Circulating neutrophil extracellular trap (NET)-forming 'rogue' neutrophil subset, immunotype [DEspR + CD11b +], mediate multi-organ failure in COVID-19-an observational study

Background

Cumulative research show association of neutrophils and neutrophil extracellular traps (NETs) with poor outcomes in severe COVID-19. However, to date, there is no curative intent therapy able to block neutrophil/NETs-mediated progression of multi-organ dysfunction. Because of emerging neutrophil heterogeneity, the study of subsets of circulating NET-forming neutrophils [NET + Ns] as mediators of multi-organ failure progression among patients with COVID-19 is critical to identification of therapeutic targets.

Methods

We conducted a prospective observational study of circulating levels of CD11b + [NET + N] immunotyped for dual endothelin-1/signal peptide receptor (DEspR ±) expression by quantitative immunofluorescence-cytology and causal mediation analysis. In 36 consented adults hospitalized with mod-severe COVID-19, May to September 2020, we measured acute multi-organ failure via SOFA-scores and respiratory failure via SaO2/FiO2 (SF)-ratio at time points t1 (average 5.5 days from ICU/hospital admission) and t2 (the day before ICU-discharge or death), and ICU-free days at day28 (ICUFD). Circulating absolute neutrophil counts (ANC) and [NET + N] subset-specific counts were measured at t1. Spearman correlation and causal mediation analyses were conducted.

Results

Spearman correlation analyses showed correlations of t1-SOFA with t2-SOFA (rho r S  = 0.80) and ICUFD (r S  = -0.76); circulating DEspR + [NET + Ns] with t1-SOFA (r S  = 0.71), t2-SOFA (r S  = 0.62), and ICUFD (r S  = -0.63), and ANC with t1-SOFA (r S  = 0.71), and t2-SOFA (r S  = 0.61).Causal mediation analysis identified DEspR + [NET + Ns] as mediator of 44.1% [95% CI:16.5,110.6] of the causal path between t1-SOFA (exposure) and t2-SOFA (outcome), with 46.9% [15.8,124.6] eliminated when DEspR + [NET + Ns] were theoretically reduced to zero. Concordantly, DEspR + [NET + Ns] mediated 47.1% [22.0,72.3%] of the t1-SOFA to ICUFD causal path, with 51.1% [22.8,80.4%] eliminated if DEspR + [NET + Ns] were reduced to zero. In patients with t1-SOFA > 1, the indirect effect of a hypothetical treatment eliminating DEspR + [NET + Ns] projected a reduction of t2-SOFA by 0.98 [0.29,2.06] points and ICUFD by 3.0 [0.85,7.09] days. In contrast, there was no significant mediation of SF-ratio through DEspR + [NET + Ns], and no significant mediation of SOFA-score through ANC.

Conclusions

Despite equivalent correlations, DEspR + [NET + Ns], but not ANC, mediated progression of multi-organ failure in acute COVID-19, and its hypothetical reduction is projected to improve ICUFD. These translational findings warrant further studies of DEspR + [NET + Ns] as potential patient-stratifier and actionable therapeutic target for multi-organ failure in COVID-19.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41231-023-00143-x.

Increased Neutrophil-Subset Associated With Severity/Mortality In ARDS And COVID19-ARDS Expresses The Dual Endothelin-1/VEGFsignal-Peptide Receptor (DEspR): An Actionable Therapeutic Target

Neutrophil-mediated secondary tissue injury underlies acute respiratory distress syndrome (ARDS) and progression to multi-organ-failure (MOF) and death, processes linked to severe COVID19. This 'innocent bystander' tissue injury arises in dysregulated hyperinflammatory states from neutrophil functions and neutrophil extracellular traps (NETs) intended to kill pathogens, but injure cells instead, causing MOF. Insufficiency of prior therapeutic approaches suggest need to identify dysregulated neutrophil-subset(s) and induce subset-specific apoptosis critical for neutrophil function-shutdown and clearance. We hypothesized that neutrophils expressing the pro-survival dual endothelin-1/signal peptide receptor, DEspR, are apoptosis-resistant just like DEspR+ cancer cells, hence comprise a consequential pathogenic neutrophil-subset in ARDS and COVID19-ARDS. Here, we report correlation of circulating DEspR+CD11b+ activated neutrophils (DESpR+actNs) and NETosing-neutrophils with severity in ARDS and in COVID19-ARDS, increased DEspR+ neutrophils and monocytes in post-mortem ARDS-patient lung sections, and neutrophil DEspR/ET1 receptor/ligand autocrine loops in severe COVID19. Unlike DEspR[-] neutrophils, ARDS patient DEspR+actNs exhibit apoptosis-resistance, which decreased upon ex vivo treatment with humanized anti-DEspR-IgG4S228P antibody, hu6g8. Ex vivo live-cell imaging of non-human primate DEspR+actNs showed hu6g8 target-engagement, internalization, and induction of apoptosis. Altogether, data differentiate DEspR+actNs as a targetable neutrophil-subset associated with ARDS and COVID19-ARDS severity, and suggest DEspR-inhibition as a potential therapeutic paradigm.

Humanized anti-DEspR IgG4S228P antibody increases overall survival in a pancreatic cancer stem cell-xenograft peritoneal carcinomatosis ratnu/nu model

BACKGROUND

Pancreatic peritoneal carcinomatosis (PPC), with the worst median overall-survival (mOS), epitomizes the incurability of metastatic cancer. Cancer stem cells (CSCs) underpin this incurability. However, inhibitors of CSC-stemness fail to increase mOS in cancer patients despite preclinical tumor-reduction. This shortfall reinforces that preclinical efficacy should be defined by increased mOS in the presence of cancer comorbidities, CSC-heterogeneity and plasticity. The primary objectives of this study are: to test the dual endothelin-1/signal peptide receptor, DEspR, as a nodal therapeutic target in PPC, given DEspR induction in anoikis-resistant pancreatic CSCs, and to validate humanized anti-DEspR antibody, hu-6g8, as a potential therapeutic for PPC.

METHODS

We used heterogeneous pools of CSCs selected for anoikis resistance from reprogrammed Panc1 and MiaPaCa2 tumor cells (TCs), and adherent TCs reprogrammed from CSCs (cscTCs). We used multiple anti-DEspR blocking antibodies (mAbs) with different epitopes, and a humanized anti-DEspR recombinant mAb cross-reactive in rodents and humans, to test DEspR inhibition effects. We measured DEspR-inhibition efficacy on multiple prometastatic CSC-functions in vitro, and on tumorigenesis and overall survival in a CSC-derived xenograft (CDX) nude rat model of PPC with comorbidities.

RESULTS

Here we show that DEspR, a stress-survival receptor, is present on subsets of PDAC Panc1-TCs, TC-derived CSCs, and CSC-differentiated TCs (cscTCs), and that DESpR-inhibition decreases apoptosis-resistance and pro-metastatic mesenchymal functions of CSCs and cscTCs in vitro. We resolve the DNA-sequence/protein-function discordance by confirming ADAR1-RNA editing-dependent DEspR-protein expression in Panc1 and MiaPaCa2 TCs. To advance DEspR-inhibition as a nodal therapeutic approach for PPC, we developed and show improved functionality of a recombinant, humanized anti-DEspR IgG4S228P antibody, hu-6g8, over murine precursor anti-DEspR mabs. Hu-6g8 internalizes and translocates to the nucleus colocalized with cyto-nuclear shuttling galectins-1/3, and induces apoptotic cell changes. DEspR-inhibition blocks transperitoneal dissemination and progression to peritoneal carcinomatosis of heterogeneous DEspR±/CD133 ± Panc1-derived CSCs in xenografted nude rats, improving mOS without chemotherapy-like adverse effects. Lastly, we show DEspR expression in Stage II-IV primary and invasive TCs in the stroma in PDAC-patient tumor arrays.

CONCLUSION

Collectively, the data support humanized anti-DEspR hu-6g8 as a potential targeted antibody-therapeutic with promising efficacy, safety and prevalence profiles for PPC patients.

Confirmation of translatability and functionality certifies the dual endothelin1/VEGFsp receptor (DEspR) protein

Background

In contrast to rat and mouse databases, the NCBI gene database lists the human dual-endothelin1/VEGFsp receptor (DEspR, formerly Dear) as a unitary transcribed pseudogene due to a stop [TGA]-codon at codon#14 in automated DNA and RNA sequences. However, re-analysis is needed given prior single gene studies detected a tryptophan [TGG]-codon#14 by manual Sanger sequencing, demonstrated DEspR translatability and functionality, and since the demonstration of actual non-translatability through expression studies, the standard-of-excellence for pseudogene designation, has not been performed. Re-analysis must meet UNIPROT criteria for demonstration of a protein’s existence at the highest (protein) level, which a priori, would override DNA- or RNA-based deductions.

Methods

To dissect the nucleotide sequence discrepancy, we performed Maxam–Gilbert sequencing and reviewed 727 RNA-seq entries. To comply with the highest level multiple UNIPROT criteria for determining DEspR’s existence, we performed various experiments using multiple anti-DEspR monoclonal antibodies (mAbs) targeting distinct DEspR epitopes with one spanning the contested tryptophan [TGG]-codon#14, assessing: (a) DEspR protein expression, (b) predicted full-length protein size, (c) sequence-predicted protein-specific properties beyond codon#14: receptor glycosylation and internalization, (d) protein-partner interactions, and (e) DEspR functionality via DEspR-inhibition effects.

Results

Maxam–Gilbert sequencing and some RNA-seq entries demonstrate two guanines, hence a tryptophan [TGG]-codon#14 within a compression site spanning an error-prone compression sequence motif. Western blot analysis using anti-DEspR mAbs targeting distinct DEspR epitopes detect the identical glycosylated 17.5 kDa pull-down protein. Decrease in DEspR-protein size after PNGase-F digest demonstrates post-translational glycosylation, concordant with the consensus-glycosylation site beyond codon#14. Like other small single-transmembrane proteins, mass spectrometry analysis of anti-DEspR mAb pull-down proteins do not detect DEspR, but detect DEspR-protein interactions with proteins implicated in intracellular trafficking and cancer. FACS analyses also detect DEspR-protein in different human cancer stem-like cells (CSCs). DEspR-inhibition studies identify DEspR-roles in CSC survival and growth. Live cell imaging detects fluorescently-labeled anti-DEspR mAb targeted-receptor internalization, concordant with the single internalization-recognition sequence also located beyond codon#14.

Conclusions

Data confirm translatability of DEspR, the full-length DEspR protein beyond codon#14, and elucidate DEspR-specific functionality. Along with detection of the tryptophan [TGG]-codon#14 within an error-prone compression site, cumulative data demonstrating DEspR protein existence fulfill multiple UNIPROT criteria, thus refuting its pseudogene designation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12867-016-0066-8) contains supplementary material, which is available to authorized users.