EMAPII Monoclonal Antibody Ameliorates Influenza A Virus-Induced Lung Injury

Abstract

Influenza A virus (IAV) remains a major worldwide health threat, especially to high-risk populations, including the young and elderly. There is an unmet clinical need for therapy that will protect the lungs from damage caused by lower respiratory infection. Here, we analyzed the role of EMAPII, a stress- and virus-induced pro-inflammatory and pro-apoptotic factor, in IAV-induced lung injury. First, we demonstrated that IAV induces EMAPII surface translocation, release, and apoptosis in cultured endothelial and epithelial cells. Next, we showed that IAV induces EMAPII surface translocation and release to bronchoalveolar lavage fluid (BALF) in mouse lungs, concomitant with increases in caspase 3 activity. Injection of monoclonal antibody (mAb) against EMAPII attenuated IAV-induced EMAPII levels, weight loss, reduction of blood oxygenation, lung edema, and increase of the pro-inflammatory cytokine TNF alpha. In accordance with the pro-apoptotic properties of EMAPII, levels of caspase 3 activity in BALF were also decreased by mAb treatment. Moreover, we detected EMAPII mAb-induced increase in lung levels of M2-like macrophage markers YM1 and CD206. All together, these data strongly suggest that EMAPII mAb ameliorates IAV-induced lung injury by limiting lung cell apoptosis and shifting the host inflammatory setting toward resolution of inflammation.

Keywords: EMAPII; IAV; apoptosis; barrier dysfunction; lung injury.

Graphical abstract

Figure 1

IAV Induces Apoptosis and EMAPII Release in Pulmonary Endothelium and Epithelium (A–C and E) Human pulmonary artery endothelial cells (HPAEC), normal human bronchial epithelial cells (NHBEC), human lung microvascular endothelial cells (HLMVEC), and human alveolar epithelial line A549 were stimulated with 1 pfu/cell IAV and then analyzed for (A and B) caspase 3 cleavage, caspase 3 (A) and EMAPII (B) expression, (C) surface annexin V staining, (D) released EMAPII levels, (E) surface EMAPII staining, or (F) concomitant caspase 3 cleavage and surface EMAPII staining. *p < 0.05 by t test when compared to control values. n = 3–6, data are shown as mean ± SEM.

Figure 2

IAV-Induced Apoptosis Is Potentiated by EMAPII and Suppressed by EMAPII mAb HLMVECs (A) and A549 (B) were stimulated with 1 pfu/cell IAV (A) in the presence of 30 μg/mL recombinant EMAPII (E) or (B) 10 μg/mL control IgG or EMAPII mAb, then analyzed for cleaved and total caspase 3 levels. n = 3–5, data are presented as mean ± SEM; *p < 0.05 by one-way ANOVA with Tukey post-hoc.

Figure 3

IAV and EMAPII Induce Hyperpermeability in Endothelial and/or Epithelial Monolayers (A) HLMVECs grown to confluence were stimulated with 0.2 and 1 pfu/cell of IAV or 1 pfu/cell of heat-inactivated IAV. (B) HPAECs were stimulated with 0.75 pfu/cell IAV in the presence of 10 μg/mL control IgG or EMAPII mAb. (C) A549 were stimulated with 2 pfu/cell IAV, 40 μg/mL recombinant EMAPII, or their combination. (D) A549 were stimulated with 40 μg/mL recombinant EMAPII (E) in the presence/absence of 9 μM QVD (Q). (E) A549 were stimulated with 2 pfu/cell IAV in the presence of 15 μg/mL control IgG or EMAPII mAb. Shown are mean ± SE of three parallel recordings; resistance is normalized to the moment of stimulation with IAV/EMAPII (shown with an arrow in A and B). *p < 0.05 by t test.

Figure 4

Self-Limiting IAV Infection in Mice Is Accompanied by Lung Injury Mice were administered 750 pfu/mouse IAV to lung and analyzed for (A) weight loss, (B) conscious blood oxygenation, (C) lung edema, (D) BALF protein extravasation, and (E) BALF white blood cell (WBC) count including total WBC (t), macrophages (m), lymphocytes (l), and neutrophils (n). (A and B) n = 5, (C and D) n = 7 for control group and 3 or 4 for all other groups; data are presented as mean ± SEM. *p < 0.05 by ANOVA with Tukey post-hoc when compared to control values.

Figure 5

IAV-Induced Lung Injury Is Accompanied by EMAPII Release and Induction of Pulmonary Apoptosis Mice were administered 750 pfu/mouse IAV to lung and analyzed for (A) BALF level of EMAPII, (B) BALF level of caspase 3/7 activity, (C) lung levels of EMAPII, (D) lung levels of cleaved caspase 3. n = 7 for control group and 3–4 for all other groups; data are presented as mean ± SEM. *p < 0.05 by ANOVA with Tukey post-hoc when compared to control values.

Figure 6

IAV-Induced Lung Injury Is Accompanied by Surface EMAPII Translocation and Caspase 3 Cleavage in Cells of Hematopoietic and Endothelial Lineage Mice infected with 750 pfu/mouse IAV were sacrificed at day 5 (A and B) or day 7 (C and D). Lungs were digested and subjected to concomitant staining for surface CD31/CD326/CD45 and EMAPII (A and C) or permeabilized and subjected to concomitant staining for CD31/CD326/CD45 and cleaved caspase 3 (B and D). n = 3–5; data are presented as mean ± SEM. *p < 0.05 by t test with Welch correction when compared to control values.

Figure 7

EMAPII mAb Subcutaneous Injections Reduce Levels of Released EMAPII, Weight Loss, and Indices of Lung Injury in IAV-Infected Mice (A) Mice received 750 pfu/mouse IAV or equal volume of saline (cntr). Half of IAV-infected mice were treated with EMAPII mAb (2.5 mg/kg) on days 4, 6, and 8 post-infection. Mice were analyzed for (B) EMAPII levels in BALF, (C) IAV-induced weight loss, (D) conscious blood oxygenation, (E) lung edema and protein in BALF (day 9), and (F) BALF caspase 3/7 activity (day 9). n = 5 for all groups; data are presented as mean ± SEM. *p < 0.05 by ANOVA with Tukey post-hoc (B and D–F) or repeated-measurements ANOVA (C).

Figure 8

EMAPII mAb Subcutaneous Injections Reduce BALF Levels of TNF-α and Increase Levels of M2 Markers in the Lung of IAV-Infected Mice At day 9, mice from Figure 6 were analyzed for (A) WBC count in BALF including total WBC (t), macrophages (m), lymphocytes (l), and neutrophils (n), (B) TNF-α levels in BALF, (D) YM1 levels in lung, (E) CD206 levels in lung. n = 5 for all groups; data are presented as mean ± SEM. *p < 0.05 by ANOVA with Tukey post-hoc; shown are differences between IAV and control, and IAV and IAV + ab groups. (C) Mice from Figures 4 and 5 were analyzed for YM1, and CD206 levels in lung; vinculin was used as a loading control.