Hepcidin and Ferritin Predict Microbial Etiology in Community-Acquired Pneumonia

Hepcidin analysis in pneumonia: Comparison of immunoassay and LC-MS/MS

BACKGROUND

The iron-regulatory hormone hepcidin is a promising biomarker to differentiate anaemia of inflammation from iron deficiency. Plasma hepcidin concentrations increase substantially during inflammation, and the amount of smaller, non-biologically active isoforms of hepcidin increase in inflammatory conditions. These smaller isoforms are measured in some, but not all analytical methods. Thus, we evaluated the comparability of two analytical methods with different isoform selectivity during and after acute-phase pneumonia as a highly inflammatory model disease.

METHODS

Blood samples from a cohort of 267 hospitalized community-acquired pneumonia patients collected at admission and a 6-week follow-up were analysed. Hepcidin was measured in plasma by an immunoassay, which recognizes all hepcidin isoforms, and a liquid chromatography tandem mass spectrometry (LC-MS/MS), which selectively measures the bioactive hepcidin-25. Additionally, a subset of serum samples was analysed by LC-MS/MS.

RESULTS

Hepcidin measurements by immunoassay were higher compared with LC-MS/MS. The relative mean difference of hepcidin plasma concentrations between the two analytical methods was larger in admission samples than in follow-up samples (admission samples <200 ng/mL: 37%, admission samples >200 ng/mL: 78%, follow-up samples >10 ng/mL: 22%). During acute-phase pneumonia, serum concentrations were on average 22% lower than plasma concentrations when measured by LC-MS/MS.

CONCLUSIONS

Immunoassay measured higher hepcidin concentrations compared with LC-MS/MS, with more pronounced differences in high-concentration samples during acute-phase pneumonia. These findings should be considered in local method validations and in future harmonization and standardization optimization of hepcidin measurements.

Elevated Urinary Hepcidin Level and Hypoferremia in Infants with Febrile Urinary Tract Infection: A Prospective Cohort Study

To evaluate the kinetics of serum and urinary hepcidin levels along with anemia-related parameters during the infection course of infants with febrile urinary tract infection (UTI), we enrolled febrile infants aged one to four months in this prospective study. Febrile patients with UTI were allocated into Escherichia coli (E. coli) or non-E. coli groups according to urine culture results. Septic workup, blood hepcidin, iron profile, urinalysis, and urinary hepcidin-creatinine ratio were collected upon admission and 3 days after antibiotic treatment. In total, 118 infants were included. On admission, the febrile UTI group showed a significant reduction in serum iron level and a significant elevation of urinary hepcidin-creatinine ratio compared to the febrile control counterpart. Moreover, urinary hepcidin-creatinine ratio had the highest odds ratio, 2.01, in logistics regression analysis. After 3 days of antibiotic treatment, hemoglobin and the urinary hepcidin-creatinine ratio were significantly decreased. Patients with an E. coli UTI had a significantly decreased urinary hepcidin-creatinine ratio after 3 days of antibiotics treatment, whereas the non-E. coli group showed insignificant changes. Our study suggested that the urinary hepcidin-creatinine ratio elevated during acute febrile urinary tract infection and significantly decreased after 3 days of antibiotics treatment, especially in E. coli UTI.

Biomarkers for iron metabolism among patients hospitalized with community-acquired pneumonia caused by infection with SARS-CoV-2, bacteria, and influenza

BACKGROUND

Ferritin, the central iron storage protein, has attracted attention as a biomarker of severe COVID-19. Few studies have investigated regulators of iron metabolism in the context of COVID-19. The aim was to evaluate biomarkers for iron metabolism in the acute phase response to community-acquired pneumonia (CAP) caused by SARS-CoV-2 compared to CAP caused by bacteria or influenza virus in hospitalized patients.

METHODS

A cross-sectional study of 164 patients from the Surviving Pneumonia Cohort recruited between January 8, 2019 and May 26, 2020. Blood samples were collected at admission and analyzed for levels of C-reactive protein (CRP), ferritin, soluble transferrin receptor, erythroferrone, and hepcidin.

RESULTS

Median (IQR) hepcidin was higher in SARS-CoV-2 with 143.8 (100.7-180.7) ng/mL compared to bacterial and influenza infection with 78.8 (40.1-125.4) and 53.5 (25.2-125.8) ng/mL, respectively. The median ferritin level was more than 2-fold higher in patients with SARS-CoV-2 compared to the other etiologies (p<0.001). Patients with SARS-CoV-2 had lower levels of erythroferrone and CRP compared to those infected with bacteria.

CONCLUSION

Higher levels of hepcidin and lower levels of erythroferrone despite lower CRP levels among patients with SARS-CoV-2 compared to those infected with bacteria indicate alterations in iron metabolism in patients with SARS-CoV-2 infection.

Host and Bacterial Iron Homeostasis, an Underexplored Area in Tuberculosis Biomarker Research

Mycobacterium tuberculosis (Mtb) "a human adapted pathogen" has found multiple ways to manipulate the host immune response during infection. The human immune response to Mtb infection is a highly complex cascade of reactions, with macrophages as preferred intracellular location. Interaction with the host through infection gives rise to expression of specific gene products for survival and multiplication within the host. The signals that the pathogens encounter during infection cause them to selectively express genes in response to signals. One strategy to identify Mtb antigens with diagnostic potential is to identify genes that are specifically induced during infection or in specific disease stages. The shortcomings of current immunodiagnostics include the failure to detect progression from latent infection to active tuberculosis disease, and the inability to monitor treatment efficacy. This highlights the need for new tuberculosis biomarkers. These biomarkers should be highly sensitive and specific diagnosing TB infection, specifically distinguishing between latent infection and active disease. The regulation of iron levels by the host plays a crucial role in the susceptibility and outcome of Mtb infection. Of interest are the siderophore biosynthetic genes, encoded by the mbt-1 and mbt-2 loci and the SUF (mobilization of sulphur) operon (sufR-sufB-sufD-sufC-csd-nifU-sufT), which encodes the primary iron-sulphur cluster biogenesis system. These genes are induced during iron limitation and intracellular growth of Mtb, pointing to their importance during infection.