Assessment of cytomegalovirus infections using neopterin and a new immunoblot

The importance of neopterin in COVID-19: The prognostic value and relation with the disease severity

Coronavirus Disease 2019 [COVID-19], caused by severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2], has rapidly evolved into a global health emergency. Neopterin [NPT], produced by macrophages when stimulated with interferon [IFN-]gamma, is an essential cytokine in the antiviral immune response. NPT has been used as a marker for the early assessment of disease severity in different diseases. The leading cause of NPT production is the pro-inflammatory cytokine IFN-. Macrophage activation has also been revealed to be linked with disease severity in SARS-CoV-2 patients. We demonstrate the importance of NPT in the pathogenesis of SARS-CoV-2 and suggest that targeting NPT in SARS-CoV-2 infection may be critical in the early prediction of disease progression and provision of timely management of infected individuals.

The prognostic role of neopterin in COVID-19 patients

In Coronavirus disease-2019 (COVID-19) cases, hyper inflammation is associated with the severity of the disease. High levels of circulating cytokines were reported in severe COVID-19 patients. Neopterin produced by macrophages on stimulation with interferon-gamma, which is an important cytokine in the antiviral immune response, hence it can be used to predict the severity of disease in COVID-19 cases. In this study, it was aimed to determine the prognostic value of the neopterin for the prediction of severe disease in patients with COVID-19. This single-center, prospective study was conducted in hospitalized COVID-19 patients and healthy volunteers. Severe and mild COVID-19 cases were compared in terms of clinical and laboratory findings as well as serum neopterin levels on hospital admission. To assess the prognostic utility of neopterin between the severe and mild COVID-19 groups, a receiver-operating characteristic (ROC) curve was generated, and the area under the curve (AUC) was calculated. The median serum neopterin level was four times higher in COVID-19 patients than the healthy controls (46 vs. 12 nmol/L; p < .001). The AUC value of serum neopterin was 0.914 (95% confidence interval, 0.85-0.97). The sensitivity and specificity of serum neopterin for the cut-off value of 90 nmol/L to identify severe COVID-19 cases were 100% and 76%, respectively. Serum neopterin levels on hospitalization were significantly higher in severe COVID-19 disease than mild COVID-19 patients. Neopterin levels can be used as an early prognostic biomarker for COVID-19 on admission.

Neopterin levels and Kyn/Trp ratios were significantly increased in dengue virus patients and subsequently decreased after recovery

OBJECTIVES

During dengue fever, a pronounced gamma-interferon immune response produces neopterin and promotes tryptophan degradation by the enzyme indoleamine-2,3-dioxygenase 1 (IDO-1). Activated IDO-1 is indicated by an increased kynurenine to tryptophan ratio (Kyn/Trp) in patients.

METHODS

Plasma levels of neopterin, kynurenine, and tryptophan were measured in 72 hospitalized dengue virus (DENV) patients and 100 healthy individuals. Plasma levels of neopterin, kynurenine, and tryptophan were also measured prospectively in a second cohort of 13 DENV patients; on the day of hospitalization, on day 2-3 at discharge, and 7-10 days after discharge. DENV RNA positivity was determined by qualitative and quantitative methodologies.

RESULTS

DENV RNA-positive patients presented significantly higher levels of neopterin (mean 36.5nmol/l) and Kyn/Trp ratios (mean 102μmol/mmol) compared to DENV RNA-negative individuals. A significant correlation between neopterin levels and Kyn/Trp ratios was observed in both DENV RNA-positive (Spearman's rho=0.37, p< 0.01) and DENV RNA-negative (Spearman's rho=0.89, p<0.001) patients. Kyn/Trp ratios were negatively correlated with platelet counts (Spearman's rho=-0.43, p<0.01) and positively correlated with liver enzymes: AST (Spearman's rho=0.68, p<0.01) and ALT (Spearman's rho=0.51, p<0.05). In addition, the follow-up data presented a significant decrease in neopterin levels and Kyn/Trp ratios within 10 days after hospital entry.

CONCLUSIONS

Neopterin levels and Kyn/Trp ratios were significantly increased in DENV patients and subsequently decreased after recovery.

Serum Neopterin in Differential Diagnosis of Bacterial Diarrhea in Pediatric Patients

Background: Neopterin, regarded as a marker of cellular immune activation, has been used in diagnosis of infection caused by intracellular pathogens. We have aimed to evaluate the clinical usefulness of serum neopterin (NPT) in acute bacterial diarrhea caused by group C enteropathogenic Escherichia coli (EPECs) and group D Salmonella spp.

Methods: Serum concentration of NPT was determined by ELISA. The study group included 47 children with diagnosis of bacterial diarrhea: 32 caused by group C enteropathogenic Escherichia coli (EPECs) and 15 by group D Salmonella spp. 105 healthy children constituted the control group.

Results: Serum concentration of NPT in children infected with group D Salmonella spp. turned out to be higher than in the other groups. The fraction of Salmonella-infected patients with serum neopterin above 11 nmol/l proved higher as compared to children with diarrhea caused by group C EPECs or to the healthy controls. The prevalence of a C-reactive protein (CRP) to NPT ratio of greater than 1 did not differ significantly between children with diarrhea of various etiology.

Conclusions: Neopterin can be used as a non-specific marker differentiating between bacterial diarrhea of various etiology.

Macrophage activation is associated with poorer long-term outcomes in renal transplant patients

Long-term graft and patient survival after renal transplantation are largely determined by progression of chronic allograft dysfunction and cardiovascular disease. Inflammation plays a crucial role in both disease processes. We prospectively analyzed the association of early peri-transplant inflammatory burden on long-term outcomes in 144 consecutive deceased donor renal allograft recipients. Single time point and cumulative levels of markers of acute phase response (serum amyloid A [SAA] and C-reactive protein [SCRP]) and macrophage activation (serum and urine neopterin) were measured daily during the immediate post-operative period. Mean patient follow-up was 16 yr. Graft and patient survival rates at one-, five-, and 10-yr were 90%, 70%, and 51%, and 97%, 77%, and 59%, respectively. Graft loss occurred in 90 patients, of whom 71 died with a functioning graft and 19 returned to dialysis. CRP, SAA and neopterin (NEOP) levels were all elevated post-operatively. High levels of NEOP, in contrast to SAA or SCRP, were associated with poorer graft and patient survival (p < 0.05), specifically with death from cardiovascular events and cytomegalovirus IgG positivity. These findings strongly suggest that early post-transplant macrophage activation, as reflected by NEOP levels, is associated with poorer long-term graft and patient survival.

Can we use neopterin as marker of viral infections in pregnant women with symptoms of imminent spontaneous abortion?

PURPOSE

To find out if determination of neopterin can be used for the detection of viral infections in pregnant women with symptoms of imminent spontaneous abortion.

METHODS

Eighty-eight pregnant women with symptoms of imminent spontaneous abortion (investigated group) and 88 healthy pregnant women were evaluated (control group). Neopterin level and IgM and IgG antibodies for eight viruses in the blood were determined.

RESULTS

Parvo B19 virus and elevated neopterin values were found in significantly higher number in investigated group than in control. There was no correlation between women with acute ParvoB19 infection and elevated neopterin level.

CONCLUSIONS

The determination of neopterin in the sera cannot be used for screening of viral infections in pregnancy.

Evaluation of neopterin levels in patients undergoing hemodialysis

Neopterin is a diagnostic or a prognostic biomarker for several pathologies including renal diseases. However, the association between neopterin status and causative main reasons such as diabetes and hypertension for renal disease remains unclear. The aim of the study was to evaluate neopterin levels in diabetes and hypertension patients treated with/without hemodialysis. According to primary renal disorders, the patients undergoing hemodialysis were classified into 4 groups as diabetic nephropathy, hypertensive nephropathy, reflux nephropathy or interstitial nephritis, and others. The controls consisted of healthy subjects, hypertensive subjects, and diabetic individuals without any renal disorder. In the study, both urinary and serum neopterin levels were measured using high performance liquid chromatography and enzyme-linked immunosorbant assay in patients undergoing regular hemodialysis therapy (n=71). The effects of the duration of hemodialysis and treatment of erythropoietin and/or iron on neopterin levels were also evaluated. Neopterin levels were found to be higher in hemodialysis patients than in the healthy controls (P<0.05). A significant difference in neopterin levels was also found between diabetic control patients and diabetic nephropathy patients (P<0.05). A similar significant difference was detected in neopterin levels between hypertensive patients with/without nephropathy (P<0.05). Neopterin may be an early critical marker for progression of nephropathy in diabetic and hypertensive patients in early stages.

High serum levels of neopterin in patients with Crimean-Congo hemorrhagic fever and its relation with mortality

OBJECTIVE

Neopterin is generated and released in increased amounts by macrophages upon activation by interferon-gamma during cellular immune response. In this study, we aimed to investigate serum neopterin levels in patients with Crimean-Congo hemorrhagic fever (CCHF) and its clinical significance as a predictor factor of mortality.

METHODS

Neopterin concentrations on the first day of hospitalization were measured in serum samples from 51 CCHF patients. Serum neopterin levels and other clinical-laboratory parameters for fatal and nonfatal CCHF patients were compared.

RESULTS

Serum neopterin levels (73.22+/-54.30 nmol/L) were highly elevated in all CCHF patients (p<0.0001) with higher levels in fatal group (153.66+/-81.34 nmol/L, p=0.0001) compared to nonfatal disease (55.99+/-24.09 nmol/L). In univariate analysis, the level of neopterin on the first day of hospitalization, bleeding, platelet count, aspartate transferase and lactate dehydrogenase were associated with mortality. In multivariate analysis, only the serum level of neopterin was associated with mortality. As a mortality risk factor, area under the curve was 0.939 (p=0.0001, 95% confidence interval: 0.85-1.00).

CONCLUSIONS

In this first study of serum neopterin levels for CCHF, elevated serum neopterin level showing strong activation of monocytes/macrophages was a risk factor for CCHF.

The value of serum neopterin, interferon-gamma levels and interleukin-12B polymorphisms in predicting acute renal allograft rejection

Acute rejection remains a poor predictor of graft outcome. In this study, we measured serum levels of interferon (IFN)-gamma and neopterin by enzyme-linked immunosorbent assay and a single nucleotide polymorphism (SNP) within the 3' untranslated region of the interleukin (IL)-12 B gene (1188 A/C) to determine whether either of these factors could predict acute rejection in renal transplantation. Significantly higher early post-transplant neopterin levels (days 5-7; 35.7 versus 19.9 nmol/l) were observed in recipients who subsequently rejected their grafts. Post-transplant neopterin levels showed a strong positive correlation with 1-month creatinine levels (Spearman's correlation 0.62, P < 0.001), suggesting macrophage activation early after transplantation. Pretransplant neopterin and IFN-gamma levels and the IL-12B gene SNP did not predict acute rejection in this small retrospective study. The ability to predict acute rejection non-invasively early after transplantation could lead to individual tailoring of immunosuppressive regimens and perhaps lead eventually to longer graft survival.

Detection of serum neopterin for early assessment of dengue virus infection

Objective

Neopterin is generated and released in increased amounts by macrophages upon activation by interferon-γ during Th1-type immune response. The potential usefulness of neopterin in early prognostic information of dengue virus infection was investigated.

Methods

Neopterin concentrations were determined in serum samples from 110 dengue fever (DF) patients. The neopterin levels were compared with those in 50 measles and 40 influenza patients; 155 healthy blood donors served as controls.

Results

In acute sera of DF patients mean neopterin concentration was 48.2 nmol/L, which was higher than that in patients with measles (mean: 36.3 nmol/L) and influenza (18.8 nmol/L) and in healthy controls (6.7 nmol/L; P < 0.001). In the patients with confirmed DF, an early neopterin elevation was detected already at the first day after the onset of symptoms and rose to a maximum level of 54.3 nmol/L 4 days after the onset. Higher increase of neopterin level in DF patients was associated with longer duration of fever and thus predicted the clinical course of the disease.

Conclusions

Neopterin concentrations were found significantly higher in DF patients compared with healthy controls and also with other viral infections (P < 0.001) and may allow early assessment of the severity of DF.

Serum neopterin for early assessment of severity of severe acute respiratory syndrome

Neopterin and C-reactive protein (CRP) concentrations were determined in serum samples from 129 severe acute respiratory syndrome (SARS) patients and 156 healthy blood donors. In the patients with confirmed SARS, an early neopterin elevation was detected already at the day of onset of symptoms and rose to a maximum level of 45.0 nmol/L 3 days after the onset. All SARS patients had elevated neopterin concentrations (>10 nmol/L) within 9 days after the onset. The mean neopterin concentrations were 34.2 nmol/L in acute sera of SARS patients, 5.1 nmol/L in convalescent sera, and 6.7 nmol/L in healthy controls. In contrast, the mean CRP concentrations in both acute and convalescent sera of SARS patients were in the normal range (<10 mg/L). Serum neopterin level in SARS patients was associated with fever period and thus the clinical progression of the disease, while there was no significant correlation between the CRP level and the fever period. Serum neopterin may allow early assessment of the severity of SARS. The decrease of neopterin level was found after steroid treatment, which indicates that blood samples should be collected before steroid treatment for the neopterin measurement.

Long-term cytomegalovirus infection leads to significant changes in the composition of the CD8+ T-cell repertoire, which may be the basis for an imbalance in the cytokine production profile in elderly persons

In spite of the present belief that latent cytomegalovirus (CMV) infection drives CD8+ T-cell differentiation and induces premature immune senescence, no systematic studies have so far been performed to compare phenotypical and functional changes in the CD8+ T-cell repertoire in CMV-infected and noninfected persons of different age groups. In the present study, number, cytokine production, and growth potential of naive (CD45RA+ CD28+), memory (CD45RA- CD28+), and effector (CD45RA+ CD28- or CD45RA- CD28-) CD8+ T cells were analyzed in young, middle-aged, and elderly clinically healthy persons with a positive or negative CMV antibody serology. Numbers and functional properties of CMVpp65(495-503)-specific CD8+ T cells were also studied. We demonstrate that aging as well as CMV infection lead to a decrease in the size of the naive CD8+ T-cell pool but to an increase in the number of CD8+ effector T cells, which produce gamma interferon but lack substantial growth potential. The size of the CD8+ memory T-cell population, which grows well and produces interleukin-2 (IL-2) and IL-4, also increases with aging, but this increase is missing in CMV carriers. Life-long latent CMV infection seems thus to diminish the size of the naive and the early memory T-cell pool and to drive a Th1 polarization within the immune system. This can lead to a reduced diversity of CD8 responses and to chronic inflammatory processes which may be the basis of severe health problems in elderly persons.