TNF superfamily member 14 drives post-influenza depletion of alveolar macrophages, enabling secondary pneumococcal pneumonia
Christina Malainou, Christin Peteranderl, Maximiliano Ruben Ferrero, Ana Ivonne Vazquez-Armendariz, Ioannis Alexopoulos, Katharina Franz, Klara Knippenberg, Julian Better, Mohammad Estiri, Cheng-Yu Wu, Hendrik Schultheis, Judith Bushe, Maria-Luisa del Rio, Jose Ignacio Rodriguez-Barbosa, Klaus Pfeffer, Stefan Günther, Mario Looso, Achim Dieter Gruber, István Vadász, Ulrich Matt, Susanne Herold
Christina Malainou, Christin Peteranderl, Maximiliano Ruben Ferrero, Ana Ivonne Vazquez-Armendariz, Ioannis Alexopoulos, Katharina Franz, Klara Knippenberg, Julian Better, Mohammad Estiri, Cheng-Yu Wu, Hendrik Schultheis, Judith Bushe, Maria-Luisa del Rio, Jose Ignacio Rodriguez-Barbosa, Klaus Pfeffer, Stefan Günther, Mario Looso, Achim Dieter Gruber, István Vadász, Ulrich Matt, Susanne Herold
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Research Article Cell biology Infectious disease

TNF superfamily member 14 drives post-influenza depletion of alveolar macrophages, enabling secondary pneumococcal pneumonia

Abstract

Secondary bacterial infection, often caused by Streptococcus pneumoniae, is one of the most frequent and severe complications of influenza A virus–induced (IAV-induced) pneumonia. Phenotyping of the pulmonary immune cell landscape after IAV infection revealed a substantial depletion of the tissue-resident alveolar macrophage (TR-AM) population at day 7, which was associated with increased susceptibility to S. pneumoniae outgrowth. To elucidate the molecular mechanisms underlying TR-AM depletion, and to define putative targets for treatment, we combined single-cell transcriptomics and cell-specific PCR profiling in an unbiased manner, using in vivo models of IAV infection and IAV and S. pneumoniae coinfection. The TNF superfamily 14 (TNFSF14) ligand/receptor axis was revealed as the driving force behind post-influenza TR-AM death during the early infection phase, enabling the transition to pneumococcal pneumonia, whereas intrapulmonary transfer of genetically modified TR-AMs and antibody-mediated neutralization of specific pathway components alleviated disease severity. With mainly neutrophilic expression and high abundance in the bronchoalveolar fluid of patients with severe virus-induced acute respiratory distress syndrome, TNFSF14 emerged as a key determinant of virus-driven lung injury. Targeting the TNFSF14-mediated intercellular communication network in the virus-infected lung can, therefore, improve host defense, minimizing the risk of subsequent bacterial pneumonia and ameliorating the disease outcome.

Authors

Christina Malainou, Christin Peteranderl, Maximiliano Ruben Ferrero, Ana Ivonne Vazquez-Armendariz, Ioannis Alexopoulos, Katharina Franz, Klara Knippenberg, Julian Better, Mohammad Estiri, Cheng-Yu Wu, Hendrik Schultheis, Judith Bushe, Maria-Luisa del Rio, Jose Ignacio Rodriguez-Barbosa, Klaus Pfeffer, Stefan Günther, Mario Looso, Achim Dieter Gruber, István Vadász, Ulrich Matt, Susanne Herold

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Figure 2

Caspase 8 is involved in virus-independent, post-influenza TR-AM death.

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Caspase 8 is involved in virus-independent, post-influenza TR-AM death. ...
(A) Quantification of viral HA– and HA+ TR-AMs after IAV infection (n = 3–7; data indicate the mean ± SEM and were pooled from 3 independent experiments). (B) TR-AM survival following 24 hours of treatment with iBALF (n = 9 per group; data represent the mean ± SEM and were pooled from 3 independent experiments). (C and D) Caspase 3/-7 (C) and caspase 8 activity (D) after iBALF TR-AM treatment (n = 7–8; data represent the mean ± SEM and were pooled from 3 independent experiments). (E) Heatmap depicting the average fold changes of cell death–related genes in flow-sorted, HA–, mock, day 3, and day 7 p.i. BALF TR-AMs (n = 3–7 per time point; data were pooled from 4 independent experiments). Significance was determined by 2-tailed Student’s t test for the log2 fold-change values of each gene in the compared groups. (F) Percentage of apoptotic TR-AMs on days 0, 3, and 7 p.i. (n = 7–12; data represent the mean ± SEM and were pooled from 4 independent experiments). (G) Colorimetric viability assay following naive TR-AM treatment with iBALF after 3 hours of pretreatment with 50 μM of a specific caspase inhibitor (n = 6; data represent the mean ± SEM and were pooled from 2 independent experiments). (H) Experimental layout for caspase 8 inhibition in vivo experiments. Figure created with BioRender.com. (I) Weight loss after IAV infection and caspase 8 inhibition (n = 8–11; data were pooled from 6 independent experiments). (J) BALF TR-AMs on day 3 after in vivo caspase 8 inhibition (n = 11–13; data represent the mean ± SEM and were pooled from 4 independent experiments). (K) BALF viral titers on day 3 after in vivo caspase 8 inhibition (n = 3–6; data represent the mean ± SEM and were pooled from 2 independent experiments). (L) BALF TR-AMs on day 7 after in vivo caspase 8 inhibition (n = 7–10; data represent the mean ± SEM and were pooled from 7 independent experiments). *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, by 2-tailed Student’s t test (I [AUC for the compared groups] and K), 1-way ANOVA with Tukey’s post hoc test (B–D, F, J and L), and 2-way ANOVA with Tukey’s post hoc test (A and G).