Insights into the lung microenvironment after severe COVID-19

The SARS-CoV-2 is the betacoronavirus responsible for the coronavirus disease 2019 (COVID-19) pandemic. Severe COVID-19 affects approximately 10-15% of patients and results in prolonged morbidity and mortality. Little is known about the immunophenotypic changes of the lung parenchyma driven by the viral infection in patients who die of severe COVID-19. Ultrasound-guided lung biopsies (LB) were collected (IRB approval#1561/21) within few hours from death in 15 severe COVID-19 patients between November 2020 and January 2021, in two patients who underwent lung transplantation after COVID-19 and in one patient who had surgery for bacterial superinfection during COVID-19 disease. All samples underwent histologic and immunohistochemistry evaluation and molecular profiling using the nCounter Host Response and Coronavirus Panel plus. As controls, lungs from end-stage usual interstitial pneumonia (UIP;n=9) and from lobectomy for lung cancer (Norm;n=5) were used. Eleven lungs (61%) were positive for SARS-CoV-2 RNA. Signs of diffuse alveolar damage (DAD) were observed in 6 patients (30%). COVID-19 lungs showed a marked macrophage infiltration with M2 polarization compared with controls. Globally, COVID-19 lungs showed distinct molecular profiles from UIP or Norm lungs. Specifically, a marked upregulation of interferon-genes that was directly correlated with SARS-CoV-2 genes was seen in COVID-19 lungs. COVID-19-specific genes signatures (Log2FC >1.5;adj p<0.05) obtained using VENN diagram showed impairment of the STAT3-pathway accompanied by the upregulation of the NFkB signaling. Results herein provide new insights into lung alterations induced by severe COVID-19 and suggest novel potential targets for therapeutic intervention.

Involvement of the contact pathway in COVID-19 coagulopathy

Background: A novel acquired coagulopathy characterized by a severe procoagulant imbalance is common in COVID-19 patients and is associated with the clinical severity of the disease. Aim(s): Our study aims to elucidate the underlying mechanisms of coagulation activation in COVID-19 patients. Method(s): Symptomatic COVID-19 patients during Milan first wave were consecutively enrolled and stratified into 3 groups based on the intensity of care: Low, requiring only high-flow oxygen by nasal cannula;intermediate, requiring continuous positive airway pressure;high, requiring mechanical ventilation. Blood samples were tested for markers of activation of the intrinsic pathway (FXIa, FXIIa) together with its physiologic inhibitor (C1-inhibitor), of the extrinsic pathway (FVIIa), of global activation of the coagulation cascade (D-dimer, FDP, FM) and of fibrinolysis (plasminogen, t-PA, alpha2-antiplasmin, PAI-1). Result(s): 111 patients were included: 26 at low, 42 intermediate and 43 high care-intensity. Median age was 59 +/- 12 (34 patients >65 years);32 patients (29%) developed a venous thrombosis and 12 (11%) died (Table). Median D-dimer, FDP and FM plasma levels were higher in COVID-19 patients compared to controls, with a gradient of increase across the three care intensities, while all the fibrinolytic pathway parameters were in the normal range. Median plasma levels of FVIIa were lower in COVID-19 patients (27.5 mU/ml) than in controls (40.1 mU/ml) while median plasma levels of FXIIa and FXIa were higher in COVID-19 patients (11.2 and 11.3 mU/ml) than in controls (7.2 and 5.5 mU/ml), with a gradient of increase across the three care intensities. C1-inhibitor plasma levels were above the normal range in all the 3 COVID-19 patients' groups (Figure). Conclusion(s): Our study showed a prevalent activation of the contact pathway over the extrinsic pathway of the coagulation cascade in COVID-19 patients, which is proportional to the clinical severity of the infection, opening the possibility for targeted anticoagulant therapies. (Table Presented).

Reduced circulating FABP2 in patients with moderate to severe COVID-19 may indicate enterocyte functional change rather than cell death.

The gut is of importance in the pathology of COVID-19 both as a route of infection, and gut dysfunction influencing the severity of disease. Systemic changes caused by SARS-CoV-2 gut infection include alterations in circulating levels of metabolites, nutrients and microbial products which alter immune and inflammatory responses. Circulating plasma markers for gut inflammation and damage such as zonulin, lipopolysaccharide and ß-glycan increase in plasma along with severity of disease. However, Intestinal Fatty Acid Binding Protein / Fatty Acid Binding Protein 2 (I-FABP/FABP2), a widely used biomarker for gut cell death, has paradoxically been shown to be reduced in moderate to severe COVID-19. We also found this pattern in a pilot cohort of mild (n = 18) and moderately severe (n = 19) COVID-19 patients in Milan from March to June 2020. These patients were part of the first phase of COVID-19 in Europe and were therefore all unvaccinated. After exclusion of outliers, patients with more severe vs milder disease showed reduced FABP2 levels (median [IQR]) (124 [368] vs. 274 [558] pg/mL, P < 0.01). A reduction in NMR measured plasma relative lipid-CH3 levels approached significance (median [IQR]) (0.081 [0.011] vs. 0.073 [0.024], P = 0.06). Changes in circulating lipid levels are another feature commonly observed in severe COVID-19 and a weak positive correlation was observed in the more severe group between reduced FABP2 and reduced relative lipid-CH3 and lipid-CH2 levels. FABP2 is a key regulator of enterocyte lipid import, a process which is inhibited by gut SARS-CoV-2 infection. We propose that the reduced circulating FABP2 in moderate to severe COVID-19 is a marker of infected enterocyte functional change rather than gut damage, which could also contribute to the development of hypolipidemia in patients with more severe disease.

Anemia and iron metabolism in patients with sars-cov-2 infection: The role of inflammation and hypoxia

Background: Coronavirus Disease (COVID-19) could be considered as a human model of marked inflammation combined with severe hypoxia. In this setting, both erythropoiesis and iron metabolism appear to be profoundly affected by inflammatory and hypoxic stimuli, which act in the opposite direction. In patients with SARS-CoV-2 infection, Hb levels tend to be relatively high even in the context of severe disease and marked inflammation. A better understanding of erythropoiesis and iron metabolism in COVID-19 could contribute to elucidate the relationship between hypoxia and inflammation on erythropoietic control. Aims: To investigate the prevalence of anemia, the alterations of iron homeostasis,and the relationship between inflammation,hypoxia and erythropoiesis in a cohort of COVID-19 patients admitted both to medical wards and intensive care unit (ICU). Methods: We retrospectively analyzed data of 303 patients with COVID- 19 (178 subjects admitted to medical wards and 125 subjects admitted to the ICU). Biochemical parameters were collected on admission (T0), after 7 days of hospitalization (T1) and at discharge/death (T2). Results: The median age of the patients was 62 years (53-71) and 72% were males. ICU patients had lower mean Hb levels compared to non- ICU patients (11.3±1.8 vs 12.8±1.8 g/dL at T0, 10.2±1.6 vs 12.2±1.9 g/ dL at T1, 10±1.4 vs 12±1.7 g/dL at T2;p<0.001). Mean Hb concentration did not fall under 12 g/dl in the non-ICU group and under 10 g/ dl in the ICU group during hospitalization. Hb decreased by approximately 1 g/dl in both cohorts during the first 7 days of hospitalization, then remained stable until discharge. ICU patients also showed increased inflammatory markers and ferritin levels (1401 vs 839 mcg/l at T0, p<0.001;913 vs 832 mcg/L at T1, p ns;764 vs 651 mcg/L at T2, p ns). There were no significant differences in other iron parameters between groups. Hypoxia was a prominent feature of ICU patients (P/F ratio 91 vs 224, p<0.001). Patients who were anemic on admission maintained relatively constant Hb concentrations from T0 to T2 (10.8 g/dL at T0, 10.2 g/dL at T1 and 10.4 g/dL at T2), thus remaining in a range of mild to moderate anemia. Conversely, the non-anemic group displayed a greater reduction of Hb levels (13.7 g/dl at T0, 12.7 g/dl at T1, 12 g/dl at T2). Anemic subjects were more hypoxic than non-anemic patients (P/F 151 vs 292 at T0, p<0.001) and showed significantly higher levels of CRP (10.8 vs 6.6 mg/dL), IL-6 (60.3 vs 47.7 ng/L) and leukocyte count (7290 vs 6130 x109/L). Ferritin was higher in anemic patients at T0 and T1 (1220 vs 926 mcg/L and 852 vs 896 mcg/L, p ns), decreasing more at T2 (655 vs 763 mcg/L, p ns). Median hepcidin levels, which were available for a limited subset of non- ICU patients, were elevated during the whole period: 233 ng/mL at T0, 95 ng/mL at T1 and 60 ng/mL at T2. Summary/Conclusion: In patients with SARS-CoV-2 infection, two main factors influence erythropoiesis and iron homeostasis: systemic inflammation and profound hypoxia. Markedly high ferritin and hepcidin levels reflect a strong inflammatory response. However, COVID-19 patients tend to have disproportionately high Hb levels in the contest of the inflammatory milieu. The absolute reduction in Hb levels is more prominent in patients who displayed normal Hb on admission. Conversely, anemic and profoundly hypoxic subjects show constant mean Hb levels over time. Thus, we can hypothesize that the erythropoietic drive provided by hypoxia could counterbalance the effect of inflammation on hepcidin regulation, preventing Hb levels from falling dramatically during hospitalization.

Prevalence of neurological post-COVID-19 manifestations

Background and aims: Although COVID-19 infection predominantly manifests with respiratory symptoms, recent studies have also reported the occurrence of neurological involvement in the acute phase as well as in the follow-up of recovered subjects Methods: Our study focuses on assessing the prevalence of neurological sequelae in COVID-19 patients hospitalized at Ospedale Maggiore Policlinico in Milan. Seventy-five COVID-19 recovered subjects followed a general follow-up protocol including pneumological, infectious and cardiovascular assessment 5-10 months after the onset of SARS-CoV2 infection;among them, a subset of 53 patients was evaluated through a self-administered 18-item questionnaire developed ad-hoc addressing sensory, motor and cognitive neurological symptoms. Results: Collected data has shown that 77.4% patients developed at least one neurological sequela, and 46.3% presented with more than three symptoms. Among symptomatic patients, the most prevalent manifestations were insomnia (65.9%) and daytime sleepiness (46.3%), followed by walking difficulties (31.7%). Other less frequent symptoms were headache (15.1%), hyposmia and hypogeusia (15.1%), and tremor (9.4%). Prevalence of symptoms 18-item questionnare showing the distribution of neurological manifestations Conclusion: Post-COVID-19 manifestations are reported in about 90% of recovered patients. This preliminary study suggests that neurological findings represent a significant part of such manifestations. We are currently expanding the questionnaire to a larger cohort of patients and correlating our findings with patients' demographical and clinical features, as well as with the severity of the previous SARSCoV2 infection. Currently, the same questionnaire is also being validated and administered to age-and sex-matched healthy controls who have not developed symptoms suggestive of Covid-19, and a cohort of non-COVID-19 hospitalized patients.