BIOMARKER FOR INFECTIOUS DISEASE

Abstract

The present invention is a biomarker for diagnosing infectious disease wherein the biomarker is a sulfur metabolite, and the sulfur metabolite may be a sulfur metabolite present in exhaled air, and the sulfur metabolite can be detected from exhaled air condensate. The biomarker for infectious disease includes a biomarker for diagnosing bacterial and viral infection, especially new coronavirus infection; a biomarker for diagnosing pneumonias such as infectious pneumonia, especially interstitial pneumonia due to new coronavirus infection, and additionally alveolar pneumonia; and a biomarker for diagnosing exacerbation due to infection, especially for diagnosing the risk of the transition to exacerbation due to new coronavirus infection.

Description

TECHNICAL FIELD

The present invention relates to a biomarker for infectious disease, and relates to a sulfur metabolite.

BACKGROUND ART

The inventor has clarified the physiological function and the metabolic pathway of in-vivo reactive sulfur molecular species/active sulfur molecular species (reactive sulfur species, RSS) such as cysteine hydropolysulfide (CysSSH) and glutathione polysulfide (GSSH) (Non Patent Literatures 1 and 2).

Although cysteine hydropolysulfide (CysSSH) is generated in various organisms in large amounts, the biosynthesis and the physiological function thereof are hardly known. It is clear that extensive persulfides are formed in cysteine-containing proteins of E. coli and mammalian cells, and it is believed that this is produced in the posttranslational process including chemical reaction related to in-vivo sulfur metabolites.

Effective synthesis of CysSSH from the substrate L-cysteine, which is a reaction catalyzed by cysteinyl-tRNA synthetases (CARSs) of procaryotes and mammalians, is present. The targeted disruption of genes encoding mitochondrial CARSs in mouse and human cells shows that CARSs play an important role in endogenous CysSSH production, and suggests that these enzymes function as main cysteine persulfide synthases in vivo. CARS also catalyzes the co-translational cysteine persulfidation, and participates in the biosynthesis in mitochondria and the regulation of bioenergy.

Accordingly, the clarification of the CARS-dependent production mechanism of persulfurated metabolites may lead to the understanding of abnormal oxidation-reduction signal transduction under physiological and pathophysiological conditions and suggest therapeutic targets based on oxidative stress and mitochondrial dysfunction.

The chemical properties of polysulfide are not completely understood or clarified due to the reactivity or the complicated redox activity characteristics thereof. The inventor has however developed active sulfur metabolomic analysis using RSS metabolism profiling. This is revealing the in-vivo kinetics of RSSs endogenously and ubiquitously generated in both procaryotes and eukaryotes. RSSs, namely active sulfur molecules, maintain energy metabolism in mitochondria (Non Patent Literature 2), and meanwhile exhibit strong antioxidant function (Non Patent Literature 1), anti-inflammatory function (Non Patent Literature 3), and immune regulatory function (Non Patent Literature 3).

The pathosis of new coronavirus (SARS-CoV-2), which causes new coronavirus infectious disease (COVID-19), urgently needs to be clarified, and methods for preventing and treating new coronavirus infectious disease urgently needs to be established. SARS-CoV-2 protease inhibitors have been reported as therapeutic drugs for COVID-19 (Non Patent Literatures 4 and 5).

CITATION LIST

Non Patent Literature

Non Patent Literature 1

Ida T, Sawa T, Ihara H, Tsuchiya Y, Watanabe Y, Kumagai Y, Suematsu M, Motohashi H, Fujii S, Matsunaga T, Yamamoto M, Ono K, Devarie-Baez N O, Xian M, Fukuto J M, Akaike T. Reactive cysteine persulfides and S-polythiolation regulate oxidative stress and redox signaling. Proc Natl Acad Sci USA 111:7606-7611 (2014).

Non Patent Literature 2

Akaike T, Ida T, Wei F Y, Nishida M, Kumagai Y, Alam MM, Ihara H, Sawa T, Matsunaga T, Kasamatsu S, Nishimura A, Morita M, Tomizawa K, Nishimura A, Watanabe S, Inaba K, Shima H, Tanuma N, Jung M, Fujii S, Watanabe Y, hmuraya M, Nagy P, Feelisch M, Fuk to J M, Motohashi H. Cysteinyl-tRNA synthetase governs cysteine polysulfidation and mitochondrial bioenergetics. Nat Commun 8:1177 (2017).

Non Patent Literature 3

Zhang T, Ono K, Tsutsuki H, Ihara H, Islam W, Akaike T, Sawa T. Enhanced cellular polysulfides negatively regulate TLR4 signaling and mitigate lethal endotoxin shock. Cell Chem Biol 26:686-698 (2019).

Non Patent Literature 4

Zhang L, et al. Crystal structure of SARS-CoV-2 main protease provides a basis for design of improved a ketoamide inhibitors. Science 368:409-412 (2020).

Non Patent Literature 5

Jin Z, et al. Structure of Mpro from SARS-CoV-2 and discovery of its inhibitors. Nature 582:289-293 (2020).

SUMMARY OF INVENTION

Technical Problem

The present inventor has developed a drug that takes the effect of preventing and treating viral infectious disease by inhibiting protease derived from virus, namely an “antiviral drug containing an active sulfur compound as the main medicinal effective ingredient”, based on various bioactive actions of active sulfur compounds that are present in vivo (Japanese Patent Application No. 2020-167343). An object of the present invention is to achieve the usefulness of a sulfur metabolite based on active sulfur metabolomics.

Solution to Problem

The present inventor has found that a sulfur metabolite functions as a biomarker related to infectious disease in the examination of the usefulness of the sulfur metabolite in association with the antiviral effect of an activity sulfur compound based on active sulfur metabolomics.

That is, the present invention is characterized by being a biomarker for infection containing the sulfur metabolite. The sulfur metabolite may be a sulfur metabolite present in exhaled air. The sulfur metabolite can be detected from exhaled air condensate. The sulfur metabolite may be especially at least one type of sulfite ions (HSO₃⁻), thiosulfate ions (HS₂O₃⁻), and hydrogen disulfide ions (HS₂⁻); salts thereof; or compounds or molecules containing these; or derivatives thereof. The biomarker for infectious disease includes a biomarker for diagnosing bacterial and viral infection, especially new coronavirus infection; a biomarker for diagnosing pneumonia such as infectious pneumonia, especially interstitial pneumonia due to new coronavirus infection, and additionally alveolar pneumonia; and a biomarker for diagnosing exacerbation due to infection, especially for diagnosing the risk of the transition to exacerbation due to new coronavirus infection.

The present invention is further a diagnostic system for detecting a biomarker for diagnosing infection comprising a sulfur metabolite from exhaled air, and is a system for determining infection, especially for diagnosing new coronavirus infection, including: an exhaled air collector and an exhaled air collecting apparatus for collecting exhaled air of a subject, and an analysis apparatus for the qualitative and quantitative analysis of a sulfur metabolite in the collected exhaled air.

Advantageous Effect of Invention

According to the present invention, the usefulness of a sulfur metabolite was able to be achieved based on active sulfur metabolomics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a subject list of 12 healthy persons not infected with new coronavirus.

FIG. 2 is a subject list of 12 patients infected with new coronavirus.

FIG. 3 is data on the results of the quantitative analysis of the healthy persons and the patients infected with new coronavirus.

FIG. 4 is the results of measuring sulfite ions (HSO₃⁻) and thiosulfate ions (HS₂O₃⁻) of one patient infected with new coronavirus at the time of the exacerbation.

DESCRIPTION OF EMBODIMENTS

First, 12 healthy persons not infected with new coronavirus (FIG. 1) and 12 persons infected with new coronavirus (inpatients in the hospital affiliated with the medical faculty of Tokai University, FIG. 2) were analyzed for sulfur metabolites in exhaled air as subjects. It was determined based on the PCR test whether the subjects were infected with new coronavirus or not. Among the twelve persons affected with new coronavirus, two persons were mild, and ten persons were moderate. Among the ten persons, one person was exacerbated later. The classification into mild, moderate, and severe patients was based on the saturated oxygen concentrations, the respiratory symptoms, and the chest CT images. For example, this classification is described in Shingata Korona Wirusu Kansensho (COVID-19), Shinryo no Tebiki Dai 4.1 ban (New Coronavirus Infectious Disease (COVID-19), Medical care manual ver. 4.1).

An exhaled air collector (GL Sciences Inc.) and an exhaled air collecting apparatus (GL Sciences Inc.) were utilized for collecting exhaled air. The exhaled air collecting apparatus was cooled to −20 degrees Celsius beforehand. When a subject breathed for 5 to 10 minutes through the exhaled air collector (mouthpiece type, mask type), exhaled air aerosol was rapidly cooled to collect around 1 ml of exhaled air condensate.

The addition of β-(4-hydroxyphenyl)ethyl iodoacetamide (HPE-IAM), which was an electrophilic alkylating agent, to 25 μl of the exhaled air condensate to 5 mM leads to alkylation reaction at 37 degrees Celsius for 30 minutes. Formic acid was then added to 1% to stabilize sulfur metabolites as HPE-IAM adducts. The electrophilic alkylating agent alkalinizes electron pairs of sulfur, and suppresses the decomposition of the sulfur metabolites.

Furthermore, a stable isotope-labeled HPE-IAM adduct standard was added to each of the multiple sulfur metabolites so that the concentration in the solution was 10 nM. This was prepared into a sample for mass spectrometry. The HPE-IAM adducts of sulfite ions (HSO₃⁻), thiosulfate ions (HS₂O₃⁻), hydrogen disulfide ions (HS₂⁻) were quantitatively analyzed with a mass spectroscope according to Non Patent Literature 1 (Akaike T, et al. Nat Commun 2017). That is, 35 μl of the above-mentioned sample for mass spectrometry/standard was injected into the high-performance liquid chromatograph-mass spectroscope LCMS™-8060 (SHIMADZU CORPORATION) and quantitatively analyzed under the following MRM (multiple reaction monitoring) conditions (Table 1).

TABLE 1
		Precursor	Product	Collision
Compounds	Polarity	ion (m/z)	ion (m/z)	energy (V)
HSO3-HPE-IAM adduct	−	258.1	121.0	20.0
H[34S]O3-HPE-IAM	−	260.1	121.0	20.0
adduct
HS2O3-HPE-IAM adduct	−	290.0	208.2	14.0
H[34S2]O3-HPE-IAM	−	294.0	210.2	14.0
adduct
Bis-SS-HPE-IAM adduct	+	420.9	121.0	−23.0
Bis-[34S2]-HPE-IAM	+	424.9	121.0	−23.0
adduct

FIG. 3 shows data on the results of quantitatively analyzing the 12 healthy persons and the 12 persons infected with new coronavirus for these three types of ions. The concentrations of the various sulfur metabolites contained in the exhaled air condensate were generally at low generation levels as compared with in vivo. It is believed that this is influenced by the fact that the in-vivo sulfur metabolites are diluted in the exhaled air, and the exhaled air is not necessarily collected efficiently. It was then confirmed that the levels of sulfite ions (HSO₃⁻), thiosulfate ions (HS₂O₃⁻), and hydrogen disulfide ions (HS₂⁻) were significantly high in the moderate patients as compared with the healthy persons.

The symptoms of the patient (patient No. 3) in FIG. 2 changed from moderate symptoms to severe symptoms. FIG. 4 shows the results of measuring the sulfite ions (HSO₃⁻) and thiosulfate ions (HS₂O₃⁻) at the time of the exacerbation. It was found that the generation levels of thiosulfate ions (HS₂O₃⁻) were significantly high at the time of mild symptoms and also at the time of severe symptoms as compared with the healthy persons. In the moderate patient in which pneumonia was exacerbated later (patient No. 3), a marked increase in sulfite ions (HSO₃⁻) was observed in the specimen collected before the exacerbation. In the moderate patients in which pneumonia was not exacerbated, such an increase was not, however, seen. Accordingly, sulfite ions (HSO₃⁻) are promising as a biomarker for evaluating a risk of the exacerbation of pneumonia due to new coronavirus infectious disease.

Since active sulfur has antioxidant activity, and that is, active sulfur is oxidized by oxidative stress, active oxygen, and the like, it can be said that the exacerbation of pneumonia, namely the aggravation of oxidative stress shifts the profiles of the sulfur metabolites toward the oxidized state.

Claims

1. A diagnostic method to diagnose infection with infectious diseases using sulfur metabolite as a biomarker.

2. The diagnostic method according to claim 1, wherein the sulfur metabolite is collected from an exhaled air.

3. The diagnostic method according to claim 2, wherein the sulfur metabolite is produced by metabolism of an active sulfur compound in vivo.

4. The diagnostic method according to claim 3, wherein the sulfur metabolite is at least one type of sulfite ions (HSO3−), thiosulfate ions (HS2O3−), and hydrogen disulfide ions (HS2−).

5. The diagnostic method according to claim 4, wherein the infectious diseases is viral infection.

6. The diagnostic method according to claim 5, wherein the infectious diseases is new coronavirus infection.

7. The diagnostic method according to claim 5, wherein the infectious diseases is pneumonia due to the infection.

8. The diagnostic method according to claim 6, wherein the infectious diseases is pneumonia due to the infection.

9. The diagnostic method according to claim 6, wherein diagnosing a risk of exacerbation of the new coronavirus infection.

10. The diagnostic method according to claim 8, wherein the sulfur metabolite is sulfite ions (HSO3−).