Measuring microtubule dynamics

Microtubules are key players in cellular self-organization, acting as structural scaffolds, cellular highways, force generators and signalling platforms. Microtubules are polar filaments that undergo dynamic instability, i.e. transition between phases of growth and shrinkage. This allows microtubules to explore the inner space of the cell, generate pushing and pulling forces and remodel themselves into arrays with different geometry and function such as the mitotic spindle. To do this, eukaryotic cells employ an arsenal of regulatory proteins to control microtubule dynamics spatially and temporally. Plants and microorganisms have developed secondary metabolites that perturb microtubule dynamics, many of which are in active use as cancer chemotherapeutics and anti-inflammatory drugs. Here we summarise the methods used to visualise microtubules and to measure the parameters of dynamic instability to study both microtubule regulatory proteins and the action of small molecules interfering with microtubule assembly and/or disassembly

Effectiveness of successive booster vaccine doses against SARS-CoV-2 related mortality in residents of long-term care facilities in the VIVALDI study

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused severe disease in unvaccinated long-term care facility (LTCF) residents. Initial booster vaccination following primary vaccination is known to provide strong short-term protection, but data are limited on duration of protection and the protective effect of further booster vaccinations. OBJECTIVE: To evaluate the effectiveness of third, fourth and fifth dose booster vaccination against SARS-CoV-2 related mortality amongst older residents of LTCFs. DESIGN: Prospective cohort study. SETTING: LTCFs for older people in England participating in the VIVALDI study. METHODS: Residents aged >65 years at participating LTCFs were eligible for inclusion if they had at least one polymerase chain reaction or lateral flow device result within the analysis period 1 January 2022 to 31 December 2022. We excluded individuals who had not received at least two vaccine doses before the analysis period. Cox regression was used to estimate relative hazards of SARS-CoV-2 related mortality following 1-3 booster vaccinations compared with primary vaccination, stratified by previous SARS-CoV-2 infection and adjusting for age, sex and LTCF size (total beds). RESULTS: A total of 13,407 residents were included. Our results indicate that third, fourth and fifth dose booster vaccination provide additional short-term protection against SARS-CoV-2 related mortality relative to primary vaccination, with consistent stabilisation beyond 112 days to 45-75% reduction in risk relative to primary vaccination. CONCLUSIONS: Successive booster vaccination doses provide additional short-term protection against SARS-CoV-2 related mortality amongst older LTCF residents. However, we did not find evidence of a longer-term reduction in risk beyond that provided by initial booster vaccination

Duration of vaccine effectiveness against SARS-CoV-2 infection, hospitalisation, and death in residents and staff of long-term care facilities in England (VIVALDI): a prospective cohort study

Background: Residents and staff in long-term care facilities have been prioritised for vaccination against SARS-CoV-2, but data on potential waning of vaccine effectiveness and the effect of booster doses in this vulnerable population are scarce. We aimed to evaluate effectiveness of one, two, and three vaccine doses against infection and severe clinical outcomes in staff and residents of long-term care facilities in England over the first year following vaccine roll-out. Methods: The VIVALDI study is a prospective cohort study done in 331 long-term care facilities in England. Residents aged 65 years or older and staff aged 18 years or older were eligible for participation. Participants had routine PCR testing throughout the study period between Dec 8, 2020, and Dec 11, 2021. We retrieved all PCR results and cycle threshold values for PCR-positive samples from routine testing in long-term care facilities, and positive PCR results from clinical testing in hospitals through the UK's COVID-19 Datastore. PCR results were linked to participants using pseudo-identifiers based on individuals' unique UK National Health Service (NHS) numbers, which were also used to retrieve vaccination records from the National Immunisation Management Service, hospitalisation records from NHS England, and deaths data from the Office for National Statistics through the COVID-19 Datastore. In a Cox proportional hazards regression, we estimated vaccine effectiveness against SARS-CoV-2 infection, COVID-19-related hospitalisation, and COVID-19-related death after one, two, and three vaccine doses, separately by previous SARS-CoV-2 exposure. This study is registered with the ISRCTN Registry, ISRCTN 14447421. Findings: 80 186 residents and staff of long-term care facilities had records available for the study period, of whom 15 518 eligible residents and 19 515 eligible staff were included in the analysis. For residents without evidence of previous SARS-CoV-2 exposure, vaccine effectiveness decreased from 61·7% (95% CI 35·1 to 77·4) to 22·0% (–14·9 to 47·0) against infection; from 89·0% (70·6 to 95·9) to 56·3% (30·1 to 72·6) against hospitalisation; and from 96·4% (84·3 to 99·2) to 64·4% (36·1 to 80·1) against death, when comparing 14–83 days after dose two and 84 days or more after dose two. For staff without evidence of previous exposure, vaccine effectiveness against infection decreased slightly from 57·9% (43·1 to 68·9) at 14–83 days after dose two to 42·1% (29·9 to 52·2) at 84 days or more after dose two. There were no hospitalisations or deaths among unexposed staff at 14–83 days, but seven hospitalisations (vaccine effectiveness 91·0% [95% CI 74·3 to 96·8]) and one death were observed at 84 days or more after dose two. High vaccine effectiveness was restored following a third vaccine dose, with vaccine effectiveness in unexposed residents of 72·7% (55·8 to 83·1) against infection, 90·1% (80·6 to 95·0) against hospitalisation, and 97·5% (88·1 to 99·5) against death; and vaccine effectiveness in unexposed staff of 78·2% (70·0 to 84·1) against infection and 95·8% (49·9 to 99·6) against hospitalisation. There were no COVID-19-related deaths among unexposed staff after the third vaccine dose. Interpretation: Our findings showed substantial waning of SARS-CoV-2 vaccine effectiveness against all outcomes in residents of long-term care facilities from 12 weeks after a primary course of ChAdOx1-S or mRNA vaccines. Boosters restored protection, and maximised immunity across all outcomes. These findings show the importance of boosting and the need for ongoing surveillance in this vulnerable cohort

Clinical effectiveness of SARS-CoV-2 booster vaccine against Omicron infection in residents and staff of Long-Term Care Facilities: a prospective cohort study (VIVALDI)

Background: Successive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have caused severe disease in long-term care facility (LTCF) residents. Primary vaccination provides strong short-term protection, but data are limited on duration of protection following booster vaccines, particularly against the Omicron variant. We investigated the effectiveness of booster vaccination against infections, hospitalizations, and deaths among LTCF residents and staff in England. Methods: We included residents and staff of LTCFs within the VIVALDI study (ISRCTN 14447421) who underwent routine, asymptomatic testing (December 12, 2021–March 31, 2022). Cox regression was used to estimate relative hazards of SARS-CoV-2 infection, and associated hospitalization and death at 0–13, 14–48, 49–83, 84–111, 112–139, and 140+ days after dose 3 of SARS-CoV-2 vaccination compared with 2 doses (after 84+ days), stratified by previous SARS-CoV-2 infection and adjusting for age, sex, LTCF capacity, and local SARS-CoV-2 incidence. Results: A total of 14 175 residents and 19 793 staff were included. In residents without prior SARS-CoV-2 infection, infection risk was reduced 0–111 days after the first booster, but no protection was apparent after 112 days. Additional protection following booster vaccination waned but was still present at 140+ days for COVID-associated hospitalization (adjusted hazard ratio [aHR], 0.20; 95% CI, 0.06–0.63) and death (aHR, 0.50; 95% CI, 0.20–1.27). Most residents (64.4%) had received primary course vaccine of AstraZeneca, but this did not impact pre- or postbooster risk. Staff showed a similar pattern of waning booster effectiveness against infection, with few hospitalizations and no deaths. Conclusions: Our findings suggest that booster vaccination provided sustained protection against severe outcomes following infection with the Omicron variant, but no protection against infection from 4 months onwards. Ongoing surveillance for SARS-CoV-2 in LTCFs is crucial

Robust SARS-CoV-2-specific and heterologous immune responses in vaccine-naïve residents of long-term care facilities who survive natural infection

We studied humoral and cellular immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 152 long-term care facility staff and 124 residents over a prospective 4-month period shortly after the first wave of infection in England. We show that residents of long-term care facilities developed high and stable levels of antibodies against spike protein and receptor-binding domain. Nucleocapsid-specific responses were also elevated but waned over time. Antibodies showed stable and equivalent levels of functional inhibition against spike-angiotensin-converting enzyme 2 binding in all age groups with comparable activity against viral variants of concern. SARS-CoV-2 seropositive donors showed high levels of antibodies to other beta-coronaviruses but serostatus did not impact humoral immunity to influenza or other respiratory syncytial viruses. SARS-CoV-2-specific cellular responses were similar across all ages but virus-specific populations showed elevated levels of activation in older donors. Thus, survivors of SARS-CoV-2 infection show a robust and stable immunity against the virus that does not negatively impact responses to other seasonal viruses

SARS-CoV-2 anti-spike antibody levels following second dose of ChAdOx1 nCov-19 or BNT162b2 in residents of long-term care facilities in England (VIVALDI)

General population studies have shown strong humoral response following SARS-CoV-2 vaccination with subsequent waning of anti-spike antibody levels. Vaccine-induced immune responses are often attenuated in frail and older populations, but published data are scarce. We measured SARS-CoV-2 anti-spike antibody levels in Long-Term Care Facility residents and staff following second vaccination dose with Oxford-AstraZeneca or Pfizer-BioNTech. Vaccination elicited robust antibody responses in older residents, suggesting comparable levels of vaccine-induced immunity to that in the general population. Antibody levels are higher after Pfizer-BioNTech vaccination but fall more rapidly compared to Oxford-AstraZeneca recipients and are enhanced by prior infection in both groups

Strong peak immunogenicity but rapid antibody waning following third vaccine dose in older residents of care homes

Third-dose coronavirus disease 2019 vaccines are being deployed widely but their efficacy has not been assessed adequately in vulnerable older people who exhibit suboptimal responses after primary vaccination series. This observational study, which was carried out by the VIVALDI study based in England, looked at spike-specific immune responses in 341 staff and residents in long-term care facilities who received an mRNA vaccine following dual primary series vaccination with BNT162b2 or ChAdOx1. Third-dose vaccination strongly increased antibody responses with preferential relative enhancement in older people and was required to elicit neutralization of Omicron. Cellular immune responses were also enhanced with strong cross-reactive recognition of Omicron. However, antibody titers fell 21–78% within 100 d after vaccine and 27% of participants developed a breakthrough Omicron infection. These findings reveal strong immunogenicity of a third vaccine in one of the most vulnerable population groups and endorse an approach for widespread delivery across this population. Ongoing assessment will be required to determine the stability of immune protection

Outcomes of SARS-CoV-2 omicron infection in residents of long-term care facilities in England (VIVALDI): a prospective, cohort study

Background: The SARS-CoV-2 omicron variant (B.1.1.529) is highly transmissible, but disease severity appears to be reduced compared with previous variants such as alpha and delta. We investigated the risk of severe outcomes following infection in residents of long-term care facilities. Methods: We did a prospective cohort study in residents of long-term care facilities in England who were tested regularly for SARS-CoV-2 between Sept 1, 2021, and Feb 1, 2022, and who were participants of the VIVALDI study. Residents were eligible for inclusion if they had a positive PCR or lateral flow device test during the study period, which could be linked to a National Health Service (NHS) number, enabling linkage to hospital admissions and mortality datasets. PCR or lateral flow device test results were linked to national hospital admission and mortality records using the NHS-number-based pseudo-identifier. We compared the risk of hospital admission (within 14 days following a positive SARS-CoV-2 test) or death (within 28 days) in residents who had tested positive for SARS-CoV-2 in the period shortly before omicron emerged (delta-dominant) and in the omicron-dominant period, adjusting for age, sex, primary vaccine course, past infection, and booster vaccination. Variants were confirmed by sequencing or spike-gene status in a subset of samples. Results: 795 233 tests were done in 333 long-term care facilities, of which 159 084 (20·0%) could not be linked to a pseudo-identifier and 138 012 (17·4%) were done in residents. Eight residents had two episodes of infection (>28 days apart) and in these cases the second episode was excluded from the analysis. 2264 residents in 259 long-term care facilities (median age 84·5 years, IQR 77·9–90·0) were diagnosed with SARS-CoV-2, of whom 253 (11·2%) had a previous infection and 1468 (64·8%) had received a booster vaccination. About a third of participants were male. Risk of hospital admissions was markedly lower in the 1864 residents infected in the omicron-period (4·51%, 95% CI 3·65–5·55) than in the 400 residents infected in the pre-omicron period (10·50%, 7·87–13·94), as was risk of death (5·48% [4·52–6·64] vs 10·75% [8·09–14·22]). Adjusted hazard ratios (aHR) also indicated a reduction in hospital admissions (0·64, 95% CI 0·41–1·00; p=0·051) and mortality (aHR 0·68, 0·44–1·04; p=0·076) in the omicron versus the pre-omicron period. Findings were similar in residents with a confirmed variant. Interpretation: Observed reduced severity of the omicron variant compared with previous variants suggests that the wave of omicron infections is unlikely to lead to a major surge in severe disease in long-term care facility populations with high levels of vaccine coverage or natural immunity. Continued surveillance in this vulnerable population is important to protect residents from infection and monitor the public health effect of emerging variants. Funding: UK Department of Health and Social Care