (1000 PFUs), P2Y₂^+/+ and P2Y₂^−/− mice were monitored daily for survival (<b>A</b>) and weight loss (<b>B</b>). Weight curves (mean ± SEM) are relative to initial body weight. The displayed data result from the pooling of four independent experiments.</p

Quantification of neutrophils and macrophages, and their recruiters in the lungs of PVM-infected P2Y₂^+/+ and P2Y₂^−/− mice.

<p><b>A–D.</b> The level of the chemokines KC/CXCL-1 (A), MIP-2/CXCL-2 (B), MIP-1α/CCL3 (C) and MCP-1/CCL2 (D) was determined by ELISA in the BALFs of PVM-infected P2Y₂^+/+ and P2Y₂^−/− mice. (N = 9) <b>E.</b> Flow cytometry quantification of neutrophils and macrophages in the BALFs of PVM-infected P2Y₂^+/+ and P2Y₂^−/− mice at day 8 and 10 post-inoculation (N = 12). <b>F.</b> Cytospin preparations were made from BALFs of P2Y₂^+/+ and P2Y₂^−/− mice at day 8 post-infection using a Shandon III cytocentrifuge and were stained using Diff-Quick staining. Magnification: ×400.</p

Defective infiltration of DCs, CD4⁺ T cells and CD8⁺ T cells in the lungs of PVM-infected P2Y₂-deficient mice.

<p><b>A.</b> The percentage of DCs (MHC II⁺ CD11c⁺ CD11b⁺), CD4⁺ T cells and CD8⁺ T cells were determined by flow cytometry analysis in BALFs of P2Y₂^+/+ and P2Y₂^−/− mice at day 8 and days 10 (d8 and d10) post-infection (N = 5). <b>B.</b> Analysis of viral titer in P2Y₂^+/+ and P2Y₂^−/− lungs after infection with PVM. PVM viral titer was quantified by quantitative PCR in lung homogenates of P2Y₂^+/+ and P2Y₂^−/− mice 8 or 10 days post-infection. Data were normalized to the viral titer obtained for P2Y₂^+/+ lungs at d8. <b>C.</b> IL-12, IFN-γ, TNF-α and IL-6 levels were determined by ELISA in the BALFs of PVM-infected P2Y₂^+/+ and P2Y₂^−/− mice (N = 11). <b>D.</b> The level of DC recruiters was determined by ELISA (MIP-3α, IP-10) or qPCR (BRAK) in the BALFs of PVM-infected P2Y₂^+/+ and P2Y₂^−/− mice (N = 5).</p

Cellular infiltration in the lungs of PVM-infected P2Y₂^+/+ and P2Y₂^−/− mice.

<p>50 µL of the viral suspension were instilled into the nostrils of the anesthetized mouse maintained in a vertical position as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050385#s2" target="_blank">Materials and Methods</a>. <b>A</b>, BALF was collected and the total number of cells was evaluated at days 8, 9, 10 and 12 (N = 7). <b>B.</b> Quantification of ATP level in the BALF of PVM-infected P2Y₂^+/+ and P2Y₂^−/− mice. ATP level was quantified in the BALF of P2Y₂^+/+ and P2Y₂^−/− mice using ATP detection assay system ATPlite at d8, d9 and d10 post-infection with PVM. <b>C</b>, Histological analysis of representative lungs of P2Y₂^+/+ and P2Y₂^−/− mice 10 days and 15 days after infection with PVM. Paraffin sections (7 µM) of lungs of P2Y₂^+/+ and P2Y₂^−/− mice infected by PVM were stained with haematoxylin-eosin (magnification: ×200).</p

Vientiane Times, Vol. 24, Iss. 034, February 10, 2017

&lt;p&gt;To determine if fatal infections caused by different highly virulent influenza A viruses share the same pathogenesis, we compared 2 different influenza A virus subtypes, H1N1 and H5N1. The subtypes, which had shown no pathogenicity in laboratory mice, were forced to evolve by serial passaging. Although both adapted viruses evoked diffuse alveolar damage and showed a similar 50% mouse lethal dose and the same peak lung concentration, each had a distinct pathologic signature and caused a different course of acute respiratory distress syndrome. In the absence of any virus labeling, a histologist could readily distinguish infections caused by these 2 viruses. The different histologic features described in this study here refute the hypothesis of a single, universal cytokine storm underlying all fatal influenza diseases. Research is thus crucially needed to identify sets of virulence markers and to examine whether treatment should be tailored to the influenza virus pathotype.&lt;/p&gt;</p