Role of CD39 in COVID-19 Severity: Dysregulation of Purinergic Signaling and Thromboinflammation

CD39/NTPDase1 has emerged as an important molecule that contributes to maintain inflammatory and coagulatory homeostasis. Various studies have hypothesized the possible role of CD39 in COVID-19 pathophysiology since no confirmatory data shed light in this regard. Therefore, we aimed to quantify CD39 expression on COVID-19 patients exploring its association with severity clinical parameters and ICU admission, while unraveling the role of purinergic signaling on thromboinflammation in COVID-19 patients. We selected a prospective cohort of patients hospitalized due to severe COVID-19 pneumonia (n=75), a historical cohort of Influenza A pneumonia patients (n=18) and sex/age-matched healthy controls (n=30). CD39 was overexpressed in COVID-19 patients’ plasma and immune cell subsets and related to hypoxemia. Plasma soluble form of CD39 (sCD39) was related to length of hospital stay and independently associated with intensive care unit admission (adjusted odds ratio 1.04, 95%CI 1.0-1.08, p=0.038), with a net reclassification index of 0.229 (0.118-0.287; p=0.036). COVID-19 patients showed extracellular accumulation of adenosine nucleotides (ATP and ADP), resulting in systemic inflammation and pro-coagulant state, as a consequence of purinergic pathway dysregulation. Interestingly, we found that COVID-19 plasma caused platelet activation, which was successfully blocked by the P2Y₁₂ receptor inhibitor, ticagrelor. Therefore, sCD39 is suggested as a promising biomarker for COVID-19 severity. As a conclusion, our study indicates that CD39 overexpression in COVID-19 patients could be indicating purinergic signaling dysregulation, which might be at the basis of COVID-19 thromboinflammation disorder.

IFITM3 and severe influenza virus infection. No evidence of genetic association

Influenza virus infection (IVI) is typically subclinical or causes a self-limiting upper respiratory disease. However, in a small subset of patients IVI rapidly progresses to primary viral pneumonia (PVP) with respiratory failure; a minority of patients require intensive care unit admission. Inherited and acquired variability in host immune responses may influence susceptibility and outcome of IVI. However, the molecular basis of such human factors remains largely elusive. It has been proposed that homozygosity for IFITM3 rs12252-C is associated with a population-attributable risk of 5.4 % for severe IVI in Northern Europeans and 54.3 % for severe H1N1pdm infection in Chinese. A total of 148 patients with confirmed IVI were considered for recruitment; 118 Spanish patients (60 of them hospitalized with PVP) and 246 healthy Spanish individuals were finally included in the statistical analysis. PCR-RFLP was used with confirmation by Sanger sequencing. The allele frequency for rs12252-C was found to be 3.5 % among the general Spanish population. We found no rs12252-C homozygous individuals in our control group. The only Spanish patient homozygous for rs12252-C had a neurological disorder (a known risk factor for severe IVI) and mild influenza. Our data do not suggest a role of rs12252-C in the development of severe IVI in our population. These data may be relevant to recognize whether patients homozygous for rs12252-C are at risk of severe influenza, and hence require individualized measures in the case of IVI.

Surfactant protein A genetic variants associate with severe respiratory insufficiency in pandemic influenza A virus infection

Introduction

Inherited variability in host immune responses influences susceptibility and outcome of Influenza A virus (IAV) infection, but these factors remain largely unknown. Components of the innate immune response may be crucial in the first days of the infection. The collectins surfactant protein (SP)-A1, -A2, and -D and mannose-binding lectin (MBL) neutralize IAV infectivity, although only SP-A2 can establish an efficient neutralization of poorly glycosylated pandemic IAV strains.

Methods

We studied the role of polymorphic variants at the genes of MBL (MBL2), SP-A1 (SFTPA1), SP-A2 (SFTPA2), and SP-D (SFTPD) in 93 patients with H1N1 pandemic 2009 (H1N1pdm) infection.

Results

Multivariate analysis showed that two frequent SFTPA2 missense alleles (rs1965708-C and rs1059046-A) and the SFTPA2 haplotype 1A⁰ were associated with a need for mechanical ventilation, acute respiratory failure, and acute respiratory distress syndrome. The SFTPA2 haplotype 1A¹ was a protective variant. Kaplan-Meier analysis and Cox regression also showed that diplotypes not containing the 1A¹ haplotype were associated with a significantly shorter time to ICU admission in hospitalized patients. In addition, rs1965708-C (P = 0.0007), rs1059046-A (P = 0.0007), and haplotype 1A⁰ (P = 0.0004) were associated, in a dose-dependent fashion, with lower PaO₂/FiO₂ ratio, whereas haplotype 1A¹ was associated with a higher PaO₂/FiO₂ ratio (P = 0.001).

Conclusions

Our data suggest an effect of genetic variants of SFTPA2 on the severity of H1N1pdm infection and could pave the way for a potential treatment with haplotype-specific (1A¹) SP-A2 for future IAV pandemics.