Assessment of vitamin B6 status in never-pregnant, pregnant and postpartum women and their infants.

PURPOSE: Pyridoxal 5´-phosphate (PLP) is the main form of vitamin B6 in humans and functions a coenzyme for more than 160 different enzymatic reactions. The purpose of the study was to find plasma PLP concentrations, which ensure an optimal vitamin B6 status determined by a metabolic marker, in never-pregnant, pregnant and lactating women and their infants. METHODS: In an observational, prospective study, plasma PLP and the metabolic marker, HKr (hydroxykynurenine/(kynurenic acid + anthranilic acid + xanthurenic acid + hydroxyanthranilic acid) were assessed in women (n = 114) from pregnancy week 18 to 6 months postpartum and related to infant status. Never-pregnant women 18-40 years (n = 127) were included as controls. RESULTS: Compared to controls, plasma PLP decreased during pregnancy and increased postpartum, while HKr increased from week 18 to 6 weeks postpartum, indicating maternal vitamin B6 insufficiency during this period. In never-pregnant women, HKr increased gradually with plasma PLP < 100 nmol/L, and in pregnancy week 28 a sharp increase in HKr was seen at plasma PLP < 30 nmol/L. Despite correcting for maternal vitamin B6 status, infant median plasma PLP decreased with months of exclusive breastfeeding. CONCLUSIONS: Plasma PLP and kynurenine concentrations differ substantially between never-pregnant, pregnant and postpartum women and infants. A plasma PLP concentration in the range of 50-100 nmol/L seems to ensure an optimal vitamin B6 status for never-pregnant women, whereas a plasma PLP > 30 nmol/L in pregnancy week 28 ensures an adequate vitamin B6 status during pregnancy and lactation. Infant vitamin B6 status at age 6 months is inversely correlated to number of months of exclusive breastfeeding.

Strong Association between Diarrhea and Concentration of Enterotoxigenic Escherichia coli Strain TW10722 in Stools of Experimentally Infected Volunteers.

Enterotoxigenic Escherichia coli (ETEC) strains are a major cause of diarrheal illness in children and travelers in low- and middle-income countries. When volunteers are infected with ETEC strains, as part of experimental infection studies, some do not develop diarrhea. To improve our understanding of how these volunteers are protected, we investigated the association between stool ETEC DNA concentration, as determined by quantitative PCR, and the development and severity of disease in 21 volunteers who had been experimentally infected with ETEC strain TW10722. We found a strong association between maximum stool ETEC DNA concentration and the development of diarrhea: all of the 11 volunteers who did not develop diarrhea had <0.99% TW10722-specific DNA in their stools throughout the follow-up period of up to 9 days, while all of the 10 volunteers who did develop diarrhea had maximum DNA concentrations of ≥0.99%. Most likely, these maximum stool TW10722 DNA concentrations reflect the level of intestinal colonization and the risk of experiencing diarrhea, thereby, seems to be directly dependent on the level of colonization. Thus, the development and availability of vaccines and other prophylactic measures, even if they only partially reduce colonization, could be important in the effort to reduce the burden of ETEC diarrhea.

Lower levels of the neuroprotective tryptophan metabolite, kynurenic acid, in users of estrogen contraceptives.

Changes in kynurenine metabolites are reported in users of estrogen containing contraception. We have assessed kynurenines, vitamin B6, vitamin B2 and the inflammation markers, C-reactive protein (CRP) and neopterin, in healthy, never-pregnant women between 18 and 40 years (n = 123) and related this to their use of hormonal contraception. The population included 58 women, who did not use hormonal contraceptives (non-users), 51 users of estrogen-containing contraceptives (EC-users), and 14 users of progestin only contraceptives (PC-users). EC-users had significantly lower plasma kynurenic acid (KA) and higher xanthurenic acid (XA) levels compared to non-users. Serum CRP was significantly higher and negatively associated with both vitamin B6 and B2 status in EC-user compared to non-users. No significant differences in any parameters were seen between PC-users and non-users (p > 0.1). The low KA and high XA concentration in users of estrogen containing contraception resemble the biochemical profile observed in vitamin B6 deficiency. The hormonal effect may result from interference with the coenzyme function of vitamin B6 and B2 for particular enzymes in the kynurenine metabolism. KA has been suggested to be neuroprotective and the significantly reduced concentration in EC-users may be of importance in the observed increased risk of mood disorders among users of oral contraceptives.

A Vegetarian Diet Significantly Changes Plasma Kynurenine Concentrations.

Tryptophan is an essential amino acid and a precursor of a number of physiologically important metabolites, including serotonin, melatonin, tryptamine, and kynurenines. We assessed tryptophan, kynurenines, and vitamin B2 and B6, as well as biomarkers of liver function and inflammation, in a group of 158 female omnivores and vegetarians aged 18-40 years. The majority of women were omnivores, and 22% were vegetarians. Vegetarians had 25% lower serum ALT, significantly higher pyridoxal concentrations, and significantly lower plasma concentrations of most kynurenines, varying from 8% lower concentrations of median plasma kynurenine to 42% lower concentrations of plasma xanthurenic acid, compared to omnivores. No significant differences were observed in vitamin B2 status or in inflammation markers, C-reactive protein and neopterin between the groups. Vegetarians had lower levels of several plasma kynurenines compared to omnivores. The reason for this is unknown; however, lower ALT concentrations, suggesting a better liver status, and a more favourable vitamin B6 status might be contributing factors.

Reduced Plasma Guanylin Levels Following Enterotoxigenic Escherichia coli-Induced Diarrhea.

The intestinal peptide hormones guanylin (GN) and uroguanylin (UGN) interact with the epithelial cell receptor guanylate cyclase C to regulate fluid homeostasis. Some enterotoxigenic Escherichia coli (ETEC) produce heat-stable enterotoxin (ST), which induces diarrhea by mimicking GN and UGN. Plasma concentrations of prohormones of GN (proGN) and UGN (proUGN) are reportedly decreased during chronic diarrheal diseases. Here we investigate whether prohormone concentrations also drop during acute diarrhea caused by ST-producing ETEC strains TW10722 and TW11681. Twenty-one volunteers were experimentally infected with ETEC. Blood (n = 21) and urine (n = 9) specimens were obtained immediately before and 1, 2, 3, and 7 days after ETEC ingestion. Concentrations of proGN and proUGN were measured by ELISA. Urine electrolyte concentrations were measured by photometry and mass spectrometry. Ten volunteers developed diarrhea (D group), and eleven did not (ND group). In the D group, plasma proGN, but not proUGN, concentrations were substantially reduced on days 2 and 3, coinciding with one day after diarrhea onset. No changes were seen in the ND group. ETEC diarrhea also seemed to affect diuresis, the zinc/creatinine ratio, and sodium and chloride secretion levels in urine. ETEC-induced diarrhea causes a reduction in plasma proGN and could potentially be a useful marker for intestinal isotonic fluid loss.

Persistent Fever and Positive PCR 90 Days Post-SARS-CoV-2 Infection in a Rituximab-Treated Patient: A Case of Late Antiviral Treatment.

Background: Persistent fever after SARS-CoV-2 infection in rituximab-treated patients has been reported. Due to reduced sensitivity in conventional sampling methods and unspecific symptoms in these patients, distinguishing between low-grade viral replication or hyperinflammation is challenging. Antiviral treatment is recommended as prophylactic or early treatment in the at-risk population; however, no defined treatment approaches for protracted SARS-CoV-2 infection exist. Results: We present a case of 96 days of persistent fever and SARS-CoV-2 infection in a patient receiving B cell depletion therapy for multiple sclerosis. Migratory lung infiltrates and positive PCR tests from serum (day-58 post infection) and lower airways (day-90 post infection) confirmed continuous viral replication. The dominant symptoms were continuous high fever, dyspnea and mild to moderate hypoxemia, which never developed into severe respiratory failure. The patient was hospitalized three times, with transient improvement after late antiviral treatment and full recovery 6 months post-rituximab infusion. Conclusions: A strategy for securing samples from lower airways and serum should be a prioritization to strengthen diagnostic certainty in immunocompromised patients. B-cell-deprived patients could benefit from late treatment with SARS-CoV-2-specific monoclonal antibodies and antivirals. Importantly, increased intervals between immunosuppressive therapy should be considered where feasible.

Whole blood preservation methods alter chemokine receptor detection in mass cytometry experiments.

A potential hurdle when applying mass cytometry to the field study setting is the streamlining of sample collection while at the same time protecting the integrity of important cell epitopes. Whole blood preservation kits applying fixation and/or permeabilization agents are increasingly used in clinical trials to preserve leukocytes needed for downstream analysis. We here present a structured overview of leukocyte surface marker detectability in samples processed with four commercially available whole blood preservation kits; 1) Proteomic Stabilizer, 2) Stable-Lyse V2 and Stable-Store V2, 3) Cytodelics and 4) Lyse/Fix Buffer, as well as in samples treated with buffers included in Mass-tag Cellular Barcoding kits. Isolated leukocytes were stained with a 28-marker panel (including 7 chemokine receptors) of metal-conjugated antibodies and analysed on a mass cytometer. Exploration of the data by manual gating and viSNE analysis showed that although many markers were similarly detected across all sample conditions, most of the chemokine receptors in our panel, particularly CXCR3, CCR4, CCR6 and CXCR5, were incorrectly detected in the preserved samples and thus incompatible with the fixation and permeabilization agents found in whole blood preservation kits and in buffers used prior to barcoding.

A new human challenge model for testing heat-stable toxin-based vaccine candidates for enterotoxigenic Escherichia coli diarrhea - dose optimization, clinical outcomes, and CD4+ T cell responses.

TRIAL REGISTRATION: ClinicalTrials.gov ClinicalTrials.gov, Project ID: NCT02870751.

Proliferation of enterotoxigenic Escherichia coli strain TW11681 in stools of experimentally infected human volunteers.

BACKGROUND: As part of the effort to develop an enterotoxigenic Escherichia coli (ETEC) human challenge model for testing new heat-stable toxin (ST)-based vaccine candidates, a controlled human infection model study based on the ST-producing ETEC strain TW11681 was undertaken. Here, we estimate stool TW11681 DNA concentration and evaluate its association with dose, clinical symptoms, and with levels of antibodies targeting the CfaB subunit of the ETEC Colonization Factor Antigen I and the E. coli mucinase YghJ. Nine volunteers ingested different doses of the strain and were subsequently followed for 9 days with daily stool specimen collection and clinical examination. Stool DNA was purified by using a newly developed microplate-based method, and DNA originating from TW11681 was quantified by using a probe-based quantitative PCR assay. Antibody levels against CfaB and YghJ were measured in serum collected before and 10 and 28 days after TW11681 was ingested by using a bead-based flow cytometry immunoassay. RESULTS: For 6 of the 9 volunteers, the stool TW11681 DNA concentration increased sharply a median 3.5 (range 2-5) days after dose ingestion, peaking at a median of 5.4% (range 3.3-8.2%) of the total DNA in the specimen. The concentration then fell sharply during the subsequent days, sometimes even before the onset of antibiotic treatment. The size or timing of these proliferation peaks did not seem to be associated with the number of TW11681 bacteria ingested, but the 2 volunteers who developed diarrhea and all five who experienced abdominal pains or cramps had these peaks. The 3 volunteers who did not have the proliferation peaks experienced fewer symptoms and they generally had relatively low CfaB- and YghJ-specific antibody levels before ingesting the strain and subsequently weaker responses than the other volunteers afterwards. CONCLUSIONS: Since the lack of proliferation peaks appears to be associated with fewer clinical symptoms and lower serum antibody responses to virulence factors of the infecting strain, it may be important to account for proliferation peaks when explaining results from controlled human infection model studies and for improving the accuracy of protective efficacy estimates when testing new ETEC diarrhea vaccine candidates.