Characterization of the SARS-CoV-2 ExoN (nsp14ExoN-nsp10) complex: implications for its role in viral genome stability and inhibitor identification

The SARS-CoV-2 coronavirus is the causal agent of the current global pandemic. SARS-CoV-2 belongs to an order, Nidovirales, with very large RNA genomes. It is proposed that the fidelity of coronavirus (CoV) genome replication is aided by an RNA nuclease complex, comprising the non-structural proteins 14 and 10 (nsp14-nsp10), an attractive target for antiviral inhibition. Our results validate reports that the SARS-CoV-2 nsp14-nsp10 complex has RNase activity. Detailed functional characterization reveals nsp14-nsp10 is a versatile nuclease capable of digesting a wide variety of RNA structures, including those with a blocked 3'-terminus. Consistent with a role in maintaining viral genome integrity during replication, we find that nsp14-nsp10 activity is enhanced by the viral RNA-dependent RNA polymerase complex (RdRp) consisting of nsp12-nsp7-nsp8 (nsp12-7-8) and demonstrate that this stimulation is mediated by nsp8. We propose that the role of nsp14-nsp10 in maintaining replication fidelity goes beyond classical proofreading by purging the nascent replicating RNA strand of a range of potentially replication-terminating aberrations. Using our developed assays, we identify drug and drug-like molecules that inhibit nsp14-nsp10, including the known SARS-CoV-2 major protease (Mpro) inhibitor ebselen and the HIV integrase inhibitor raltegravir, revealing the potential for multifunctional inhibitors in COVID-19 treatment.

A randomized, double-blind, negatively controlled pilot study to determine whether the use of emollients or calcipotriol alters the sensitivity of the skin to ultraviolet radiation during phototherapy with narrowband ultraviolet B

BACKGROUND

There is contradictory evidence suggesting that emollients increase, decrease or have no effect on minimal erythema dose (MED) or minimal phototoxic dose values prior to phototherapy. Few studies have looked at the in vivo use of emollients or calcipotriol prior to narrowband ultraviolet (UV) B (NB-UVB) treatment.

OBJECTIVES

To investigate whether emollients or calcipotriol alter MED readings of skin on the back of healthy subjects prior to NB-UVB irradiation.

METHODS

Topical agents were applied to the backs of 20 healthy volunteers for 30 min prior to MED testing. These agents were aqueous cream, 50:50 white soft paraffin and liquid paraffin, Diprobase(®) (Schering-Plough, Welwyn Garden City, U.K.), Epaderm(®) (Medlock, Oldham, U.K.) and calcipotriol ointment and cream. A control MED strip was used with no topical agent applied prior to testing. MED readings were recoded as integer steps between 1 and 9 (one is lowest MED dose for skin type; eight is highest; nine is no response, i.e. a higher MED).

RESULTS

The median MED was between step 5 and 6 for all treatments and control. There was no significant difference at the 5% level between control and each topical agent. The study was powered to detect a median difference of approximately 0·4-0·6 steps.

CONCLUSIONS

This has important implications at a practical level when advising patients not to apply creams prior to treatment with NB-UVB. Studies where agents are applied immediately prior to phototherapy have been more likely to show that emollients block transmission of UV radiation. If they are applied at least 30 min prior to treatment, they have no effect.

Effect of water hardness on cardiovascular mortality: an ecological time series approach

BACKGROUND

Numerous studies have suggested an inverse relationship between drinking water hardness and cardiovascular disease. However, the weight of evidence is insufficient for the WHO to implement a health-based guideline for water hardness. This study followed WHO recommendations to assess the feasibility of using ecological time series data from areas exposed to step changes in water hardness to investigate this issue.

METHOD

Monthly time series of cardiovascular mortality data, subdivided by age and sex, were systematically collected from areas reported to have undergone step changes in water hardness, calcium and magnesium in England and Wales between 1981 and 2005. Time series methods were used to investigate the effect of water hardness changes on mortality.

RESULTS

No evidence was found of an association between step changes in drinking water hardness or drinking water calcium and cardiovascular mortality. The lack of areas with large populations and a reasonable change in magnesium levels precludes a definitive conclusion about the impact of this cation. We use our results on the variability of the series to consider the data requirements (size of population, time of water hardness change) for such a study to have sufficient power. Only data from areas with large populations (>500,000) are likely to be able to detect a change of the size suggested by previous studies (rate ratio of 1.06).

CONCLUSION

Ecological time series studies of populations exposed to changes in drinking water hardness may not be able to provide conclusive evidence on the links between water hardness and cardiovascular mortality unless very large populations are studied. Investigations of individuals may be more informative.

A national evaluation of school breakfast clubs: evidence from a cluster randomized controlled trial and an observational analysis

STUDY OBJECTIVE

To measure the health, educational and social impacts of breakfast club provision in schools serving deprived areas across England.

DESIGN

A cluster randomized controlled trial and an observational analysis.

SETTING

England, the UK.

INTERVENTION

funding to establish a school-based breakfast club vs. control (no funding).

MAIN RESULTS

Intention to treat analysis showed improved concentration (Trail Making Test Part A) amongst the intervention group at 3 months. Fewer pupils within the intervention group reported having skipped classes within the last month and fewer pupils within the intervention group reported having skipped 1 or more days of school within the last month at 1 year. Observational analysis at 1 year showed a higher proportion of primary-aged breakfast club attendees reported eating fruit for breakfast in comparison to non-attendees. A higher proportion of breakfast club attendees had borderline or abnormal conduct and total difficulties scores (primary-aged pupils) and prosocial score (secondary-aged pupils).

CONCLUSIONS

Analyses revealed a mixed picture of benefit and apparent disbenefit. This study illustrated the challenges of evaluating a complex intervention in which the evaluators had less control than is usual in randomized trials over recruitment, eligibility checking and implementation. If the impact of new policy initiatives is to be assessed using the most robust forms of evaluation, social policy needs to be organized so that evaluations can be constructed as experiments. This is likely to prove most difficult where the perceived value of implementing an intervention rapidly is high.

Shared patients: multiple health and social care contact

The paper describes results from the 'Tracking Project', a new method for examining agency overlap, repeat service use and shared clients/patients amongst social and health care agencies in the community. This is the first project in this country to combine total population databases from a range of social, health care and criminal justice agencies to give a multidisciplinary database for one county (n = 97,162 cases), through standardised anonymisation of agency databases, using SOUNDEX, a software programme. A range of 20 community social and health care agencies were shown to have a large overlap with each other in a two-year period, indicating high proportions of shared patients/clients. Accident and Emergency is used as an example of major overlap: 16.2% (n = 39,992) of persons who attended a community agency had attended Accident and Emergency as compared to 8.2% (n = 775,000) of the total population of the county. Of these, 96% who had attended seven or more different community agencies had also attended Accident and Emergency. Further statistical analysis of Accident and Emergency attendance as a characteristic of community agency populations (n = 39,992) revealed that increasing frequency of attendance at Accident and Emergency was very strongly associated with increasing use of other services. That is, the patients that repeatedly attend Accident and Emergency are much more likely to attend more other agencies, indicating the possibility that they share more problematic or difficult patients. Research questions arising from these data are discussed and future research methods suggested in order to derive predictors from the database and develop screening instruments to identify multiple agency attenders for targeting or multidisciplinary working. It is suggested that Accident and Emergency attendance might serve as an important predictor of multiple agency attendance.

Plasma and urine riboflavin during riboflavin-free nutrition in very-low-birth-weight infants

BACKGROUND

Very-low-birth-weight (VLBW; birth weight <1500 g) infants receive enteral and parenteral nutriture that provides greater daily riboflavin (vitamin B2) than does term infant nutriture, and elevated plasma riboflavin develops in these infants after birth. The purpose of this study was to measure plasma and urine riboflavin concentrations in VLBW infants during riboflavin-free nutrition. Our hypothesis was that elevated plasma riboflavin develops in VLBW infants because of high daily intake and immature renal riboflavin elimination.

METHODS

Eighteen clinically healthy VLBW infants received parenteral nutrition and preterm infant formula during the first postnatal month. On postnatal days 10 and 28, the infants received specially prepared riboflavin-free enteral and parenteral nutrition for the 24-hour study period. Serial collections of plasma were made at time 0 and at 12 and 24 hours. Urine was collected continuously for the 24-hour period in 4-hour aliquots. Samples were analyzed for riboflavin concentration.

RESULTS

During the 24-hour riboflavin-free study period on postnatal day 10, plasma riboflavin decreased 56% from 185 +/- 37 ng/mL (mean +/- SEM), and urine riboflavin decreased 75% from 3112 +/- 960 mg/mL. Similarly, on postnatal day 28, plasma riboflavin decreased 79% from 184 +/- 32 ng/mL, and urine riboflavin concentration decreased 91% from 5092 +/- 743 ng/mL during the 24-hour riboflavin-free study period. Riboflavin half-life (t(1/2)) was 18.5 hours on postnatal day 10 and decreased 48% by postnatal day 28. Riboflavin elimination was 145.1 +/- 20.6 mg/kg per day on postnatal day 10 and increased 40% by postnatal day 28.

CONCLUSION

The VLBW infants who received parenteral nutrition and preterm infant formula had elevated plasma riboflavin on postnatal days 10 and 28. Plasma riboflavin t(1,2) was shorter and renal riboflavin elimination was greater on postnatal day 28 than on postnatal day 10. Plasma riboflavin was normal after 24 hours of riboflavin-free nutrition. The pattern of plasma and urine riboflavin in VLBW infants suggests a lower daily intake would maintain plasma riboflavin close to normal.

Immunisation with phage displaying peptides representing single epitopes of the glycoprotein G can give rise to partial protective immunity to HSV-2

Filamentous phage displaying peptides representing single epitopes of the glycoprotein G of HSV-2 (gG2) were used as immunogens via the subcutaneous route in Balb/c mice without additional adjuvant. The phage were isolated from a random phage peptide display library and contain 15-mer peptide inserts that mimic epitopes of gG2. In each case, an antibody response to gG2 was generated that was dependent on the dose of phage administered and on the presence of the peptide insert. Phage displaying epitopes of gG2, which map to amino acids 551-570, were the most immunogenic; interestingly, this region of gG2 is frequently recognised by patients infected with HSV-2. The data also provide interesting information as regards choice of peptide mimics for use as immunogens because, surprisingly, the most antigenic of the individual clones was the least immunogenic. In two of the experiments, mice immunised with phage displaying a single epitope of gG2 were protected against challenge with a lethal dose of whole HSV-2. This suggests a possible role for phage-displayed peptides in inducing protective immunity against pathogens and provides a model system for investigating the underlying mechanisms.

Effects of oxidants on properties of fluorescent calcium indicators

An increasing number of studies use calcium-sensitive fluorescent dyes to address the relationship between elevated levels of intracellular calcium and free-radical-mediated damage in a variety of pathophysiological phenomena. The present study evaluates the effects of reactive oxygen species on the spectral properties of widely used calcium probes such as Fura-2 and Fluo-3. We found that both Fura-2 and Fluo-3 are rapidly inactivated by hydroxyl radicals and enzymatically inactivated by peroxidase/H2O2. This results in a decrease in the dynamic range of sensitivity of both dyes to Ca2+, as well as in a decrease in the affinity of Fluo-3 for Ca2+. The data suggest that oxidation of the calcium probes affects the measurement of calcium in vitro and may alter the interpretation of in vivo data since the absence of or small changes in the calcium fluorescence signal can be the result of probe deactivation by free oxygen radicals rather than the lack of actual Ca2+ changes.

Fatal fat embolism syndrome in a child with undiagnosed hemoglobin S/beta+ thalassemia: a complication of acute parvovirus B19 infection

Anemia, mental status changes, and fatal respiratory failure complicated a febrile illness in a previously healthy 14-year-old black female. At autopsy, widespread fat emboli and bone marrow necrosis were found. Hemoglobin electrophoresis on an antemortem, pretransfusion specimen revealed hemoglobin S/beta+ thalassemia. Acute parvovirus B19 (PV B19) infection was suspected. Postmortem serum and a variety of paraffin-embedded tissues were assayed for PV B19 DNA using the polymerase chain reaction (PCR). The expected PCR product was identified in the serum specimen and in paraffin-embedded sections of bone marrow, kidney, spleen, parathyroid, thyroid, adrenal, and gastrointestinal tract: lung, liver, ovary, fallopian tube, uterus, brain, heart, and pancreas were negative. PV B19 infection is highly contagious and may be rapidly fatal in children with hemoglobinopathies by several mechanisms, including fat embolism. Therefore, there exists the risk of multiple deaths within a family. The acute infection may be easily and expeditiously diagnosed using serum or a variety of paraffin-embedded tissues.

Lipid accumulation and body fat distribution is influenced by type of dietary fat fed to rats

The amount of fat in the diet is known to influence body weight and body composition, but it is not clear whether dietary fat composition can affect body composition independently. We studied the effects of six months of feeding diets containing lard (L), corn oil (CO), fish oil (FO) or medium chain triglycerides (MCT) on body weight and body composition in adult male Wistar rats. Although FO fats ate slightly less total energy than the other groups, there were no differences among groups in body weight at any time during the study. However, body composition, the composition of depot triglyceride, body fat distribution and insulin resistance were all influenced by the type of fat in the diet. FO rats had less total body fat, less intra-abdominal fat, and less insulin resistance than all other groups. Although some of these metabolic effects may have been secondary to a slightly lower energy intake, we believe these data demonstrate the potential impact which dietary fat composition can have on metabolism and body weight regulation.

Arachidonic acid epoxygenase: structural characterization and quantification of epoxyeicosatrienoates in plasma

Gas chromatographic/mass spectroscopic and chiral analysis showed the presence of enzymatically derived 8,9-, 11,12- and 14,15-EET in rat plasma (2.8:1:3.4 molar ratio, respectively; 10.2 +/- 0.4 ng total EET/ml plasma). Greater than 90% of the plasma EETs was esterified to the phospholipids of circulating lipoproteins. The lipoprotein fraction with the highest EET concentration was LDL (8.1 +/- 0.9 ng/mg of protein) followed by HDL and VLDL (3.5 +/- 0.1 and 1.9 +/- 0.3 ng/mg of protein, respectively). In light of the biological activities of the EETs, these results suggest a potential systemic function for the cytochrome P-450 epoxygenase.

Intravenous vitamins for very-low-birth-weight infants

Term infants and children appear to adapt to large variations in vitamin intakes. This is supported by the finding of similar blood levels of vitamins despite several-fold differences in intake on a body weight basis. By contrast, the finding of marked elevation of some vitamins and low levels of others seen in very-low-birth-weight (VLBW) infants (less than 1500 g) suggest that this group has less adaptive capacity to high- or low-dose intakes. This indicates that their vitamin intakes need to be more closely aligned with actual needs. This paper reviews previously published data on vitamins A, E, B2, and B6 from VLBW infants receiving total parenteral nutrition (TPN). Vitamin A. VLBW infants are relatively deficient in retinol (R) at birth. During TPN large losses of R onto the delivery sets result in a further decline in stores of R as reflected in a progressive decline in plasma R during TPN. Because of the reported lower incidence of bronchopulmonary dysplasia associated with intramuscular vitamin A treatment, alternative methods of vitamin A delivery during TPN have been suggested. First, the vitamins were mixed with Intralipid (IL) and, second, retinyl palmitate (RP) rather than R was used. There was little in vitro loss of R when mixed with IL, and in vivo treatment resulted in higher blood levels after 1 month of retinol administration in IL than seen previously (21.4 +/- 4.2 vs 14.1 +/- 3.7 micrograms/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of clonidine hydrochloride versus atenolol monotherapy on serum lipids, lipid subfractions, and apolipoproteins in mild hypertension

The study objective was to determine the effects of monotherapy with clonidine and atenolol versus placebo on serum lipids, apolipoproteins, and blood pressure in patients with mild primary hypertension. The protocol comprised a double blind, randomized, placebo-controlled 5-month prospective study carried out in an outpatient general internal medicine clinic in a university medical center. There were 92 patients ages 18 to 70, with mild primary hypertension (sitting diastolic blood pressure of greater than 90 mm Hg and less than 105 mm Hg) without significant cardiac, renal, cerebrovascular, hepatic, neoplastic, or hematologic disorders. Patients with severe hyperlipidemia or peripheral vascular disease were also excluded. All factors known to effect serum lipids were held constant throughout the study (i.e., diet, weight, exercise, caffeine, tobacco). Atenolol and clonidine significantly reduced blood pressure when compared with placebo. Atenolol caused significant increases in serum triglycerides and apolipoprotein B (p less than 0.05) and significant reductions in high-density lipoprotein-cholesterol, apolipoproteins A-I and A-II (p less than 0.05). Atenolol also induced a significant adverse effect on all lipid ratios, increasing total cholesterol/high density lipoprotein-cholesterol, low density lipoprotein-cholesterol/high density lipoprotein-cholesterol, apolipoprotein B/apolipoprotein A-I and apolipoprotein B/apolipoprotein A-II ratios and decreasing low density lipoprotein-cholesterol/apolipoprotein-B ratio (p less than 0.05). Clonidine caused significant reductions in high-density lipoprotein-cholesterol, apolipoproteins AI and AII (p less than 0.05 but was neutral on all other lipids, lipid subfractions, and apolipoproteins. Clonidine did not significantly alter any of the lipid ratios.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte membrane abnormalities in Duchenne muscular dystrophy monitored by saturation transfer electron paramagnetic resonance spectroscopy

Saturation transfer electron paramagnetic resonance and the spin label 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl were used to study erythrocytes from patients with Duchenne muscular dystrophy or Becker syndrome and from age-matched normal boys. There were significant differences in the spectral intensities of erythrocytes from Duchenne patients when compared to controls. Spectral intensities increased with time in the former; no such change was observed in the latter. Saturation transfer electron paramagnetic resonance spectra of erythrocytes from patients with Becker syndrome were significantly different from those from Duchenne patients but were not significantly different from normals. These observations suggest the possible usefulness of these techniques in the differential diagnosis of Duchenne muscular dystrophy. Spin label concentration spectral studies suggest that the observed spectral differences between Duchenne patients and controls were due to differential spin exchange phenomena.