Assessing the stability-indicating properties of alternative potency assays for inactivated influenza vaccine

Determination of the potency of a vaccine is critical to ensuring that an appropriate dose is delivered, lot-to-lot consistency is maintained, and that the formulation is stable over the life of the vaccine. The potency of inactivated influenza vaccines is determined routinely by the Single Radial Immunodiffusion (SRID) assay. A number of alternative potency assays have been proposed and have been under evaluation in recent years. The aim of this study was to compare a surface plasmon resonance-based assay and two different enzyme linked immunoassays against the current potency assay, SRID, and against mouse immunogenicity when haemagglutinin antigen of the A(H1N1)pdm09 component of an inactivated influenza vaccine is stressed by elevated temperature, low pH and freezing. This analysis demonstrated that the alternative assays had good correspondence with SRID for samples from most stress conditions and that the immunogenicity in mice corresponded with potency in SRID for all stress samples. Subject to further analysis, the assays have been shown to have the potential to possibly replace, and at least complement, SRID.

International Horizon Scanning the impact of Covid-19 on increasing the health gap and vulnerability

 

The COVID-19 pandemic has caused unprecedented challenges for populations, health systems and governments worldwide, which have resulted in lasting economic, social and health impacts. The results of such have been felt disproportionately throughout society and existing vulnerabilities have been highlighted and heightened. A clear understanding of the extent of these vulnerabilities is needed in order to fully address the problem. The World Health Organization Collaborating Centre on Investment for Health and Well-being (WHOCC), Public Health Wales has developed a summary report focusing on the existing and emerging inequalities resulting from the pandemic, as identified through international evidence and learning from the International Horizon Scanning Reports. These reports, undertaken between May 2020 - August 2021, are based upon rapid evidence synthesis reviews of international literature. The summary report focuses on global learning and best practices in order to better understand and address the unequal impacts of the pandemic. The information has been categorised according to the five essential conditions required to enable a healthy life as presented within the WHO health equity conditions framework. The report provides evidence on groups most vulnerable to both direct and indirect impacts of the pandemic as well as promising practice to address the resulting inequity. Inequalities and related factors explored within the report include but are not limited to, level of deprivation and education. Taking a global perspective, this report summarises international evidence to support inclusive, sustainable, and equitable solutions, such as protecting economic well-being and taking an intergenerational lens in both response and recovery. To address and mitigate the impact of the pandemic upon vulnerable groups, collating and sharing international evidence and best practice has proven to support equitable long-term socio-economic and environmental recovery.

Key messages

• International learning provides vital insights to support recovery in Wales and beyond.

• Responses to the pandemic should address the needs of the vulnerable to reduce existing health gaps.

COVID-19 International Horizon Scanning – informing a response and recovery in Wales and beyond

Issue

The rapidly evolving nature and uncertainties of the COVID-19 pandemic have led to unprecedented challenges for health systems, as well as to wellbeing, social and economic impacts for individuals and communities across the globe. Effective, dynamic, innovative and evidence-based solutions are needed to address these challenges.

Description of Problem

The World Health Organization (WHO) Collaborating Centre on Investment for Health and Well-being, Public Health Wales, has initiated and continues to perform International Horizon Scanning work to inform the evolving COVID-19 public health response and recovery plans in Wales by learning from best practices from other countries. The learning and intelligence is systematically synthesized in rapid regular reports published every week/two weeks. The focus and scope vary, depending on the COVID-19 situation and public health and policy needs.

Results

The work stream has provided Welsh Government, the National Health Service (NHS), Public Health Wales and other key stakeholders with continuous and timely learning from the experience of other countries along with emerging evidence and guidance, provided by key international organisations. This includes international evidence, epidemiological data, experience, measures and recovery approaches, to understand and explore solutions. Reports have given a consistent overview of approaches across countries such as a comparative analysis of the vaccine roll-out or a systematic overview of the R-value and measures implemented accordingly.

Lessons

To understand, mitigate and address the impacts of the pandemic in Wales and beyond, a timely, dynamic and evidence-informed actionable intelligence has proven to be essential to inform and support decision-making on government and health system level to address the pandemic and mitigate harms from COVID-19.

Key messages

International learning has and continues to inform the evolving COVID-19 public health response in Wales.

Public Health Wales is contributing to an evidence-informed inclusive recovery from the pandemic in Wales and beyond.

Neutralizing and Neuraminidase Antibodies Correlate With Protection Against Influenza During a Late Season A/H3N2 Outbreak Among Unvaccinated Military Recruits

Background

Antibodies that inhibit hemagglutination have long been considered a correlate of protection against influenza, but these antibodies are only a subset of potentially protective antibodies. Neutralizing and neuraminidase antibodies may also contribute to protection, but data on their associations with protection are limited.

Methods

We measured preoutbreak hemagglutinin pseudovirus neutralization (PVN) and neuraminidase inhibition (NAI) antibody titers in unvaccinated military recruits who experienced an H3N2 influenza outbreak during training. We conducted a case-control study to investigate the association between titers and protection against influenza illness or H3N2-associated pneumonia using logistic regression.

Results

With every 2-fold increase in PVN titer, the odds of medically attended polymerase chain reaction–confirmed H3N2 infection (H3N2⁺) decreased by 41% (odds ratio [OR], 0.59; 95% confidence interval [CI], .45 to .77; P < .001). Among those who were H3N2⁺, the odds for pneumonia decreased by 52% (OR, 0.48; CI, .25 to .91; P = .0249). With every 2-fold increase in NAI titer, the odds of medically attended H3N2 infection decreased by 32% (OR, 0.68; 95% CI, .53 to .87; P = .0028), but there was no association between NAI titers and H3N2-associated pneumonia. There was also no synergistic effect of PVN and NAI antibodies.

Conclusions

PVN and NAI titers were independently associated with reduced risk of influenza illness. NAI titers associated with protection had greater breadth of reactivity to drifted strains than PVN titers. These findings show that PVN and NAI titers are valuable biomarkers for assessing the odds of influenza infection.

Innovative data analysis approach informing policy action to improve wellbeing and health equity

Wales is leading the way as one of the first countries supporting the World Health Organization to take forward the work of the Health Equity Status Report Initiative (HESRi) at a national level. The Welsh Health Equity Status Report Initiative (WHESRi) has been established to strengthen this global wellbeing and health equity agenda, applying a cutting-edge HESRi methodology first in Wales, providing valuable lessons and experience, which can enable other countries to take action to address health inequity. WHESRi includes three research streams: a) Health equity data analysis; b) Policy analysis and c) Health economic analysis.

The National Survey for Wales (NSW) (cross-sectional study design) is used to 'decompose' the gap in a health outcome using the Blinder-Oaxaca decomposition methodology. The analysis breaks down contributions to the inequitable health outcomes observed between different population groups, by factors that differ systematically between the groups. Factors, which align to the five HESRi health equity conditions (Health Services, Income Security & Social Protection, Living Conditions, Social & Human Capital and Employment & Working Conditions).

The work is also exploring how different health outcomes e.g. mental health and life satisfaction, result in different relative contributions to inequities in those outcomes from the five conditions.

Analysis of the 2016-17 NSW shows that the prevalence of good health is significantly higher in those who are not materially deprived (75.6% CI 74.5% to 76.6%) compared to those who are (55.3% CI 52.3% to 58.4%). Preliminary data suggests that when decomposing the gap in self-reported health between those who are materially deprived and those who are not, the largest contributing factor to the inequity is systematic differences in the degree of Income Security and Social Protection (39%).

The analysis identifies priority policy areas for action and further analysis.

Key messages

The health gap can be stratified and explained by five essential health equity conditions. Explaining the health gap informs cross-sector policy action and investment prioritisation towards healthy prosperous lives for all.

The neuraminidase of A(H3N2) influenza viruses circulating since 2016 is antigenically distinct from the A/Hong Kong/4801/2014 vaccine strain

A(H3N2) virus predominated recent influenza seasons, which has resulted in the rigorous investigation of haemagglutinin, but whether neuraminidase (NA) has undergone antigenic change and contributed to the predominance of A(H3N2) virus is unknown. Here, we show that the NA of the circulating A(H3N2) viruses has experienced significant antigenic drift since 2016 compared with the A/Hong Kong/4801/2014 vaccine strain. This antigenic drift was mainly caused by amino acid mutations at NA residues 245, 247 (S245N/S247T; introducing an N-linked glycosylation site at residue 245) and 468. As a result, the binding of the NA of A(H3N2) virus by some human monoclonal antibodies, including those that have broad reactivity to the NA of the 1957 A(H2N2) and 1968 A(H3N2) reference pandemic viruses as well as contemporary A(H3N2) strains, was reduced or abolished. This antigenic drift also reduced NA-antibody-based protection against in vivo virus challenge. X-ray crystallography showed that the glycosylation site at residue 245 is within a conserved epitope that overlaps the NA active site, explaining why it impacts antibody binding. Our findings suggest that NA antigenic drift impacts protection against influenza virus infection, thus highlighting the importance of including NA antigenicity for consideration in the optimization of influenza vaccines.

Use of lentiviral pseudotypes as an alternative to reassortant or Triton X-100-treated wild-type Influenza viruses in the neuraminidase inhibition enzyme-linked lectin assay

BACKGROUND

Formulation of neuraminidase (NA) within influenza vaccines is gaining importance in light of recent human studies. The enzyme-linked lectin assay (ELLA) is considered a reliable assay to evaluate human anti-NA antibodies.

OBJECTIVES

To overcome interference by hemagglutinin (HA)-specific antibodies and detect neuraminidase inhibitory (NI) antibodies only, two different sources of antigen have been studied in ELLA: reassortant viruses with a mismatched avian origin-HA or Triton X-100 (Tx)-treated wild-type viruses. Pseudotypes or pseudovirus (PV), characterized by a lentivirus core bearing human influenza NA and avian influenza HA, were investigated as an alternative source of antigen and compared to HA-mismatched and Tx-treated viruses, since represent a safer product to be handled.

METHODS

Two independent panels of sera were analyzed by ELLA to evaluate the anti-NA response against N1 (A/California/07/2009 (H1N1pdm)) and N2 (A/Hong Kong/4801/2014 (H3N2)). The NA inhibition (NI) antibody titers measured as either the 50% end point or 50% inhibitory concentration (IC50 ) were compared for every source of antigen.

RESULTS

The ELLA assay performed well with all three sources of antigen. NI titers measured using each antigen type correlated well when reported either as end point titers or as the IC50 .

CONCLUSIONS

This study suggests that HA-mismatched whole virus, Triton-treated wild-type virus or PV can be used to measure NI antibody titers of human sera, but further comparability/validation assays should be performed to assess statistical differences. The data support the use of PV as an attractive alternative source of antigen and justify further investigation to improve stability of this antigen source.

Measuring Influenza Neuraminidase Inhibition Antibody Titers by Enzyme-linked Lectin Assay

Antibodies to neuraminidase (NA), the second most abundant surface protein on influenza virus, contribute toward protection against influenza. Traditional methods to measure NA inhibiting (NI) antibody titers are not practical for routine serology. This protocol describes the enzyme-linked lectin assay (ELLA), a practical alternative method to measure NI titers that is performed in 96 well plates coated with a large glycoprotein substrate, fetuin. NA cleaves terminal sialic acids from fetuin, exposing the penultimate sugar, galactose. Peanut agglutinin (PNA) is a lectin with specificity for galactose and therefore the extent of desialylation can be quantified using a PNA-horseradish peroxidase conjugate, followed by addition of a chromogenic peroxidase substrate. The optical density that is measured is proportional to NA activity. To measure NI antibody titers, serial dilutions of sera are incubated at 37 °C O/N on fetuin-coated plates with a fixed amount of NA. The reciprocal of the highest serum dilution that results in ≥50% inhibition of NA activity is designated as the NI antibody titer. The ELLA provides a practical format for routine evaluation of human antibody responses following influenza infection or vaccination.

Comparability of neuraminidase inhibition antibody titers measured by enzyme-linked lectin assay (ELLA) for the analysis of influenza vaccine immunogenicity

Neuraminidase-inhibition (NI) antibody titers can be used to evaluate the immunogenicity of inactivated influenza vaccines and have provided evidence of serologic cross-reactivity between seasonal and pandemic H1N1 viruses. The traditional thiobarbituric acid assay is impractical for large serologic analyses, and therefore many laboratories use an enzyme-linked lectin assay (ELLA) to determine serum NI antibody titers. The comparability of ELLA NI antibody titers when measured in different laboratories was unknown. Here we report a study conducted through the Consortium for the Standardisation of Influenza SeroEpidemiology (CONSISE) to evaluate the variability of the ELLA. NI antibody titers of a set of 12 samples were measured against both N1 and N2 neuraminidase antigens in 3 independent assays by each of 23 laboratories. For a sample repeated in the same assay, ≥96% of N1 and N2 assays had less than a 4-fold difference in titer. Comparison of the titers measured in assays conducted on 3 different days in the same laboratory showed that a four-fold difference in titer was uncommon. Titers of the same sera measured in different laboratories spanned 3 to 6 two-fold dilutions (i.e., 8-64 fold difference in titer), with an average percent geometric coefficient of variation (%GCV) of 112 and 82% against N1 and N2 antigens, respectively. The difference in titer as indicated by fold range and %GCV was improved by normalizing the NI titers to a standard that was included in each assay. This study identified background signal and the amount of antigen in the assay as critical factors that influence titer, providing important information toward development of a consensus ELLA protocol.

Optimization of an enzyme-linked lectin assay suitable for rapid antigenic characterization of the neuraminidase of human influenza A(H3N2) viruses

Antibodies to neuraminidase (NA), the second most abundant surface protein of the influenza virus, contribute to protection against influenza virus infection. Although traditional and miniaturized thiobarbituric acid (TBA) neuraminidase inhibition (NI) assays have been successfully used to characterize the antigenic properties of NA, these methods are cumbersome and not easily amendable to rapid screening. An additional difficulty of the NI assay is the interference by hemagglutinin (HA)-specific antibodies. To prevent interference of HA-specific antibodies, most NI assays are performed with recombinant viruses containing a mismatched HA. However, generation of these viruses is time consuming and unsuitable for large-scale surveillance. The feasibility of using the recently developed enzyme-linked lectin assay (ELLA) to evaluate the antigenic relatedness of NA of wild type A(H3N2) viruses was assessed. Rather than using recombinant viruses, wild type A(H3N2) viruses were used as antigen with ferret sera elicited against recombinant viruses with a mismatched HA. In this study, details of the critical steps that are needed to modify and optimize the NI ELLA in a format that is reproducible, highly sensitive, and useful for influenza virus surveillance to monitor antigenic drift of NA are provided.

Structural characterization of a protective epitope spanning A(H1N1)pdm09 influenza virus neuraminidase monomers

A(H1N1)pdm09 influenza A viruses predominated in the 2013–2014 USA influenza season, and although most of these viruses remain sensitive to Food and Drug Administration-approved neuraminidase (NA) inhibitors, alternative therapies are needed. Here we show that monoclonal antibody CD6, selected for binding to the NA of the prototypic A(H1N1)pdm09 virus, A/California/07/2009, protects mice against lethal virus challenge. The crystal structure of NA in complex with CD6 Fab reveals a unique epitope, where the heavy-chain complementarity determining regions (HCDRs) 1 and 2 bind one NA monomer, the light-chain CDR2 binds the neighbouring monomer, whereas HCDR3 interacts with both monomers. This 30-amino-acid epitope spans the lateral face of an NA dimer and is conserved among circulating A(H1N1)pdm09 viruses. These results suggest that the large, lateral CD6 epitope may be an effective target of antibodies selected for development as therapeutic agents against circulating H1N1 influenza viruses.

Neuraminidase inhibitors offer a line of defence against flu infections, but resistance can occur even in the absence of prior exposure. Here Wan et al. describe the mode of action of CD6, a monoclonal antibody that protects against a common influenza strain, as a new therapeutic intervention model.

An optimized enzyme-linked lectin assay to measure influenza A virus neuraminidase inhibition antibody titers in human sera

Antibodies to neuraminidase (NA), the second most abundant surface protein on influenza virus, contribute toward protection against influenza. The traditional thiobarbituric acid (TBA) method to quantify NA inhibiting antibodies is cumbersome and not suitable for routine serology. An enzyme-linked lectin assay (ELLA) described by Lambre et al. (1990) is a practical alternative method for measuring NA inhibition (NI) titers. This report describes optimization of the ELLA for measuring NI titers in human sera against influenza A viruses, using H6N1 and H6N2 viruses as antigens. The optimized ELLA is subtype-specific and reproducible. While the titers measured by ELLA are somewhat greater than those measured by a miniaturized TBA method, seroconversion rates are the same, suggesting similarity in assay sensitivity under these optimized conditions. The ELLA described in this report provides a practical format for routine evaluation of human antibody responses to NA.

Stability of neuraminidase in inactivated influenza vaccines

Influenza vaccines are effective in protecting against illness and death caused by this seasonal pathogen. Antibodies that block the function of either hemagglutinin (HA) or neuraminidase (NA) contribute to vaccine efficacy, however vaccine potency is based only on HA content. NA protein content in vaccines varies from season to season due to differences in the relative amounts of HA and NA in influenza A, H1N1 and H3N2, and influenza B viruses that are selected for each manufacturing campaign. This, as well as potential inherent differences in NA immunogenicity, may result in varying responses from year to year. Moreover, the antigenic stability of NA is likely to dictate whether similar antibody responses will be obtained to this antigen throughout the shelf-life of the vaccine. To address this factor, we subjected NAs of influenza A (subtypes N1 and N2) and B viruses to denaturing conditions to evaluate the stability of enzyme activity. Each NA type/subtype had unique sensitivity to denaturing conditions. The N2 enzyme activity was more thermostable than that of N1 or influenza B, while the NA activity of influenza B was most resistant to detergent. N1 enzyme activity was most resistant of the three NAs to freeze-thaw cycling. In these experiments, enzyme activity was indicative of the immunogenicity of NA, but was strain-dependent, with greater neuraminidase inhibiting (NI) antibody titers elicited following immunization with the 2009 H1N1 pandemic virus A/California/7/2009, than the previously circulating seasonal H1N1 strain, A/Brisbane/59/2007. Robust NI antibody titers against both N1 and N2 components were induced following vaccination of mice with a trivalent inactivated influenza vaccine. When stored under recommended conditions, the NA of both N1 and N2 subtypes remained immunogenic well after the vaccine expiry date.

Protection against a lethal H5N1 influenza challenge by intranasal immunization with virus-like particles containing 2009 pandemic H1N1 neuraminidase in mice

Highly pathogenic H5N1 influenza shares the same neuraminidase (NA) subtype with the 2009 pandemic (H1N1pdm09), and cross-reactive NA immunity might protect against or mitigate lethal H5N1 infection. In this study, mice were either infected with a sublethal dose of H1N1pdm09 or were vaccinated and boosted with virus-like particles (VLP) consisting of the NA and matrix proteins, standardized by NA activity and administered intranasally, and were then challenged with a lethal dose of HPAI H5N1 virus. Mice previously infected with H1N1pdm09 survived H5N1 challenge with no detectable virus or respiratory tract pathology on day 4. Mice immunized with H5N1 or H1N1pdm09 NA VLPs were also fully protected from death, with a 100-fold and 10-fold reduction in infectious virus, respectively, and reduced pathology in the lungs. Human influenza vaccines that elicit not only HA, but also NA immunity may provide enhanced protection against the emergence of seasonal and pandemic viruses.

Fight for anaesthetic nurses

I must congratulate Greenwich District Hospital on running their theatres without Operating Department Assistants (Nursing Standard week ending October 31), lam sure the two ODAs who did not have their names printed had no reason to feel personally insulted. As I read the article, it was attacking the idea of ODAs, not individual people. My own opinion is that people who are neither doctors nor nurses and have only a City and Guilds training, should not be allowed to do the things that they do unsupervised. A nurse takes three years plus, training before working in anaesthetics and is not allowed to do many of the things that ODAs are.