An Optimized Hemagglutination Inhibition (HI) Assay to Quantify Influenza-specific Antibody Titers

Immunogenicity and biodistribution of lipid nanoparticle formulated self-amplifying mRNA vaccines against H5 avian influenza

This study reports on the immunogenicity and biodistribution of H5 hemagglutinin (HA)-based self-amplifying (sa) mRNA vaccines in mice. Four sa-mRNA vaccines encoding either a secreted full-length HA, a secreted HA head domain, a secreted HA stalk domain, or a full-length membrane-anchored HA were investigated. All vaccines elicited an adaptive immune response. However, the full-length HA sa-RNA vaccines demonstrated superior performance compared to head and stalk domain vaccines. The antibody titers positively correlated with the vaccine dose. Cellular immune responses and antigen-specific IgA antibodies in the lungs were also observed. The comparison of the sa-mRNA vaccines encoding the secreted and membrane-anchored full-length HA revealed that anchoring of the HA to the membrane significantly enhanced the antibody and cellular responses. In addition to the injection site, the intramuscularly injected sa-mRNA-LNPs were also detected in the draining lymph nodes, spleen, and to a lesser extent, in the lung, kidney, liver, and heart.

Immunomodulatory and AntiOxidant Potential of Polyherbal Dhatryadi Rasayana in the Form of Churna and Granules

Dhatryadi Rasayana revitalizes the human body and helps in maintaining health with the elimination of ill effects of various diseases. The effective delivery systems for Rasayana may affect the profound effect of active principles in the body. The present study deals with investigation and evaluation of phytochemical constituents, physicochemical characteristics, along with antioxidant and immunomodulatory effects of Dhatryadi Rasayana in churna (powder) and granule formulations. Dhatryadi Rasayana churna and its granules were studied for various physicochemical parameters, e.g., moisture content, ash-value, acid-insoluble ash content, water-soluble extractive, alcohol-soluble extractive, bulk density, tapped density, angle of repose, Carr's index, Hausner's ratio, total sugar, reducing sugar, non-reducing sugar, heavy metals, total microbial load, etc. In vitro antioxidant potential of Dhatryadi Rasayana churna and its granules was determined by scavenging the DPPH and FRAP assays. The immunomodulatory activities of Dhatryadi Rasayana churna and its granules were studied in Wistar albino rats and the complete blood count (CBC), delayed-type hypersensitivity reaction (DTH), and hemagglutination antibody titer were assessed. Dhatryadi Rasayana churna contained alkaloids (0.50 ± 0.298% w/w), tannins (9.84 ± 1.527% w/w), saponins (4.18 ± 2.126% w/w), and flavonoids (9.34 ± 1.026% w/w), while its granules contained 11.08 ± 2.468% w/w total tannins, 2.40 ± 1.132% w/w alkaloids, and 12.46 ± 2.645% w/w total flavonoids. The DPPH scavenging effect was determined by IC50 (churna - 23.89 μg/mL; granules - 9.33 μg/mL), and the antioxidant capacity assessed by FRAP was 77.0 mmol/100 g equivalent of ascorbic acid for churna and 50 mmol/100 g equivalent of ascorbic acid for granules. Dhatryadi Rasayana churna and its granules reflected a significant immunostimulatory effect on both the cell-mediated and humoral immune systems in Wistar albino rats. Moreover, churna and granules of Dhatryadi Rasayana revealed significant antioxidant and immunomodulatory activities and these may be applied for treating different diseases as well as improving the immunity of the body.

Pandemic H1N1 influenza virus triggers a strong T helper cell response in human nasopharynx-associated lymphoid tissues

The pH1N1 belongs to influenza A family that is sometimes transmitted to humans via contact with pigs. Human tonsillar immune cells are widely used as in vitro models to study responses to influenza viruses. In the current study, human memory (M) and naïve (N) T cells responses in mononuclear cells of tonsil (TMCs) and peripheral blood (PBMCs) were stimulated by pH1N1/sH1N1, and then stained for estimation of T cells proliferation index. Individuals with an anti-pH1N1 hemagglutination (HA) inhibition (HAI) titer of forty or greater exhibited stronger HA-specific M-CD4+ T cells responses to pH1N1 in TMCs/PBMCs than those with an HAI titer of less than forty (P < 0.01). In addition, a positive correlation was observed between proliferation indices of M-CD4+ T cells induced by exposure to sH1N1/pH1N1 (p < 0.01). Moreover, a strong correlation (p < 0.001) was detected between subjects' age and their HA-specific M-CD4+ T cells induced by pH1N1 exposure, indicating that this response was age-dependent. Finally, stimulation of TMCs with pH1N1-HA resulted in a significant M-CD8+ T cells response (p < 0.05). In conclusion, pH1N1 HA elicits a strong M-CD4+ T cells response in TMCs. Additionally, this response correlates with the response to sH1N1 suggesting cross-reactivity in T cells epitopes directed against HAs of both viral strains.

Safety and immunogenicity of influenza A(H3N2) component vaccine in juvenile systemic lupus erythematosus

INTRODUCTION

Seasonal influenza A (H3N2) virus is an important cause of morbidity and mortality in the last 50 years in population that is greater than the impact of H1N1. Data assessing immunogenicity and safety of this virus component in juvenile systemic lupus erythematosus (JSLE) is lacking in the literature.

OBJECTIVE

To evaluate short-term immunogenicity and safety of influenza A/Singapore (H3N2) vaccine in JSLE.

METHODS

24 consecutive JSLE patients and 29 healthy controls (HC) were vaccinated with influenza A/Singapore/INFIMH-16-0019/2016(H3N2)-like virus. Influenza A (H3N2) seroprotection (SP), seroconversion (SC), geometric mean titers (GMT), factor increase in GMT (FI-GMT) titers were assessed before and 4 weeks post-vaccination. Disease activity, therapies and adverse events (AE) were also evaluated.

RESULTS

JSLE patients and controls were comparable in current age [14.5 (10.1-18.3) vs. 14 (9-18.4) years, p = 0.448] and female sex [21 (87.5%) vs. 19 (65.5%), p = 0.108]. Before vaccination, JSLE and HC had comparable SP rates [22 (91.7%) vs. 25 (86.2%), p = 0.678] and GMT titers [102.3 (95% CI 75.0-139.4) vs. 109.6 (95% CI 68.2-176.2), p = 0.231]. At D30, JSLE and HC had similar immune response, since no differences were observed in SP [24 (100%) vs. 28 (96.6%), p = 1.000)], SC [4 (16.7%) vs. 9 (31.0%), p = 0.338), GMT [162.3 (132.9-198.3) vs. 208.1 (150.5-287.8), p = 0.143] and factor increase in GMT [1.6 (1.2-2.1) vs. 1.9 (1.4-2.5), p = 0.574]. SLEDAI-2K scores [2 (0-17) vs. 2 (0-17), p = 0.765] and therapies remained stable throughout the study. Further analysis of possible factors influencing vaccine immune response among JSLE patients demonstrated similar GMT between patients with SLEDAI < 4 compared to SLEDAI ≥ 4 (p = 0.713), as well as between patients with and without current use of prednisone (p = 0.420), azathioprine (p = 1.0), mycophenolate mofetil (p = 0.185), and methotrexate (p = 0.095). No serious AE were reported in both groups and most of them were asymptomatic (58.3% vs. 44.8%, p = 0.958). Local and systemic AE were alike in both groups (p > 0.05).

CONCLUSION

This is the first study that identified adequate immune protection against H3N2-influenza strain with additional vaccine-induced increment of immune response and an adequate safety profile in JSLE. ( www.

CLINICALTRIALS

gov , NCT03540823).

Robust immunogenicity to the H3N2 component of influenza A vaccine in primary Sjögren syndrome

INTRODUCTION

Influenza A (H3N2) virus is the major cause of morbidity/mortality due to seasonal influenza over 50 years. Data about the safety/immunogenicity of influenza A/Singapore (H3N2) vaccine are scarce in primary Sjögren syndrome (pSS).

METHODS

Twenty-one consecutive pSS patients and 42 HC (healthy control individuals) were immunized with influenza A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus. Rates of SP (seroprotection) and SC (seroconversion), GMT (geometric mean titers), FI-GMT (factor increase in GMT), ESSDAI (EULAR Sjögren's Syndrome Disease Activity Index), and adverse events were appraised before and 4 weeks post-vaccination.

RESULTS

pSS and HC had similar mean age (51.2 ± 14.2 vs. 50.6 ± 12.1 years, p = 0.886). Pre-vaccination SP rates were high in pSS and HC (90.5% vs. 71.4%, p = 0.114), and GMT were higher in pSS [80.0 (52.4-160.0) vs. 40.0 (20.0-80.0), p = 0.001]. The percentage of influenza vaccination in the preceding two years was elevated and similar in pSS and HC (94.1% vs. 94.6%, p = 1.000). GMT values augmented in both groups four weeks after vaccination and persisted higher in the first group [160.0 (80.0-320.0) vs. 80.0 (40.0-80.0), p < 0.001] with equivalent FI-GMT [1.4 (1.0-2.8) vs. 1.4 (1.0-2.0), p = 0.410]. Both groups had low and similar SC rates (19.0% vs. 9.5%, p = 0.423). ESSDAI values persisted steadily during the study (p = 0.313). No serious adverse events have occurred.

CONCLUSION

The novel demonstration that the influenza A/Singapore (H3N2) vaccine induces a different pattern of immunogenicity from other influenza A constituents in pSS, featured by a desirable high pre- and post-vaccination immunogenicity, is in line with reported differences in immune responses between strains in trivalent vaccines and may be related to pre-existing immunity.

CLINICALTRIALS

gov: #NCT03540823. Key Points • This prospective study demonstrated a robust pre- and post-vaccination immunogenicity to influenza A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus in primary Sjögren's syndrome (pSS). • This high immunogenicity pattern may be related to pre-existing immunization, or else it is related to immunogenicity differences of each strain. • This vaccine had an adequate safety profile in pSS, with no impact on disease activity.

Induction of humoral and cell-mediated immunity to the NS1 protein of TBEV with recombinant Influenza virus and MVA affords partial protection against lethal TBEV infection in mice

Introduction

Tick-borne encephalitis virus (TBEV) is one of the most relevant tick-transmitted neurotropic arboviruses in Europe and Asia and the causative agent of tick-borne encephalitis (TBE). Annually more than 10,000 TBE cases are reported despite having vaccines available. In Europe, the vaccines FSME-IMMUN® and Encepur® based on formaldehyde-inactivated whole viruses are licensed. However, demanding vaccination schedules contribute to sub-optimal vaccination uptake and breakthrough infections have been reported repeatedly. Due to its immunogenic properties as well as its role in viral replication and disease pathogenesis, the non-structural protein 1 (NS1) of flaviviruses has become of interest for non-virion based flavivirus vaccine candidates in recent years.

Methods

Therefore, immunogenicity and protective efficacy of TBEV NS1 expressed by neuraminidase (NA)-deficient Influenza A virus (IAV) or Modified Vaccinia virus Ankara (MVA) vectors were investigated in this study.

Results

With these recombinant viral vectors TBEV NS1-specific antibody and T cell responses were induced. Upon heterologous prime/boost regimens partial protection against lethal TBEV challenge infection was afforded in mice.

Discussion

This supports the inclusion of NS1 as a vaccine component in next generation TBEV vaccines.

A Small Molecule RIG-I Agonist Serves as an Adjuvant to Induce Broad Multifaceted Influenza Virus Vaccine Immunity

Retinoic acid-inducible gene I (RIG-I) is essential for activating host cell innate immunity to regulate the immune response against many RNA viruses. We previously identified that a small molecule compound, KIN1148, led to the activation of IFN regulatory factor 3 (IRF3) and served to enhance protection against influenza A virus (IAV) A/California/04/2009 infection. We have now determined direct binding of KIN1148 to RIG-I to drive expression of IFN regulatory factor 3 and NF-κB target genes, including specific immunomodulatory cytokines and chemokines. Intriguingly, KIN1148 does not lead to ATPase activity or compete with ATP for binding but activates RIG-I to induce antiviral gene expression programs distinct from type I IFN treatment. When administered in combination with a vaccine against IAV, KIN1148 induces both neutralizing Ab and IAV-specific T cell responses compared with vaccination alone, which induces comparatively poor responses. This robust KIN1148-adjuvanted immune response protects mice from lethal A/California/04/2009 and H5N1 IAV challenge. Importantly, KIN1148 also augments human CD8+ T cell activation. Thus, we have identified a small molecule RIG-I agonist that serves as an effective adjuvant in inducing noncanonical RIG-I activation for induction of innate immune programs that enhance adaptive immune protection of antiviral vaccination.

Predicting Antigenic Distance from Genetic Data for PRRSV-Type 1: Applications of Machine Learning

The control of porcine reproductive and respiratory syndrome (PRRS) remains a significant challenge due to the genetic and antigenic variability of the causative virus (PRRSV). Predominantly, PRRSV management includes using vaccines and live virus inoculations to confer immunity against PRRSV on farms. While understanding cross-protection among strains is crucial for the continued success of these interventions, understanding how genetic diversity translates to antigenic diversity remains elusive. We developed machine learning algorithms to estimate antigenic distance in silico, based on genetic sequence data, and identify differences in specific amino acid sites associated with antigenic differences between viruses. First, we obtained antigenic distance estimates derived from serum neutralization assays cross-reacting PRRSV monospecific antisera with virus isolates from 27 PRRSV1 viruses circulating in Europe. Antigenic distances were weakly to moderately associated with ectodomain amino acid distance for open reading frames (ORFs) 2 to 4 (ρ < 0.2) and ORF5 (ρ = 0.3), respectively. Dividing the antigenic distance values at the median, we then categorized the sera-virus pairs into two levels: low and high antigenic distance (dissimilarity). In the machine learning models, we used amino acid distances in the ectodomains of ORFs 2 to 5 and site-wise amino acid differences between the viruses as potential predictors of antigenic dissimilarity. Using mixed-effect gradient boosting models, we estimated the antigenic distance (high versus low) between serum-virus pairs with an accuracy of 81% (95% confidence interval, 76 to 85%); sensitivity and specificity were 86% and 75%, respectively. We demonstrate that using sequence data we can estimate antigenic distance and potential cross-protection between PRRSV1 strains. IMPORTANCE Understanding cross-protection between cocirculating PRRSV1 strains is crucial to reducing losses associated with PRRS outbreaks on farms. While experimental studies to determine cross-protection are instrumental, these in vivo studies are not always practical or timely for the many cocirculating and emerging PRRSV strains. In this study, we demonstrate the ability to rapidly estimate potential immunologic cross-reaction between different PRRSV1 strains in silico using sequence data routinely collected by production systems. These models can provide fast turn-around information crucial for improving PRRS management decisions such as selecting vaccines/live virus inoculation to be used on farms and assessing the risk of outbreaks by emerging strains on farms previously exposed to certain PRRSV strains and vaccine development among others.

T Cell Transcriptional Signatures of Influenza A/H3N2 Antibody Response to High Dose Influenza and Adjuvanted Influenza Vaccine in Older Adults

Older adults experience declining influenza vaccine-induced immunity and are at higher risk of influenza and its complications. For this reason, high dose (e.g., Fluzone) and adjuvanted (e.g., Fluad) vaccines are preferentially recommended for people age 65 years and older. However, T cell transcriptional activity shaping the humoral immune responses to Fluzone and Fluad vaccines in older adults is still poorly understood. We designed a study of 234 older adults (≥65 years old) who were randomly allocated to receive Fluzone or Fluad vaccine and provided blood samples at baseline and at Day 28 after immunization. We measured the humoral immune responses (hemagglutination inhibition/HAI antibody titer) to influenza A/H3N2 and performed mRNA-Seq transcriptional profiling in purified CD4+ T cells, in order to identify T cell signatures that might explain differences in humoral immune response by vaccine type. Given the large differences in formulation (higher antigen dose vs adjuvant), our hypothesis was that each vaccine elicited a distinct transcriptomic response after vaccination. Thus, the main focus of our study was to identify the differential gene expression influencing the antibody titer in the two vaccine groups. Our analyses identified three differentially expressed, functionally linked genes/proteins in CD4+ T cells: the calcium/calmodulin dependent serine/threonine kinase IV (CaMKIV); its regulator the TMEM38B/transmembrane protein 38B, involved in maintenance of intracellular Ca2+ release; and the transcriptional coactivator CBP/CREB binding protein, as regulators of transcriptional activity/function in CD4+ T cells that impact differences in immune response by vaccine type. Significantly enriched T cell-specific pathways/biological processes were also identified that point to the importance of genes/proteins involved in Th1/Th2 cell differentiation, IL-17 signaling, calcium signaling, Notch signaling, MAPK signaling, and regulation of TRP cation Ca2+ channels in humoral immunity after influenza vaccination. In summary, we identified the genes/proteins and pathways essential for cell activation and function in CD4+ T cells that are associated with differences in influenza vaccine-induced humoral immunity by vaccine type. These findings provide an additional mechanistic perspective for achieving protective immunity in older adults.

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.

Stress-Induced Immunosuppression Affects Immune Response to Newcastle Disease Virus Vaccine via Circulating miRNAs

Simple Summary

Circulating miRNAs play important roles in immune response and stress-induced immunosuppression, but the function and mechanism of stress-induced immunosuppression affecting the NDV vaccine immune response remain unknown. In our study, key timepoints, functions, mechanisms, and potential biomarkers of circulating miRNAs involved in immune response and immunosuppression were discovered, providing a theoretical basis for studying the roles of circulating miRNAs in immune regulation.

Abstract

Studies have shown that circulating microRNAs (miRNAs) are important players in the immune response and stress-induced immunosuppression. However, the function and mechanism of stress-induced immunosuppression affecting the immune response to the Newcastle disease virus (NDV) vaccine remain largely unknown. This study analyzed the changes of 15 NDV-related circulating miRNAs at different immune stages by qRT-PCR, aiming to explore the key timepoints, potential biomarkers, and mechanisms for the functional regulation of candidate circulating miRNAs under immunosuppressed conditions. The results showed that stress-induced immunosuppression induced differential expressions of the candidate circulating miRNAs, especially at 2 days post immunization (dpi), 14 dpi, and 28 dpi. In addition, stress-induced immunosuppression significantly affected the immune response to NDV vaccine, which was manifested by significant changes in candidate circulating miRNAs at 2 dpi, 5 dpi, and 21 dpi. The featured expressions of candidate circulating miRNAs indicated their potential application as biomarkers in immunity and immunosuppression. Bioinformatics analysis revealed that the candidate circulating miRNAs possibly regulated immune function through key targeted genes, such as Mg²⁺/Mn²⁺-dependent 1A (PPM1A) and Nemo-like kinase (NLK), in the MAPK signaling pathway. This study provides a theoretical reference for studying the function and mechanism of circulating miRNAs in immune regulation.

Stress-induced immunosuppression affecting avian influenza virus vaccine immune response through miR-20a-5p/NR4A3 pathway in chicken

Stress-induced immunosuppression is one of the most common hazards in poultry intensive production, which often leads to vaccination failure and severe economic losses. At present, there is no report about the function and mechanism of circulating miRNA on stress-induced immunosuppression affecting immune response. In this study, the changes of circulating miR-20a-5p under stress-induced immunosuppressive condition were analyzed by qRT-PCR, and the key time points, tissues and mechanisms for functional regulation of miR-20a-5p in the process of stress-induced immunosuppression affecting avian influenza virus (AIV) vaccine immune response were identified. The results showed that stress-induced immunosuppression down-regulated miR-20a-5p and further affected AIV vaccine immune response, in which 5 day post immunization (dpi) was a key time point, and the heart, lung, and proventriculus were the important tissues. The game relationship analysis between miR-20a-5p and its target nuclear receptor subfamily 4 group A member 3 (NR4A3) gene showed that "miR-20a-5p/NR4A3" pathway was the potential key mechanism of this process, especially for heart and lung. This study provides insights into the molecular mechanisms of stress-induced immunosuppression affecting immune response.

Design and Functional Analysis of Heterobifunctional Multivalent Phage Capsid Inhibitors Blocking the Entry of Influenza Virus

Multiple conjugation of virus-binding ligands to multivalent carriers is a prominent strategy to construct highly affine virus binders for the inhibition of viral entry into host cells. In a previous study, we introduced rationally designed sialic acid conjugates of bacteriophages (Qβ) that match the triangular binding site geometry on hemagglutinin spike proteins of influenza A virions, resulting in effective infection inhibition in vitro and in vivo. In this work, we demonstrate that even partially sialylated Qβ conjugates retain the inhibitory effect despite reduced activity. These observations not only support the importance of trivalent binding events in preserving high affinity, as supported by computational modeling, but also allow us to construct heterobifunctional modalities. Capsids carrying two different sialic acid ligand–linker structures showed higher viral inhibition than their monofunctional counterparts. Furthermore, capsids carrying a fluorescent dye in addition to sialic acid ligands were used to track their interaction with cells. These findings support exploring broader applications as multivalent inhibitors in the future.

A Single Vaccination of Chimeric Bivalent Virus-Like Particle Vaccine Confers Protection Against H9N2 and H3N2 Avian Influenza in Commercial Broilers and Allows a Strategy of Differentiating Infected from Vaccinated Animals

H9N2 and H3N2 are the two most important subtypes of low pathogenic avian influenza viruses (LPAIV) because of their ongoing threat to the global poultry industry and public health. Although commercially available inactivated H9N2 vaccines are widely used in the affected countries, endemic H9N2 avian influenza remains uncontrolled. In addition, there is no available avian H3N2 vaccine. Influenza virus-like particles (VLPs) are one of the most promising vaccine alternatives to traditional egg-based vaccines. In this study, to increase the immunogenic content of VLPs to reduce production costs, we developed chimeric bivalent VLPs (cbVLPs) co-displaying hemagglutinin (HA) and neuraminidase (NA) of H9N2 and H3N2 viruses with the Gag protein of bovine immunodeficiency virus (BIV) as the inner core using the Bac-to-Bac baculovirus expression system. The results showed that a single immunization of chickens with 40μg/0.3mL cbVLPs elicited an effective immune response and provided complete protection against H9N2 and H3N2 viruses. More importantly, cbVLPs with accompanying serological assays can successfully accomplish the strategy of differentiating infected animals from vaccinated animals (DIVA), making virus surveillance easier. Therefore, this cbVLP vaccine candidate would be a promising alternative to conventional vaccines, showing great potential for commercial development.

Pathophysiology of Influenza D Virus Infection in Specific-Pathogen-Free Lambs with or without Prior Mycoplasma ovipneumoniae Exposure

Polymicrobial pneumonias occur frequently in cattle, swine, and sheep, resulting in major economic losses. Individual pathogens comprising these complex infections may be mild on their own but can instead exhibit synergism or increase host susceptibility. Two examples of such pathogens, Mycoplasma ovipneumoniae (M. ovipneumoniae) and influenza D viruses (IDVs), naturally infect domestic sheep. In sheep, the role of M. ovipneumoniae in chronic nonprogressive pneumonia is well-established, but the pathogenesis of IDV infection has not previously been studied. We utilized a specific-pathogen-free sheep flock to study the clinical response to IDV infection in naïve vs. M. ovipneumoniae-exposed lambs. Lambs were inoculated intranasally with M. ovipneumoniae or mock infection, followed after four weeks by infection with IDV. Pathogen shedding was tracked, and immunological responses were evaluated by measuring acute phase response and IDV-neutralizing antibody titers. While lamb health statuses remained subclinical, M. ovipneumoniae-exposed lambs had significantly elevated body temperatures during IDV infection compared to M. ovipneumoniae-naïve, IDV-infected lambs. Moreover, we found a positive correlation between prior M. ovipneumoniae burden, early-infection IDV shedding, and IDV-neutralizing antibody response. Our findings suggest that IDV infection may not induce clinical symptoms in domestic sheep, but previous M. ovipneumoniae exposure may promote mild IDV-associated inflammation.

Investigation of Avian Influenza H5N6 Virus-like Particles as a Broad-Spectrum Vaccine Candidate against H5Nx Viruses

Highly pathogenic avian influenza (HPAI) clade 2.3.4.4 viruses have been reported to be the source of infections in several outbreaks in the past decades. In a previous study, we screened out a broad-spectrum virus strain, H5N6-Sichuan subtype, by using a lentiviral pseudovirus system. In this project, we aimed to investigate the potential of H5N6 virus-like particles (VLPs) serving as a broad-spectrum vaccine candidate against H5Nx viruses. We cloned the full-length M1 gene and H5, N6 genes derived from the H5N6-Sichuan into pFASTBac vector and generated the VLPs using the baculovirus-insect cell system. H5N6 VLPs were purified by sucrose gradient centrifugation, and the presence of H5, N6 and M1 proteins was verified by Western blot and SDS-PAGE. The hemagglutination titer of H5N6 VLPs after purification reached 5120 and the particle structure remained as viewed by electron microscopy. The H5N6 VLPs and 293T mammalian cell-expressed H5+N6 proteins were sent for mice immunization. Antisera against the H5+N6 protein showed 80 to 320 neutralizing antibody titers to various H5Nx pseudoviruses. In contrast, H5N6 VLPs not only elicited higher neutralizing antibody titers, ranging from 640 to 1280, but also induced higher IL-2, IL-4, IL-5, IFN-γ and TNF production, thus indicating that H5N6 VLPs may be a potential vaccine candidate for broad-spectrum H5Nx avian influenza vaccines.

Induction of broadly reactive influenza antibodies increases susceptibility to autoimmunity

Infection and vaccination repeatedly expose individuals to antigens that are conserved between influenza virus subtypes. Nevertheless, antibodies recognizing variable influenza epitopes greatly outnumber antibodies reactive against conserved epitopes. Elucidating factors contributing to the paucity of broadly reactive influenza antibodies remains a major obstacle for developing a universal influenza vaccine. Here, we report that inducing broadly reactive influenza antibodies increases autoreactive antibodies in humans and mice and exacerbates disease in four distinct models of autoimmune disease. Importantly, transferring broadly reactive influenza antibodies augments disease in the presence of inflammation or autoimmune susceptibility. Further, broadly reactive influenza antibodies spontaneously arise in mice with defects in B cell tolerance. Together, these data suggest that self-tolerance mechanisms limit the prevalence of broadly reactive influenza antibodies, which can exacerbate disease in the context of additional risk factors.

Cross-protective efficacy of inactivated whole influenza vaccines against Korean Y280 and Y439 lineage H9N2 viruses in mice

Since June 2020, the Y280 lineage H9N2 virus, which is distinct from the previously endemic Y439 lineage, has been circulating in poultry in Korea. In this study, we developed two whole inactivated vaccines, rgHS314 and vac564, against the Y280 and Y439 lineages, respectively, and evaluated their immunogenicity and protective efficacy against homologous or heterologous viral challenge in mice. Serum neutralizing antibody titers in the rgHS314-vaccinated group were higher (68 ± 8.4 10log₂) than in the vac564-vaccinated group (18 ± 8.4 10log₂). In homologous challenge, rgHS314 conferred 100% protection, with no severe clinical signs, no body weight loss, and no viral replication in any tissues tested except the nasal turbinate. Viral replication in the lungs at 1, 3, 5, and 7 days post-infection (dpi) was significantly lower than in the sham group (p < 0.01). By contrast, all mice in the sham group were dead by 8 dpi with severe clinical signs and weight loss. Likewise, vac564 conferred 100% protection with no weight loss and with significantly lower viral replication in the lung than in the sham group at 3 dpi (p < 0.01). However, both vaccines showed partial protection in heterologous challenge. Our results suggest that both the rgHS314 and vac564 vaccines could be candidate vaccines for further evaluation in humans.

Mosaic Hemagglutinin-Based Whole Inactivated Virus Vaccines Induce Broad Protection Against Influenza B Virus Challenge in Mice

Influenza viruses undergo antigenic changes in the immuno-dominant hemagglutinin (HA) head domain, necessitating annual re-formulation of and re-vaccination with seasonal influenza virus vaccines for continuing protection. We previously synthesized mosaic HA (mHA) proteins of influenza B viruses which redirect the immune response towards the immuno-subdominant conserved epitopes of the HA via sequential immunization. As ~90% of current influenza virus vaccines are manufactured using the inactivated virus platform, we generated and sequentially vaccinated mice with inactivated influenza B viruses displaying either the homologous (same B HA backbones) or the heterologous (different B HA backbones) mosaic HAs. Both approaches induced long-lasting and cross-protective antibody responses showing strong antibody-dependent cellular cytotoxicity (ADCC) activity. We believe the B virus mHA vaccine candidates represent a major step towards a universal influenza B virus vaccine.

An Overview of Influenza Viruses and Vaccines

Influenza remains one of the major public health concerns because it causes annual epidemics and can potentially instigate a global pandemic. Numerous countermeasures, including vaccines and antiviral treatments, are in use against seasonal influenza infection; however, their effectiveness has always been discussed due to the ongoing resistance to antivirals and relatively low and unpredictable efficiency of influenza vaccines compared to other vaccines. The growing interest in vaccines as a promising approach to prevent and control influenza may provide alternative vaccine development options with potentially increased efficiency. In addition to currently available inactivated, live-attenuated, and recombinant influenza vaccines on the market, novel platforms such as virus-like particles (VLPs) and nanoparticles, and new vaccine formulations are presently being explored. These platforms provide the opportunity to design influenza vaccines with improved properties to maximize quality, efficacy, and safety. The influenza vaccine manufacturing process is also moving forward with advancements relating to egg- and cell-based production, purification processes, and studies into the physicochemical attributes and vaccine degradation pathways. These will contribute to the design of more stable, optimized vaccine formulations guided by contemporary analytical testing methods and via the implementation of the latest advances in the field.

Emergence of a Novel Reassortant H5N3 Avian Influenza Virus in Korean Mallard Ducks in 2018

INTRODUCTION

The avian influenza (AI) virus causes a highly contagious disease which is common in wild and domestic birds and sporadic in humans. Mutations and genetic reassortments among the 8 negative-sense RNA segments of the viral genome alter its pathogenic potential, demanding well-targeted, active surveillance for infection control.

METHODS

Wild duck fecal samples were collected during the 2018 bird health annual surveillance in South Korea for tracking variations of the AI virus. One low-pathogenic avian influenza H5N3 reassortment virus (A/mallard duck/South Korea/KNU18-91/2018 [H5N3]) was isolated and genomically characterized by phylogenetic and molecular analyses in this study.

RESULTS

It was devoid of polybasic amino acids at the hemagglutinin (HA) cleavage site and exhibited a stalk region without deletion in the neuraminidase (NA) gene and NA inhibitor resistance-linked E/D627K/N and D701N marker mutations in the PB2 gene, suggesting its low-pathogenic AI. It showed a potential of a reassortment where only HA originated from the H5N3 poultry virus of China and other genes were derived from Mongolia. In phylogenetic analysis, HA was different from that of the isolate of H5N3 in Korea, 2015. In addition, this novel virus showed adaptation in Madin-Darby canine kidney cells, with 8.05 ± 0.14 log10 50% tissue culture infectious dose (TCID50) /mL at 36 h postinfection. However, it could not replicate in mice well, showing positive growth at 3 days postinfection (dpi) (2.1 ± 0.13 log10 TCID50/mL) but not at 6 dpi.

CONCLUSIONS

The HA antigenic relationship of A/mallard duck/South Korea/KNU18-91/2018 (H5N3) showed differences toward one of the old low-pathogenic H5N3 viruses in Korea. These results indicated that a novel reassortment low-pathogenic avian influenza H5N3 subtype virus emerged in South Korea in 2018 via novel multiple reassortments with Eurasian viruses, rather than one of old Korean H5N3 strains.

Impaired memory B-cell recall responses in the elderly following recurrent influenza vaccination

Influenza is a highly contagious viral respiratory disease that affects million of people worldwide each year. Annual vaccination is recommended by the World Health Organization with the goal of reducing influenza severity and limiting transmission through elicitation of antibodies targeting the hemagglutinin (HA) glycoprotein. The antibody response elicited by current seasonal influenza virus vaccines is predominantly strain-specific, but pre-existing influenza virus immunity can greatly impact the serological antibody response to vaccination. However, it remains unclear how B cell memory is shaped by recurrent annual vaccination over the course of multiple seasons, especially in high-risk elderly populations. Here, we systematically profiled the B cell response in young adult (18-34 year old) and elderly (65+ year old) vaccine recipients that received annual split inactivated influenza virus vaccination for 3 consecutive seasons. Specifically, the antibody serological and memory B-cell compartments were profiled for reactivity against current and historical influenza A virus strains. Moreover, multiparametric analysis and antibody landscape profiling revealed a transient increase in strain-specific antibodies in the elderly, but with an impaired recall response of pre-existing memory B-cells, plasmablast (PB) differentiation and long-lasting serological changes. This study thoroughly profiles and compares the immune response to recurrent influenza virus vaccination in young and elderly participants unveiling the pitfalls of current influenza virus vaccines in high-risk populations.

Temporal Links Between Self-Reported Sleep and Antibody Responses to the Influenza Vaccine

BACKGROUND

Growing evidence suggests that sleep plays an important role in immunological memory, including antibody responses to vaccination. However, much of the prior research has been carried out in the laboratory limiting the generalizability of the findings. Furthermore, no study has sought to identify sensitive periods prior to or after vaccination where sleep may have a stronger influence on antibody responses.

METHODS

Eighty-three healthy young adults completed 13 days of sleep diaries and received the trivalent influenza vaccine on day 3 of the study. Measures of self-reported sleep duration, sleep efficiency, and subjective sleep quality were assessed on each day. Antibody levels to the influenza viral strains were quantified at baseline and 1 and 4 months following influenza vaccination.

RESULTS

Shorter sleep duration, averaged over the collection period, was associated with fewer antibodies to the A/New Caledonia viral strain 1 and 4 months later, independent of baseline antibodies, age, sex, and cohort year. Analyses focused on nightly sleep on the days preceding and after the vaccination revealed that shorter sleep duration on the two nights before the vaccination predicted fewer antibodies 1 and 4 months later. Measures of self-reported sleep efficiency and subjective quality were unrelated to antibody responses to the influenza vaccination.

CONCLUSION

These findings provide further support for an association between sleep duration and antibody responses to the influenza vaccine and suggest that perhaps sleep on nights prior to vaccination are critical. If replicated, these findings may support sleep as a target for enhancing vaccination efficacy.

Comparative in vitro analysis of inhibition of rhinovirus and influenza virus replication by mucoactive secretolytic agents and plant extracts

Background

Rhinoviruses and influenza viruses cause millions of acute respiratory infections annually. Symptoms of mild acute respiratory infections are commonly treated with over-the-counter products like ambroxol, bromhexine, and N-acetyl cysteine, as well as of thyme and pelargonium extracts today. Because the direct antiviral activity of these over-the-counter products has not been studied in a systematic way, the current study aimed to compare their inhibitory effect against rhinovirus and influenza virus replication in an in vitro setting.

Methods

The cytotoxicity of ambroxol, bromhexine, and N-acetyl cysteine, as well as of thyme and pelargonium extracts was analyzed in Madin Darby canine kidney (MDCK) and HeLa Ohio cells. The antiviral effect of these over-the-counter products was compared by analyzing the dose-dependent inhibition (i) of rhinovirus A2- and B14-induced cytopathic effect in HeLa Ohio cells and (ii) of influenza virus A/Hong Kong/68 (subtype H3N2)- and A/Jena/8178/09 (subtype H1N1, pandemic)-induced cytopathic effect in MDCK cells at non-cytotoxic concentrations. To get insights into the mechanism of action of pelargonium extract against influenza virus, we performed time-of-addition assays as well as hemagglutination and neuraminidase inhibition assays.

Results

N-acetyl cysteine, thyme and pelargonium extract showed no or only marginal cytotoxicity in MDCK and HeLa Ohio cells in the tested concentration range. The 50% cytotoxic concentration of ambroxol and bromhexine was 51.85 and 61.24 μM, respectively. No anti-rhinoviral activity was detected at non-cytotoxic concentrations in this in vitro study setting. Ambroxol, bromhexine, and N-acetyl cysteine inhibited the influenza virus-induced cytopathic effect in MDCK cells no or less than 50%. In contrast, a dose-dependent anti-influenza virus activity of thyme and pelargonium extracts was demonstrated. The time-of addition assays revealed an inhibition of early and late steps of influenza virus replication by pelargonium extract whereas zanamivir acted on late steps only. The proven block of viral neuraminidase activity might explain the inhibition of influenza virus replication when added after viral adsorption.

Conclusion

The study results indicate a distinct inhibition of influenza A virus replication by thyme and pelargonium extract which might contribute to the beneficial effects of these plant extracts on acute respiratory infections symptoms.

A Self-Adjuvanted, Modular, Antigenic VLP for Rapid Response to Influenza Virus Variability

The continuous evolution of influenza A virus (IAV) requires the influenza vaccine formulations to be updated annually to provide adequate protection. Recombinant protein-based vaccines provide safer, faster, and a more scalable alternative to the conventional embryonated egg approach for developing vaccines. However, these vaccines are typically poorer in immunogenicity than the vaccines containing inactivated or attenuated influenza viruses and require administration of a large antigen dosage together with potent adjuvants. The presentation of protein antigens on the surface of virus-like particles (VLP) provides an attractive strategy to rapidly induce stronger antigen-specific immune responses. Here we have examined the immunogenic potential and protective efficacy of P22 VLPs conjugated with multiple copies of the globular head domain of the hemagglutinin (HA) protein from the PR8 strain of IAV in a murine model of influenza pathogenesis. Using a covalent attachment strategy (SpyTag/SpyCatcher), we conjugated the HA globular head, which was recombinantly expressed in a genetically modified E. coli strain and found to refold as a monomer, to preassembled P22 VLPs. Immunization of mice with this P22-HA_head conjugate provided full protection from morbidity and mortality following infection with a homologous IAV strain. Moreover, the P22-HA_head conjugate also elicited an accelerated and enhanced HA head specific IgG response, which was significantly higher than the soluble HA head, or the admixture of P22 and HA head without the need for adjuvants. Thus, our results show that the HA head can be easily prepared by in vitro refolding in a modified E. coli strain, maintaining its intact structure and enabling the induction of a strong immune response when conjugated to P22 VLPs, even when presented as a monomer. These results also demonstrate that the P22 VLPs can be rapidly modified in a modular fashion, resulting in an effective vaccine construct that can generate protective immunity without the need for additional adjuvants.

Identification of influenza urban transmission patterns by geographical, epidemiological and whole genome sequencing data: protocol for an observational study

INTRODUCTION

Urban transmission patterns of influenza viruses are complex and poorly understood, and multiple factors may play a critical role in modifying transmission. Whole genome sequencing (WGS) allows the description of patient-to-patient transmissions at highest resolution. The aim of this study is to explore urban transmission patterns of influenza viruses in high detail by combining geographical, epidemiological and immunological data with WGS data.

METHODS AND ANALYSIS

The study is performed at the University Hospital Basel, University Children's Hospital Basel and a network of paediatricians and family doctors in the Canton of Basel-City, Switzerland. The retrospective study part includes an analysis of PCR-confirmed influenza cases from 2013 to 2018. The prospective study parts include (1) a household survey regarding influenza-like illness (ILI) and vaccination against influenza during the 2015/2016 season; (2) an analysis of influenza viruses collected during the 2016/2017 season using WGS-viral genomic sequences are compared with determine genetic relatedness and transmissions; and (3) measurement of influenza-specific antibody titres against all vaccinated and circulated strains during the 2016/2017 season from healthy individuals, allowing to monitor herd immunity across urban quarters. Survey data and PCR-confirmed cases are linked to data from the Statistics Office of the Canton Basel-City and visualised using geo-information system mapping. WGS data will be analysed in the context of patient epidemiological data using phylodynamic analyses, and the obtained herd immunity for each quarter. Profound knowledge on the key geographical, epidemiological and immunological factors influencing urban influenza transmission will help to develop effective counter measurements.

ETHICS AND DISSEMINATION

The study is registered and approved by the regional ethics committee as an observational study (EKNZ project ID 2015-363 and 2016-01735). It is planned to present the results at conferences and publish the data in scientific journals.

TRIAL REGISTRATION NUMBER

NCT03010007.

Antigen Extraction and B Cell Activation Enable Identification of Rare Membrane Antigen Specific Human B Cells

Determining antigen specificity is vital for understanding B cell biology and for producing human monoclonal antibodies. We describe here a powerful method for identifying B cells that recognize membrane antigens expressed on cells. The technique depends on two characteristics of the interaction between a B cell and an antigen-expressing cell: antigen-receptor-mediated extraction of antigen from the membrane of the target cell, and B cell activation. We developed the method using influenza hemagglutinin as a model viral membrane antigen, and tested it using acetylcholine receptor (AChR) as a model membrane autoantigen. The technique involves co-culturing B cells with adherent, bioorthogonally labeled cells expressing GFP-tagged antigen, and sorting GFP-capturing, newly activated B cells. Hemagglutinin-specific B cells isolated this way from vaccinated human donors expressed elevated CD20, CD27, CD71, and CD11c, and reduced CD21, and their secreted antibodies blocked hemagglutination and neutralized viral infection. Antibodies cloned from AChR-capturing B cells derived from patients with myasthenia gravis bound specifically to the receptor on cell membrane. The approach is sensitive enough to detect antigen-specific B cells at steady state, and can be adapted for any membrane antigen.