Standardization of Hemagglutination Inhibition Assay for Influenza Serology Allows for High Reproducibility between Laboratories

Influenza Vaccine Effectiveness and Progress Towards a Universal Influenza Vaccine

At various times in recent decades, surges have occurred in optimism about the potential for universal influenza vaccines that provide strong, broad, and long-lasting protection and could substantially reduce the disease burden associated with seasonal influenza epidemics as well as the threat posed by pandemic influenza. Each year more than 500 million doses of seasonal influenza vaccine are administered around the world, with most doses being egg-grown inactivated subunit or split-virion vaccines. These vaccines tend to have moderate effectiveness against medically attended influenza for influenza A(H1N1) and influenza B, and somewhat lower for influenza A(H3N2) where differences between vaccine strains and circulating strains can occur more frequently due to antigenic drift and egg adaptations in the vaccine strains. Several enhanced influenza vaccine platforms have been developed including cell-grown antigen, the inclusion of adjuvants, or higher antigen doses, to improve immunogenicity and protection. During the COVID-19 pandemic there was unprecedented speed in development and roll-out of relatively new vaccine platforms, including mRNA vaccines and viral vector vaccines. These new platforms present opportunities to improve protection for influenza beyond existing products. Other approaches continue to be explored. Incremental improvements in influenza vaccine performance should be achievable in the short to medium term.

Evaluation of Vaccine Immunogenicity-Correlates to Real-World Protection: Influenza

Recent events highlighted that, despite decades of studying vaccine immunogenicity and efforts toward finding correlates of protection, evaluating real-world vaccine efficacy as well as establishing meaningful licensing criteria still represents a significant challenge. In this paper, we review all aspects of influenza vaccine immunogenicity, including animal and human challenge studies, humoral and cellular immunity parameters, and their potential correlation with real-life protection from disease.

Progress in Treatment and Diagnostics of Infectious Disease with Polymers

In this era of advanced technology and innovation, infectious diseases still cause significant morbidity and mortality, which need to be addressed. Despite overwhelming success in the development of vaccines, transmittable diseases such as tuberculosis and AIDS remain unprotected, and the treatment is challenging due to frequent mutations of the pathogens. Formulations of new or existing drugs with polymeric materials have been explored as a promising new approach. Variations in shape, size, surface charge, internal morphology, and functionalization position polymer particles as a revolutionary material in healthcare. Here, an overview is provided of major diseases along with statistics on infection and death rates, focusing on polymer-based treatments and modes of action. Key issues are discussed in this review pertaining to current challenges and future perspectives.

The convergent evolution of influenza A virus: Implications, therapeutic strategies and what we need to know

Influenza virus infection, more commonly known as the 'cold flu', is an etiological agent that gives rise to recurrent annual flu and many pandemics. Dated back to the 1918- Spanish Flu, the influenza infection has caused the loss of many human lives and significantly impacted the economy and daily lives. Influenza virus can be classified into four different genera: influenza A-D, with the former two, influenza A and B, relevant to humans. The capacity of antigenic drift and shift in Influenza A has given rise to many novel variants, rendering vaccines and antiviral therapies useless. In light of the emergence of a novel betacoronavirus, the SARS-CoV-2, unravelling the underpinning mechanisms that support the recurrent influenza epidemics and pandemics is essential. Given the symptom similarities between influenza and covid infection, it is crucial to reiterate what we know about the influenza infection. This review aims to describe the origin and evolution of influenza infection. Apart from that, the risk factors entail the implication of co-infections, especially regarding the COVID-19 pandemic is further discussed. In addition, antiviral strategies, including the potential of drug repositioning, are discussed in this context. The diagnostic approach is also critically discussed in an effort to understand better and prepare for upcoming variants and potential influenza pandemics in the future. Lastly, this review encapsulates the challenges in curbing the influenza spread and provides insights for future directions in influenza management.

[Mathematical model for assessing the level of cross-immunity between strains of influenza virus subtype H3N2]

INTRODUCTION

The WHO regularly updates influenza vaccine recommendations to maximize their match with circulating strains. Nevertheless, the effectiveness of the influenza A vaccine, specifically its H3N2 component, has been low for several seasons. The aim of the study is to develop a mathematical model of cross-immunity based on the array of published WHO hemagglutination inhibition assay (HAI) data.

MATERIALS AND METHODS

In this study, a mathematical model was proposed, based on finding, using regression analysis, the dependence of HAI titers on substitutions in antigenic sites of sequences. The computer program we developed can process data (GISAID, NCBI, etc.) and create real-time databases according to the set tasks.

RESULTS

Based on our research, an additional antigenic site F was identified. The difference in 1.6 times the adjusted R2, on subsets of viruses grown in cell culture and grown in chicken embryos, demonstrates the validity of our decision to divide the original data array by passage histories. We have introduced the concept of a degree of homology between two arbitrary strains, which takes the value of a function depending on the Hamming distance, and it has been shown that the regression results significantly depend on the choice of function. The provided analysis showed that the most significant antigenic sites are A, B, and E. The obtained results on predicted HAI titers showed a good enough result, comparable to similar work by our colleagues.

CONCLUSION

The proposed method could serve as a useful tool for future forecasts, with further study to confirm its sustainability.

The effect of metformin on influenza vaccine responses in nondiabetic older adults: a pilot trial

BACKGROUND

Aging is associated with progressive declines in immune responses leading to increased risk of severe infection and diminished vaccination responses. Influenza (flu) is a leading killer of older adults despite availability of seasonal vaccines. Geroscience-guided interventions targeting biological aging could offer transformational approaches to reverse broad declines in immune responses with aging. Here, we evaluated effects of metformin, an FDA approved diabetes drug and candidate anti-aging drug, on flu vaccination responses and markers of immunological resilience in a pilot and feasibility double-blinded placebo-controlled study.

RESULTS

Healthy older adults (non-diabetic/non-prediabetic, age: 74.4 ± 1.7 years) were randomized to metformin (n = 8, 1500 mg extended release/daily) or placebo (n = 7) treatment for 20 weeks and were vaccinated with high-dose flu vaccine after 10 weeks of treatment. Peripheral blood mononuclear cells (PBMCs), serum, and plasma were collected prior to treatment, immediately prior to vaccination, and 1, 5, and 10 weeks post vaccination. Increased serum antibody titers were observed post vaccination with no significant differences between groups. Metformin treatment led to trending increases in circulating T follicular helper cells post-vaccination. Furthermore, 20 weeks of metformin treatment reduced expression of exhaustion marker CD57 in circulating CD4 T cells.

CONCLUSIONS

Pre-vaccination metformin treatment improved some components of flu vaccine responses and reduced some markers of T cell exhaustion without serious adverse events in nondiabetic older adults. Thus, our findings highlight the potential utility of metformin to improve flu vaccine responses and reduce age-related immune exhaustion in older adults, providing improved immunological resilience in nondiabetic older adults.

Haemagglutination inhibition and virus microneutralisation serology assays: use of harmonised protocols and biological standards in seasonal influenza serology testing and their impact on inter-laboratory variation and assay correlation: A FLUCOP collaborative study

Introduction

The haemagglutination inhibition assay (HAI) and the virus microneutralisation assay (MN) are long-established methods for quantifying antibodies against influenza viruses. Despite their widespread use, both assays require standardisation to improve inter-laboratory agreement in testing. The FLUCOP consortium aims to develop a toolbox of standardised serology assays for seasonal influenza. Building upon previous collaborative studies to harmonise the HAI, in this study the FLUCOP consortium carried out a head-to-head comparison of harmonised HAI and MN protocols to better understand the relationship between HAI and MN titres, and the impact of assay harmonisation and standardisation on inter-laboratory variability and agreement between these methods.

Methods

In this paper, we present two large international collaborative studies testing harmonised HAI and MN protocols across 10 participating laboratories. In the first, we expanded on previously published work, carrying out HAI testing using egg and cell isolated and propagated wild-type (WT) viruses in addition to high-growth reassortants typically used influenza vaccines strains using HAI. In the second we tested two MN protocols: an overnight ELISA-based format and a 3-5 day format, using reassortant viruses and a WT H3N2 cell isolated virus. As serum panels tested in both studies included many overlapping samples, we were able to look at the correlation of HAI and MN titres across different methods and for different influenza subtypes.

Results

We showed that the overnight ELISA and 3-5 day MN formats are not comparable, with titre ratios varying across the dynamic range of the assay. However, the ELISA MN and HAI are comparable, and a conversion factor could possibly be calculated. In both studies, the impact of normalising using a study standard was investigated, and we showed that for almost every strain and assay format tested, normalisation significantly reduced inter-laboratory variation, supporting the continued development of antibody standards for seasonal influenza viruses. Normalisation had no impact on the correlation between overnight ELISA and 3-5 day MN formats.

H3N2 influenza hemagglutination inhibition method qualification with data driven statistical methods for human clinical trials

Introduction

Hemagglutination inhibition (HAI) antibody titers to seasonal influenza strains are important surrogates for vaccine-elicited protection. However, HAI assays can be variable across labs, with low sensitivity across diverse viruses due to lack of standardization. Performing qualification of these assays on a strain specific level enables the precise and accurate quantification of HAI titers. Influenza A (H3N2) continues to be a predominant circulating subtype in most countries in Europe and North America since 1968 and is thus a focus of influenza vaccine research.

Methods

As a part of the National Institutes of Health (NIH)-funded Collaborative Influenza Vaccine Innovation Centers (CIVICs) program, we report on the identification of a robust assay design, rigorous statistical analysis, and complete qualification of an HAI assay using A/Texas/71/2017 as a representative H3N2 strain and guinea pig red blood cells and neuraminidase (NA) inhibitor oseltamivir to prevent NA-mediated agglutination.

Results

This qualified HAI assay is precise (calculated by the geometric coefficient of variation (GCV)) for intermediate precision and intra-operator variability, accurate calculated by relative error, perfectly linear (slope of -1, R-Square 1), robust (<25% GCV) and depicts high specificity and sensitivity. This HAI method was successfully qualified for another H3N2 influenza strain A/Singapore/INFIMH-16-0019/2016, meeting all pre-specified acceptance criteria.

Discussion

These results demonstrate that HAI qualification and data generation for new influenza strains can be achieved efficiently with minimal extra testing and development. We report on a qualified and adaptable influenza serology method and analysis strategy to measure quantifiable HAI titers to define correlates of vaccine mediated protection in human clinical trials.

Discrimination of the H1N1 and H5N2 Variants of Influenza A Virus Using an Isomeric Sialic Acid-Conjugated Graphene Field-Effect Transistor

There has been a continuous effort to fabricate a fast, sensitive, and inexpensive system for influenza virus detection to meet the demand for effective screening in point-of-care testing. Herein, we report a sialic acid (SA)-conjugated graphene field-effect transistor (SA-GFET) sensor designed using α2,3-linked sialic acid (3'-SA) and α2,6-linked sialic acid (6'-SA) for the detection and discrimination of the hemagglutinin (HA) protein of the H5N2 and H1N1 viruses. 3'-SA and 6'-SA specific for H5 and H1 influenza were used in the SA-GFET to capture the HA protein of the influenza virus. The net charge of the captured viral sample led to a change in the electrical current of the SA-GFET platform, which could be correlated to the concentration of the viral sample. This SA-GFET platform exhibited a highly sensitive response in the range of 10¹-10⁶ pfu mL^-1, with a limit of detection (LOD) of 10¹ pfu mL^-1 in buffer solution and a response time of approximately 10 s. The selectivity of the SA-GFET platform for the H1N1 and H5N2 influenza viruses was verified by testing analogous respiratory viruses, i.e., influenza B and the spike protein of SARS-CoV-2 and MERS-CoV, on the SA-GFET. Overall, the results demonstrate that the developed dual-channel SA-GFET platform can potentially serve as a highly efficient and sensitive sensing platform for the rapid detection of infectious diseases.

An external quality assessment feasibility study; cross laboratory comparison of haemagglutination inhibition assay and microneutralization assay performance for seasonal influenza serology testing: A FLUCOP study

Introduction

External Quality Assessment (EQA) schemes are designed to provide a snapshot of laboratory proficiency, identifying issues and providing feedback to improve laboratory performance and inter-laboratory agreement in testing. Currently there are no international EQA schemes for seasonal influenza serology testing. Here we present a feasibility study for conducting an EQA scheme for influenza serology methods.

Methods

We invited participant laboratories from industry, contract research organizations (CROs), academia and public health institutions who regularly conduct hemagglutination inhibition (HAI) and microneutralization (MN) assays and have an interest in serology standardization. In total 16 laboratories returned data including 19 data sets for HAI assays and 9 data sets for MN assays.

Results

Within run analysis demonstrated good laboratory performance for HAI, with intrinsically higher levels of intra-assay variation for MN assays. Between run analysis showed laboratory and strain specific issues, particularly with B strains for HAI, whilst MN testing was consistently good across labs and strains. Inter-laboratory variability was higher for MN assays than HAI, however both assays showed a significant reduction in inter-laboratory variation when a human sera pool is used as a standard for normalization.

Discussion

This study has received positive feedback from participants, highlighting the benefit such an EQA scheme would have on improving laboratory performance, reducing inter laboratory variation and raising awareness of both harmonized protocol use and the benefit of biological standards for seasonal influenza serology testing.

Detection Methods for H1N1 Virus

Influenza A virus H1N1, a respiratory virus transmitted via droplets and responsible for the global pandemic in 2009, belongs to the Orthomyxoviridae family, a single-negative-stranded RNA. It possesses glycoprotein spikes neuraminidase (NA), hemagglutinin (HA), and a matrix protein named M2. The Covid-19 pandemic affected the world population belongs to the respiratory virus category is currently mutating, this can also be observed in the case of H1N1 influenza A virus. Mutations in H1N1 can enhance the viral capacity which can lead to another pandemic. This virus affects children below 5 years, pregnant women, old age people, and immunocompromised individuals due to its high viral capacity. Its early detection is necessary for the patient's recovery time. In this book chapter, we mainly focus on the detection methods for H1N1, from traditional ones to the most advance including biosensors, RT-LAMP, multi-fluorescent PCR.

Multiple HA substitutions in highly pathogenic avian influenza H5Nx viruses contributed to the change in the NA subtype preference

Novel highly pathogenic avian influenza (HPAI) H5Nx viruses are predominantly circulating worldwide, with an increasing potential threat of an outbreak in humans. It remains largely unknown how the stably maintained HPAI H5N1 suddenly altered its neuraminidase (NA) to other NA subtypes, which resulted in the emergence and evolution of H5Nx viruses. Here, we found that a combination of four specific amino acid (AA) substitutions (S123P-T156A-D183N- S223 R) in the hemagglutinin (HA) protein consistently observed in the H5Nx markedly altered the NA preference of H5N1 viruses. These molecular changes in H5N1 impaired its fitness, particularly viral growth and the functional activities of the HA and NA proteins. Among the AA substitutions identified, the T156A substitution, which contributed to the NA shift, also dramatically altered the antigenicity of H5N1 viruses, suggesting an occurrence of antigenic drift triggered by selective pressure. Our study shows the importance of how HA and NA complement each other and that antigenic drift in HA can potentially cause a shift in the NA protein in influenza A virus evolution.

IAV-CNN: A 2D Convolutional Neural Network Model to Predict Antigenic Variants of Influenza A Virus

The rapid evolution of influenza viruses constantly leads to the emergence of novel influenza strains that are capable of escaping from population immunity. The timely determination of antigenic variants is critical to vaccine design. Empirical experimental methods like hemagglutination inhibition (HI) assays are time-consuming and labor-intensive, requiring live viruses. Recently, many computational models have been developed to predict the antigenic variants without considerations of explicitly modeling the interdependencies between the channels of feature maps. Moreover, the influenza sequences consisting of similar distribution of residues will have high degrees of similarity and will affect the prediction outcome. Consequently, it is challenging but vital to determine the importance of different residue sites and enhance the predictive performance of influenza antigenicity. We have proposed a 2D convolutional neural network (CNN) model to infer influenza antigenic variants (IAV-CNN). Specifically, we apply a new distributed representation of amino acids, named ProtVec that can be applied to a variety of downstream proteomic machine learning tasks. After splittings and embeddings of influenza strains, a 2D squeeze-and-excitation CNN architecture is constructed that enables networks to focus on informative residue features by fusing both spatial and channel-wise information with local receptive fields at each layer. Experimental results on three influenza datasets show IAV-CNN achieves state-of-the-art performance combining the new distributed representation with our proposed architecture. It outperforms both traditional machine algorithms with the same feature representations and the majority of existing models in the independent test data. Therefore we believe that our model can be served as a reliable and robust tool for the prediction of antigenic variants.

Obesity, rather than high fat diet, exacerbates the outcome of influenza virus infection in influenza-sensitized mice

Introduction

Obesity is associated with impaired immune function and increased susceptibility to infection. High fat (HF) diet-induced obesity is a commonly used animal model. However, HF diet itself is known to affect immune function and infection. Thus, it is not discernable which one, HF diet or adiposity, is the major contributor to the observed impairment in immunity and susceptibility to infection in HF diet-induced obesity. We hypothesized that obesity is a major contributor to impaired immune function.

Methods and results

Weight-matched outbred female CD-1 mice (1-mo) were randomly assigned to either a HF (45%) or a low fat (LF, 10%) diet group. Ten week after feeding their respective diets, weight gain in the mice fed the HF diet varied greatly. Thus, based on the average body weight, mice in HF diet group were divided into two sub-groups: HF lean (HF-L) and HF obese (HF-O). After 25-week, mice were immunized with an influenza A/Puerto Rico/8/34 vaccine and boosted 3-week later. Five week after the booster, mice were infected with influenza A/Puerto Rico/8/34 virus, and body weight was recorded daily for 1 month. HF-O mice exhibited significant weight loss after influenza virus challenge compared to LF and HF-L mice while LF and HF-L mice largely maintained their weight to a similar extent.

Conclusion

Our findings suggest that obesity, rather than HF diet, per se, may impair the efficacy of influenza vaccination.

Physical activity and acute exercise benefit influenza vaccination response: A systematic review with individual participant data meta-analysis

Whether the vaccine adjuvant potential of acute exercise is uniform among different populations, e.g., inactive persons, is unknown. This meta-analysis examines influenza vaccine antibody responses and the effect of physical activity, acute exercise, and their interaction. Inclusion criteria comprised randomized controlled trials with acute exercise intervention and influenza vaccination antibody measurements at baseline and 4-6 weeks, and participant baseline physical activity measurement; there were no exclusion criteria. Searching via six databases (Medline, Embase, CINAHL, Scopus, Web of Science, and Physiotherapy Evidence) and two clinical registries (WHO and NIH), nine studies were identified and assessed with the Cochrane revised risk-of-bias tool. Data analysis comprised one-stage random-effects generalized linear mixed-effects models with random intercept. Seven of nine identified studies, all of high risk of bias, provided data for 550 included participants. Clinical measures of antibody response tended to be higher in the acute-exercised participants compared to rested controls and physically active compared to inactive. Physical activity significantly increased H1 strain seroconversion (adjusted odds ratio (aOR) 1.69, 95%CI: 1.02-2.82) among all participants and titer response (aOR 1.20, 95%CI: 1.03-1.39) among the acute exercise group. Increasing age frequently reduced immunogenic responses whereas body mass index and sex had little-to-no effect. Adjuvant effects were more pronounced with interventions exercising the same arm in which the vaccination was administered. H1 response was increased by both physical activity and the acute exercise-physical activity interaction. Given the observed modifications by age and the subset analysis suggesting the benefit is more pronounced in older populations, future attention is due for acute exercise-PA interactions to impact vaccination response in the at-risk population of older adults. Further, we identify localized exercise as the likely most-effective protocol and encourage its use to augment the available evidence.

Elimination of receptor binding by influenza hemagglutinin improves vaccine-induced immunity

The binding of influenza hemagglutinin (HA) to sialic acid (SA) receptors plays a well-defined role in shaping infection but the impact of such binding on vaccine responses has not yet been explored. We generated a virus-like particle (VLP) vaccine bearing the HA of H1N1 A/California/07/09 that is unable to bind to its α(2,6)-linked SA receptor (H1_Y98F-VLP) and compared its immunogenicity and efficacy to a wild-type H1-VLP (H1_WT-VLP) in mice. The H1_Y98F-VLP elicited significantly stronger and more durable antibody responses (hemagglutination inhibition and microneutralization titers) and greater avidity maturation, likely attributable to improved germinal center formation. H1_Y98F-VLP also resulted in a robust population of IL-2⁺TNFα⁺IFNγ⁻ CD4⁺ T cells that correlated with antibody responses. Compared to H1_WT-VLP vaccination, mice immunized with H1_Y98F-VLP had 2.3-log lower lung viral loads and significantly lower pulmonary inflammatory cytokine levels 5 days post-challenge. These findings suggest that abrogation of HA-SA interactions may be a promising strategy to improve the quality and durability of influenza vaccine-induced humoral responses.

End-to-end antigenic variant generation for H1N1 influenza HA protein using sequence to sequence models

The growing risk of new variants of the influenza A virus is the most significant to public health. The risk imposed from new variants may have been lethal, as witnessed in the year 2009. Even though the improvement in predicting antigenicity of influenza viruses has rapidly progressed, few studies employed deep learning methodologies. The most recent literature mostly relied on classification techniques, while a model that generates the HA protein of the antigenic variant is not developed. However, the antigenic pair of influenza virus A can be determined in a laboratory setup, the process needs a tremendous amount of time and labor. Antigenic shift and drift which are caused by changes in surface protein favored the influenza A virus in evading immunity. The high frequency of the minor changes in the surface protein poses a challenge to identifying the antigenic variant of an emerging virus. These changes slow down vaccine selection and the manufacturing process. In this vein, the proposed model could help save the time and efforts exerted to identify the antigenic pair of the influenza virus. The proposed model utilized an end-to-end learning methodology relying on deep sequence-to-sequence architecture to generate the antigenic variant of a given influenza A virus using surface protein. Employing the BLEU score to evaluate the generated HA protein of the antigenic variant of influenza virus A against the actual variant, the proposed model achieved a mean accuracy of 97.57%.

Interlaboratory Reproducibility of Standardized Hemagglutination Inhibition Assays

The hemagglutination inhibition (HI) assay is a prominent and commonly accepted method used to determine quantitative antibody titers for influenza virus. However, the reproducibility and consistency of this assay may be affected by several factors, including its reliance on biological reagents that are difficult to standardize, such as red blood cells. This report assesses HI assay performance across three accredited, global laboratories when using test virus and a human serum panel aliquoted and distributed from a centrally located reagent stock. The panel of human sera comprised samples with expected low, medium, and high HI titers against two influenza viruses: A/H1N1/California/07/2009 and B/Victoria/Brisbane/60/2008. HI analysis followed a consensus test protocol. Overall, the HI assay reproducibility within each laboratory was high for both influenza strains, with a within-assay run and intraday precision of 100%. Interlab reproducibility was assessed by comparing the geometric mean titer (GMT) of each sample at each laboratory to the consensus GMT of the sample. A/H1N1 had 100% interlab reproducibility, and none of the individual laboratory GMT values exceeded a 2-fold difference compared to the consensus GMT in any tested sample. B/Victoria had an overall reproducibility of 83%. The results demonstrate that with standardization of key reagents and the use of a common protocol by trained staff, the biologically based HI assay can provide similar results between geographically dispersed laboratories. IMPORTANCE Licensure of influenza vaccines relies on the hemagglutination inhibition (HI) assay as the primary method to determine quantitative functional antibody titers. The HI assay is also widely used for influenza virus surveillance, characterization, and epidemiology studies. However, the HI assay has a notable lack of reproducibility and consistency. If serology results are required from multiple concurrent studies supporting the development and regulatory approval of a product, the testing capacity of any given testing laboratory may be exceeded and data from more than one testing laboratory included in regulatory filings. Thus, understanding the reproducibility of HI assay results over time and between testing laboratories is necessary to support a robust clinical trial serology data set. Our results demonstrate that with standardization of key reagents and use of a common protocol by experienced and trained staff, the biologically based HI assay can provide similar results between geographically dispersed laboratories.

Impaired Memory B-Cell Response to Influenza Immunization in Patients With Common Variable Immunodeficiency (CVID)

Background:

Common variable immunodeficiency (CVID) is a heterogeneous primary immunodeficiency characterized by low serum antibody levels and recurrent infections. The cellular response to immunization in patients with CVID has not been fully investigated. In this study, we aimed to characterize vaccination-induced influenza-specific memory B-cell responses in CVID.

Methods:

Eleven individuals affected with CVID and 9 unaffected control individuals were immunized with the 2010-2011 non-adjuvanted seasonal influenza vaccine. Blood samples were collected on the day of vaccination and at week 8 and week 16 after vaccination, and PBMCs were immunophenotyped by flow cytometry. Influenza specific serology was determined using hemagglutination inhibition and microneutralization against vaccine antigens. Influenza-specific memory B-cell responses were determined by ELISpot.

Results:

Individuals with CVID showed wide variability in the frequency of CD19+ B cells in blood. The CVID group had significantly reduced frequencies of CD19+CD27+ memory B cells. Frequencies of circulating T follicular helper (CD4+CXCR5+) cells were similar between those with CVID and healthy controls. In terms of serology, compared to healthy controls, the CVID group overall showed significantly reduced boosting to vaccine antigens by hemagglutination inhibition and microneutralization assays at 8 weeks compared to controls and failed to maintain responses by 16 weeks compared to controls, resulting in a post-vaccination geometric mean titer (GMT) ≥ 40 to strain A/H1N1 in only 27% at 8 weeks, and 22% at 12 weeks for patients with CVID vs 78% and 75%, respectively for healthy controls. In addition, there was a GMT ≥ 40 to A/H3N2 in only 9% at 8 weeks and 22% at 12 weeks for patients with CVID vs 56% and 50%, respectively for healthy controls. Healthy participants showed significant increases in flu-specific IgM-secreting memory B cells after vaccination, whereas patients with CVID showed non-signifi-cant mild increases. Before vaccination, patients with CVID had significantly lower frequencies of background level influenza-specific IgG and IgA memory B cells. Half of the patients with CVID showed an increase in influenza-specific IgG-secreting memory B cells post vaccination, whereas the other half showed none. All control participants exhibited an increase in influenza-specific IgG-secreting B cells. None of the patients with CVID developed influenza-specific IgA memory B-cell response post vaccination, compared to 5/8 in healthy controls. At week 16, the frequency of influenza-specific memory B-cell responses decayed but to non-zero baseline in healthy controls and to zero baseline in patients with CVID.

Conclusions:

Together, these data demonstrate that patients with CVID respond heterogeneously, but as a group poorly, to non-adjuvanted influenza vaccine, with a subgroup unable to generate influenza-specific memory B-cell responses. No patient with CVID was able to maintain memory response for prolonged periods. Together, our results suggest a defect in Ig class switching and memory B-cell maintenance in patients with CVID during a de novo vaccine immune response.

The Standardization and Control of Serology and Nucleic Acid Testing for Infectious Diseases

Historically, the detection of antibodies against infectious disease agents was achieved using test systems that utilized biological functions such as neutralization, complement fixation, hemagglutination, or visualization of binding of antibodies to specific antigens, by testing doubling dilutions of the patient sample to determine an endpoint. These test systems have since been replaced by automated platforms, many of which have been integrated into general medical pathology. Methods employed to standardize and control clinical chemistry testing have been applied to these serology tests. However, there is evidence that these methods are not suitable for infectious disease serology. An overriding reason is that, unlike testing for an inert chemical, testing for specific antibodies to infectious disease agents is highly variable; the measurand for each test system varies in choice of antigen, antibody classes/subclasses, modes of detection, and assay kinetics, and individuals' immune responses vary with time after exposure, individual immune-competency, nutrition, treatment, and exposure to variable circulating sero- or genotypes or organism mutations. Therefore, unlike that of inert chemicals, the quantification of antibodies cannot be standardized using traditional methods. However, there is evidence that the quantification of nucleic acid testing, reporting results in international units, has been successful across many viral load tests. Similarly, traditional methods used to control clinical chemistry testing, such as Westgard rules, are not appropriate for serology testing for infectious diseases, mainly due to variability due to frequent reagent lot changes. This review investigates the reasons why standardization and control of infectious diseases should be further investigated and more appropriate guidelines should be implemented.

Enhancing influenza vaccine immunogenicity and efficacy through infection mimicry using silk microneedles

Traditional bolus vaccine administration leads to rapid clearance of vaccine from lymphoid tissue. However, there is increasing evidence suggesting that the kinetics of antigen delivery can impact immune responses to vaccines, particularly when tailored to mimic natural infections. Here, we present the specific enhancements sustained release immunization confers to seasonal influenza vaccine, including the magnitude, durability, and breadth of humoral responses. To achieve sustained vaccine delivery kinetics, we have developed a microneedle array patch (MIMIX), with silk fibroin-formulated vaccine tips designed to embed in the dermis after a short application to the skin and release antigen over 1-2 weeks, mimicking the time course of a natural influenza infection. In a preclinical murine model, a single influenza vaccine administration via MIMIX led to faster seroconversion, response-equivalence to prime-boost bolus immunization, higher HAI titers against drifted influenza strains, and improved protective efficacy upon lethal influenza challenge when compared with intramuscular injection. These results highlight infection mimicry, achieved through sustained release silk microneedles, as a powerful approach to improve existing seasonal influenza vaccines, while also suggesting the broader potential of this platform technology to enable more efficacious next-generation vaccines and vaccine combinations.

Assay Harmonization and Use of Biological Standards To Improve the Reproducibility of the Hemagglutination Inhibition Assay: a FLUCOP Collaborative Study

The hemagglutination inhibition (HAI) assay is an established technique for assessing influenza immunity, through measurement of antihemagglutinin antibodies. Improved reproducibility of this assay is required to provide meaningful data across different testing laboratories. This study assessed the impact of harmonizing the HAI assay protocol/reagents and using standards on interlaboratory variability. Human pre- and postvaccination sera from individuals (n = 30) vaccinated against influenza were tested across six laboratories. We used a design of experiment (DOE) method to evaluate the impact of assay parameters on interlaboratory HAI assay variability. Statistical and mathematical approaches were used for data analysis. We developed a consensus protocol and assessed its performance against in-house HAI testing. We additionally tested the performance of several potential biological standards. In-house testing with four reassortant viruses showed considerable interlaboratory variation (geometric coefficient of variation [GCV] range of 50% to 117%). The age, concentration of turkey red blood cells, incubation duration, and temperature were key assay parameters affecting variability. Use of a consensus protocol with common reagents, including viruses, significantly reduced GCV between laboratories to 22% to 54%. Pooled postvaccination human sera from different vaccination campaigns were effective as biological standards. Our results demonstrate that the harmonization of protocols and critical reagents is effective in reducing interlaboratory variability in HAI assay results and that pools of postvaccination human sera have potential as biological standards that can be used over multiple vaccination campaigns. Moreover, the use of standards together with in-house protocols is as potent as the use of common protocols and reagents in reducing interlaboratory variability.

IMPORTANCE The hemagglutination inhibition (HAI) assay is the most commonly used serology assay to detect antibodies from influenza vaccination or influenza virus infection. This assay has been used for decades but requires improved standardization of procedures to provide meaningful data. We designed a large study to assess selected parameters for their contribution to assay variability and developed a standard protocol to promote consistent HAI testing methods across laboratories. The use of this protocol and common reagents resulted in lower levels of variability in results between participating laboratories than achieved using in-house HAI testing. Human sera sourced from vaccination campaigns over several years, and thus including antibody to different influenza vaccine strains, served as effective assay standards. Based on our findings, we recommend the use of a common protocol and/or human serum standards, if available, for testing human sera for the presence of antibodies against seasonal influenza using turkey red blood cells.

Vaccine Considerations for Multiple Sclerosis in the COVID-19 Era

People with multiple sclerosis (MS) are at risk for infections that can result in amplification of baseline symptoms and possibly trigger clinical relapses. Vaccination can prevent infection through the activation of humoral and cellular immune responses. This is particularly pertinent in the era of emerging novel vaccines against severe acute respiratory syndrome coronavirus 2, the virus that causes coronavirus disease 2019 (COVID-19). MS disease-modifying therapies (DMTs), which affect the immune system, may impact immune responses to COVID-19 vaccines in people with MS. The objective of this article is to provide information on immune system responses to vaccinations and review previous studies of vaccine responses in people with MS to support the safety and importance of receiving currently available and emerging COVID-19 vaccines. Immunological studies have shown that coordinated interactions between T and B lymphocytes of the adaptive immune system are key to successful generation of immunological memory and production of neutralizing antibodies following recognition of vaccine antigens by innate immune cells. CD4+ T cells are essential to facilitate CD8+ T cell and B cell activation, while B cells drive and sustain T cell memory. Data suggest that some classes of DMT, including type 1 interferons and glatiramer acetate, may not significantly impair the response to vaccination. DMTs-such as sphingosine-1-phosphate receptor modulators, which sequester lymphocytes from circulation; alemtuzumab; and anti-CD20 therapies, which rely on depleting populations of immune cells-have been shown to attenuate responses to conventional vaccines. Currently, three COVID-19 vaccines have been granted emergency use authorization in the USA on the basis of promising interim findings of ongoing trials. Because analyses of these vaccines in people with MS are not available, decisions regarding COVID-19 vaccination and DMT choice should be informed by data and expert consensus, and personalized with considerations for disease burden, risk of infection, and other factors.

Detection of Viruses and Virus-Neutralizing Antibodies Using Synthetic Erythrocytes: Toward a Tuneable Tool for Virus Surveillance

The hemagglutination inhibition assay (HAI) is a classical method used worldwide in many analytical applications, including pathogen identification, vaccine production monitoring, and detection and characterization of pathogen-neutralizing antibodies (n-Ab). This is also a World Health Organization (WHO) reference method for the global surveillance of influenza viruses, which provides the information needed for the annual reformulation of the flu vaccine. HAI is a simple and inexpensive method that is performed without sophisticated equipment. However, it has to be carried out with fresh red blood cells (RBCs), a highly variable, unstable, and hard to mass-produce reagent, which impairs assay reproducibility. Here, we used the tests employed for influenza surveillance as a model to develop synthrocytes^©, a synthetic reagent that could substitute animal erythrocytes in HAI. Contrary to previous examples exploiting sophisticated production paths to generate therapeutic synthetic RBCs, we founded production on the identification of microparticles able to generate different sedimentation patterns when agglutinated or not, which is the main requirement for HAI testing. Upon incorporation of influenza-binding receptors and optimization of production and assay conditions, synthrocytes succeeded in binding influenza A(H1N1) and B viruses as erythrocytes do, but were faster and more stable. Synthrocytes were finally employed in an HAI-like assay to detect the WHO reference reagents for influenza surveillance. Our results show that it is possible to substitute erythrocytes in classical HAI by a highly tuneable and potentially mass-produced synthetic reagent, which should facilitate worldwide HAI standardization with minimal equipment or training requirements.

Meeting report: Convening on the influenza human viral challenge model for universal influenza vaccines, Part 1: Value; challenge virus selection; regulatory, industry and ethical considerations; increasing standardization, access and capacity

In response to global interest in the development of a universal influenza vaccine, the Bill & Melinda Gates Foundation, PATH, and the Global Funders Consortium for Universal Influenza Vaccine Development convened a meeting of experts (London, UK, May 2018) to assess the role of a standardized controlled human influenza virus infection model (CHIVIM) towards the development of novel influenza vaccine candidates. This report (in two parts) summarizes those discussions and offers consensus recommendations. This article (Part 1) covers challenge virus selection, regulatory and ethical considerations, and issues concerning standardization, access, and capacity. Part 2 covers specific methodologic considerations.

Current methods for influenza vaccine development and licensure require large costly field trials. The CHIVIM requires fewer subjects and the controlled setting allows for better understanding of influenza transmission and host immunogenicity. The CHIVIM can be used to identify immune predictors of disease for at-risk populations and to measure efficacy of potential vaccines for further development.

Limitations to the CHIVIM include lack of standardization, limited access to challenge viruses and assays, lack of consensus regarding role of the CHIVIM in vaccine development pathway, and concerns regarding risk to study participants and community. To address these issues, the panel of experts recommended that WHO and other key stakeholders provide guidance on standardization, challenge virus selection, and risk management. A common repository of well-characterized challenge viruses, harmonized protocols, and standardized assays should be made available to researchers. A network of research institutions performing CHIVIM trials should be created, and more study sites are needed to increase capacity.

Experts agreed that a research network of institutions working with a standardized CHIVIM could contribute important data to support more rapid development and licensure of novel vaccines capable of providing long-lasting protection against seasonal and pandemic influenza strains.

Effects of MS disease-modifying therapies on responses to vaccinations: A review

BACKGROUND

Development of long-term immunologic memory relies upon humoral and cellular immune responses. Vaccinations aim to stimulate these responses against pathogens. Several studies have evaluated the impact of multiple sclerosis disease-modifying therapies on immune response to vaccines. Findings from these studies have important implications for people with multiple sclerosis who require vaccination and are using disease-modifying therapies.

METHODS

Searches using PubMed and other engines were conducted in May 2020 to collect studies evaluating the impact of various disease-modifying therapies on immune responses to vaccination.

RESULTS

Several studies demonstrated preserved immune responses in people treated with beta-interferons to multiple vaccine types. Limited data suggest vaccine responses to be preserved with dimethyl fumarate treatment, as well. Vaccine responses were reduced to varying degrees in those treated with glatiramer acetate, teriflunomide, sphingosine-1-phosphate receptor modulators, and natalizumab. The timing of vaccination played an important role in those treated with alemtuzumab. Humoral vaccine responses were significantly impaired by B cell depleting anti-CD20 monoclonal antibody therapies, particularly to a neoantigen. Data are lacking on vaccine responses in patients with multiple sclerosis taking cladribine and high-dose corticosteroids. Notably, the majority of these studies have focused on humoral responses, with few examining cellular immune responses to vaccination.

CONCLUSIONS

Prior investigations into the effects of individual disease-modifying therapies on immune responses to existing vaccines can serve as a guide to expected responses to a SARS-CoV-2 vaccine. Responses to any vaccination depend on the vaccine type, the type of response (recall versus response to a novel antigen), and the impact of the individual disease-modifying therapy on humoral and cellular immunity in response to that vaccine type. When considering a given therapy, clinicians should weigh its efficacy against MS for the individual patient versus potential impact on responses to vaccinations that may be needed in the future.

Immunogenicity and Safety of an MF59-adjuvanted Quadrivalent Seasonal Influenza Vaccine in Young Children at High Risk of Influenza-associated Complications: A Phase III, Randomized, Observer-blind, Multicenter Clinical Trial

BACKGROUND

Vaccination against seasonal influenza is recommended for all children with a history of medical conditions placing them at increased risk of influenza-associated complications. The immunogenicity and efficacy of conventional influenza vaccines among young children are suboptimal; one strategy to enhance these is adjuvantation. We present immunogenicity and safety data for an MF59-adjuvanted quadrivalent influenza vaccine (aIIV4) in healthy children and those at a high risk of influenza-associated complications, based on the results of a recently completed phase III study.

METHODS

Children 6 months to 5 years of age (N = 10,644) were enrolled. The study was conducted across northern hemisphere seasons 2013-2014 and 2014-2015. Subjects received either aIIV4 or a nonadjuvanted comparator influenza vaccine. Antibody responses were assessed by hemagglutination inhibition assay against vaccine and heterologous strains. Long-term antibody persistence was assessed (ClinicalTrials.gov: NCT01964989).

RESULTS

aIIV4 induced significantly higher antibody titers than nonadjuvanted vaccine in high-risk subjects. aIIV4 antibody responses were of similar magnitude in high-risk and healthy subjects. Incidence of solicited local and systemic adverse events (AEs) was slightly higher in aIIV4 than nonadjuvanted vaccinees, in both the healthy and high-risk groups. Incidence of unsolicited AEs, serious AEs and AEs of special interest were similar for adjuvanted and nonadjuvanted vaccinees in the healthy and high-risk groups.

CONCLUSION

aIIV4 was more immunogenic than nonadjuvanted vaccine in both the healthy and high-risk study groups. The reactogenicity and safety profiles of aIIV4 and the nonadjuvanted vaccine were acceptable and similar in 6-month- to 5-year-old high-risk and healthy children.

Harnessing the potential of blood donation archives for influenza surveillance and control

Many blood donation services around the globe maintain large archives of serum and/or plasma specimens of blood donations which could potentially be used for serologic surveillance and risk assessment of influenza. Harnessing this potential requires robust evidence that the outcomes of influenza serology in plasma, which is rarely used, is consistent with that in serum, which is the conventional choice of specimens for influenza serology. We harvested EDTA-plasma specimens from the blood donation archives of Hong Kong Red Cross Transfusion Services, where EDTA is the type of anticoagulant used for plasma collection, compared their antibody titers and responses to that in serum. Influenza A/H1N1/California/7/2009 and A/H3N2/Victoria/208/2009 were the test strains. Our results showed that antibody titers in 609 matched serum/EDTA-plasma specimens (i.e. obtained from the same donor at the same time) had good agreement inferred by Intraclass Correlation Coefficient, the value of which was 0.82 (95% CI: 0.77-0.86) for hemagglutination inhibition assay and 0.95 (95% CI: 0.93-0.96) for microneutralization assay; seroconversion rates (based on hemagglutination inhibition titers) during the 2010 and 2011 influenza seasons in Hong Kong inferred from paired EDTA-plasma were similar to that inferred from paired sera. Our study provided the proof-of-concept that blood donation archives could be leveraged as a valuable source of longitudinal blood specimens for the surveillance, control and risk assessment of both pandemic and seasonal influenza.

Big Is Beautiful: Enhanced saRNA Delivery and Immunogenicity by a Higher Molecular Weight, Bioreducible, Cationic Polymer

Self-amplifying RNA (saRNA) vaccines are highly advantageous, as they result in enhanced protein expression compared to mRNA (mRNA), thus minimizing the required dose. However, previous delivery strategies were optimized for siRNA or mRNA and do not necessarily deliver saRNA efficiently due to structural differences of these RNAs, thus motivating the development of saRNA delivery platforms. Here, we engineer a bioreducible, linear, cationic polymer called "pABOL" for saRNA delivery and show that increasing its molecular weight enhances delivery both in vitro and in vivo. We demonstrate that pABOL enhances protein expression and cellular uptake via both intramuscular and intradermal injection compared to commercially available polymers in vivo and that intramuscular injection confers complete protection against influenza challenge. Due to the scalability of polymer synthesis and ease of formulation preparation, we anticipate that this polymer is highly clinically translatable as a delivery vehicle for saRNA for both vaccines and therapeutics.

Universal Influenza Vaccine Approaches Using Full-Length or Head-Only Hemagglutinin Proteins

There is currently an unmet need to develop an effective broadly reactive or universal vaccine against influenza viruses capable of conferring protection against both seasonal and prepandemic strains. Influenza vaccines elicit immune responses that are protective against antigenically similar viruses within a subtype. These vaccines elicit antibodies that target the surface viral glycoproteins hemagglutinin and neuraminidase. If there is an antigenic mismatch between these proteins in the influenza vaccines and cocirculating influenza isolates, there is a decrease in the vaccine effectiveness in vaccinated persons. Various novel influenza vaccine candidates are being evaluated in animal studies and clinical human trials. This article focuses on the advantages and potential shortcomings of broadly reactive or universal vaccine candidates based on the hemagglutinin globular head and the thoughts about using this antigen as the basis for future influenza vaccine strategies.

An open source tool to infer epidemiological and immunological dynamics from serological data: serosolver

We present a flexible, open source R package designed to obtain biological and epidemiological insights from serological datasets. Characterising past exposures for multi-strain pathogens poses a specific statistical challenge: observed antibody responses measured in serological assays depend on multiple unobserved prior infections that produce cross-reactive antibody responses. We provide a general modelling framework to jointly infer infection histories and describe immune responses generated by these infections using antibody titres against current and historical strains. We do this by linking latent infection dynamics with a mechanistic model of antibody kinetics that generates expected antibody titres over time. Our aim is to provide a flexible package to identify infection histories that can be applied to a range of pathogens. We present two case studies to illustrate how our model can infer key immunological parameters, such as antibody titre boosting, waning and cross-reaction, as well as latent epidemiological processes such as attack rates and age-stratified infection risk.

Comparison of influenza-specific neutralizing antibody titers determined using different assay readouts and hemagglutination inhibition titers: good correlation but poor agreement

Determination of influenza-specific antibody titers is commonly done using the hemagglutination inhibition assay (HAI) and the viral microneutralization assay (MN). Both assays are characterized by high intra- and inter-laboratory variability. The HAI assay offers little opportunity for standardization. For the MN assay, variability might be due to the use of different assay protocols employing different readouts. We therefore aimed at investigating which of the MN assay readout methods currently in use would be the most suitable choice for a standardized MN assay that could serve as a substitute for the HAI assay. For this purpose, human serum samples were tested for the presence of influenza specific neutralizing antibodies against A/California/7/09 H1N1 (49 sera) or A/Hong Kong/4801/2014 (50 sera) using four different infection readout methods for the MN assay (cytopathic effect, hemagglutination, ELISA, RT qPCR) and using the HAI assay. The results were compared by correlation analysis and by determining the level of agreement before and after normalization to a standard serum. Titers as measured by the 4 MN assay readouts showed good correlation, with high Person's r for most comparisons. However, agreement between nominal titers varied with readouts compared and virus strain used. In addition, Pearson's correlation of MN titers with HAI titers was high but agreement of nominal titers was moderate and the average difference between the readings of two assays (bias) was virus strain-dependent. Normalization to a standard serum did not result in better agreement of assay results. Our study demonstrates that different MN readouts result in nominally different antibody titers. Accordingly, the use of a common and standardized MN assay protocol will be crucial to minimize inter-laboratory variability. Based on reproducibility, cost effectiveness and unbiased assessment of results we elected the MN assay with ELISA readout as most suitable for a possible replacement of the HAI assay.

Detection methods for influenza A H1N1 virus with special reference to biosensors: a review

H1N1 (Swine flu) is caused by influenza A virus, which is a member of Orthomyxoviridae family. Transmission of H1N1 occurs from human to human through air or sometimes from pigs to humans. The influenza virus has different RNA segments, which can reassert to make new virus strain with the possibility to create an outbreak in unimmunized people. Gene reassortment is a process through which new strains are emerging in pigs, as it has specific receptors for both human influenza and avian influenza viruses. H1N1 binds specifically with an α-2,6 glycosidic bond, which is present in human respiratory tract cells as well as in pigs. Considering the fact of fast multiplication of viruses inside the living cells, rapid detection methods need an hour. Currently, WHO recommended methods for the detection of swine flu include real-time PCR in specific testing centres that take 3-4 h. More recently, a number of methods such as Antigen-Antibody or RT-LAMP and DNA biosensors have also been developed that are rapid and more sensitive. This review describes the various challenges in the diagnosis of H1N1, and merits and demerits of conventional vis-à-vis latest methods with special emphasis on biosensors.

Hemagglutination Inhibition Assay

The hemagglutination inhibition (HI) assay for influenza A virus has been used since the 1940s. The assay may be utilized to detect or quantify antibodies to influenza A viruses and can be used to characterize differences in antigenic reactivity between influenza isolates. In addition, data from HI assays are routinely used for antigenic cartography, influenza virus surveillance, epidemiology, and vaccine-seed strain selection. For antibody quantification, the HI assay is a fast and inexpensive method; other than a source of red blood cells, no expensive or unusual lab equipment is needed, and results can be obtained within a few hours. Historically, the HI assay has also served as a primary method of subtype identification and is still used widely. However, as gene sequencing technology has evolved to be cheaper and faster, it is replacing the HI assay for this purpose.

Immunogenicity and safety of high-dose versus standard-dose inactivated influenza vaccine in rheumatoid arthritis patients: a randomised, double-blind, active-comparator trial

BACKGROUND

Patients with rheumatoid arthritis have increased risk of seasonal influenza and influenza-related complications but have reduced vaccine immunogenicity. It is unknown whether patients with rheumatoid arthritis would benefit from more immunogenic vaccine formulations. This study investigated the immunogenicity and safety of a high-dose trivalent inactivated influenza vaccine (HD-TIV) in patients with rheumatoid arthritis compared to a standard-dose quadrivalent influenza vaccine (SD-QIV).

METHODS

This study was a treatment-stratified, randomised, double-blind trial to compare the immunogenicity and safety of SD-QIV (15 μg of haemagglutinin [HA] per strain) versus HD-TIV (60 μg of HA per strain) in adults with rheumatoid arthritis who are positive for rheumatoid factor or anti-cyclic citrullinated peptide, or both, recruited during the 2016-17 and 2017-18 influenza seasons at three hospitals affiliated with McGill University (Montreal, QC, Canada). Participants had received treatment for rheumatoid arthritis with conventional or targeted synthetic disease-modifying antirheumatic drugs (DMARDs) or biological DMARDs, or combinations of them, were still on treatment at the time of enrolment, and their treatment had not been modified during the 3 months before enrolment. They were stratified into one of three groups according to treatment. Patients who, at enrolment, were taking conventional or targeted synthetic DMARDs (methotrexate, hydroxychloroquine, and sulfasalazine) as monotherapy or in combination were stratified to group 1; those who were taking a biological DMARD (anti-tumour necrosis factor or anti-interleukin 6), with or without methotrexate, hydroxychloroquine, or sulfasalazine (or a combination thereof) were stratified to group 2; and those who were taking abatacept, tofacitinib, or rituximab, with or without methotrexate, hydroxychloroquine, or sulfasalazine (or a combination thereof) were stratified to group 3. Participants were randomly allocated (1:1) to receive the SD-QIV or HD-TIV vaccine. Randomisation was based on a computer-generated allocation sequence, and participants, investigators, and research nurses responsible for safety assessments were masked to vaccine assignment. The primary outcome was the seroconversion rate (as measured by haemagglutination-inhibition assay) per strain at day 28. Analysis was done in the modified intention-to-treat population, which included all randomly assigned participants for whom seroconversion status was available. Safety was assessed throughout the surveillance period (day 0-186). This trial is registered at ClinicalTrials.gov, number NCT02936180.

FINDINGS

Between Oct 24, 2016, and Dec 6, 2017, 696 patients with rheumatoid arthritis were invited to participate in the study and 279 were randomly assigned and vaccinated (140 [50%] received SD-QIV and 139 [50%] HD-TIV). 136 patients who received SD-QIV and 138 who received HD-TIV were included in the modified intention-to-treat anaysis. Patients who received HD-TIV were more likely to seroconvert than those who received SD-QIV: the odds ratio was 2·99 (95% CI 1·46-6·11) for seroconversion to strain A/H3N2, 1·95 (1·19-3·22) for seroconversion to strain B/Bris, 3·21 (1·57-6·56) for seroconversion to strain A/H1N1 (in 2016-2017), and 2·44 (1·18-5·06) for seroconversion to strain A/H1N1 (in 2017-2018). Similar results were observed in patients from groups 1 and 2; the number of individuals in group 3 was insufficient to draw conclusions. Local and systemic adverse events were similar in both vaccine groups, no serious adverse events were reported between days 0 and 28 in any group, and neither vaccine increased rheumatoid arthritis disease activity.

INTERPRETATION

Our data suggest that in patients with seropositive rheumatoid arthritis, HD-TIV is safe and more immunogenic than SD-QIV. These results are the first evidence to support the use of the HD-TIV in these patients.

FUNDING

The Arthritis Society-Canada.

Immunogenicity of Influenza Vaccination in Patients with Cancer Receiving Immune Checkpoint Inhibitors

Among prospectively enrolled adult patients with cancer receiving immune checkpoint inhibitors (ICIs; n = 46) or cytotoxic agents (n = 90), seroprotection and seroconversion rates after seasonal quadrivalent influenza vaccinations were higher with ICI than with cytotoxic chemotherapy. These results support annual influenza vaccinations for cancer patients receiving ICIs.

Clinical Trials Registration clinicaltrials.gov (NCT03590808).

Improving immunological insights into the ferret model of human viral infectious disease

Ferrets are a well-established model for studying both the pathogenesis and transmission of human respiratory viruses and evaluation of antiviral vaccines. Advanced immunological studies would add substantial value to the ferret models of disease but are hindered by the low number of ferret-reactive reagents available for flow cytometry and immunohistochemistry. Nevertheless, progress has been made to understand immune responses in the ferret model with a limited set of ferret-specific reagents and assays. This review examines current immunological insights gained from the ferret model across relevant human respiratory diseases, with a focus on influenza viruses. We highlight key knowledge gaps that need to be bridged to advance the utility of ferrets for immunological studies.

An Influenza Virus Hemagglutinin-Based Vaccine Platform Enables the Generation of Epitope Specific Human Cytomegalovirus Antibodies

Human cytomegalovirus (CMV) is a highly prevalent pathogen with ~60%–90% seropositivity in adults. CMV can contribute to organ rejection in transplant recipients and is a major cause of birth defects in newborns. Currently, there are no approved vaccines against CMV. The epitope of a CMV neutralizing monoclonal antibody against a conserved region of the envelope protein gH provided the basis for a new CMV vaccine design. We exploited the influenza A virus as a vaccine platform due to the highly immunogenic head domain of its hemagglutinin envelope protein. Influenza A variants were engineered by reverse genetics to express the epitope of an anti-CMV gH neutralizing antibody that recognizes native gH into the hemagglutinin antigenic Sa site. We determined that the recombinant influenza variants expressing 7, 10, or 13 residues of the anti-gH neutralizing antibody epitope were recognized and neutralized by the anti-gH antibody 10C10. Mice vaccinated with the influenza/CMV chimeric viruses induced CMV-specific antibodies that recognized the native gH protein and inhibited virus infection. In fact, the influenza variants expressing 7–13 gH residues neutralized a CMV infection at ~60% following two immunizations with variants expressing the 13 residue gH peptide produced the highest levels of neutralization. Collectively, our study demonstrates that a variant influenza virus inserted with a gH peptide can generate a humoral response that limits a CMV infection.

Human megakaryocytes possess intrinsic antiviral immunity through regulated induction of IFITM3

Evolving evidence indicates that platelets and megakaryocytes (MKs) have unexpected activities in inflammation and infection; whether viral infections upregulate biologically active, antiviral immune genes in platelets and MKs is unknown, however. We examined antiviral immune genes in these cells in dengue and influenza infections, viruses that are global public health threats. Using complementary biochemical, pharmacological, and genetic approaches, we examined the regulation and function of interferon-induced transmembrane protein 3 (IFITM3), an antiviral immune effector gene not previously studied in human platelets and MKs. IFITM3 was markedly upregulated in platelets isolated from patients during clinical influenza and dengue virus (DENV) infections. Lower IFITM3 expression in platelets correlated with increased illness severity and mortality in patients. Administering a live, attenuated DENV vaccine to healthy subjects significantly increased platelet IFITM3 expression. Infecting human MKs with DENV selectively increased type I interferons and IFITM3. Overexpression of IFITM3 in MKs was sufficient to prevent DENV infection. In naturally occurring, genetic loss-of-function studies, MKs from healthy subjects harboring a homozygous mutation in IFITM3 (rs12252-C, a common single-nucleotide polymorphism in areas of the world where DENV is endemic) were significantly more susceptible to DENV infection. DENV-induced MK secretion of interferons prevented infection of bystander MKs and hematopoietic stem cells. Thus, viral infections upregulate IFITM3 in human platelets and MKs, and IFITM3 expression is associated with adverse clinical outcomes. These observations establish, for the first time, that human MKs possess antiviral functions, preventing DENV infection of MKs and hematopoietic stem cells after local immune signaling.

MF59-adjuvanted seasonal trivalent inactivated influenza vaccine: Safety and immunogenicity in young children at risk of influenza complications

OBJECTIVE

To assess the safety and immunogenicity of the MF59-adjuvanted seasonal trivalent inactivated influenza vaccine (aIIV3; Fluad) in children aged 6 months through 5 years who are at risk of influenza complications.

METHODS

A retrospective analysis was performed to examine unsolicited adverse events (AEs) in an integrated dataset from six randomized clinical studies that compared aIIV3 with non-adjuvanted inactivated influenza vaccines (IIV3). The integrated safety set comprised 10 784 children, of whom 373 (3%) were at risk of influenza complications.

RESULTS

The at-risk safety population comprised 373 children aged 6 months through 5 years: 179 received aIIV3 and 194 received non-adjuvanted IIV3 (128 subjects received a licensed IIV3). The most important risk factors were respiratory system illnesses (62-70%) and infectious and parasitic diseases (33-39%). During the treatment period, unsolicited AEs occurred in 54% of at-risk children and 55% of healthy children who received aIIV3; of those receiving licensed IIV3, 59% of at-risk and 62% of healthy subjects reported an unsolicited AE. The most common AEs were infections, including upper respiratory tract infection. Serious AEs (SAEs) were reported in <10% of at-risk subjects, and no vaccine-related SAEs were observed. In the immunogenicity subset (involving 103 participants from one study), geometric mean titers (GMTs) were approximately 2- to 3-fold higher with aIIV3 than with IIV3 for all three homologous strains (A/H1N1, A/H3N2, and B). Seroconversion rates were high for both aIIV3 (79-96%) and IIV3 (83-89%).

CONCLUSIONS

In young children at risk of influenza complications, aIIV3 was well-tolerated and had a safety profile that was generally similar to that of non-adjuvanted IIV3. Similar to the not-at-risk population, the immune response in at-risk subjects receiving aIIV3 was increased over those receiving IIV3, suggesting aIIV3 is a valuable option in young children at risk of influenza complications.

Predicting antigenic variants of H1N1 influenza virus based on epidemics and pandemics using a stacking model

H1N1 is the earliest emerging subtype of influenza A viruses with available genomic sequences, has caused several pandemics and seasonal epidemics, resulting in millions of deaths and enormous economic losses. Timely determination of new antigenic variants is crucial for the vaccine selection and flu prevention. In this study, we chronologically divided the H1N1 strains into several periods in terms of the epidemics and pandemics. Computational models have been constructed to predict antigenic variants based on epidemic and pandemic periods. By sequence analysis, we demonstrated the diverse mutation patterns of HA1 protein on different periods and that an individual model built upon each period can not represent the variations of H1N1 virus. A stacking model was established for the prediction of antigenic variants, combining all the variation patterns across periods, which would help assess a new influenza strain’s antigenicity. Three different feature extraction methods, i.e. residue-based, regional band-based and epitope region-based, were applied on the stacking model to verify its feasibility and robustness. The results showed the capability of determining antigenic variants prediction with accuracy as high as 0.908 which performed better than any of the single models. The prediction performance using the stacking model indicates clear distinctions of mutation patterns and antigenicity between epidemic and pandemic strains. It would also facilitate rapid determination of antigenic variants and influenza surveillance.

Preclinical evaluation of the efficacy of an H5N8 vaccine candidate (IDCDC-RG43A) in mouse and ferret models for pandemic preparedness

Because H5N1 influenza viruses continuously threaten the public health, the WHO has prepared various clades of H5N1 mock-up vaccines as one of the measures for pandemic preparedness. The recent worldwide outbreak of H5Nx virus which belongs to clade 2.3.4.4 and of which H5N6 subtype belongs and already caused human infection also increases the need of pandemic vaccine for such novel emerging viruses. In this study, we evaluated the protective efficacy and immunogenicity of an egg-based and inactivated whole-virus H5N8 (IDCDC-RG43A) developed by CDC containing HA and NA gene of the parent virus A/gyrfalcon/Washington/41088-6/2014. Mice vaccinated two times elicited low to moderate antibody titer in varying amount of antigen doses against the homologous H5N8 vaccine virus and heterologous intra-clade 2.3.4.4 H5N6 (A/Sichuan/26221/2014) virus. Mice immunized with at least 3.0 µg/dose of IDCDC-RG43A with aluminum hydroxide adjuvant were completely protected from lethal challenge with the mouse-adapted H5N8 (A/Environment/Korea/ma468/2015, maH5N8) as well as cleared the viral replication in tissues including lung, brain, spleen, and kidney. Vaccinated ferrets induced high antibody titers against clade 2.3.4.4 H5N8/H5N6 viruses and the antibody showed high cross-reactivity to clade 2.2 H5N1 but not to clade 1 and 2.3.4 viruses as measured by hemagglutinin inhibition and serum neutralization assays. Furthermore, administration of the vaccine in ferrets resulted in attenuation of clinical disease signs and virus spread to peripheral organs including lung, spleen, and kidney from high dose challenge with maH5N8 virus. The protective and immunogenic characteristic of the candidate vaccine are essential attributes to be considered for further clinical trials as a pre-pandemic vaccine for a potential pandemic virus.

Harnessing the Power of T Cells: The Promising Hope for a Universal Influenza Vaccine

Next-generation vaccines that utilize T cells could potentially overcome the limitations of current influenza vaccines that rely on antibodies to provide narrow subtype-specific protection and are prone to antigenic mismatch with circulating strains. Evidence from animal models shows that T cells can provide heterosubtypic protection and are crucial for immune control of influenza virus infections. This has provided hope for the design of a universal vaccine able to prime against diverse influenza virus strains and subtypes. However, multiple hurdles exist for the realisation of a universal T cell vaccine. Overall primary concerns are: extrapolating human clinical studies, seeding durable effective T cell resident memory (Trm), population human leucocyte antigen (HLA) coverage, and the potential for T cell-mediated immune escape. Further comprehensive human clinical data is needed during natural infection to validate the protective role T cells play during infection in the absence of antibodies. Furthermore, fundamental questions still exist regarding the site, longevity and duration, quantity, and phenotype of T cells needed for optimal protection. Standardised experimental methods, and eventually simplified commercial assays, to assess peripheral influenza-specific T cell responses are needed for larger-scale clinical studies of T cells as a correlate of protection against influenza infection. The design and implementation of a T cell-inducing vaccine will require a consensus on the level of protection acceptable in the community, which may not provide sterilizing immunity but could protect the individual from severe disease, reduce the length of infection, and potentially reduce transmission in the community. Therefore, increasing the standard of care potentially offered by T cell vaccines should be considered in the context of pandemic preparedness and zoonotic infections, and in combination with improved antibody vaccine targeting methods. Current pandemic vaccine preparedness measures and ongoing clinical trials under-utilise T cell-inducing vaccines, reflecting the myriad questions that remain about how, when, where, and which T cells are needed to fight influenza virus infection. This review aims to bring together basic fundamentals of T cell biology with human clinical data, which need to be considered for the implementation of a universal vaccine against influenza that harnesses the power of T cells.

Antigenic cartography of H1N1 influenza viruses using sequence-based antigenic distance calculation

BACKGROUND

The ease at which influenza virus sequence data can be used to estimate antigenic relationships between strains and the existence of databases containing sequence data for hundreds of thousands influenza strains make sequence-based antigenic distance estimates an attractive approach to researchers. Antigenic mismatch between circulating strains and vaccine strains results in significantly decreased vaccine effectiveness. Furthermore, antigenic relatedness between the vaccine strain and the strains an individual was originally primed with can affect the cross-reactivity of the antibody response. Thus, understanding the antigenic relationships between influenza viruses that have circulated is important to both vaccinologists and immunologists.

RESULTS

Here we develop a method of mapping antigenic relationships between influenza virus stains using a sequence-based antigenic distance approach (SBM). We used a modified version of the p-all-epitope sequence-based antigenic distance calculation, which determines the antigenic relatedness between strains using influenza hemagglutinin (HA) genetic coding sequence data and provide experimental validation of the p-all-epitope calculation. We calculated the antigenic distance between 4838 H1N1 viruses isolated from infected humans between 1918 and 2016. We demonstrate, for the first time, that sequence-based antigenic distances of H1N1 Influenza viruses can be accurately represented in 2-dimenstional antigenic cartography using classic multidimensional scaling. Additionally, the model correctly predicted decreases in cross-reactive antibody levels with 87% accuracy and was highly reproducible with even when small numbers of sequences were used.

CONCLUSION

This work provides a highly accurate and precise bioinformatics tool that can be used to assess immune risk as well as design optimized vaccination strategies. SBM accurately estimated the antigenic relationship between strains using HA sequence data. Antigenic maps of H1N1 virus strains reveal that strains cluster antigenically similar to what has been reported for H3N2 viruses. Furthermore, we demonstrated that genetic variation differs across antigenic sites and discuss the implications.

Predictive Modeling of Influenza Shows the Promise of Applied Evolutionary Biology

Seasonal influenza is controlled through vaccination campaigns. Evolution of influenza virus antigens means that vaccines must be updated to match novel strains, and vaccine effectiveness depends on the ability of scientists to predict nearly a year in advance which influenza variants will dominate in upcoming seasons. In this review, we highlight a promising new surveillance tool: predictive models. Based on data-sharing and close collaboration between the World Health Organization and academic scientists, these models use surveillance data to make quantitative predictions regarding influenza evolution. Predictive models demonstrate the potential of applied evolutionary biology to improve public health and disease control. We review the state of influenza predictive modeling and discuss next steps and recommendations to ensure that these models deliver upon their considerable biomedical promise.

The establishment of surrogates and correlates of protection: Useful tools for the licensure of effective influenza vaccines?

The search for a test that can predict vaccine efficacy is an important part of any vaccine development program. Although regulators hesitate to acknowledge any test as a true ‘correlate of protection’, there are many precedents for defining ‘surrogate’ assays. Surrogates can be powerful tools for vaccine optimization, licensure, comparisons between products and development of improved products. When such tests achieve ‘reference’ status however, they can inadvertently become barriers to new technologies that do not work the same way as existing vaccines. This is particularly true when these tests are based upon circularly-defined ‘reference’ or, even worse, proprietary reagents. The situation with inactivated influenza vaccines is a good example of this phenomenon. The most frequently used tests to define vaccine-induced immunity are all serologic assays: hemagglutination inhibition (HI), single radial hemolysis (SRH) and microneutralization (MN). The first two, and particularly the HI assay, have achieved reference status and criteria have been established in many jurisdictions for their use in licensing new vaccines and to compare the performance of different vaccines. However, all of these assays are based on biological reagents that are notoriously difficult to standardize and can vary substantially by geography, by chance (i.e. developing reagents in eggs that may not antigenitically match wild-type viruses) and by intention (ie: choosing reagents that yield the most favorable results). This review describes attempts to standardize these assays to improve their performance as surrogates, the dangers of over-reliance on ‘reference’ serologic assays, the ways that manufacturers can exploit the existing regulatory framework to make their products ‘look good’ and the implications of this long-established system for the introduction of novel influenza vaccines.

Randomized Comparison of Immunogenicity and Safety of Quadrivalent Recombinant Versus Inactivated Influenza Vaccine in Healthy Adults 18-49 Years of Age

Background

Seasonal influenza vaccines are transitioning to quadrivalent formulations including the hemagglutinins of influenza A subtypes H1N1 and H3N2 and B lineages Yamagata and Victoria.

Methods

A new quadrivalent recombinant influenza vaccine (RIV4) was compared directly with a standard-dose, egg-grown, quadrivalent-inactivated influenza vaccine (IIV4) for immunogenicity and safety in adults 18-49 years of age. The coprimary endpoints for noninferiority were hemagglutination inhibition seroconversion rates and postvaccination geometric mean titer ratios for each antigen using US regulatory criteria. Reactogenicity solicited for 7 days, other safety events collected for 28 days, and serious or medically attended adverse events collected for 6 months after vaccination comprised the safety evaluation.

Results

The immunogenicity of RIV4 was comparable to that of IIV4; the coprimary noninferiority criteria were met for 3 antigens, and the antibody responses to the fourth antigen, influenza B/Brisbane/60/2008, were low in each group, making comparisons uninterpretable. Systemic and injection site reactions were mild, transient, and similar in each group, whereas none of the spontaneously reported adverse events, serious or nonserious, were considered related to study vaccine.

Conclusions

This first head-to-head comparison of recombinant versus inactivated quadrivalent influenza vaccines in 18-49 year old adults showed comparable immunogenicity, safety, and tolerability for both vaccines.