Differential dysregulation of β-TrCP1 and -2 by HIV-1 Vpu leads to inhibition of canonical and non-canonical NF-κB pathways in infected cells

The HIV-1 Vpu protein is expressed late in the virus lifecycle to promote infectious virus production and avoid innate and adaptive immunity. This includes the inhibition of the NF-κB pathway which, when activated, leads to the induction of inflammatory responses and the promotion of antiviral immunity. Here we demonstrate that Vpu can inhibit both canonical and non-canonical NF-κB pathways, through the direct inhibition of the F-box protein β-TrCP, the substrate recognition portion of the Skp1-Cul1-F-box (SCF)β-TrCP ubiquitin ligase complex. There are two paralogues of β-TrCP (β-TrCP1/BTRC and β-TrCP2/FBXW11), encoded on different chromosomes, which appear to be functionally redundant. Vpu, however, is one of the few β-TrCP substrates to differentiate between the two paralogues. We have found that patient-derived alleles of Vpu, unlike those from lab-adapted viruses, trigger the degradation of β-TrCP1 while co-opting its paralogue β-TrCP2 for the degradation of cellular targets of Vpu, such as CD4. The potency of this dual inhibition correlates with stabilization of the classical IκBα and the phosphorylated precursors of the mature DNA-binding subunits of canonical and non-canonical NF-κB pathways, p105/NFκB1 and p100/NFκB2, in HIV-1 infected CD4+ T cells. Both precursors act as alternative IκBs in their own right, thus reinforcing NF-κB inhibition at steady state and upon activation with either selective canonical or non-canonical NF-κB stimuli. These data reveal the complex regulation of NF-κB late in the viral replication cycle, with consequences for both the pathogenesis of HIV/AIDS and the use of NF-κB-modulating drugs in HIV cure strategies. IMPORTANCE The NF-κB pathway regulates host responses to infection and is a common target of viral antagonism. The HIV-1 Vpu protein inhibits NF-κB signaling late in the virus lifecycle, by binding and inhibiting β-TrCP, the substrate recognition portion of the ubiquitin ligase responsible for inducing IκB degradation. Here we demonstrate that Vpu simultaneously inhibits and exploits the two different paralogues of β-TrCP by triggering the degradation of β-TrCP1 and co-opting β-TrCP2 for the destruction of its cellular targets. In so doing, it has a potent inhibitory effect on both the canonical and non-canonical NF-κB pathways. This effect has been underestimated in previous mechanistic studies due to the use of Vpu proteins from lab-adapted viruses. Our findings reveal previously unappreciated differences in the β-TrCP paralogues, revealing functional insights into the regulation of these proteins. This study also raises important implications for the role of NF-κB inhibition in the immunopathogenesis of HIV/AIDS and the way that this may impact on HIV latency reversal strategies based on the activation of the non-canonical NF-κB pathway.

The P681H Mutation in the Spike Glycoprotein of the Alpha Variant of SARS-CoV-2 Escapes IFITM Restriction and Is Necessary for Type I Interferon Resistance

The appearance of new dominant variants of concern (VOC) of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) threatens the global response to the coronavirus disease 2019 (COVID-19) pandemic. Of these, the alpha variant (also known as B.1.1.7), which appeared initially in the United Kingdom, became the dominant variant in much of Europe and North America in the first half of 2021. The spike (S) glycoprotein of alpha acquired seven mutations and two deletions compared to the ancestral virus, including the P681H mutation adjacent to the polybasic cleavage site, which has been suggested to enhance S cleavage. Here, we show that the alpha spike protein confers a level of resistance to beta interferon (IFN-β) in human lung epithelial cells. This correlates with resistance to an entry restriction mediated by interferon-induced transmembrane protein 2 (IFITM2) and a pronounced infection enhancement by IFITM3. Furthermore, the P681H mutation is essential for resistance to IFN-β and context-dependent resistance to IFITMs in the alpha S. P681H reduces dependence on endosomal cathepsins, consistent with enhanced cell surface entry. However, reversion of H681 does not reduce cleaved spike incorporation into particles, indicating that it exerts its effect on entry and IFN-β downstream of furin cleavage. Overall, we suggest that, in addition to adaptive immune escape, mutations associated with VOC may well also confer a replication and/or transmission advantage through adaptation to resist innate immune mechanisms. IMPORTANCE Accumulating evidence suggests that variants of concern (VOC) of SARS-CoV-2 evolve to evade the human immune response, with much interest focused on mutations in the spike protein that escape from antibodies. However, resistance to the innate immune response is essential for efficient viral replication and transmission. Here, we show that the alpha (B.1.1.7) VOC of SARS-CoV-2 is substantially more resistant to type I interferons than the parental Wuhan-like virus. This correlates with resistance to the antiviral protein IFITM2 and enhancement by its paralogue IFITM3. The key determinant of this is a proline-to-histidine change at position 681 in S adjacent to the furin cleavage site, which in the context of the alpha spike modulates cell entry pathways of SARS-CoV-2. Reversion of the mutation is sufficient to restore interferon and IFITM2 sensitivity, highlighting the dynamic nature of the SARS CoV-2 as it adapts to both innate and adaptive immunity in the humans.

A neutralizing epitope on the SD1 domain of SARS-CoV-2 spike targeted following infection and vaccination

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike is the target for neutralizing antibodies elicited following both infection and vaccination. While extensive research has shown that the receptor binding domain (RBD) and, to a lesser extent, the N-terminal domain (NTD) are the predominant targets for neutralizing antibodies, identification of neutralizing epitopes beyond these regions is important for informing vaccine development and understanding antibody-mediated immune escape. Here, we identify a class of broadly neutralizing antibodies that bind an epitope on the spike subdomain 1 (SD1) and that have arisen from infection or vaccination. Using cryo-electron microscopy (cryo-EM) and hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS), we show that SD1-specific antibody P008_60 binds an epitope that is not accessible within the canonical prefusion states of the SARS-CoV-2 spike, suggesting a transient conformation of the viral glycoprotein that is vulnerable to neutralization.

ChAdOx1 nCoV-19 vaccine elicits monoclonal antibodies with cross-neutralizing activity against SARS-CoV-2 viral variants

Although the antibody response to COVID-19 vaccination has been studied extensively at the polyclonal level using immune sera, little has been reported on the antibody response at the monoclonal level. Here, we isolate a panel of 44 anti-SARS-CoV-2 monoclonal antibodies (mAbs) from an individual who received two doses of the ChAdOx1 nCoV-19 (AZD1222) vaccine at a 12-week interval. We show that, despite a relatively low serum neutralization titer, Spike-reactive IgG+ B cells are still detectable 9 months post-boost. Furthermore, mAbs with potent neutralizing activity against the current SARS-CoV-2 variants of concern (Alpha, Gamma, Beta, Delta, and Omicron) are present. The vaccine-elicited neutralizing mAbs form eight distinct competition groups and bind epitopes overlapping with neutralizing mAbs elicited following SARS-CoV-2 infection. AZD1222-elicited mAbs are more mutated than mAbs isolated from convalescent donors 1-2 months post-infection. These findings provide molecular insights into the AZD1222 vaccine-elicited antibody response.

Disrupted Peyer's Patch Microanatomy in COVID-19 Including Germinal Centre Atrophy Independent of Local Virus

Confirmed SARS-coronavirus-2 infection with gastrointestinal symptoms and changes in microbiota associated with coronavirus disease 2019 (COVID-19) severity have been previously reported, but the disease impact on the architecture and cellularity of ileal Peyer's patches (PP) remains unknown. Here we analysed post-mortem tissues from throughout the gastrointestinal (GI) tract of patients who died with COVID-19. When virus was detected by PCR in the GI tract, immunohistochemistry identified virus in epithelium and lamina propria macrophages, but not in lymphoid tissues. Immunohistochemistry and imaging mass cytometry (IMC) analysis of ileal PP revealed depletion of germinal centres (GC), disruption of B cell/T cell zonation and decreased potential B and T cell interaction and lower nuclear density in COVID-19 patients. This occurred independent of the local viral levels. The changes in PP demonstrate that the ability to mount an intestinal immune response is compromised in severe COVID-19, which could contribute to observed dysbiosis.

Combined epidemiological and genomic analysis of nosocomial SARS-CoV-2 infection early in the pandemic and the role of unidentified cases in transmission

OBJECTIVES

To analyse nosocomial transmission in the early stages of the coronavirus 2019 (COVID-19) pandemic at a large multisite healthcare institution. Nosocomial incidence is linked with infection control interventions.

METHODS

Viral genome sequence and epidemiological data were analysed for 574 consecutive patients, including 86 nosocomial cases, with a positive PCR test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the first 19 days of the pandemic.

RESULTS

Forty-four putative transmission clusters were found through epidemiological analysis; these included 234 cases and all 86 nosocomial cases. SARS-CoV-2 genome sequences were obtained from 168/234 (72%) of these cases in epidemiological clusters, including 77/86 nosocomial cases (90%). Only 75/168 (45%) of epidemiologically linked, sequenced cases were not refuted by applying genomic data, creating 14 final clusters accounting for 59/77 sequenced nosocomial cases (77%). Viral haplotypes from these clusters were enriched 1-14x (median 4x) compared to the community. Three factors implicated unidentified cases in transmission: (a) community-onset or indeterminate cases were absent in 7/14 clusters (50%), (b) four clusters (29%) had additional evidence of cryptic transmission, and (c) in three clusters (21%) diagnosis of the earliest case was delayed, which may have facilitated transmission. Nosocomial cases decreased to low levels (0-2 per day) despite continuing high numbers of admissions of community-onset SARS-CoV-2 cases (40-50 per day) and before the impact of introducing universal face masks and banning hospital visitors.

CONCLUSION

Genomics was necessary to accurately resolve transmission clusters. Our data support unidentified cases-such as healthcare workers or asymptomatic patients-as important vectors of transmission. Evidence is needed to ascertain whether routine screening increases case ascertainment and limits nosocomial transmission.

Real-world deployment of lateral flow SARS-CoV-2 antigen detection in the emergency department to provide rapid, accurate and safe diagnosis of COVID-19

BACKGROUND

Point-of-care (POC) SARS-CoV-2 lateral-flow antigen detection (LFD) testing in the emergency department (ED) could inform rapid infection control decisions but requirements for safe deployment have not been fully defined.

METHODS

Review of LFD test results, laboratory and POC-RT-PCR results and ED-performance metrics during a two-week high SARS-CoV-2 prevalence period followed by several months of falling prevalence.

AIM

Determine whether LFD testing can be safely deployed in ED to provide an effective universal SARS-CoV-2 testing capability.

FINDINGS

93% (345/371) of COVID-19 patients left ED with a virological diagnosis during the 2-week universal LFD evaluation period compared to 77% with targeted POC-RT-PCR deployment alone, on background of approximately one-third having an NHS Track and Trace RT-PCR test-result at presentation. LFD sensitivity and specificity was 70.7% and 99.1% respectively providing a PPV of 97.7% and NPV of 86.4% with disease prevalence of 34.7%. ED discharge-delays (breaches) attributable to COVID-19 fell to 33/3532 (0.94%) compared with the preceding POC-RT-PCR period (107/4114 (2.6%); p=<0.0001). Importantly, LFD testing identified 1 or 2 clinically-unsuspected COVID-19 patients/day. Three clinically-confirmed LFD false positive patients were appropriately triaged based on LFD action-card flowchart, and only 5 of 95 false-negative LFD results were inappropriately admitted to non-COVID-19 areas where no onward-transmission was identified. LFD testing was restricted to asymptomatic patients when disease prevalence fell below 5% and detected 1-3 cases/week.

CONCLUSION

Universal SARS-CoV-2 LFD testing can be safely and effectively deployed in ED alongside POC-RT-PCR testing during periods of high and low disease prevalence.

Neutralizing antibody activity in convalescent sera from infection in humans with SARS-CoV-2 and variants of concern

COVID-19 vaccine design and vaccination rollout need to take into account a detailed understanding of antibody durability and cross-neutralizing potential against SARS-CoV-2 and emerging variants of concern (VOCs). Analyses of convalescent sera provide unique insights into antibody longevity and cross-neutralizing activity induced by variant spike proteins, which are putative vaccine candidates. Using sera from 38 individuals infected in wave 1, we show that cross-neutralizing activity can be detected up to 305 days pos onset of symptoms, although sera were less potent against B.1.1.7 (Alpha) and B1.351 (Beta). Over time, despite a reduction in overall neutralization activity, differences in sera neutralization potency against SARS-CoV-2 and the Alpha and Beta variants decreased, which suggests that continued antibody maturation improves tolerance to spike mutations. We also compared the cross-neutralizing activity of wave 1 sera with sera from individuals infected with the Alpha, the Beta or the B.1.617.2 (Delta) variants up to 79 days post onset of symptoms. While these sera neutralize the infecting VOC and parental virus to similar levels, cross-neutralization of different SARS-CoV-2 VOC lineages is reduced. These findings will inform the optimization of vaccines to protect against SARS-CoV-2 variants.

Resilient SARS-CoV-2 diagnostics workflows including viral heat inactivation

There is a worldwide need for reagents to perform SARS-CoV-2 detection. Some laboratories have implemented kit-free protocols, but many others do not have the capacity to develop these and/or perform manual processing. We provide multiple workflows for SARS-CoV-2 nucleic acid detection in clinical samples by comparing several commercially available RNA extraction methods: QIAamp Viral RNA Mini Kit (QIAgen), RNAdvance Blood/Viral (Beckman) and Mag-Bind Viral DNA/RNA 96 Kit (Omega Bio-tek). We also compared One-step RT-qPCR reagents: TaqMan Fast Virus 1-Step Master Mix (FastVirus, ThermoFisher Scientific), qPCRBIO Probe 1-Step Go Lo-ROX (PCR Biosystems) and Luna® Universal Probe One-Step RT-qPCR Kit (Luna, NEB). We used primer-probes that detect viral N (EUA CDC) and RdRP. RNA extraction methods provided similar results, with Beckman performing better with our primer-probe combinations. Luna proved most sensitive although overall the three reagents did not show significant differences. N detection was more reliable than that of RdRP, particularly in samples with low viral titres. Importantly, we demonstrated that heat treatment of nasopharyngeal swabs at 70°C for 10 or 30 min, or 90°C for 10 or 30 min (both original variant and B 1.1.7) inactivated SARS-CoV-2 employing plaque assays, and had minimal impact on the sensitivity of the qPCR in clinical samples. These findings make SARS-CoV-2 testing portable in settings that do not have CL-3 facilities. In summary, we provide several testing pipelines that can be easily implemented in other laboratories and have made all our protocols and SOPs freely available at https://osf.io/uebvj/.

Comparative performance of SARS-CoV-2 lateral flow antigen tests and association with detection of infectious virus in clinical specimens: a single-centre laboratory evaluation study

BACKGROUND

Lateral flow devices (LFDs) for rapid antigen testing are set to become a cornerstone of SARS-CoV-2 mass community testing, although their reduced sensitivity compared with PCR has raised questions of how well they identify infectious cases. Understanding their capabilities and limitations is, therefore, essential for successful implementation. We evaluated six commercial LFDs and assessed their correlation with infectious virus culture and PCR cycle threshold (Ct) values.

METHODS

In a single-centre, laboratory evaluation study, we did a head-to-head comparison of six LFDs commercially available in the UK: Innova Rapid SARS-CoV-2 Antigen Test, Spring Healthcare SARS-CoV-2 Antigen Rapid Test Cassette, E25Bio Rapid Diagnostic Test, Encode SARS-CoV-2 Antigen Rapid Test Device, SureScreen COVID-19 Rapid Antigen Test Cassette, and SureScreen COVID-19 Rapid Fluorescence Antigen Test. We estimated the specificities and sensitivities of the LFDs using stored naso-oropharyngeal swabs collected at St Thomas' Hospital (London, UK) for routine diagnostic SARS-CoV-2 testing by real-time RT-PCR (RT-rtPCR). Swabs were from inpatients and outpatients from all departments of St Thomas' Hospital, and from health-care staff (all departments) and their household contacts. SARS-CoV-2-negative swabs from the same population (confirmed by RT-rtPCR) were used for comparative specificity determinations. All samples were collected between March 23 and Oct 27, 2020. We determined the limit of detection (LOD) for each test using viral plaque-forming units (PFUs) and viral RNA copy numbers of laboratory-grown SARS-CoV-2. Additionally, LFDs were selected to assess the correlation of antigen test result with RT-rtPCR Ct values and positive viral culture in Vero E6 cells. This analysis included longitudinal swabs from five infected inpatients with varying disease severities. Furthermore, the sensitivities of available LFDs were assessed in swabs (n=23; collected from Dec 4, 2020, to Jan 12, 2021) confirmed to be positive (RT-rtPCR and whole-genome sequencing) for the B.1.1.7 variant, which was the dominant genotype in the UK at the time of study completion.

FINDINGS

All LFDs showed high specificity (≥98·0%), except for the E25Bio test (86·0% [95% CI 77·9-99·9]), and most tests reliably detected 50 PFU/test (equivalent SARS-CoV-2 N gene Ct value of 23·7, or RNA copy number of 3 × 106/mL). Sensitivities of the LFDs on clinical samples ranged from 65·0% (55·2-73·6) to 89·0% (81·4-93·8). These sensitivities increased to greater than 90% for samples with Ct values of lower than 25 for all tests except the SureScreen fluorescence (SureScreen-F) test. Positive virus culture was identified in 57 (40·4%) of 141 samples; 54 (94·7%) of the positive cultures were from swabs with Ct values lower than 25. Among the three LFDs selected for detailed comparisons (the tests with highest sensitivity [Innova], highest specificity [Encode], and alternative technology [SureScreen-F]), sensitivity of the LFDs increased to at least 94·7% when only including samples with detected viral growth. Longitudinal studies of RT-rtPCR-positive samples (tested with Innova, Encode, and both SureScreen-F and the SureScreen visual [SureScreen-V] test) showed that most of the tests identified all infectious samples as positive. Test performance (assessed for Innova and SureScreen-V) was not affected when reassessed on swabs positive for the UK variant B.1.1.7.

INTERPRETATION

In this comprehensive comparison of antigen LFDs and virus infectivity, we found a clear relationship between Ct values, quantitative culture of infectious virus, and antigen LFD positivity in clinical samples. Our data support regular testing of target groups with LFDs to supplement the current PCR testing capacity, which would help to rapidly identify infected individuals in situations in which they would otherwise go undetected.

FUNDING

King's Together Rapid COVID-19, Medical Research Council, Wellcome Trust, Huo Family Foundation, UK Department of Health, National Institute for Health Research Comprehensive Biomedical Research Centre.

More than the Eye Can See: Shedding New Light on SARS-CoV-2 Lateral Flow Device-Based Immunoassays

Containing the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has been an unprecedented challenge due to high horizontal transmissivity and asymptomatic carriage rates. Lateral flow device (LFD) immunoassays were introduced in late 2020 to detect SARS-CoV-2 infection in asymptomatic or presymptomatic individuals rapidly. While LFD technologies have been used for over 60 years, their widespread use as a public health tool during a pandemic is unprecedented. By the end of 2020, data from studies into the efficacy of the LFDs emerged and showed these point-of-care devices to have very high specificity (ability to identify true negatives) but inadequate sensitivity with high false-negative rates. The low sensitivity (<50%) shown in several studies is a critical public health concern, as asymptomatic or presymptomatic carriers may wrongly be assumed to be noninfectious, posing a significant risk of further spread in the community. Here, we show that the direct visual readout of SARS-CoV-2 LFDs is an inadequate approach to discriminate a potentially infective viral concentration in a biosample. We quantified significant immobilized antigen-antibody-labeled conjugate complexes within the LFDs visually scored as negative using high-sensitivity synchrotron X-ray fluorescence imaging. Correlating quantitative X-ray fluorescence measurements and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) determined numbers of viral copies, we identified that negatively scored samples could contain up to 100 PFU (equivalent here to ∼10 000 RNA copies/test). The study demonstrates where the shortcomings arise in many of the current direct-readout SARS-CoV-2 LFDs, namely, being a deficiency in the readout as opposed to the potential level of detection of the test, which is orders of magnitude higher. The present findings are of importance both to public health monitoring during the Coronavirus Disease 2019 (COVID-19) pandemic and to the rapid refinement of these tools for immediate and future applications.

Antibody longevity and cross-neutralizing activity following SARS-CoV-2 wave 1 and B.1.1.7 infections

As SARS-CoV-2 variants continue to emerge globally, a major challenge for COVID-19 vaccination is the generation of a durable antibody response with cross-neutralizing activity against both current and newly emerging viral variants. Cross-neutralizing activity against major variants of concern (B.1.1.7, P.1 and B.1.351) has been observed following vaccination, albeit at a reduced potency, but whether vaccines based on the Spike glycoprotein of these viral variants will produce a superior cross-neutralizing antibody response has not been fully investigated. Here, we used sera from individuals infected in wave 1 in the UK to study the long-term cross-neutralization up to 10 months post onset of symptoms (POS), as well as sera from individuals infected with the B.1.1.7 variant to compare cross-neutralizing activity profiles. We show that neutralizing antibodies with cross-neutralizing activity can be detected from wave 1 up to 10 months POS. Although neutralization of B.1.1.7 and B.1.351 is lower, the difference in neutralization potency decreases at later timepoints suggesting continued antibody maturation and improved tolerance to Spike mutations. Interestingly, we found that B.1.1.7 infection also generates a cross-neutralizing antibody response, which, although still less potent against B.1.351, can neutralize parental wave 1 virus to a similar degree as B.1.1.7. These findings have implications for the optimization of vaccines that protect against newly emerging viral variants.

Neutralization potency of monoclonal antibodies recognizing dominant and subdominant epitopes on SARS-CoV-2 Spike is impacted by the B.1.1.7 variant

Interaction of the SARS-CoV-2 Spike receptor binding domain (RBD) with the receptor ACE2 on host cells is essential for viral entry. RBD is the dominant target for neutralizing antibodies, and several neutralizing epitopes on RBD have been molecularly characterized. Analysis of circulating SARS-CoV-2 variants has revealed mutations arising in the RBD, N-terminal domain (NTD) and S2 subunits of Spike. To understand how these mutations affect Spike antigenicity, we isolated and characterized >100 monoclonal antibodies targeting epitopes on RBD, NTD, and S2 from SARS-CoV-2-infected individuals. Approximately 45% showed neutralizing activity, of which ∼20% were NTD specific. NTD-specific antibodies formed two distinct groups: the first was highly potent against infectious virus, whereas the second was less potent and displayed glycan-dependant neutralization activity. Mutations present in B.1.1.7 Spike frequently conferred neutralization resistance to NTD-specific antibodies. This work demonstrates that neutralizing antibodies targeting subdominant epitopes should be considered when investigating antigenic drift in emerging variants.

The Polybasic Cleavage Site in SARS-CoV-2 Spike Modulates Viral Sensitivity to Type I Interferon and IFITM2

The cellular entry of severe acute respiratory syndrome-associated coronaviruses types 1 and 2 (SARS-CoV-1 and -2) requires sequential protease processing of the viral spike glycoprotein. The presence of a polybasic cleavage site in SARS-CoV-2 spike at the S1/S2 boundary has been suggested to be a factor in the increased transmissibility of SARS-CoV-2 compared to SARS-CoV-1 by facilitating maturation of the spike precursor by furin-like proteases in the producer cells rather than endosomal cathepsins in the target. We investigate the relevance of the polybasic cleavage site in the route of entry of SARS-CoV-2 and the consequences this has for sensitivity to interferons (IFNs) and, more specifically, the IFN-induced transmembrane (IFITM) protein family that inhibit entry of diverse enveloped viruses. We found that SARS-CoV-2 is restricted predominantly by IFITM2, rather than IFITM3, and the degree of this restriction is governed by route of viral entry. Importantly, removal of the cleavage site in the spike protein renders SARS-CoV-2 entry highly pH and cathepsin dependent in late endosomes, where, like SARS-CoV-1 spike, it is more sensitive to IFITM2 restriction. Furthermore, we found that potent inhibition of SARS-CoV-2 replication by type I but not type II IFNs is alleviated by targeted depletion of IFITM2 expression. We propose that the polybasic cleavage site allows SARS-CoV-2 to mediate viral entry in a pH-independent manner, in part to mitigate against IFITM-mediated restriction and promote replication and transmission. This suggests that therapeutic strategies that target furin-mediated cleavage of SARS-CoV-2 spike may reduce viral replication through the activity of type I IFNs.IMPORTANCE The furin cleavage site in the spike protein is a distinguishing feature of SARS-CoV-2 and has been proposed to be a determinant for the higher transmissibility between individuals, compared to SARS-CoV-1. One explanation for this is that it permits more efficient activation of fusion at or near the cell surface rather than requiring processing in the endosome of the target cell. Here, we show that SARS-CoV-2 is inhibited by antiviral membrane protein IFITM2 and that the sensitivity is exacerbated by deletion of the furin cleavage site, which restricts viral entry to low pH compartments. Furthermore, we find that IFITM2 is a significant effector of the antiviral activity of type I interferons against SARS-CoV-2 replication. We suggest that one role of the furin cleavage site is to reduce SARS-CoV-2 sensitivity to innate immune restriction, and thus, it may represent a potential therapeutic target for COVID-19 treatment development.

Resilient SARS-CoV-2 diagnostics workflows including viral heat inactivation

There is a worldwide need for reagents to perform SARS-CoV-2 detection. Some laboratories have implemented kit-free protocols, but many others do not have the capacity to develop these and/or perform manual processing. We provide multiple workflows for SARS-CoV-2 nucleic acid detection in clinical samples by comparing several commercially available RNA extraction methods: QIAamp Viral RNA Mini Kit (QIAgen), RNAdvance Blood/Viral (Beckman) and Mag-Bind Viral DNA/RNA 96 Kit (Omega Bio-tek). We also compared One-step RT-qPCR reagents: TaqMan Fast Virus 1-Step Master Mix (FastVirus, ThermoFisher Scientific), qPCRBIO Probe 1-Step Go Lo-ROX (PCR Biosystems) and Luna ® Universal Probe One-Step RT-qPCR Kit (Luna, NEB). We used primer-probes that detect viral N (EUA CDC) and RdRP (PHE guidelines). All RNA extraction methods provided similar results. FastVirus and Luna proved most sensitive. N detection was more reliable than that of RdRP, particularly in samples with low viral titres. Importantly, we demonstrate that treatment of nasopharyngeal swabs with 70 degrees for 10 or 30 min, or 90 degrees for 10 or 30 min (both original variant and B 1.1.7) inactivates SARS-CoV-2 employing plaque assays, and that it has minimal impact on the sensitivity of the qPCR in clinical samples. These findings make SARS-CoV-2 testing portable to settings that do not have CL-3 facilities. In summary, we provide several testing pipelines that can be easily implemented in other laboratories and have made all our protocols and SOPs freely available at https://osf.io/uebvj/ .

Clinical utility of targeted SARS-CoV-2 serology testing to aid the diagnosis and management of suspected missed, late or post-COVID-19 infection syndromes: Results from a pilot service implemented during the first pandemic wave

During the first wave of the global COVID-19 pandemic the clinical utility and indications for SARS-CoV-2 serological testing were not clearly defined. The urgency to deploy serological assays required rapid evaluation of their performance characteristics. We undertook an internal validation of a CE marked lateral flow immunoassay (LFIA) (SureScreen Diagnostics) using serum from SARS-CoV-2 RNA positive individuals and pre-pandemic samples. This was followed by the delivery of a same-day named patient SARS-CoV-2 serology service using LFIA on vetted referrals at central London teaching hospital with clinical interpretation of result provided to the direct care team. Assay performance, source and nature of referrals, feasibility and clinical utility of the service, particularly benefit in clinical decision-making, were recorded. Sensitivity and specificity of LFIA were 96.1% and 99.3% respectively. 113 tests were performed on 108 participants during three-week pilot. 44% participants (n = 48) had detectable antibodies. Three main indications were identified for serological testing; new acute presentations potentially triggered by recent COVID-19 e.g. pulmonary embolism (n = 5), potential missed diagnoses in context of a recent COVID-19 compatible illness (n = 40), and making infection control or immunosuppression management decisions in persistently SARS-CoV-2 RNA PCR positive individuals (n = 6). We demonstrate acceptable performance characteristics, feasibility and clinical utility of using a LFIA that detects anti-spike antibodies to deliver SARS-CoV-2 serology service in adults and children. Greatest benefit was seen where there is reasonable pre-test probability and results can be linked with clinical advice or intervention. Experience from this pilot can help inform practicalities and benefits of rapidly implementing new tests such as LFIAs into clinical service as the pandemic evolves.

Impact of the B.1.1.7 variant on neutralizing monoclonal antibodies recognizing diverse epitopes on SARS-CoV-2 Spike

The interaction of the SARS-CoV-2 Spike receptor binding domain (RBD) with the ACE2 receptor on host cells is essential for viral entry. RBD is the dominant target for neutralizing antibodies and several neutralizing epitopes on RBD have been molecularly characterized. Analysis of circulating SARS-CoV-2 variants has revealed mutations arising in the RBD, the N-terminal domain (NTD) and S2 subunits of Spike. To fully understand how these mutations affect the antigenicity of Spike, we have isolated and characterized neutralizing antibodies targeting epitopes beyond the already identified RBD epitopes. Using recombinant Spike as a sorting bait, we isolated >100 Spike-reactive monoclonal antibodies from SARS-CoV-2 infected individuals. ≈45% showed neutralizing activity of which ≈20% were NTD-specific. None of the S2-specific antibodies showed neutralizing activity. Competition ELISA revealed that NTD-specific mAbs formed two distinct groups: the first group was highly potent against infectious virus, whereas the second was less potent and displayed glycan-dependant neutralization activity. Importantly, mutations present in B.1.1.7 Spike frequently conferred resistance to neutralization by the NTD-specific neutralizing antibodies. This work demonstrates that neutralizing antibodies targeting subdominant epitopes need to be considered when investigating antigenic drift in emerging variants.

Longitudinal observation and decline of neutralizing antibody responses in the three months following SARS-CoV-2 infection in humans

Antibody responses to SARS-CoV-2 can be detected in most infected individuals 10-15 d after the onset of COVID-19 symptoms. However, due to the recent emergence of SARS-CoV-2 in the human population, it is not known how long antibody responses will be maintained or whether they will provide protection from reinfection. Using sequential serum samples collected up to 94 d post onset of symptoms (POS) from 65 individuals with real-time quantitative PCR-confirmed SARS-CoV-2 infection, we show seroconversion (immunoglobulin (Ig)M, IgA, IgG) in >95% of cases and neutralizing antibody responses when sampled beyond 8 d POS. We show that the kinetics of the neutralizing antibody response is typical of an acute viral infection, with declining neutralizing antibody titres observed after an initial peak, and that the magnitude of this peak is dependent on disease severity. Although some individuals with high peak infective dose (ID50 > 10,000) maintained neutralizing antibody titres >1,000 at >60 d POS, some with lower peak ID50 had neutralizing antibody titres approaching baseline within the follow-up period. A similar decline in neutralizing antibody titres was observed in a cohort of 31 seropositive healthcare workers. The present study has important implications when considering widespread serological testing and antibody protection against reinfection with SARS-CoV-2, and may suggest that vaccine boosters are required to provide long-lasting protection.

Comparative assessment of multiple COVID-19 serological technologies supports continued evaluation of point-of-care lateral flow assays in hospital and community healthcare settings

There is a clear requirement for an accurate SARS-CoV-2 antibody test, both as a complement to existing diagnostic capabilities and for determining community seroprevalence. We therefore evaluated the performance of a variety of antibody testing technologies and their potential use as diagnostic tools. Highly specific in-house ELISAs were developed for the detection of anti-spike (S), -receptor binding domain (RBD) and -nucleocapsid (N) antibodies and used for the cross-comparison of ten commercial serological assays-a chemiluminescence-based platform, two ELISAs and seven colloidal gold lateral flow immunoassays (LFIAs)-on an identical panel of 110 SARS-CoV-2-positive samples and 50 pre-pandemic negatives. There was a wide variation in the performance of the different platforms, with specificity ranging from 82% to 100%, and overall sensitivity from 60.9% to 87.3%. However, the head-to-head comparison of multiple sero-diagnostic assays on identical sample sets revealed that performance is highly dependent on the time of sampling, with sensitivities of over 95% seen in several tests when assessing samples from more than 20 days post onset of symptoms. Furthermore, these analyses identified clear outlying samples that were negative in all tests, but were later shown to be from individuals with mildest disease presentation. Rigorous comparison of antibody testing platforms will inform the deployment of point-of-care technologies in healthcare settings and their use in the monitoring of SARS-CoV-2 infections.

Real-world evaluation of a novel technology for quantitative simultaneous antibody detection against multiple SARS-CoV-2 antigens in a cohort of patients presenting with COVID-19 syndrome

An evaluation of a rapid portable gold-nanotechnology measuring SARS-CoV-2 IgM, IgA and IgG antibody response to spike 1 (S1), spike 2 (S) and nucleocapsid (N) antigens using serum from 74 RNA(+) patients and RNA(+) 47 control patients.

An evaluation of a rapid portable gold-nanotechnology measuring SARS-CoV-2 IgM, IgA and IgG antibody concentrations against spike 1 (S1), spike 2 (S) and nucleocapsid (N) was conducted using serum samples from 74 patients tested for SARS-CoV-2 RNA on admission to hospital, and 47 historical control patients from March 2019. 59 patients were RNA(+) and 15 were RNA(–). A serum (±) classification was derived for all three antigens and a quantitative serological profile was obtained. Serum(+) was identified in 30% (95% CI 11–48) of initially RNA(–) patients, in 36% (95% CI 17–54) of RNA(+) patients before 10 days, 77% (95% CI 67–87) between 10 and 20 days and 95% (95% CI 86–100) after 21 days. The patient-level diagnostic accuracy relative to RNA(±) after 10 days displayed 88% sensitivity (95% CI 75–95) and 75% specificity (95% CI 22–99), although specificity compared with historical controls was 100% (95%CI 91–100). This study provides robust support for further evaluation and validation of this novel technology in a clinical setting and highlights challenges inherent in assessment of serological tests for an emerging disease such as COVID-19.

HIV-1 Vpu Downregulates Tim-3 from the Surface of Infected CD4+ T Cells

Along with other immune checkpoints, T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) is expressed on exhausted CD4+ and CD8+ T cells and is upregulated on the surface of these cells upon infection by human immunodeficiency virus type 1 (HIV-1). Recent reports have suggested an antiviral role for Tim-3. However, the molecular determinants of HIV-1 which modulate cell surface Tim-3 levels have yet to be determined. Here, we demonstrate that HIV-1 Vpu downregulates Tim-3 from the surface of infected primary CD4+ T cells, thus attenuating HIV-1-induced upregulation of Tim-3. We also provide evidence that the transmembrane domain of Vpu is required for Tim-3 downregulation. Using immunofluorescence microscopy, we determined that Vpu is in close proximity to Tim-3 and alters its subcellular localization by directing it to Rab 5-positive (Rab 5+) vesicles and targeting it for sequestration within the trans- Golgi network (TGN). Intriguingly, Tim-3 knockdown and Tim-3 blockade increased HIV-1 replication in primary CD4+ T cells, thereby suggesting that Tim-3 expression might represent a natural immune mechanism limiting viral spread.IMPORTANCE HIV infection modulates the surface expression of Tim-3, but the molecular determinants remain poorly understood. Here, we show that HIV-1 Vpu downregulates Tim-3 from the surface of infected primary CD4+ T cells through its transmembrane domain and alters its subcellular localization. Tim-3 blockade increases HIV-1 replication, suggesting a potential negative role of this protein in viral spread that is counteracted by Vpu.

The social invisibility of mental health: understanding social exclusion through place & space

Background

The European target that the 5% of the healthcare service budget goes to mental health might not be enough to cover the inequity between health and mental health provision. The project is a multi-disciplinary, research-through-arts project, involving a Faculty of the Built Environment, a Division of Psychiatry and a School of Art. The project aims to identify elements demonstrating inequality demonstrated from place and space related to the facility provision.

Methods

The research compares mental vs healthcare facilities inside a catchment area, with photographs of the facades of the buildings and mapping their proximity to public transportation. It juxtaposes mental/healthcare facilities for access, condition and status compared to their surroundings.

Results

A book and an exhibition close to Bentham’s auto-icon, the designer of Panopticon custodial facility, demonstrated inverse links between his Panopticon, and the invisibility that NIMBYism produces towards the mentally ill that resulted in their exclusion, within deprived, vandalized, under-funded, isolated from public transport facilities “in the community”.

Conclusions

The project identified factors that contribute to the isolation of mental health facilities in terms of both space and place, and set the basis for further research in future projects. It demonstrated visually the under-budgeting of mental health facilities and their stigmatization as expressed by the centrality of locations and their overall projected image. This outlined the path for integrated, transdisciplinary research in the future involving architecture, arts and psychiatry. The project increased the awareness of the general public on social injustice, stigma and mental health. It combats NIMBYism and supports the fairer allocation of resources and placement of health facilities, aiming to put pressure to stakeholders involved in the NHS decision. Actions have been taken by the Trust involved to change.

Key messages

Inequalities between building (facades and location) contribute to mental illness stigma: this is what the general public views daily. Architecture can be a powerful medium to support inclusion.

Upregulation of BST-2 by Type I Interferons Reduces the Capacity of Vpu To Protect HIV-1-Infected Cells from NK Cell Responses

The HIV-1 accessory protein Vpu enhances viral release by counteracting the restriction factor BST-2. Furthermore, Vpu promotes NK cell evasion by downmodulating cell surface NTB-A and PVR, known ligands of the NK cell receptors NTB-A and DNAM-1, respectively. While it has been established that Vpu's transmembrane domain (TMD) is required for the interaction and intracellular sequestration of BST-2, NTB-A, and PVR, it remains unclear how Vpu manages to target these proteins simultaneously. In this study, we show that upon upregulation, BST-2 is preferentially downregulated by Vpu over its other TMD substrates. We found that type I interferon (IFN)-mediated BST-2 upregulation greatly impairs the ability of Vpu to downregulate NTB-A and PVR. Our results suggest that occupation of Vpu by BST-2 affects its ability to downregulate other TMD substrates. Accordingly, knockdown of BST-2 increases Vpu's potency to downmodulate NTB-A and PVR in the presence of type I IFN treatment. Moreover, we show that expression of human BST-2, but not that of the macaque orthologue, decreases Vpu's capacity to downregulate NTB-A. Importantly, we show that type I IFNs efficiently sensitize HIV-1-infected cells to NTB-A- and DNAM-1-mediated direct and antibody-dependent NK cell responses. Altogether, our results reveal that type I IFNs decrease Vpu's polyfunctionality, thus reducing its capacity to protect HIV-1-infected cells from NK cell responses.IMPORTANCE The restriction factor BST-2 and the NK cell ligands NTB-A and PVR are among a growing list of membrane proteins found to be downregulated by HIV-1 Vpu. BST-2 antagonism enhances viral release, while NTB-A and PVR downmodulation contributes to NK cell evasion. However, it remains unclear how Vpu can target multiple cellular factors simultaneously. Here we provide evidence that under physiological conditions, BST-2 is preferentially targeted by Vpu over NTB-A and PVR. Specifically, we show that type I IFNs decrease Vpu's polyfunctionality by upregulating BST-2, thus reducing its capacity to protect HIV-1-infected cells from NK cell responses. This indicates that there is a hierarchy of Vpu substrates upon IFN treatment, revealing that for the virus, targeting BST-2 as part of its resistance to IFN takes precedence over evading NK cell responses. This reveals a potential weakness in HIV-1's immunoevasion mechanisms that may be exploited therapeutically to harness NK cell responses against HIV-1.

HLA-C downregulation by HIV-1 adapts to host HLA genotype

HIV-1 can downregulate HLA-C on infected cells, using the viral protein Vpu, and the magnitude of this downregulation varies widely between primary HIV-1 variants. The selection pressures that result in viral downregulation of HLA-C in some individuals, but preservation of surface HLA-C in others are not clear. To better understand viral immune evasion targeting HLA-C, we have characterized HLA-C downregulation by a range of primary HIV-1 viruses. 128 replication competent viral isolates from 19 individuals with effective anti-retroviral therapy, show that a substantial minority of individuals harbor latent reservoir virus which strongly downregulates HLA-C. Untreated infections display no change in HLA-C downregulation during the first 6 months of infection, but variation between viral quasispecies can be detected in chronic infection. Vpu molecules cloned from plasma of 195 treatment naïve individuals in chronic infection demonstrate that downregulation of HLA-C adapts to host HLA genotype. HLA-C alleles differ in the pressure they exert for downregulation, and individuals with higher levels of HLA-C expression favor greater viral downregulation of HLA-C. Studies of primary and mutant molecules identify 5 residues in the transmembrane region of Vpu, and 4 residues in the transmembrane domain of HLA-C, which determine interactions between Vpu and HLA. The observed adaptation of Vpu-mediated downregulation to host genotype indicates that HLA-C alleles differ in likelihood of mediating a CTL response that is subverted by viral downregulation, and that preservation of HLA-C expression is favored in the absence of these responses. Finding that latent reservoir viruses can downregulate HLA-C could have implications for HIV-1 cure therapy approaches in some individuals.

Inhibiting the Ins and Outs of HIV Replication: Cell-Intrinsic Antiretroviral Restrictions at the Plasma Membrane

Like all viruses, human immunodeficiency viruses (HIVs) and their primate lentivirus relatives must enter cells in order to replicate and, once produced, new virions need to exit to spread to new targets. These processes require the virus to cross the plasma membrane of the cell twice: once via fusion mediated by the envelope glycoprotein to deliver the viral core into the cytosol; and secondly by ESCRT-mediated scission of budding virions during release. This physical barrier thus presents a perfect location for host antiviral restrictions that target enveloped viruses in general. In this review we will examine the current understanding of innate host antiviral defences that inhibit these essential replicative steps of primate lentiviruses associated with the plasma membrane, the mechanism by which these viruses have adapted to evade such defences, and the role that this virus/host battleground plays in the transmission and pathogenesis of HIV/AIDS.

HIV-1 Vpu Mediates HLA-C Downregulation

Many pathogens evade cytotoxic T lymphocytes (CTLs) by downregulating HLA molecules on infected cells, but the loss of HLA can trigger NK cell-mediated lysis. HIV-1 is thought to subvert CTLs while preserving NK cell inhibition by Nef-mediated downregulation of HLA-A and -B but not HLA-C molecules. We find that HLA-C is downregulated by most primary HIV-1 clones, including transmitted founder viruses, in contrast to the laboratory-adapted NL4-3 virus. HLA-C reduction is mediated by viral Vpu and reduces the ability of HLA-C restricted CTLs to suppress viral replication in CD4+ cells in vitro. HLA-A/B are unaffected by Vpu, and primary HIV-1 clones vary in their ability to downregulate HLA-C, possibly in response to whether CTLs or NK cells dominate immune pressure through HLA-C. HIV-2 also suppresses HLA-C expression through distinct mechanisms, underscoring the immune pressure HLA-C exerts on HIV. This viral immune evasion casts new light on the roles of CTLs and NK cells in immune responses against HIV.

Retroviral retention activates a Syk-dependent HemITAM in human tetherin

Tetherin (BST2/CD317) restricts the release of enveloped viral particles from infected cells. Coupled to this virion retention, hominid tetherins induce proinflammatory gene expression via activating NF-κB. We investigated the events initiating this tetherin-induced signaling and show that physical retention of retroviral particles induces the phosphorylation of conserved tyrosine residues in the cytoplasmic tails of tetherin dimers. This phosphorylation induces the recruitment of spleen tyrosine kinase (Syk), which is required for downstream NF-κB activation, indicating that the tetherin cytoplasmic tail resembles the hemi-immunoreceptor tyrosine-based activation motifs (hemITAMs) found in C-type lectin pattern recognition receptors. Retroviral-induced tetherin signaling is coupled to the cortical actin cytoskeleton via the Rac-GAP-containing protein RICH2 (ARHGAP44), and a naturally occurring tetherin polymorphism with reduced RICH2 binding exhibits decreased phosphorylation and NF-κB activation. Thus, upon virion retention, this linkage to the actin cytoskeleton likely triggers tetherin phosphorylation and subsequent signal transduction to induce an antiviral state.

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A hemITAM in human tetherin is phosphorylated upon viral restriction

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Tetherin phosphorylation recruits and is dependent upon the kinase Syk

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The RICH2-tetherin interaction couples tetherin signaling to the actin cytoskeleton

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A human polymorphism in tetherin abolishes RICH2 interactions and signal transduction

The weight debate

Therapeutic interventions administered on Critical Care are often dosed on the basis of patient body size, to ensure treatments are effective in achieving their goals and to prevent harm from overdose. Many treatment modalities use predicted weights estimated from descriptors such as sex, weight and height to reduce error that is associated with using total body weight in critically ill patients. In this article we review the size descriptors that have been described, their origin and calculation. We then examine the role they play in dosing of common therapies utilised in Critical Care and potential areas of research for the future.

Preservation of tetherin and CD4 counter-activities in circulating Vpu alleles despite extensive sequence variation within HIV-1 infected individuals

The HIV-1 Vpu protein is expressed from a bi-cistronic message late in the viral life cycle. It functions during viral assembly to maximise infectious virus release by targeting CD4 for proteosomal degradation and counteracting the antiviral protein tetherin (BST2/CD317). Single genome analysis of vpu repertoires throughout infection in 14 individuals infected with HIV-1 clade B revealed extensive amino acid diversity of the Vpu protein. For the most part, this variation in Vpu increases over the course of infection and is associated with predicted epitopes of the individual's MHC class I haplotype, suggesting CD8+ T cell pressure is the major driver of Vpu sequence diversity within the host. Despite this variability, the Vpu functions of targeting CD4 and counteracting both physical virus restriction and NF-κB activation by tetherin are rigorously maintained throughout HIV-1 infection. Only a minority of circulating alleles bear lesions in either of these activities at any given time, suggesting functional Vpu mutants are heavily selected against even at later stages of infection. Comparison of Vpu proteins defective for one or several functions reveals novel determinants of CD4 downregulation, counteraction of tetherin restriction, and inhibition of NF-κB signalling. These data affirm the importance of Vpu functions for in vivo persistence of HIV-1 within infected individuals, not simply for transmission, and highlight its potential as a target for antiviral therapy.

The accessory protein Vpu, encoded by HIV-1, performs at least two major roles in the virus life cycle, namely the degradation of newly synthesized CD4 molecules and the counteraction of a host antiviral protein, tetherin. These activities promote the release of infectious viruses from host cells, and recent evidence suggests that Vpu function has been crucial for the cross-species transmission of HIV-1 from chimpanzees, and its subsequent pandemic spread in humans. Here we studied the functional variation in Vpu in infected individuals. We found that the Vpu amino acid sequence can be highly variable within an individual, and that this variation is likely to result from host immune responses targeting antigens derived from Vpu. However, despite this variation, Vpu's major functions are preserved, with only a minority of circulating alleles showing defects throughout the course of infection. These data suggest that defective Vpu proteins are selected against within the infected individual, implying that Vpu functions are critical for HIV-1 replication throughout natural infection, not simply at transmission. Therefore Vpu may represent a novel target for antiviral therapy to augment current treatment strategies for HIV/AIDS.

Innate sensing of HIV-1 assembly by Tetherin induces NFκB-dependent proinflammatory responses

Antiviral proteins that recognize pathogen-specific or aberrantly located molecular motifs are perfectly positioned to act as pattern-recognition receptors and signal to the immune system. Here we investigated whether the interferon-induced viral restriction factor tetherin (CD317/BST2), which is known to inhibit HIV-1 particle release by physically tethering virions to the cell surface, has such a signaling role. We find that upon restriction of Vpu-defective HIV-1, tetherin acts as a virus sensor to induce NFκB-dependent proinflammatory gene expression. Signaling requires both tetherin's extracellular domain involved in virion retention and determinants in the cytoplasmic tail, including an endocytic motif, although signaling is independent of virion endocytosis. Furthermore, recruitment of the TNF-receptor-associated factor TRAF6 and activation of the mitogen-activated protein kinase TAK1 are critical for signaling. Human tetherin's ability to mediate efficient signaling may have arisen as a result of a five amino acid deletion that occurred in hominids after their divergence from chimpanzees.

Cumulus gene expression as a predictor of human oocyte fertilisation, embryo development and competence to establish a pregnancy

The close relationship between cumulus cell function and oocyte developmental competence indicates that analysis of cumulus gene expression is a potential non-invasive method to aid embryo selection and IVF outcome. Cumulus was isolated from 674 oocytes from 75 women undergoing ICSI and gene expression analysed by quantitative RT-PCR. Cumulus expression of cyclooxygenase 2 (PTGS2) was higher with mature oocytes, whereas brain-derived neurotrophic factor (BDNF) was lower when fertilisation was normal. Expression levels of gremlin (GREM1) and BDNF were weak positive and negative predictors of embryo quality respectively. Ranking of GREM1 expression within cohorts of oocytes showed that oocytes associated with the highest GREM1 expression were more likely to be transferred or cryopreserved than discarded (49 vs 33%, P<0.02), although the clinical pregnancy rate was not significantly different. This study demonstrates both the feasibility and difficulties of this method of analysis in the largest such group studied thus far. Novel relationships between BDNF expression and fertilisation were identified, and the potential value of GREM1 expression as a marker of embryo quality supports the further assessment of GREM1 analysis in the context of embryo selection.

Behavior of TiO2 thin film in a nanocapacitor

Gold and platinum nanocapacitors have been fabricated using a magnetron sputtering technique. TiO2 is used as a dielectric material to separate the metal layers which act as the parallel plates for the capacitors. The thickness for metal films and TiO2 layer is 80 nm and 400 nm, respectively. Capacitance of the nanocapacitors has been measured and dielectric constant of TiO2 calculated. Both capacitance and dielectric constant are observed to have strong frequency dependence.

Three hundred and thirty cycles of preimplantation genetic diagnosis for serious genetic disease: clinical considerations affecting outcome

OBJECTIVE

To report on our experience with preimplantation genetic diagnosis (PGD) cycles performed for serious genetic disease in relation to the clinical factors affecting outcome.

DESIGN

Retrospective review of data from a single centre.

SETTING

Tertiary referral PGD centre in a London teaching hospital.

METHODS

The PGD cycles included 172 cycles for chromosome rearrangements, 96 cycles for single-gene disorders and 62 cycles for X-linked disorders. In vitro fertilisation was the preferred method in chromosome rearrangement and X-linked cases, while intra cytoplasmic sperm injection was used in all single-gene disorders. Appropriate in situ hybridisation fluorescence probes were used in chromosome rearrangement and X-linked cases and polymerase chain reaction was used in single-gene disorders. All pregnancies were followed till delivery.

MAIN OUTCOME MEASURE

Live birth rate per PGD cycle started.

RESULTS

Eighty-six percent of cycles started (283) reached oocyte retrieval and 3743 eggs were collected, of which 2086 fertilised normally (55.7%). Two hundred and fifty cycles (76%) had embryos sutiable for biopsy on day 3 of in vitro culture, 1714 embryos were biopsied, and in 205 cycles (62%), there was at least one unaffected embryo available for transfer, resulting in 90 pregnancies, 68 clinical pregnancies and 58 live birth. The live birth rate was 18% per cycle started, 21% per egg retrieval and 28% per embryo transfer which significantly affected the live birth outcome. Woman age, number of eggs collected and achieving cryopreservation of surplus embryos had no statistically significant effect on treatment outcome.

CONCLUSIONS

The live birth outcome of PGD cycles for serious genetic disorder is modest and is affected by the number of embryos genetically suitable for transfer.

Breeding and longevity in captive Australian sea lions Neophoca cinerea at zoos and aquaria in Australia: 1965-2003

Australian sea lions (Neophoca cinerea) are known to have been kept in aquaria and zoos in Australia since 1965. During that time at least 41 births were recorded, of which 19 were in Adelaide, 15 at Adelaide Zoo and 4 at Marineland of South Australia. The mean interval between successive births in Adelaide was 538.9 � 9.5 days (18.0 months; n = 10) and the mean assumed pregnancy period, including embryonic diapause, was 536.0 � 11.4 days (17.9 months; n = 9). The mean interval between parturition and presumed successful mating was 8.4 � 1.6 days (n = 5). Births occurred in all months except January, June, August and December. Figures for New South Wales and Queensland establishments are too small and scattered over time for any pregnancy periods or birth intervals to be determined. Likewise, latitudinal differences, if any, were not evident, because of the paucity of data from these more northerly places. One female at the Adelaide Zoo produced 8 pups between 1986 and 1997; she is still alive after 22 years in captivity. The youngest known-age (captive-born) female was 4 years, 8 months old when she gave birth to her first pup; and the oldest female in captivity to give birth to a pup was aged approximately 21 years, 8 months. The longest recorded captive period for a female was more than 25 years by 31 December 2003, and for a male it was 21 years, 11 months. A captive-bred female was still alive after 18 years, 2 months, 24 days; another such female died aged 18 years, 2 months, 18 days. These life spans appear to be similar to those that meagre data suggest for tagged N. cinerea in the wild.

Phospholipase Cζ causes Ca2+ oscillations and parthenogenetic activation of human oocytes

At fertilization in mammals the sperm activates development of the oocyte by inducing a prolonged series of oscillations in the cytosolic free Ca2+concentration. One theory of signal transduction at fertilization suggests that the sperm cause the Ca2+oscillations by introducing a protein factor into the oocyte after gamete membrane fusion. We recently identified this sperm-specific protein as phospholipase Cζ (PLCζ), and we showed that PLCζ triggers Ca2+oscillations in unfertilized mouse oocytes. Here we report that microinjection of the complementary RNA for human PLCζ causes prolonged Ca2+oscillations in aged human oocytes that had failed to fertilize duringin vitrofertilization or intracytoplasmic sperm injection. The frequency of Ca2+oscillations was related to the concentration of complementary RNA injected. At low concentrations, PLCζ stimulated parthenogenetic activation of oocytes. These embryos underwent cleavage divisions and some formed blastocysts. These data show that PLCζ is a novel parthenogenetic stimulus for human oocytes and that it is unique in its ability to mimic the repetitive nature of the Ca2+stimulus provided by the sperm during human fertilization.

LPA1 receptor-deficient mice have phenotypic changes observed in psychiatric disease

Several psychiatric diseases, including schizophrenia, are thought to have a developmental aetiology, but to date no clear link has been made between psychiatric disease and a specific developmental process. LPA(1) is a G(i)-coupled seven transmembrane receptor with high affinity for lysophosphatidic acid. Although LPA(1) is expressed in several peripheral tissues, in the nervous system it shows relatively restricted temporal expression to neuroepithelia during CNS development and to myelinating glia in the adult. We report the detailed neurological and behavioural analysis of mice homozygous for a targeted deletion at the lpa(1) locus. Our observations reveal a marked deficit in prepulse inhibition, widespread changes in the levels and turnover of the neurotransmitter 5-HT, a brain region-specific alteration in levels of amino acids, and a craniofacial dysmorphism in these mice. We suggest that the loss of LPA(1) receptor generates defects resembling those found in psychiatric disease.

Initial management of ocular hypertension and primary open-angle glaucoma: an evaluation of the royal college of ophthalmologists' guidelines

PURPOSE

The purpose of this study was to identify any consensus of opinion among consultant ophthalmologists in Wales with respect to the initial management of glaucoma referrals based on the published guidelines of the Royal College of Ophthalmologists (RCO) and to compare consultant opinion with the practice in a typical hospital.

METHOD

The RCO guidelines document was studied to identify clear statements, which could be adopted as standards for audit purposes. A questionnaire was designed and sent to all consultant ophthalmologists in Wales (n=37) to obtain their opinions. An audit was performed of 100 consecutive patients referred to our unit as glaucoma suspects with regard to initial management. Descriptive statistical analysis was performed.

RESULTS

A good response rate for a postal questionnaire was obtained (81%) with 79.1% of responders finding the guidelines of at least some help. Levels of agreement with the definitions of ocular hypertension (OH) and primary open-angle glaucoma (POAG) were 76.7 and 86.7%, respectively. There was consensus of consultant opinion regarding many of the elements of the baseline clinical assessment with the significant exceptions of the necessity for dilated fundoscopy, gonioscopy, retinal nerve fibre layer assessment, and drawing of optic discs. The various 'clinical scenarios' for management of the RCO document were not all endorsed. The clinical audit results of the initial management of glaucoma referrals accurately reflected the consensus of the consultant opinion.

DISCUSSION

The RCO guidelines document represents a useful contribution to the management of patients with OH and POAG. Nevertheless, considerable variation in opinion exists concerning even the most basic areas. With the advent of clinical governance, bridging the gap between the conclusions of College working parties and realities of everyday practice will assume greater importance.

Neuropilin-2 is required in vivo for selective axon guidance responses to secreted semaphorins

Neuropilins are receptors for class 3 secreted semaphorins, most of which can function as potent repulsive axon guidance cues. We have generated mice with a targeted deletion in the neuropilin-2 (Npn-2) locus. Many Npn-2 mutant mice are viable into adulthood, allowing us to assess the role of Npn-2 in axon guidance events throughout neural development. Npn-2 is required for the organization and fasciculation of several cranial nerves and spinal nerves. In addition, several major fiber tracts in the brains of adult mutant mice are either severely disorganized or missing. Our results show that Npn-2 is a selective receptor for class 3 semaphorins in vivo and that Npn-1 and Npn-2 are required for development of an overlapping but distinct set of CNS and PNS projections.

Bilateral thalamic stimulation for the treatment of essential tremor

OBJECTIVE

To determine the safety and efficacy of bilateral thalamic stimulation in the treatment of essential tremor (ET).

METHODS

Nine ET patients with disabling tremor refractory to pharmacotherapy underwent bilateral staged implants. Tremor was assessed by the Fahn-Tolosa-Marin Tremor Rating Scale at baseline 1 (before first implant), baseline 2 (before second implant), and at 6-month and 1-year follow-up. Blinded evaluations were performed at 3 months. Associated changes in speech were evaluated in six patients. There were seven men and two women with a mean age of 73.8 years.

RESULTS

There was a significant improvement in the mean total tremor score from a baseline of 66.1+/-11.6 to 28.4+/-12.8 12 months after the second surgery. Similarly, the mean motor tremor subscore was 20.1+/-5.0 before the first surgery and improved significantly to 14.1+/-3.6 before the second surgery. Motor tremor scores 6 months after the second surgery (6.0+/-3.7) and 12 months after the second surgery (7.5+/-3.9) also improved significantly relative to the preoperative scores. The mean activities of daily living (ADL) subscore at baseline was 18.2+/-2.9 and improved significantly before the second surgery to 9.0+/-3.2. These ADL scores further improved 6 months (6.2+/-5.2) and 12 months (7.9+/-5.7) following the second surgery, but these gains were not significant. Blinded evaluations also revealed a similar degree of improvement. Complications were noted in five patients: asymptomatic intracranial hematoma (1), postoperative seizures (1), a hematoma over the implanted pulse generator (IPG) (1), lead repositioning (1), and IPG malfunction (1). Adverse effects related to stimulation were mild and resolved with adjustment of the stimulation parameters. Three of the six patients demonstrated worsening of dysarthria with both stimulators on.

CONCLUSIONS

Bilateral thalamic stimulation is effective in reducing tremor and functional disability in ET; however, dysarthria is a possible complication.

The relationship of attributional beliefs to self-esteem

Several studies have reported that beliefs about the causes of events (i.e., causal attributions) are related to achievement-oriented behavior. Skinner (1995) has suggested that achievement-oriented behavior is related to beliefs about successful strategies and beliefs about the capacity to enact those strategies. Based on Skinner's research, Wellborn, Connell, and Skinner (1989) developed the Students' Perception of Control Questionnaire (SPOCQ). In the present investigation, the SPOCQ was adapted for use with adolescents and adults. The SPOCQ and the Rosenberg Self-esteem Scale were administered to 147 college students. The internal consistency and the intercorrelations of the SPOCQ subscales were found to be acceptable. Additionally, SPOCQ scores were related to self-esteem and grade point average. There were statistically significant differences in the SPOCQ scores for males and females and in the relation of SPOCQ scores to self-esteem. It is suggested that the three constructs measured by the SPOCQ (control, strategies, and capacity) provide a more complete description of attributional beliefs than do previous scales.

Cost effectiveness of a single-function treatment center for cataract surgery

PURPOSE

To compare the clinical and cost effectiveness of two models for cataract treatment: a single-function Cataract Treatment Centre (CTC) and a general ophthalmology service.

SETTING

Cataract Treatment Centre and the general ophthalmology service at Sunderland Eye Infirmary, Sunderland, United Kingdom.

METHODS

Two hundred patients were studied using two models of care: 100 in the CTC and 100 in the general ophthalmology service. Outcome measures were best corrected visual at 3 months postoperatively or at discharge and occurrence of surgery-related complications. All direct costs to the National Health Service were identified, measure, and assessed.

RESULTS

Clinical outcomes in the two groups were similar. The average cost per patient was 496.90 pounds ($760.25) at the CTC and 566.34 pounds ($866.50) at the general ophthalmology service. The cost per patient treated as a day case in the general service group was 495.84 pounds ($758.63). Thus, treatment at the CTC was more cost effective than in the mixed service group and as cost effective as in the day case subgroup.

CONCLUSIONS

Depending on local circumstances, day care must be delivered more cost effectively in a single-function center than in a general ophthalmology service. We recommend day care using local anesthesia and protocols for assessment, surgery, and follow-up.