SARS-CoV-2 antibodies persist up to 12 months after natural infection in healthy employees working in non-medical contact-intensive professions

OBJECTIVES

This study aimed to evaluate dynamics of antibody levels after exposure to SARS-CoV-2 for 12 months in Dutch non-vaccinated hairdressers and hospitality staff.

METHODS

In this prospective cohort study, blood samples were collected every 3 months for 1 year and analyzed using a qualitative total antibody enzyme-linked immunosorbent assay (ELISA) and a quantitative immunoglobulin (Ig)G antibody ELISA. Participants completed questionnaires, providing information on demographics, health, and work. Differences in antibody levels were evaluated using Mann-Whitney U and Wilcoxon signed-rank tests. Beta coefficients (β) and 95% confidence intervals (CIs) were calculated using linear regression.

RESULTS

Ninety-five of 497 participants (19.1%) had ≥1 seropositive measurement before their last visit using the qualitative ELISA. Only 2.1% (2/95) seroreverted during follow-up. Of 95 participants, 82 (86.3%) tested IgG seropositive in the quantitative ELISA too. IgG antibody levels significantly decreased in the first months (P <0.01) but remained detectable for up to 12 months in all participants. Older age (β, 10-years increment: 24.6, 95% CI: 5.7-43.5) and higher body mass index (β, 5kg/m² increment: 40.0, 95% CI: 2.9-77.2) were significantly associated with a higher peak of antibody levels.

CONCLUSION

In this cohort, SARS-CoV-2 antibodies persisted for up to 1 year after initial seropositivity, suggesting long-term natural immunity.

Self-testing for the detection of SARS-CoV-2 infection with rapid antigen tests for people with suspected COVID-19 in the community

Objectives

To evaluate the performance of nasal mid-turbinate self-testing using rapid antigen detection tests (RDT) for persons with suspected coronavirus disease 2019 (COVID-19) in the community. Self-testing for COVID-19 infection with lateral flow assay severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RDT, provides rapid results and could enable frequent and extensive testing in the community, thereby improving the control of SARS-CoV-2.

Methods

Participants visiting a municipal SARS-CoV-2 testing centre, received self-testing kits containing either the BD Veritor System (BD-RDT) or Roche SARS-CoV-2 antigen detection test (Roche-RDT). Oro-nasopharyngeal swabs were collected from the participants for quantitative RT-PCR (qRT-PCR) testing. As a proxy for contagiousness, viral culture was performed on a selection of qRT-PCR positive samples to determine the Ct-value at which the chance of a positive culture dropped below 0.5 (Ct-value cut-off). Sensitivity and specificity of self-testing were compared to qRT-PCR with a Ct-value below the Ct value cut-off. Determinants independently associated with a false-negative self-test result were determined.

Results

A total of 3201 participants were included (BD-RDT n = 1595; Roche-RDT n = 1606). Sensitivity and specificity of self-testing compared with the qRT-PCR results with a Ct-value below the Ct-value cut-off were 78.4% (95% CI 73.2%–83.5%) and 99.4% (95% CI 99.1%–99.7%), respectively. A higher age was independently associated with a false-negative self-testing result with an odds ratio of 1.024 (95% CI 1.003–1.044).

Conclusions

Self-testing using currently available RDT has a high specificity and relatively high sensitivity to identify individuals with a high probability of contagiousness.

Transmission of SARS-CoV-2 on mink farms between humans and mink and back to humans

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a zoonotic virus—one that spilled over from another species to infect and transmit among humans. We know that humans can infect other animals with SARS-CoV-2, such as domestic cats and even tigers in zoos. Oude Munnink et al. used whole-genome sequencing to show that SARS-CoV-2 infections were rife among mink farms in the southeastern Netherlands, all of which are destined to be closed by March 2021 (see the Perspective by Zhou and Shi). Toward the end of June 2020, 68% of mink farm workers tested positive for the virus or had antibodies to SARS-CoV-2. These large clusters of infection were initiated by human COVID-19 cases with viruses that bear the D614G mutation. Sequencing has subsequently shown that mink-to-human transmission also occurred. More work must be done to understand whether there is a risk that mustelids may become a reservoir for SARS-CoV-2.

Science, this issue p. 172; see also p. 120

Animal experiments have shown that nonhuman primates, cats, ferrets, hamsters, rabbits, and bats can be infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In addition, SARS-CoV-2 RNA has been detected in felids, mink, and dogs in the field. Here, we describe an in-depth investigation using whole-genome sequencing of outbreaks on 16 mink farms and the humans living or working on these farms. We conclude that the virus was initially introduced by humans and has since evolved, most likely reflecting widespread circulation among mink in the beginning of the infection period, several weeks before detection. Despite enhanced biosecurity, early warning surveillance, and immediate culling of animals in affected farms, transmission occurred between mink farms in three large transmission clusters with unknown modes of transmission. Of the tested mink farm residents, employees, and/or individuals with whom they had been in contact, 68% had evidence of SARS-CoV-2 infection. Individuals for which whole genomes were available were shown to have been infected with strains with an animal sequence signature, providing evidence of animal-to-human transmission of SARS-CoV-2 within mink farms.

Two Community Clusters of Legionnaires' Disease Directly Linked to a Biologic Wastewater Treatment Plant, the Netherlands

A biologic wastewater treatment plant was identified as a common source for 2 consecutive Legionnaires' disease clusters in the Netherlands in 2016 and 2017. Sequence typing and transmission modeling indicated direct and long-distance transmission of Legionella, indicating this source type should also be investigated in sporadic Legionnaires' disease cases.

Familiarity of general practitioners with Q fever decreases hospitalisation risk

INTRODUCTION

Between 2007 and 2010, the Netherlands experienced large outbreaks of Q fever with over 4000 cases. There were unexplained geographical differences in hospitalisation rates of notified patients. We examined the extent of this geographic variation in Q fever hospitalisation and its potential association with general practitioner (GP) experience with Q fever.

METHODS

We included Q fever cases notified by GPs in 2008 and 2009 in the affected public health region. We used linear regression to describe trends of hospitalisation over time and tested for statistical differences in hospitalisation between municipalities with the chi-square test. We used the number of previously diagnosed Q fever cases of an individual GP as a proxy for Q fever experience, grouped into four categories of GP experience (1; 2; 3-7 and 8 or more cases). We calculated adjusted odds ratios (OR) using logistic regression, taking into account clustering at the GP level.

RESULTS

The proportion of hospitalised cases was highly variable between municipalities (range 0-56%, p-value < 0.001). The proportion of hospitalised cases decreased monthly by 0.7% (95% confidence interval (CI): 0.03-1.3%). The risk of hospitalisation was lower when GPs had seen eight or more Q fever cases compared with GPs who had seen only one case (OR 0.4 [95% CI: 0.2-0.8]).

DISCUSSION

Our findings suggest that increased GP experience was associated with a reduction in hospitalisations. This supports the public health initiatives to disseminate epidemiological updates and information regarding diagnostic and therapeutic options for Q fever to GPs to reduce Q fever related hospitalisation.

Cytosolic 5'-nucleotidase 1A autoantibody profile and clinical characteristics in inclusion body myositis

OBJECTIVES

Autoantibodies directed against cytosolic 5'-nucleotidase 1A have been identified in many patients with inclusion body myositis. This retrospective study investigated the association between anticytosolic 5'-nucleotidase 1A antibody status and clinical, serological and histopathological features to explore the utility of this antibody to identify inclusion body myositis subgroups and to predict prognosis.

MATERIALS AND METHODS

Data from various European inclusion body myositis registries were pooled. Anticytosolic 5'-nucleotidase 1A status was determined by an established ELISA technique. Cases were stratified according to antibody status and comparisons made. Survival and mobility aid requirement analyses were performed using Kaplan-Meier curves and Cox proportional hazards regression.

RESULTS

Data from 311 patients were available for analysis; 102 (33%) had anticytosolic 5'-nucleotidase 1A antibodies. Antibody-positive patients had a higher adjusted mortality risk (HR 1.89, 95% CI 1.11 to 3.21, p=0.019), lower frequency of proximal upper limb weakness at disease onset (8% vs 23%, adjusted OR 0.29, 95% CI 0.12 to 0.68, p=0.005) and an increased prevalence of excess of cytochrome oxidase deficient fibres on muscle biopsy analysis (87% vs 72%, adjusted OR 2.80, 95% CI 1.17 to 6.66, p=0.020), compared with antibody-negative patients.

INTERPRETATION

Differences were observed in clinical and histopathological features between anticytosolic 5'-nucleotidase 1A antibody positive and negative patients with inclusion body myositis, and antibody-positive patients had a higher adjusted mortality risk. Stratification of inclusion body myositis by anticytosolic 5'-nucleotidase 1A antibody status may be useful, potentially highlighting a distinct inclusion body myositis subtype with a more severe phenotype.

Estimation of acute and chronic Q fever incidence in children during a three-year outbreak in the Netherlands and a comparison with international literature

Background

In the Dutch 2007–2009 Q fever outbreak Coxiella burnetii was transmitted aerogenically from dairy goat farms to those living in the surrounding areas. Relatively few children were reported. The true number of pediatric infections is unknown. In this study, we estimate the expected number of acute and chronic childhood infections.

Methods

As Coxiella was transmitted aerogenic to those living near infected dairy goat farms, we could use adult seroprevalence data to estimate infection risk for inhabitants, children and adults alike. Using Statistics Netherlands data we estimated the number of children at (high) risk for developing chronic Q fever. Literature was reviewed for childhood (0–15 years) Q fever reports and disease rates. We compared this with Dutch reported and our estimated data for 2007–2009.

Results

In The Netherlands epidemic, 44 children were reported (1.2 % of total notifications). The childhood incidence was 0.15 compared to 2.6 per 10,000 inhabitants for adults. No complications were reported. Based on the expected similarity in childhood and adult exposure we assume that 9.8 % of children in the high-risk area had Q fever infection, resulting in 1562 acute infections during the Q fever epidemic interval. Based on the prevalence of congenital heart disease, at least 13 children are at high risk for developing chronic Q fever. In medical literature, 42 case reports described 140 childhood Q fever cases with a serious outcome (four deaths). In chronic Q fever, cardiac infections were predominant. Four outbreaks were reported involving children, describing 11 childhood cases. 36 National and/or regional studies reported seroprevalences varying between 0 and 70 %.

Conclusion

In the 3-year Dutch epidemic, few childhood cases were reported, with pulmonary symptoms leading, and none with a serious presentation. With an estimated 13 high-risk children for chronic infection in the high exposure area, and probably forty in the whole country, we may expect several chronic Q fever complications in the coming years in paediatric practice.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-015-1389-0) contains supplementary material, which is available to authorized users.

Long-Term Serological Follow-Up of Acute Q-Fever Patients after a Large Epidemic

Background

Serological follow-up of acute Q-fever patients is important for detection of chronic infection but there is no consensus on its frequency and duration. The 2007–2009 Q-fever epidemic in the Netherlands allowed for long-term follow-up of a large cohort of acute Q-fever patients. The aim of this study was to validate the current follow-up strategy targeted to identify patients with chronic Q-fever.

Methods

A cohort of adult acute Q-fever patients, diagnosed between 2007 and 2009, for whom a twelve-month follow-up sample was available, was invited to complete a questionnaire and provide a blood sample, four years after the acute episode. Antibody profiles, determined by immunofluorescence assay in serum, were investigated with a special focus on high titres of IgG antibodies against phase I of Coxiella burnetii, as these are considered indicative for possible chronic Q-fever.

Results

Of the invited 1,907 patients fulfilling inclusion criteria, 1,289 (67.6%) were included in the analysis. At any time during the four-year follow-up period, 58 (4.5%) patients were classified as possible, probable, or proven chronic Q-fever according to the Dutch Q-fever Consensus Group criteria (which uses IgG phase I ≥1:1,024 to as serologic criterion for chronic Q-fever). Fifty-two (89.7%) of these were identified within the first year after the acute episode. Of the six patients that were detected for the first time at four-year follow-up, five had an IgG phase I titre of 1:512 at twelve months.

Conclusions

A twelve-month follow-up check after acute Q-fever is recommended as it adequately detects chronic Q-fever in patients without known risk factors. Additional serological and clinical follow-up is recommended for patients with IgG phase I ≥1:512, as they showed the highest risk to progress to chronic Q-fever.

Ongoing transmission of hepatitis B virus in rural parts of the Netherlands, 2009-2013

Background

Reported acute hepatitis B incidence in the Netherlands reached its nadir in 2013. However, regional signals about increased number of hepatitis B cases raised the question how hepatitis B incidence was distributed over the country. In this study, regional differences in hepatitis B epidemiology were investigated using epidemiological and molecular data.

Methods

Acute hepatitis B virus (HBV) infections, reported between 2009–2013, were included. If serum was available, a fragment of S and C gene of the HBV was amplified and sequenced. Regional differences in incidence were studied by geographical mapping of cases and cluster analysis. Regional differences in transmission were studied by constructing regional maximum parsimony trees based on the C gene to assess genetic clustering of cases.

Results

Between 2009 and 2013, 881 cases were notified, of which respectively 431 and 400 cases had serum available for S and C gene sequencing. Geographical mapping of notified cases revealed that incidences in rural border areas of the Netherlands were highest. Cluster analysis identified two significant clusters (p<0.000) in the South-western and North-eastern regions. Genetic cluster analysis showed that rural border areas had relatively large clusters of cases with indistinguishable sequences, while other regions showed more single introductions.

Conclusion

This study showed that regional differences in HBV epidemiology were present in the Netherlands. Rural border regions showed higher incidences and more ongoing transmission, mainly among MSM, than the more urban inland areas. Therefore, preventive measures should be enhanced in these regions.

Routine screening for Coxiella burnetii infection during pregnancy: a clustered randomised controlled trial during an outbreak, the Netherlands, 2010

Between 2007 and 2010, the Netherlands experienced one of the largest outbreaks of Q fever. Since asymptomatic Coxiella burnetii infection has been associated with maternal and obstetric complications, evidence about the effectiveness of routine screening during pregnancy in outbreak areas is needed. We performed a clustered randomised controlled trial during the Dutch outbreak, in which 55 midwife centres were randomised to recruit pregnant women for an intervention or control strategy. In both groups a serum sample was taken between 20 and 32 weeks of gestation. In the intervention group (n=536), the samples were analysed immediately by indirect immunofluorescence assay for the presence of IgM and IgG (phase I/II) and treatment was given during pregnancy in case of an acute or chronic infection. In the control group (n=693), sera were frozen for analysis after delivery. In both groups 15% were seropositive. In the intervention group 2.2% of the women were seropositive and had an obstetric complication, compared with 1.4% in the control group (Odds ratio: 1.54 (95% confidence interval 0.60-3.96)). During a large Q fever outbreak, routine C. burnetii screening starting at 20 weeks of gestation was not associated with a relevant reduction in obstetric complications and should therefore not be recommended.

The use of typing methods and infection prevention measures to control a bullous impetigo outbreak on a neonatal ward

BACKGROUND

We describe an outbreak of Bullous Impetigo (BI), caused by a (methicillin susceptible, fusidic acid resistant) Staphylococcus aureus (SA) strain, spa-type t408, at the neonatal and gynaecology ward of the Jeroen Bosch hospital in the Netherlands, from March-November 2011.

METHODS

We performed an outbreak investigation with revision of the hygienic protocols, MSSA colonization surveillance and environmental sampling for MSSA including detailed typing of SA isolates. Spa typing was performed to discriminate between the SA isolates. In addition, Raman-typing was performed on all t408 isolates.

RESULTS

Nineteen cases of BI were confirmed by SA positive cultures. A cluster of nine neonates and three health care workers (HCW) with SA t408 was detected. These strains were MecA-, PVL-, Exfoliative Toxin (ET)A-, ETB+, ETAD-, fusidic acid-resistant and methicillin susceptible. Eight out of nine neonates and two out of three HCW t408 strains yielded a similar Raman type. Positive t408 HCW were treated and infection control procedures were reinforced. These measures stopped the outbreak.

CONCLUSIONS

We conclude that treatment of patients and HCW carrying a predominant SA t408, and re-implementing and emphasising hygienic measures were effective to control the outbreak of SA t408 among neonates.

Proximity to goat farms and Coxiella burnetii seroprevalence among pregnant women

During 2007-2009, we tested serum samples from 2,004 pregnant women living in an area of high Q fever incidence in the Netherlands. Results confirmed that presence of antibodies against Coxiella burnetii is related to proximity to infected dairy goat farms. Pregnant women and patients with certain cardiovascular conditions should avoid these farms.

Relation between Q fever notifications and Coxiella burnetii infections during the 2009 outbreak in the Netherlands

Binary file ES_Abstracts_Final_ECDC.txt matches

Relation between Q fever notifications and Coxiella burnetii infections during the 2009 outbreak in The Netherlands

Large outbreaks of Q fever in the Netherlands from 2007 to 2009 were monitored using notification data of acute clinical Q fever. However, the notification system provides no information on infections that remain subclinical or for which no medical attention is sought. The present study was carried out immediately after the peak of the 2009 outbreak to estimate the ratio between Coxiella burnetii infections and Q fever notifications. In 23 postcode areas in the high-incidence area, notification rates were compared with seroconversion rates in blood donors from whom serial samples were available. This resulted in a ratio of one Q fever notification to 12.6 incident infections of C. burnetii. This ratio is time and place specific and is based on a small number of seroconversions, but is the best available factor for estimating the total number of infections. In addition, as subclinical C. burnetii infection may lead to chronic Q fever, the ratio can be used to estimate the expected number of chronic Q fever patients in the coming years and as input for cost–benefit analyses of screening options.

Shifting priorities in the aftermath of a Q fever epidemic in 2007 to 2009 in the Netherlands: from acute to chronic infection

From 2007 to 2009, the Netherlands faced large seasonal outbreaks of Q fever, in which infected dairy goat farms were identified as the primary sources. Veterinary measures including vaccination of goats and sheep and culling of pregnant animals on infected farms seem to have brought the Q fever problem under control. However, the epidemic is expected to result in more cases of chronic Q fever among risk groups in the coming years. In the most affected area, in the south of the country, more than 12% of the population now have antibodies against Coxiella burnetii. Questions remain about the follow-up of acute Q fever patients, screening of groups at risk for chronic Q fever, screening of donors of blood and tissue, and human vaccination. There is a considerable ongoing research effort as well as enhanced veterinary and human surveillance.

Shifting priorities in the aftermath of a Q fever epidemic in 2007 to 2009 in The Netherlands: from acute to chronic infection

From 2007 to 2009, the Netherlands faced large seasonal outbreaks of Q fever, in which infected dairy goat farms were identified as the primary sources. Veterinary measures including vaccination of goats and sheep and culling of pregnant animals on infected farms seem to have brought the Q fever problem under control. However, the epidemic is expected to result in more cases of chronic Q fever among risk groups in the coming years. In the most affected area, in the south of the country, more than 12% of the population now have antibodies against Coxiella burnetii. Questions remain about the follow-up of acute Q fever patients, screening of groups at risk for chronic Q fever, screening of donors of blood and tissue, and human vaccination. There is a considerable ongoing research effort as well as enhanced veterinary and human surveillance.

Cost-effectiveness of a screening strategy for Q fever among pregnant women in risk areas: a clustered randomized controlled trial

Background

In The Netherlands the largest human Q fever outbreak ever reported in the literature is currently ongoing with more than 2300 notified cases in 2009. Pregnant women are particularly at risk as Q fever during pregnancy may cause maternal and obstetric complications. Since the majority of infected pregnant women are asymptomatic, a screening strategy might be of great value to reduce Q fever related complications. We designed a trial to assess the (cost-)effectiveness of a screening program for Q fever in pregnant women living in risks areas in The Netherlands.

Methods/design

We will conduct a clustered randomized controlled trial in which primary care midwife centres in Q fever risk areas are randomized to recruit pregnant women for either the control group or the intervention group. In both groups a blood sample is taken around 20 weeks postmenstrual age. In the intervention group, this sample is immediately analyzed by indirect immunofluorescence assay for detection of IgG and IgM antibodies using a sensitive cut-off level of 1:32. In case of an active Q fever infection, antibiotic treatment is recommended and serological follow up is performed. In the control group, serum is frozen for analysis after delivery. The primary endpoint is a maternal (chronic Q fever or reactivation) or obstetric complication (low birth weight, preterm delivery or fetal death) in Q fever positive women. Secondary aims pertain to the course of infection in pregnant women, diagnostic accuracy of laboratory tests used for screening, histo-pathological abnormalities of the placenta of Q fever positive women, side effects of therapy, and costs. The analysis will be according to the intention-to-screen principle, and cost-effectiveness analysis will be performed by comparing the direct and indirect costs between the intervention and control group.

Discussion

With this study we aim to provide insight into the balance of risks of undetected and detected Q fever during pregnancy.

Trial registration

ClinicalTrials.gov, protocol record NL30340.042.09.

[Three years of Q fever in the Netherlands: faster diagnosis]

OBJECTIVE

To assess if more rapid diagnosis and treatment is possible and to assess if this could be improved, since the first outbreak of Q fever in 2007.

DESIGN

Retrospective study of secondary data.

METHODS

Analysis of surveillance data regarding Q fever over the period 2007 to 2009 and additional information on some patients from 2007 and 2008 obtained from general practitioners.

RESULTS

Diagnostic delay fell sharply between 2007 and 2009 and to a lesser extent, so did therapeutic delay from 2007 to 2008. In high incidence areas, diagnosis and treatment was faster with a lower proportion of patients admitted to hospital than in low incidence areas.

CONCLUSION

It appears that familiarity with the condition leads to faster diagnosis coupled with a lower percentage of hospital admissions. In order to react quickly it is necessary that doctor and patient should be aware of Q fever, especially in areas of low incidence. Polymerase chain reaction diagnostic techniques should also be available.

Q fever outbreak in the Netherlands: a preliminary report

On 29 May 2007, a general practitioner (GP) from a rural village in the province of Noord- Brabant, in the south of the Netherlands, alerted the municipal health service about an unusual increase in pneumonia cases among adults in his practice.

[More and faster notification of infectious disease if notification is carried out by the laboratories instead of the diagnosing physician]

OBJECTIVE

To investigate if notification by the laboratories of a number of Group B diseases (meningococcal disease, whooping cough and hepatitis A) which according to the Communicable Disease Law of 999 must be reported to the local public health authority, would increase the number of reports and the speed at which the reports were made.

DESIGN

Comparative study.

METHOD

In the participating regions (Den Bosch and north-east Brabant) it was decided that the laboratories would notify the authorities of cases ofmeningococcal disease, whooping cough and hepatitis A. The notifications were compared with those from the middle-Brabant region which was used as a control. This took place in 1997/'98, prior to the start of the notification project and in 2000/'02 when it was running. The number of positive cases of infectious disease confirmed by the laboratories that were reported to the local health authorities and to the Inspectorate of Public Health Services was examined - this is known as the degree of notification. The number of days from diagnosis to notification of the local health authorities was also examined - this is known as the speed of notification.

RESULTS

The degree of notification for these three diseases improved from 6I-89% to 87-95% if the authorities were notified by the laboratories. In the control region the degree of notification improved from 29-4I% to 54-60%. The speed of notification increased significantly if notification was done by the laboratories.

CONCLUSION

Based on these results it is recommended that the Communicable Disease Law be adapted to allow the laboratories to notify the authorities of cases of infectious disease.

Tea flavonoids: bioavailability in vivo and effects on cell signaling pathways in vitro

The elucidation of the potential health benefits of tea beverage continues to be a focus of research in many laboratories. Beneficial effects of tea have been particularly evident in animal tumorigenesis models, with green and black tea frequently demonstrating similar effectivity. Human data are now emerging to support a beneficial role for tea in cardiovascular disease, but the data with respect to cancer risk at various sites remain inconclusive. The constituent flavonoids of green and black tea beverage are known to be potent antioxidants, and although this may be a major factor in explaining their biological activity, it appears that the gallated flavonoids in particular (e.g., epigallocatechin gallate and the gallated theaflavins) impact on a wide range of molecular targets that influence cell growth and more specifically pathways such as those involving angiogenesis. Data on the pharmacokinetic properties of tea flavonoids, primarily on the catechins and therefore related most closely to green tea, have provided indications of the plasma levels and circulating molecular forms that may be expected in humans following tea consumption. The structural complexity of black tea flavonoids, in particular the thearubigins, has hindered efforts to describe their bioavailability and to perform mechanistic studies. Recent studies on the effects of catechins and theaflavins on growth factor-, nuclear factor-kappaB-, and stress-mediated signal transductions are described in this review, where possible in relation to their bioavailability in vivo. These studies indicate that effects that may be relevant to both cancer and atherosclerosis are often observed at tea flavonoid levels that could realistically be encountered in vivo. However, more studies need to be performed using those molecular forms of tea flavonoids (methylated, sulfated, and glucuronidated conjugates) that are the major circulating species encountered following tea consumption. Such studies, combined with further human epidemiological and interventional data, should ultimately elucidate the full beneficial potential of tea beverage on human health.

Acyl and alkyl chain length of GPI-anchors is critical for raft association in vitro

We determined the acyl and alkyl chain composition of GPI-anchors isolated from MDCK and Fischer rat thyroid (FRT) cells. Both cell lines synthesize GPI-anchors containing C16/C18 or C18/C18 saturated acyl and alkyl chains. The GPI-anchored placental alkaline phosphatase (PLAP) expressed in both cells is raft-associated and PLAP purified from FRT cells is raft-associated in vitro when reconstituted into liposomes containing raft lipids. In contrast, the GPI-anchored variant surface glycoprotein from Trypanosoma brucei which contains C14 acyl and alkyl chains shows no significant raft association after reconstitution in vitro. These data indicate that the acyl and alkyl chain composition of GPI-anchors determines raft association.

Association of sterol- and glycosylphosphatidylinositol-linked proteins with Drosophila raft lipid microdomains

In vertebrates, the formation of raft lipid microdomains plays an important part in both polarized protein sorting and signal transduction. To establish a system in which raft-dependent processes could be studied genetically, we have analyzed the protein and lipid composition of these microdomains in Drosophila melanogaster. Using mass spectrometry, we identified the phospholipids, sphingolipids, and sterols present in Drosophila membranes. Despite chemical differences between Drosophila and mammalian lipids, their structure suggests that the biophysical properties that allow raft formation have been preserved. Consistent with this, we have identified a detergent-insoluble fraction of Drosophila membranes that, like mammalian rafts, is rich in sterol, sphingolipids, and glycosylphosphatidylinositol-linked proteins. We show that the sterol-linked Hedgehog N-terminal fragment associates specifically with this detergent-insoluble membrane fraction. Our findings demonstrate that raft formation is preserved across widely separated phyla in organisms with different lipid structures. They further suggest sterol modification as a novel mechanism for targeting proteins to raft membranes and raise the possibility that signaling and polarized intracellular transport of Hedgehog are based on raft association.

Influenza viruses select ordered lipid domains during budding from the plasma membrane

During the budding of enveloped viruses from the plasma membrane, the lipids are not randomly incorporated into the envelope, but virions seem to have a lipid composition different from the host membrane. Here, we have analyzed lipid assemblies in three different viruses: fowl plague virus (FPV) from the influenza virus family, vesicular stomatitis virus (VSV), and Semliki Forest virus (SFV). Analysis of detergent extractability of proteins, cholesterol, phosphoglycerolipids, and sphingomyelin in virions showed that FPV contains high amounts of detergent-insoluble complexes, whereas such complexes are largely absent from VSV or SFV. Cholesterol depletion from the viral envelope by methyl-beta-cyclodextrin results in increased solubility of sphingomyelin and of the glycoproteins in the FPV envelope. This biochemical behavior suggests that so-called raft-lipid domains are selectively incorporated into the influenza virus envelope. The "fluidity" of the FPV envelope, as measured by the fluorescence polarization of diphenylhexatriene, was significantly lower than compared with VSV or SFV. Furthermore, influenza virus hemagglutinin incorporated into the envelope of recombinant VSV was largely detergent-soluble, indicating the depletion of raft-lipid assemblies from this membrane. The results provide a model for lipid selectivity during virus budding and support the view of lipid rafts as cholesterol-dependent, ordered domains in biological membranes.

The differential miscibility of lipids as the basis for the formation of functional membrane rafts

The formation of sphingolipid-cholesterol microdomains in cellular membranes has been proposed to function in sorting and transport of lipids and proteins as well as in signal transduction. An increasing number of cell biological and biochemical studies now supports this concept. Here we discuss the structural properties of lipids in a cell biological context. The sphingolipid-cholesterol microdomains or rafts are described as dispersed liquid ordered phase domains. These domains are dynamic assemblies to which specific proteins are selectively sequestered while others are excluded. The proteins associated to rafts can act as organizers and can modulate raft size and function.

The perceptual prominence of fundamental frequency peaks

Five perception experiments were conducted that investigated how the perceived prominence of F0 maxima in accented syllables in Dutch is affected by the variation of F0 minima that is supposed to relate to variation in global pitch range. The purpose of the first two experiments was to test the predictions of a model in which the reference line is directly given by an interpolation between observable F0 minima. The results showed that the model was inadequate, and confirmed earlier research suggesting that the reference line is calculated in a less direct way. The next three experiments investigated the role of the F0 of the unaccented portions of speech at the beginning ("onset") and at the end ("offset") of the contour, and show that only the (low) onset is used to calibrate the reference line. The results also suggest that longer onsets affect the abstract reference more than do shorter onsets.

Influence of perinatal conditions on C-reactive protein production

C-reactive protein rises in blood in an acute-phase response in adults, children, and neonates. In a prospective study of the influence of perinatal asphyxia, premature rupture of membranes, hyperbilirubinemia, and respiratory distress syndrome on levels of C-reactive protein in the neonate, we detected no confounding effect on the rise of C-reactive protein level in infants with these pathologic perinatal conditions, as compared with the results of a control group.

The effect of cytochrome c oxidase on lipid polymorphism of model membranes containing cardiolipin

The effect of cytochrome c oxidase incorporation on the lipid polymorphism of the cardiolipin-Ca2+ system was investigated by 31P NMR and freeze-fracture electron microscopy. The integral membrane protein has a stabilizing effect on the bilayer organization of cardiolipin, in that it inhibits the Ca2+-induced HII phase formation of this lipid for Ca2+/cardiolipin molar ratios of 1-10. At a Ca2+/cardiolipin molar ratio of 25, about 80% of the lipid is organized in the HII phase and a structural phase separation occurs between the cardiolipin-Ca2+ complex organized in the hexagonal HII phase without protein and bilayer structures with incorporated protein.

Preferential lipid association and mode of penetration of apocytochrome c in mixed model membranes as monitored by tryptophanyl fluorescence quenching using brominated phospholipids

The fluorescence of the single tryptophan residue at position 59 in apocytochrome c, the biosynthetic precursor of the inner mitochondrial membrane protein cytochrome c, was studied in small unilamellar vesicles composed of phosphatidylserine (PS) and phosphatidylcholine (PC) with or without specifically Br-labelled acyl chains at the sn-2 position. The protein has a very high affinity for PS-containing vesicles (dissociation constant Kd less than 1 microM). From the relative quenching efficiency by the brominated phospholipids, it could be concluded that the protein specifically associates with the PS component in mixed vesicles and that maximal quenching occurred with phospholipids in which the bromine was present at the 6,7-position of the 2-acyl chain suggesting that (part of) the bound protein penetrates 7-8 A deep into the hydrophobic core of the bilayer.

Phospholipids as a possible instrument for translocation of nascent proteins across biological membranes

The interaction of phospholipids with precursor proteins, particularly with the mitochondrial precursor protein apocytochrome c is reviewed and integrated with other aspects of protein insertion and translocation, leading to a model for (apo)cytochrome c import into mitochondria, in which phospholipids play a dominant role.

Preferential association of apocytochrome c with negatively charged phospholipids in mixed model membranes

The mitochondrial precursor protein, apocytochrome c, binds to model membranes containing negatively charged phospholipids (Rietveld, A., Sijens, R., Verkleij, A.J. and Kruijff, B. (1983) EMBO J. 2, 907-913). In the present paper the effect of apocytochrome c on the lipid distribution in model membranes, consisting of neutral and acidic phospholipids, is examined. Both ESR and fluorescence energy transfer experiments show that the protein preferentially interacts with the negatively charged phospholipid in the mixed model membranes. Semi-quantitative analysis of the fluorescence energy transfer from the single tryptophan in apocytochrome c to the parinaric acid in phosphatidylserine or phosphatidylcholine in mixed bovine brain phosphatidylserine/egg phosphatidylcholine vesicles reveals and average donor-acceptor distance of 22-26 A and 26-30 A for phosphatidylserine and phosphatidylcholine, respectively. In addition, these experiments demonstrate that this preferential interaction does not induce the separation of large domains enriched in complexes of apocytochrome c with negatively charged phospholipids and domains enriched in neutral lipids.

Apocytochrome c binding to negatively charged lipid dispersions studied by spin-label electron spin resonance

The interaction of apocytochrome c with aqueous dispersions of phosphatidylserine from bovine spinal cord and with other negatively charged phospholipids has been studied as a function of pH and salt concentration by using spin-label electron spin resonance (ESR) spectroscopy and chemical binding assays. The ESR spectra of phospholipids spin-labeled at different positions on the sn-2 chain indicate a generalized decrease in mobility of the lipids, while the characteristic flexibility gradient toward the terminal methyl end of the chain is maintained, on binding of apocytochrome c to phosphatidylserine dispersions. This perturbation of the bulk lipid mobility or ordering is considerably greater than that observed on binding of cytochrome c. In addition, a second, more motionally restricted, lipid component is observed with lipids labeled close to the terminal methyl ends of the chains. This second component is not observed on binding of cytochrome c and can be taken as direct evidence for penetration of apocytochrome c into the lipid bilayer. It is less strongly motionally restricted than similar spectral components observed with integral membrane proteins and displays a steep flexibility gradient. The proportion of this second component increases with increasing protein-to-lipid ratio, but the stoichiometry per protein bound decreases from 4.5 lipids per 12 000-dalton protein at low protein contents to 2 lipids per protein at saturating amounts of protein. Apocytochrome c binding to phosphatidylserine dispersions decreases with increasing salt concentration from a saturation value corresponding to approximately 5 lipids per protein in the absence of salt to practically zero at 0.4 M NaCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the lipid dependency and mechanism of the translocation of the mitochondrial precursor protein apocytochrome c across model membranes

The lipid dependency of apocytochrome c binding to model membranes and of the translocation of the precursor protein across these membranes was studied by using large unilamellar, trypsin-containing vesicles. These vesicles were improved with respect to those used in a previous article (Rietveld, A., and de Kruijff, B. (1984) J. Biol. Chem. 259, 6704-6706), in the sense that a lower amount of trypsin was enclosed. In mixed egg phosphatidylcholine/bovine brain phosphatidylserine vesicles, both the Kd of apocytochrome c binding (about 20 microM) and the number of phosphatidylserine molecules interacting with the protein was found to be constant. When the phosphatidylserine fraction in the vesicles is more than 15-30% apocytochrome c addition results in the exposure of (a part of) the protein to the internal, trypsin-containing vesicle medium, which process we conceive as a translocation event. Also the interaction of apocytochrome c with vesicles composed of phosphatidylcholine and another acidic phospholipid in a 1:1 ratio, leads to the translocation of the protein across the model membrane. The affinity of this binding was found to be in the order cardiolipin greater than phosphatidylglycerol greater than phosphatidylinositol greater than phosphatidylserine. By varying the lipid composition of the vesicles, it could be demonstrated that the translocation requires a fluid bilayer. In addition, protein specificity was shown for the translocation process. Although apocytochrome c-lipid interaction causes vesicle aggregation, fusion by lipid mixing could not be detected. Due to the apocytochrome c-lipid interaction also, protein aggregates and oligomers have been formed. These results will be discussed in the light of a model for translocation of a precursor protein across a model membrane. The relevance for the mitochondrial system will also be discussed.

Molecular aspects of the bilayer stabilization induced by poly(L-lysines) of varying size in cardiolipin liposomes

The interaction between poly(L-lysines) of varying size with cardiolipin was investigated via binding assays, X-ray diffraction, freeze-fracture electron microscopy, and 31P- and 13C-NMR. Binding of polylysines to the lipid only occurred when three or more lysine residues were present per molecule. The strength of the binding was highly dependent on the polymerization degree, suggesting a cooperative interaction of the lysines within the polymer. Upon binding, a structural reorganization of the lipids takes place, resulting in a closely packed multilamellar system in which the polylysines are sandwiched in between subsequent bilayers. Acyl chain motion is reduced in these liquid-crystalline peptide-lipid complexes. From competition experiments with Ca2+ it could be concluded that when the affinity of the polylysine for cardiolipin was much larger than that of Ca2+, a lamellar polylysine-lipid complex was formed, irrespective of whether an excess of Ca2+ was added prior to or after the polypeptide. When the affinity of the polylysine for cardiolipin was less or of the same order as that of Ca2+, the lipid was organized in the hexagonal HII phase in the presence of Ca2+. These results are discussed in the light of the peptide specificity of bilayer (de)stabilization in cardiolipin model membranes.

Investigations on the insertion of the mitochondrial precursor protein apocytochrome c into model membranes

Different aspects of the interaction of apocytochrome c and model membranes composed of negatively charged lipids, were studied in order to get insight into the nature of this interaction. The effect of the protein on the lipid packing properties are revealed by DSC, ESR and monolayer techniques. These experiments clearly demonstrate that upon electrostatic interaction with the negatively charged phospholipids, apocytochrome c is able to penetrate into the hydrophobic region of the model membrane. In the case of 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol, this results in a perturbation of 160 lipid molecules per apocytochrome c molecule. Most likely, apocytochrome c disrupts the formation of the gel phase and restricts the lipid chain motion above the gel to liquid-crystalline phase transition. Tryptophan fluorescence measurements confirm that at least a part of the protein penetrates into the bilayer, and suggest that after this penetration, the tryptophan (residue no. 59) is located in the glycerol backbone region of the phospholipids. Although the secondary structure of apocytochrome c is predicted to contain about 35% of alpha-helical structure, the CD pattern of an aqueous solution of the protein is featureless. However, negatively charged lipids are able to express this alpha-helical potency in the apocytochrome c, which might be important for the insertion of the protein into lipid membranes.

Is the mitochondrial precursor protein apocytochrome c able to pass a lipid barrier?

To obtain insight into the role of lipids in the translocation of extramitochondrially synthesized proteins, we studied the ability of apocytochrome c to pass lipid bilayers. With polyacrylamide gel electrophoresis, the digestion of externally added apocytochrome c by trypsin, enclosed in lipid vesicles, was followed. The experiments demonstrate that apocytochrome c is able to pass a lipid barrier and this process shows both a lipid- and protein specificity. The most probable molecular mechanisms involved in this phenomenon are discussed.

Interaction of human plasma kallikrein and its light chain with alpha 2-macroglobulin

Human plasma kallikrein participates in the contact activation system of plasma. The light chain of kallikrein contains the enzymatic active site; the heavy chain is required for binding to high molecular weight kininogen and for surface-dependent activation of coagulation. This study has examined the functional contributions of the heavy chain of kallikrein and of high molecular weight kininogen in the inactivation of kallikrein and of its isolated light chain by alpha 2-macroglobulin (alpha 2M). Irreversible inhibition was observed for both kallikrein and its light chain, with the initial formation of a reversible enzyme-inhibitor complex. The second-order rate constants for these reactions were 3.5 X 10(5) and 4.8 X 10(5) M-1 min-1 for kallikrein and its light chain, respectively. When present in excess, high molecular weight kininogen decreased the rate of kallikrein inactivation by alpha 2M, whereas the rate of inactivation of the light chain was unaffected by high molecular weight kininogen. Although at a drastically reduced rate, high molecular weight kininogen was cleaved by alpha 2M-bound kallikrein. Sodium dodecyl sulfate gradient polyacrylamide gel electrophoresis was used to study complex formation between alpha 2M and kallikrein or its light chain. Under reducing conditions, four kallikrein-alpha 2M complexes were observed. Three of these complexes consisted of alpha 2M and the light chain of kallikrein (Mr 123 000, 235 000, and 330 000). Two alpha 2M-kallikrein light chain complexes incorporated [3H]diisopropyl fluorophosphate ( [3H]DFP) whereas the Mr 330 000 complex did not react with [3H]DFP.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of cytochrome c and its precursor apocytochrome c with various phospholipids

The effects of cytochrome c and apocytochrome c on the structural properties of various membrane phospholipids in model systems were compared by binding, calorimetric, permeability, P n.m.r. and freeze-fracture experiments. Both cytochrome c and apocytochrome c experience strong interactions only with negatively charged phospholipids; apocytochrome c interacted more strongly than cytochrome c. These interactions are primarily electrostatic but also have a hydrophobic character. Cytochrome c as well as apocytochrome c induces changes in the structure of cardiolipin liposomes as is shown by P n.m.r. and freeze-fracture electron microscopy. Cytochrome c does not affect the bilayer structure of phosphatidylserine. In contrast, interaction of apocytochrome c with this phospholipid results in changes of the P n.m.r. bilayer spectrum of the liposomes and also particles are observed at the fracture faces. The results are discussed in relation to the import of the protein into the mitochondrion.

13C-NMR detection of lipid polymorphism in model and biological membranes

1. The application of the 13C-NMR technique to the study of lipid polymorphism is described for various model and biological membranes. 2. The 13-C-NMR line-width of various resonances of the lipid molecule and sensitive to the bilayer in equilibrium hexagonal and the bilayer in equilibrium 'isotropic' phase transition. The latter transition in some cases is accompanied by the occurrence of lipidic particles as detected by freeze-fracturing. Thus, specific 13C-labeling experiments allow the study of the individual phase behaviour of lipids in mixed lipid systems. 3. In diet experiments using rats, the choline group of phosphatidylcholine present in erythrocyte, endoplasmic and sarcoplasmic reticulum membranes could be specifically 13C-labeled. The 13C line-widths of the resonance from the erythrocyte are typical for a lamellar arrangement of the membrane lipids. In strong contrast, the line-width observed at 37 degree C for the endoplasmic and sarcoplasmic reticulum membranes is much smaller, typical of the isotropic phases observed in model membranes. In isolated rat liver microsomes and liver slices, the 13C line-width is strongly temperature dependent. At lower temperatures the line-widths strongly increase towards values typical of lipids in a bilayer structure.

Structural properties of phospholipids in the rat liver inner mitochondrial membrane

1. The 31P-NMR characteristics of intact rat liver mitochondria, mitoplasts and isolated inner mitochondrial membranes, as well as mitochondrial phosphatidylethanolamine and phosphatidylcholine, have been examined. 2. Rat liver mitochondrial phosphatidylethanolamine hydrated in excess aqueous buffer undergoes a bilayer-to-hyexagonal (HII) polymorphic phase transition as the temperature is increased through 10 degrees C, and thus prefers the HII arrangement at 37 degrees C. Rat liver mitochondiral phosphatidylcholine, on the other hand, adopts the bilayer phase at 37 degrees C. 3. Total inner mitochondrial membrane lipids. dispersed in an excess of aqueous buffer, exhibit 31P-NMR spectra consistent with a bilayer arrangment for the majority of the endogeneous phospholipids; the remainer exhibit spectra consistent with structure allowing isotropic motional averaging. Addition of Ca2+ results in hexagonal (HII) phase formation for a portion of the phospholipids, as well as formation of 'lipidic particles' as detected by freeze-fracture techniques. 4. Preparations of inner mitochondrial membrane at 4 and 37 degrees C exhibit 31P-NMR spectra consistent with a bilayer arrangement of the large majority of the endogenous phospholipids which are detected. Approx. 10% of the signal intensity has characteristics indicating isotropic motional averaging processes. Addition of Ca2+ results in an increase in the size of this component, which can become the domiant spectral feature. 5. Intact mitochondria, at 4 degrees C, exhibit 31P-NMR spectra arising from both phospholid and small water-soluble molecules (ADP, Pi, etc.). The phospholipid spectrum is characteristic of a bilayer arrangement. At 37 degrees C the phospholipids again give spectra consistent with a bilayer; however, the labile nature of these systems is reflected by increased isotropic motion at longer (at least 30 min) incubation times. 6. It is suggested that the uncoupling action of high Ca2+ concentrations on intact mitochondria may be related to a Ca2+-induced disruption of the integrity of the inner mitochondrial phospholipid bilayer. Further, the possibility that non-bilayer lipid structures such as inverted micelles occur in the inner mitochondrial membrane cannot be excluded.