Elevated NET, Calprotectin, and Neopterin Levels Discriminate between Disease Activity in COVID-19, as Evidenced by Need for Hospitalization among Patients in Northern Italy

Coronavirus disease 2019 (COVID-19) displays clinical heterogeneity, but little information is available for patients with mild or very early disease. We aimed to characterize biomarkers that are useful for discriminating the hospitalization risk in a COVID-19 cohort from Northern Italy during the first pandemic wave. We enrolled and followed for four weeks 76 symptomatic SARS-CoV-2 positive patients and age/sex-matched healthy controls. Patients with mild disease were discharged (n.42), and the remaining patients were hospitalized (n.34). Blood was collected before any anti-inflammatory/immunosuppressive therapy and assessed for soluble C5b-9/C5a, H3-neutrophil extracellular traps (NETs), calprotectin, and DNase plasma levels via ELISA and a panel of proinflammatory cytokines via ELLA. Calprotectin and NET levels discriminate between hospitalized and non-hospitalized patients, while DNase negatively correlates with NET levels; there are positive correlations between calprotectin and both NET and neopterin levels. Neopterin levels increase in patients at the beginning of the disease and do so more in hospitalized than non-hospitalized patients. C5a and sC5b-9, and other acute phase proteins, correlate with neopterin, calprotectin, and DNase. Both NET and neopterin levels negatively correlate with platelet count. We show that calprotectin, NETs, and neopterin are important proinflammatory parameters potentially useful for discriminating between COVID-19 patients at risk of hospitalization.

Epstein-Barr virus reactivation is not causative for post-COVID-19-syndrome in individuals with asymptomatic or mild SARS-CoV-2 disease course

PURPOSE

Post-COVID-19-Syndrome (PCS) frequently occurs after an infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). However, the understanding of causative mechanisms is still limited. Aim of this study was to determine the PCS rate among SARS-CoV-2 seropositive blood donors as representatives of supposedly healthy adults, who had experienced an asymptomatic or mild COVID-19 disease course, and to examine whether Epstein-Barr virus (EBV) is reactivated in individuals reporting PCS.

METHODS

The PCS rate was determined using questionnaires that included questions about infection and persistent symptoms. Pre-pandemic blood samples and samples collected at regular, pre-defined times after a SARS-CoV-2 infection were analysed for neopterin, a marker for antiviral immune responses, by an enzyme-linked immunosorbent assay (ELISA). Additionally, we determined the rate of SARS-CoV-2 anti-N total antibodies using an electrochemiluminescence immunoassay (ECLIA). Furthermore, quantitative real-time polymerase chain reaction (qPCR) to detect EBV DNA and ECLIA screening for EBV viral capsid-antigen (VCA) IgM, IgG and EBV nuclear antigen 1 (EBNA) IgG were performed.

RESULTS

Our data reveal that 18% of all infections result in PCS, with symptoms lasting for up to one year. In individuals reporting PCS, no elevated levels of neopterin were detected, indicating no persisting pro-inflammatory, antiviral immune response. SARS-CoV-2 antibody levels were declining in all participants in comparable manner over time, pointing to a successful virus clearance. In individuals with PCS, no EBV DNA could be detected. Furthermore, no differences in EBV specific antibody levels could be shown in PCS groups compared to non-PCS groups.

CONCLUSION

Our data suggest that PCS in per se healthy, immunocompetent adults cannot be ascribed to a reactivation of EBV.

Inflammatory markers calprotectin, NETs, syndecan-1 and neopterin in COVID-19 convalescent blood donors

Persisting inflammation has been discovered in lungs and other parenchymatous organs of some COVID-19 convalescents. Calprotectin, neutrophil extracellular traps (NETs), syndecan-1 and neopterin are general key inflammatory markers, and systemically enhanced levels of them may remain after the COVID-19 infection. These inflammatory markers were therefore measured in serum samples of 129 COVID-19 convalescent and 27 healthy blood donors or employees at Oslo Blood bank, Norway. Also antibodies against SARS-CoV-2 nucleocapsid antigen were measured, and timing of sampling and severity of infection noted. Whereas neopterin and NETs values remained low and those for syndecan-1 were not raised to statistically significant level, concentrations for calprotectin, as measured by a novel mixed monoclonal assay, were significantly increased in the convalescents. Antibodies against SARS-CoV-2 nucleocapsid antigen were elevated, but did not correlate with levels of inflammatory markers. Difference between the groups in only one biomarker makes evaluation of ongoing or residual inflammation in the convalescents difficult. If there is a low-grade inflammation, it would in that case involve neutrophils.

Assessment of neopterin level and severity in lichen planus patients treated with narrow-band ultraviolet B

BACKGROUND

Neopterin is a cellular immunity biochemical marker. Serum and saliva neopterin levels have been reported to increase in lichen Planus. Nonetheless, analysis has not yet been made for the direct link between narrow band ultraviolet B and severity of Lichen planus.

AIM

We aimed to assess serum neopterin levels in patients who receive narrow band ultraviolet B therapy treatment with lichen planus, paired with the severity of the disease.

PATIENTS AND METHODS

The study consisted of 35 lichen planus patients and 30 healthy individuals. A 35 patient group received narrow band ultraviolet B therapy. An enzyme-related immunosorbent assay procedure was used in serum neopterin analysis before and post-therapy.

RESULTS

The correlation between the level and severity of the patient group was statistically significant (P = .001). In patients with severe disease, serum neopterin levels were significantly increased. Also, in the severe lichen planus group, the serum neopterin level was statistically higher than that of the mild or moderate groups (P = .001).Also, a significant decrease was seen following therapy according to serum neopterin level.

CONCLUSION

Serum neopterin levels are a useful marker for the assessment of the severity and effectiveness of narrow band ultraviolet therapy. Thus, our findings may provide a new approach with the management of disease and follow-up strategies in patients with lichen planus.

Specific immunotherapy normalizes tryptophan concentrations in patients with allergic rhinitis

BACKGROUND/AIMS

An immune shift towards Th2-type immunity seems to be critical in the pathogenesis of allergic asthma and rhinitis. In a previous study, we found higher serum tryptophan concentrations in patients with seasonal tree or grass pollen rhinoconjunctivitis who underwent specific immunotherapy (SCIT) than in controls, and those with the highest levels at baseline responded less well to SCIT. In the present study, we examined whether 'booster immunotherapy' after cessation of SCIT had any influence on tryptophan metabolism during follow-up.

METHODS

Serum concentrations of tryptophan, kynurenine and neopterin were assayed in 19 patients (mean age: 26.2 years; 6 females) allergic to grass and/or tree pollen before and after they had received a booster immunotherapy with 4 injections of an allergoid vaccine (Pollinex Quattro; Bencard Vienna, Austria) over 8 ± 3 months outside the pollen season.

RESULTS

Serum tryptophan and kynurenine concentrations decreased after booster immunotherapy (mean ± SD, before immunotherapy: 81.1 ± 14.2 µmol/l, after immunotherapy: 61.4 ± 20.9 µmol/l and before immunotherapy: 2.25 ± 0.44, after immunotherapy: 1.69 ± 0.70 µmol/l, respectively; both p < 0.01); this was especially true in those responders who also tended to have lower baseline kynurenine concentrations as compared with nonresponders (p = 0.05). Finally, a correlation between changes in tryptophan metabolism and neopterin concentrations was observed after immunotherapy.

CONCLUSIONS

The decrease in tryptophan and kynurenine concentrations following booster immunotherapy in hay fever patients strengthens the hypothesis that tryptophan metabolism might be involved in the course of allergic responses. However, it is still unclear whether the abnormal tryptophan metabolism in pollinosis patients is related to indoleamine 2,3-dioxygenase and/or to a specific cytokine background.

Protein chip for the parallel quantification of high and low abundant biomarkers for sepsis

We present herein a protein chip for diagnosis of sepsis that combines both a sandwich and a binding inhibition format in order to quantify high (CRP) and low abundant proteins (cytokines, PCT, neopterin) in parallel. Using the combined assay format the lowest detectable concentrations for CRP, IL-6, IL-8, IL-10, TNFα, PCT, and neopterin are 3 mg/L, 15 ng/L, 26 ng/L, 65 ng/L, 40 ng/L, 78 ng/L, and 0.46 μg/L. Four different combined assay formats are tested, using separate or joint incubation steps of analytes and detection antibodies. Yet, low limit of detection (LOD) and short processing time are contradictory: while the combined assay performed in a multistep protocol is extremely sensitive (e.g., the LOD for IL-6 is 15 ng/L), but more time-consuming (4 h), the all-in-one protocol takes only 2.5 h, but suffers from lower sensitivity compared with the multistep protocol (e.g., the LOD for IL-6 is up to 40 times enhanced). Reproducibility is good in both cases (CV 5-20%).

Plasma kynurenine levels are elevated in suicide attempters with major depressive disorder

BACKGROUND

Inflammation has been linked to depression and suicide risk. One inflammatory process that has been minimally investigated in this regard is cytokine-stimulated production of kynurenine (KYN) from tryptophan (TRP). Recent data suggest that KYN increases in cerebrospinal fluid (CSF) are associated with depressive symptoms secondary to immune activation. KYN may alter dopaminergic and glutamatergic tone, thereby contributing to increased arousal, agitation and impulsivity - important risk factors in suicide. We hypothesized that patients with major depressive disorder (MDD) and a history of suicide attempt would have higher levels of KYN than depressed nonattempters, who in turn would have higher levels than healthy volunteers.

METHODS

Plasma KYN, TRP, and neopterin were assayed by high performance liquid chromatography in three groups: healthy volunteers (n=31) and patients with MDD with (n=14) and without (n=16) history of suicide attempt. Analysis of variance tested for group differences in KYN levels.

RESULTS

KYN levels differed across groups (F=4.03, df=(2,58), and p=0.023): a priori planned contrasts showed that KYN was higher in the MDD suicide attempter subgroup compared with MDD non-attempters (t=2.105, df=58, and p=0.040), who did not differ from healthy volunteers (t=0.418, df=58, and p=0.677). In post hoc testing, KYN but not TRP was associated with attempt status, and only suicide attempters exhibited a positive correlation of the cytokine activation marker neopterin with the KYN:TRP ratio, suggesting that KYN production may be influenced by inflammatory processes among suicide attempters.

CONCLUSION

These preliminary results suggest that KYN and related molecular pathways may be implicated in the pathophysiology of suicidal behavior.

Serum neopterin levels in spontaneous urticaria and atopic dermatitis

Serum neopterin may be considered a diagnostic marker of the degree of activation of the immune system. This preliminary study was performed to measure serum neopterin levels in patients with acute spontaneous urticaria (ASU), chronic spontaneous urticaria (CSU) and atopic dermatitis (AD). In total, 180 patients [96 men, 84 women; mean age 23.1 years; 41 with spontaneous urticaria (13 ASU and 28 CSU), 48 with AD] and 96 healthy controls were enrolled in the study. Patients with ASU had the highest neopterin levels, and all three groups of patients (ASU, CSU and AD) had higher values than normal subjects. This preliminary study demonstrates that serum neopterin could be a biomarker of immune activation in patients with SU or AD.

Serum neopterin is not increased in obese juveniles

Objective. Cardiovascular disease is associated with inflammation and immune activation, concentrations of immune activation markers like neopterin predict outcome in adults. Methods. Serum neopterin concentrations and early metabolic and pre-atherosclerotic symptoms were analyzed in 295 obese juveniles and 101 normal weight controls of similar age. Additionally, the influence of a 12 months weight reduction program on neopterin levels was investigated in 31 obese juveniles. Results. Intima-media thickness of common carotid arteries (IMT) and the concentrations of C-reactive protein (CRP) were increased in the obese juveniles (P < .001). Also triglycerides, oxidized LDL, fasted insulin levels, HOMA-index, leptin, liver transaminases and uric acid were increased compared to the controls. However, serum neopterin was decreased in the obese versus non-obese juveniles (P < .03). The intervention consisting of regular sports, nutritional devices, and a psychologic attendance led after 12 months to an increase of neopterin concentration (P < .05; paired test). Conclusions. Neopterin concentrations in juvenile obesity behaved considerably different from what was demonstrated in adults, levels did not correlate with metabolic and pre-atherosclerotic symptoms found in early phases although early vascular burden and chronic low grade inflammation was indicated by increased IMT and CRP. Neopterin concentrations increased after a 12 months intervention program.

Sublingual immunotherapy may affect serum neopterin: preliminary findings

BACKGROUND

Neopterin is a protein produced by monocytes/macrophages. It has been considered a biomarker of immune activation in several disorders. However, there are few studies in allergic rhinitis (AR). This study evaluated the serum neopterin levels in patients with pollen-induced AR or treated with sublingual immunotherapy (SLIT) and in healthy subjects.

METHODS

146 subjects (70 males, median age 30.5 years): 56 with moderate-severe persistent AR, 40 with AR and successfully treated with 2 year SLIT, and 50 healthy controls were consecutively evaluated outside the pollen season. A skin prick test and blood sampling for assessing serum neopterin levels were performed in all subjects.

RESULTS

SLIT-treated patients had lower neopterin levels than untreated patients and healthy subjects (respectively p=0.012 and p=0.0001).

CONCLUSIONS

Neopterin is a biomarker for immune activation, SLIT may affect serum neopterin probably as a consequence of Treg response to SLIT.

Tryptophan metabolism in allergic rhinitis: the effect of pollen allergen exposure

This study evaluates serum tryptophan, kynurenine, kynurenine-to-tryptophan ratio, and neopterin levels in patients with pollen-induced allergic rhinitis (AR) during and outside of the pollen season, along with these values in healthy subjects. A total of 102 patients (56 female and 46 male, median age 28.7 years) were included in this study: 56 with seasonal AR evaluated outside of the pollen season and thus without allergic inflammation and symptoms, and 46 with seasonal AR evaluated during the pollen season with symptoms. A skin prick test and blood sampling for assessing serum concentrations of tryptophan and kynurenine and of immune activation marker neopterin were performed in all subjects. Tryptophan and kynurenine serum concentrations were higher in AR patients than in controls and were also higher out of pollen season than during this season. In conclusion, this preliminary study demonstrates that serum tryptophan metabolism could serve as a biomarker in patients with AR.