Regulation of pulmonary plasma cell responses during secondary infection with influenza virus

During secondary infection with influenza virus, plasma cells (PCs) develop within the lung, providing a local source of antibodies. However, the site and mechanisms that regulate this process are poorly defined. Here, we show that while circulating memory B cells entered the lung during rechallenge and were activated within inducible bronchus-associated lymphoid tissues (iBALTs), resident memory B (BRM) cells responded earlier, and their activation occurred in a different niche: directly near infected alveoli. This process required NK cells but was largely independent of CD4 and CD8 T cells. Innate stimuli induced by virus-like particles containing ssRNA triggered BRM cell differentiation in the absence of cognate antigen, suggesting a low threshold of activation. In contrast, expansion of PCs in iBALTs took longer to develop and was critically dependent on CD4 T cells. Our work demonstrates that spatially distinct mechanisms evolved to support pulmonary secondary PC responses, and it reveals a specialized function for BRM cells as guardians of the alveoli.

A tetravalent nanovaccine that inhibits growth of HPV-associated head and neck carcinoma via dendritic and T cell activation

The global incidence of human papillomavirus (HPV) associated head and neck carcinoma is on the rise, in response to this a tetravalent therapeutic vaccine named Qβ-HPVag was developed. This vaccine, utilizing virus-like particles (VLPs) loaded with toll-like receptor ligands and chemically coupled to four HPV16-derived peptides, demonstrated strong anti-tumor effects in a murine head and neck cancer model. Qβ-HPVag impeded tumor progression, increased infiltration of HPV-specific T cells, and significantly improved survival. The vaccine`s efficacy was associated with immune repolarization in the tumor microenvironment, characterized by expanded activated dendritic cell subsets (cDC1, cDC2, DC3). Notably, mice responding to treatment exhibited a higher percentage of migratory DC3 cells expressing CCR7. These findings suggest promising prospects for optimized VLP-based vaccines in treating HPV-associated head and neck cancer.

Generation of a virus-like particles based vaccine against IgE

BACKGROUND

Anti-IgE immunotherapy with monoclonal antibodies represents a breakthrough in treatment of severe allergic diseases. However, drawbacks such as short half-life and high price are not negligible. Our objective is to develop an anti-IgE vaccine based on virus-like particles (VLPs) which can induce long-lasting neutralizing IgG anti-IgE antibodies reducing allergic responses without causing intrinsic mast cell activation due to IgE cross-linking.

METHODS

The vaccines were made by chemically coupling three synthetic mouse IgE-Fc fragments to plant-derived immunologically optimized CuMVTT VLPs. The immunogenicity of the vaccines was tested by immunizing naive or allergic mice either with the coupled vaccines or the VLP control followed by systemic or local allergen challenge.

RESULTS

Mice immunized with the vaccines exhibited high titers of anti-IgE antibodies in the sera and high levels of anti-IgE secreting plasma cells in lymphoid organs. Moreover, free IgE in serum were reduced by the induced anti-IgE antibodies; therefore, less IgE was bound to FcεRI on the surface of basophils. In line with these reduced IgE levels on effector cells after vaccination, immunized mice were protected from challenge with allergens. Importantly, despite presence of anti-IgE antibodies, no signs of acute or chronic allergic response were seen in immunized allergic mice.

CONCLUSION

The generated vaccines can effectively induce anti-IgE antibodies that did not cause allergic responses in sensitized mice but were able to decrease the level of free and cell bound IgE and protected sensitized animals from allergic responses upon allergen challenge.

IgG in the control of FcεRI activation: a battle on multiple fronts

The rising global incidence of IgE-mediated allergic reactions poses a significant challenge to the quality of life of affected individuals and to healthcare systems, with current treatments being limited in effectiveness, safety, and disease-modifying capabilities. IgE acts by sensitizing the high-affinity IgE receptor FcεRI expressed by mast cells and basophils, tuning these cells for inflammatory degranulation in response to future allergen encounters. In recent years, IgG has emerged as an essential negative regulator of IgE-dependent allergic inflammation. Mechanistically, studies have proposed different pathways by which IgG can interfere with the activation of IgE-mediated inflammation. Here, we briefly summarize the major proposed mechanisms of action by which IgG controls the IgE-FcεRI inflammatory axis and how those mechanisms are currently applied as therapeutic interventions for IgE-mediated inflammation.

Influence of antigen density and TLR ligands on preclinical efficacy of a VLP-based vaccine against peanut allergy

BACKGROUND

Virus-like particle (VLP) Peanut is a novel immunotherapeutic vaccine candidate for the treatment of peanut allergy. The active pharmaceutical ingredient represents cucumber mosaic VLPs (CuMVTT -VLPs) that are genetically fused with one of the major peanut allergens, Ara h 2 (CuMVTT -Ara h 2). We previously demonstrated the immunogenicity and the protective capacity of VLP Peanut-based immunization in a murine model for peanut allergy. Moreover, a Phase I clinical trial has been initiated using VLP Peanut material manufactured following a GMP-compliant manufacturing process. Key product characterization studies were undertaken here to understand the role and contribution of critical quality attributes that translate as predictive markers of immunogenicity and protective efficacy for clinical vaccine development.

METHOD

The role of prokaryotic RNA encapsulated within VLP Peanut on vaccine immunogenicity was assessed by producing a VLP Peanut batch with a reduced RNA content (VLP Peanut low RNA). Immunogenicity and peanut allergen challenge studies were conducted with VLP Peanut low RNA, as well as with VLP Peanut in WT and TLR 7 KO mice. Furthermore, mass spectrometry and SDS-PAGE based methods were used to determine Ara h 2 antigen density on the surface of VLP Peanut particles. This methodology was subsequently applied to investigate the relationship between Ara h 2 antigen density and immunogenicity of VLP Peanut.

RESULTS

A TLR 7 dependent formation of Ara h 2 specific high-avidity IgG antibodies, as well as a TLR 7 dependent change in the dominant IgG subclass, was observed following VLP Peanut vaccination, while total allergen-specific IgG remained relatively unaffected. Consistently, a missing TLR 7 signal caused only a weak decrease in allergen tolerability after vaccination. In contrast, a reduced RNA content for VLP Peanut resulted in diminished total Ara h 2 specific IgG responses, followed by a significant impairment in peanut allergen tolerability. The discrepant effect on allergen tolerance caused by an absent TLR 7 signal versus a reduced RNA content is explained by the observation that VLP Peanut-derived RNA not only stimulates TLR 7 but also TLR 3. Additionally, a strong correlation was observed between the number of Ara h 2 antigens displayed on the surface of VLP Peanut particles and the vaccine's immunogenicity and protective capacity.

CONCLUSIONS

Our findings demonstrate that prokaryotic RNA encapsulated within VLP Peanut, including antigen density of Ara h 2 on viral particles, are key contributors to the immunogenicity and protective capacity of the vaccine. Thus, antigenicity and RNA content are two critical quality attributes that need to be determined at the stage of manufacturing, providing robust information regarding the immunogenicity and protective capacity of VLP Peanut in the mouse which has translational relevance to the human setting.

Successful Allergen-Specific Immunotherapy: Induction of Unresponsiveness by 'Vaccination'

The mechanisms of action of allergen-specific immunotherapy (AIT) are often referred to as the induction of 'tolerance'. However, immunological 'tolerance' is defined as an alteration in the function or composition of immune cells. For AIT, this is not always the case, because it can also induce allergen-specific IgG antibodies that block allergic responses. To include all possible mechanisms that may mediate successful AIT, it is advantageous to use the scientific term 'unresponsiveness' instead of 'tolerance'. In praxis, the term 'vaccination' is also appropriate, as AIT medications are specialized vaccines.

On the complexity of IgE: The role of structural flexibility and glycosylation for binding its receptors

It is well established that immunoglobulin E (IgE) plays a crucial role in atopy by binding to two types of Fcε receptors (FcεRI and FcεRII, also known as CD23). The cross-linking of FcεRI-bound IgE on effector cells, such as basophils and mast cells, initiates the allergic response. Conversely, the binding of IgE to CD23 modulates IgE serum levels and antigen presentation. In addition to binding to FcεRs, IgE can also interact with other receptors, such as certain galectins and, in mice, some FcγRs. The binding strength of IgE to its receptors is affected by its valency and glycosylation. While FcεRI shows reduced binding to IgE immune complexes (IgE-ICs), the binding to CD23 is enhanced. There is no evidence that galectins bind IgE-ICs. On the other hand, IgE glycosylation plays a crucial role in the binding to FcεRI and galectins, whereas the binding to CD23 seems to be independent of glycosylation. In this review, we will focus on receptors that bind to IgE and examine how the glycosylation and complexation of IgE impact their binding.

The next generation virus-like particle platform for the treatment of peanut allergy

BACKGROUND

Allergy to peanut is one of the leading causes of anaphylactic reactions among food allergic patients. Immunization against peanut allergy with a safe and protective vaccine holds a promise to induce durable protection against anaphylaxis caused by exposure to peanut. A novel vaccine candidate (VLP Peanut), based on virus-like particles (VLPs), is described here for the treatment of peanut allergy.

METHODS AND RESULTS

VLP Peanut consist of two proteins: a capsid subunit derived from Cucumber mosaic virus engineered with a universal T cell epitope (CuMV_TT ) and a CuMV_TT subunit fused with peanut allergen Ara h 2 (CuMV_TT -Ara h 2), forming mosaic VLPs. Immunizations with VLP Peanut in both naïve and peanut-sensitised mice resulted in a significant anti-Ara h 2 IgG response. Local and systemic protection induced by VLP Peanut were established in mouse models for peanut allergy following prophylactic, therapeutic and passive immunizations. Inhibition of FcγRIIb function resulted in a loss of protection, confirming the crucial role of the receptor in conferring cross protection against peanut allergens other than Ara h 2.

CONCLUSION

VLP Peanut can be delivered to peanut-sensitized mice without triggering allergic reactions, whilst remaining highly immunogenic and offering protection against all peanut allergens. In addition, vaccination ablates allergic symptoms upon allergen challenge. Moreover, the prophylactic immunization setting conferred the protection against subsequent peanut-induced anaphylaxis, showing the potential for preventive vaccination. This highlights the effectiveness of VLP Peanut as a prospective break-through immunotherapy vaccine candidate towards peanut allergy. VLP Peanut has now entered clinical development with the study PROTECT.

Alzheimer's Disease: A Brief History of Immunotherapies Targeting Amyloid β

Alzheimer's disease (AD) is the most common form of dementia and may contribute to 60-70% of cases. Worldwide, around 50 million people suffer from dementia and the prediction is that the number will more than triple by 2050, as the population ages. Extracellular protein aggregation and plaque deposition as well as accumulation of intracellular neurofibrillary tangles, all leading to neurodegeneration, are the hallmarks of brains with Alzheimer's disease. Therapeutic strategies including active and passive immunizations have been widely explored in the last two decades. Several compounds have shown promising results in many AD animal models. To date, only symptomatic treatments are available and because of the alarming epidemiological data, novel therapeutic strategies to prevent, mitigate, or delay the onset of AD are required. In this mini-review, we focus on our understanding of AD pathobiology and discuss current active and passive immunomodulating therapies targeting amyloid-β protein.

Vaccination using mutated receptor binding domains of SARS-CoV-2: Evidence for partial immune escape but not serotype formation

Introduction

SARS-CoV-2 has developed a number of Variants of Concern (VOC) with increased infectivity and/or reduced recognition by neutralizing antibodies specific for the receptor binding domain (RBD) of the spike protein. Extended studies of other viruses have shown that strong and broad viral escape from neutralizing serum antibodies is typically associated with the formation of serotypes.

Methods

To address the question of serotype formation for SARS-CoV-2 in detail, we generated recombinant RBDs of VOCs and displayed them on virus-like particles (VLPs) for vaccination and specific antibody responses.

Results

As expected, mice immunized with wild type (wt) RBD generated antibodies that recognized wt RBD well but displayed reduced binding to VOC RBDs, in particular those with the E484K mutation. Unexpectedly, however, antibodies induced by the VOC vaccines typically recognized best the wt RBDs, often more than the homologous VOC RBDs used for immunization. Hence, these data do not reveal different serotypes but represent a newly observed viral evolution, suggesting a unique situation where inherent differences of RBDs are responsible for induction of neutralizing antibodies.

Discussion

Therefore, besides antibody (fine) specificity, other qualities of antibodies (e.g. their affinity) determine neutralizing capability. Immune escape of SARS-CoV-2 VOCs only affects a fraction of an individual's serum antibodies. Consequently, many neutralizing serum antibodies are cross-reactive and thus protective against multiple current and future VOCs. Besides considering variant sequences for next generation vaccines, broader protection will be achieved with vaccines that induce elevated titers of high-quality antibodies.

Bacterial expression systems based on Tymovirus-like particles for the presentation of vaccine antigens

Virus-like particles (VLPs) are virus-derived artificial nanostructures that resemble a native virus-stimulating immune system through highly repetitive surface structures. Improved safety profiles, flexibility in vaccine construction, and the ease of VLP production and purification have highlighted VLPs as attractive candidates for universal vaccine platform generation, although exploration of different types of expression systems for their development is needed. Here, we demonstrate the construction of several simple Escherichia coli expression systems for the generation of eggplant mosaic virus (EMV) VLP-derived vaccines. We used different principles of antigen incorporation, including direct fusion of EMV coat protein (CP) with major cat allergen Feld1, coexpression of antigen containing and unmodified (mosaic) EMV CPs, and two coexpression variants of EMV VLPs and antigen using synthetic zipper pair 18/17 (SYNZIP 18/17), and coiled-coil forming peptides E and K (Ecoil/Kcoil). Recombinant Fel d 1 chemically coupled to EMV VLPs was included as control experiments. All EMV-Feld1 variants were expressed in E. coli, formed Tymovirus-like VLPs, and were used for immunological evaluation in healthy mice. The immunogenicity of these newly developed vaccine candidates demonstrated high titers of Feld1-specific Ab production; however, a comparably high immune response against carrier EMV was also observed. Antibody avidity tests revealed very specific Ab production (more than 50% specificity) for four out of the five vaccine candidates. Native Feld1 recognition and subclass-specific antibody tests suggested that the EMV-SZ18/17-Feld1 complex and chemically coupled EMV-Feld1 vaccines may possess characteristics for further development.

Linking Viral DNA to Endosomal Innate Immune Recognition

This Pillars of Immunology article is a commentary on “Toll-like receptor 9-mediated recognition of herpes simplex virus-2 by plasmacytoid dendritic cells,” a pivotal article written by J. Lund, A. Sato, S. Akira, R. Medzhitov, and A. Iwasaki, and published in the Journal of Experimental Medicine, in 2003. https://doi.org/10.1084/jem.20030162.

AA-amyloidosis in cats (Felis catus) housed in shelters

Systemic AA-amyloidosis is a protein-misfolding disease characterized by fibril deposition of serum amyloid-A protein (SAA) in several organs in humans and many animal species. Fibril deposits originate from abnormally high serum levels of SAA during chronic inflammation. A high prevalence of AA-amyloidosis has been reported in captive cheetahs and a horizontal transmission has been proposed. In domestic cats, AA-amyloidosis has been mainly described in predisposed breeds but only rarely reported in domestic short-hair cats. Aims of the study were to determine AA-amyloidosis prevalence in dead shelter cats. Liver, kidney, spleen and bile were collected at death in cats from 3 shelters. AA-amyloidosis was scored. Shedding of amyloid fibrils was investigated with western blot in bile and scored. Descriptive statistics were calculated. In the three shelters investigated, prevalence of AA-amyloidosis was 57.1% (16/28 cats), 73.0% (19/26) and 52.0% (13/25), respectively. In 72.9% of cats (35 in total) three organs were affected concurrently. Histopathology and immunofluorescence of post-mortem extracted deposits identified SAA as the major protein source. The duration of stay in the shelters was positively associated with a histological score of AA-amyloidosis (B = 0.026, CI95% = 0.007-0.046; p = 0.010). AA-amyloidosis was very frequent in shelter cats. Presence of SAA fragments in bile secretions raises the possibility of fecal-oral transmission of the disease. In conclusion, AA-amyloidosis was very frequent in shelter cats and those staying longer had more deposits. The cat may represent a natural model of AA-amyloidosis.

IgE glycans promote anti-IgE IgG autoantibodies that facilitate IgE serum clearance via Fc Receptors

Background

Recent studies have shown that IgE glycosylation significantly impacts the ability of IgE to bind to its high-affinity receptor FcεRI and exert effector functions. We have recently demonstrated that immunizing mice with IgE in a complex with an allergen leads to a protective, glycan-dependent anti-IgE response. However, to what extent the glycans on IgE determine the induction of those antibodies and how they facilitate serum clearance is unclear.Therefore, we investigated the role of glycan-specific anti-IgE IgG autoantibodies in regulating serum IgE levels and preventing systemic anaphylaxis by passive immunization.

Methods

Mice were immunized using glycosylated or deglycosylated IgE-allergen-immune complexes (ICs) to induce anti-IgE IgG antibodies. The anti-IgE IgG antibodies were purified and used for passive immunization.

Results

Glycosylated IgE-ICs induced a significantly higher anti-IgE IgG response and more IgG-secreting plasma cells than deglycosylated IgE-ICs. Passive immunization of IgE-sensitized mice with purified anti-IgE IgG increased the clearance of IgE and prevented systemic anaphylaxis upon allergen challenge. Anti-IgE IgG purified from the serum of mice immunized with deglycosylated IgE-ICs, led to a significantly reduced elimination and protection, confirming that the IgE glycans themselves are the primary drivers of the protectivity induced by the IgE-immune complexes.

Conclusion

IgE glycosylation is essential for a robust anti-IgE IgG response and might be an important regulator of serum IgE levels.

Emerging COVID-19 variants and their impact on SARS-CoV-2 diagnosis, therapeutics and vaccines

The emergence of novel and evolving variants of SARS-CoV-2 has fostered the need for change in the form of newer and more adaptive diagnostic methods for the detection of SARS-CoV-2 infections. On the other hand, developing rapid and sensitive diagnostic technologies is now more challenging due to emerging variants and varying symptoms exhibited among the infected individuals. In addition to this, vaccines remain the major mainstay of prevention and protection against infection. Novel vaccines and drugs are constantly being developed to unleash an immune response for the robust targeting of SARS-CoV-2 and its associated variants. In this review, we provide an updated perspective on the current challenges posed by the emergence of novel SARS-CoV-2 mutants/variants and the evolution of diagnostic techniques to enable their detection. In addition, we also discuss the development, formulation, working mechanisms, advantages, and drawbacks of some of the most used vaccines/therapeutic drugs and their subsequent immunological impact.Key messageThe emergence of novel variants of the SARS-CoV-2 in the past couple of months, highlights one of the primary challenges in the diagnostics, treatment, as well as vaccine development against the virus.Advancements in SARS-CoV-2 detection include nucleic acid based, antigen and immuno- assay-based and antibody-based detection methodologies for efficient, robust, and quick testing; while advancements in COVID-19 preventive and therapeutic strategies include novel antiviral and immunomodulatory drugs and SARS-CoV-2 targeted vaccines.The varied COVID-19 vaccine platforms and the immune responses induced by each one of them as well as their ability to battle post-vaccination infections have all been discussed in this review.

On the role of allergen-specific IgG subclasses for blocking human basophil activation

Successful treatment of IgE mediated allergies by allergen-specific immunotherapy (AIT) usually correlates with the induction of allergen-specific IgG4. However, it is not clear whether IgG4 prevents the allergic reaction more efficiently than other IgG subclasses. Here we aimed to compare allergen-specific monoclonal IgG1 and IgG4 antibodies in their capacity to inhibit type I allergic reactions by engaging FcγRIIb. We found that IgG1, which is the dominant subclass induced by viruses, binds with a similar affinity to the FcγRIIb as IgG4 and is comparable at blocking human basophil activation from allergic patients; both by neutralizing the allergen as well as engaging the inhibitory receptor FcγRIIb. Hence, the IgG subclass plays a limited role for the protective efficacy of AIT even if IgG4 is considered the best correlate of protection, most likely simply because it is the dominant subclass induced by classical AITs.

In situ delivery of nanoparticles formulated with micron-sized crystals protects from murine melanoma

Introduction

Intratumoral injections of novel therapeutics can activate tumor antigen-specific T cells for locoregional tumor control and may even induce durable systemic protection (against distant metastases) via recirculating T cells. Here we explored the possibility of a universal immunotherapy that promotes T-cell responses in situ and beyond, upon intratumoral injection of nanoparticles formulated with micron-sized crystals.

Methods

Cucumber mosaic virus-like particles containing a tetanus toxin peptide (CuMV_TT) were formulated with microcrystalline tyrosine (MCT) adjuvant and injected directly in B16F10 melanoma tumors. To further enhance immunogenicity, we loaded the nanoparticles with a TLR7/8 ligand and incorporated a universal tetanus toxin T-helper cell peptide. We assessed therapeutic efficacy and induction of local and systemic immune responses, including RNA sequencing, providing broad insight into the tumor microenvironment and correlates of protection.

Results

MCT crystals were successfully decorated with CuMV_TT nanoparticles. This ‘immune-enhancer’ formed immunogenic depots in injected tumors, enhanced polyfunctional CD8⁺ and CD4⁺ T cells, and inhibited B16F10 tumor growth locally and systemically. Local inflammation and immune responses were associated with upregulation of genes involved in complement activation and collagen formation.

Conclusions

Our new immune-enhancer turned immunologically cold tumors into hot ones and inhibited local and distant tumor growth. This type of immunotherapy does not require the identification of (patient–individual) relevant tumor antigens. It is well tolerated, non-infectious, and affordable, and can readily be upscaled for future clinical testing and broad application in melanoma and likely other solid tumors.

Intranasal administration of a virus like particles-based vaccine induces neutralizing antibodies against SARS-CoV-2 and variants of concern

BACKGROUND

The highly contagious SARS-CoV-2 is mainly transmitted by respiratory droplets and aerosols. Consequently, people are required to wear masks and maintain a social distance to avoid spreading of the virus. Despite the success of the commercially available vaccines, the virus is still uncontained globally. Given the tropism of SARS-CoV-2, a mucosal immune reaction would help to reduce viral shedding and transmission locally. Only seven out of hundreds of ongoing clinical trials are testing the intranasal delivery of a vaccine against COVID-19.

METHODS

In the current study, we evaluated the immunogenicity of a traditional vaccine platform based on virus-like particles (VLPs) displaying RBD of SARS-CoV-2 for intranasal administration in a murine model. The candidate vaccine platform, CuMVTT -RBD, has been optimized to incorporate a universal T helper cell epitope derived from tetanus-toxin and is self-adjuvanted with TLR7/8 ligands.

RESULTS

CuMVTT -RBD vaccine elicited a strong systemic RBD- and spike-IgG and IgA antibodies of high avidity. Local immune response was assessed, and our results demonstrate a strong mucosal antibody and plasma cell production in lung tissue. Furthermore, the induced systemic antibodies could efficiently recognize and neutralize different variants of concern (VOCs).

CONCLUSION

Our data demonstrate that intranasal administration of CuMVTT -RBD induces a protective systemic and local specific antibody response against SARS-CoV-2 and its VOCs.

Virus-Like Particles Are Efficient Tools for Boosting mRNA-Induced Antibodies

mRNA based vaccines against COVID-19 have proven most successful at keeping SARS-CoV-2 pandemic at bay in many countries. Recently, there is an increased interest in heterologous prime-boost vaccination strategies for COVID-19 to maintain antibody responses for the control of continuously emerging SARS-CoV-2 variants of concern (VoCs) and to overcome other obstacles such as supply shortage, costs and reduced safety issues or inadequatly induced immune-responses. In this study, we investigated the antibody responses induced by heterologous prime-boost with vaccines based on mRNA and virus-like particles (VLPs). The VLP-based mCuMV_TT-RBM vaccine candidate and the approved mRNA-1273 vaccine were used for this purpose. We find that homologous prime boost regimens with either mRNA or VLP induced high levels of high avidity antibodies. Optimal antibody responses were, however, induced by heterologous regimens both for priming with mRNA and boosting with VLP and vice versa, priming with VLP and boosting with mRNA. Thus, heterologous prime boost strategies may be able to optimize efficacy and economics of novel vaccine strategies.

Secondary influenza challenge triggers resident memory B cell migration and rapid relocation to boost antibody secretion at infected sites

Resident memory B (BRM) cells develop and persist in the lungs of influenza-infected mice and humans; however, their contribution to recall responses has not been defined. Here, we used two-photon microscopy to visualize BRM cells within the lungs of influenza -virus immune and reinfected mice. Prior to re-exposure, BRM cells were sparsely scattered throughout the tissue, displaying limited motility. Within 24 h of rechallenge, these cells increased their migratory capacity, localized to infected sites, and subsequently differentiated into plasma cells. Alveolar macrophages mediated this process, in part by inducing expression of chemokines CXCL9 and CXCL10 from infiltrating inflammatory cells. This led to the recruitment of chemokine receptor CXCR3-expressing BRM cells to infected regions and increased local antibody concentrations. Our study uncovers spatiotemporal mechanisms that regulate lung BRM cell reactivation and demonstrates their capacity to rapidly deliver antibodies in a highly localized manner to sites of viral replication.

Comparison of Bacterial Expression Systems Based on Potato Virus Y-like Particles for Vaccine Generation

Plant-based virus-like particle (VLP) vaccines have been studied for years, demonstrating their potential as antigen-presenting platforms. In this paper, we describe the development of, and compare between, simple Escherichia coli-based antigen display platforms for the generation of potato virus Y (PVY) VLP-derived vaccines, thus allowing the production of vaccines from a single bacterial cell culture. We constructed four systems with the major cat allergen Fel d 1; namely, direct fusion with plant virus PVY coat protein (CP), mosaic PVY VLPs, and two coexpression variants of conjugates (SpyTag/SpyCatcher) allowing coexpression and conjugation directly in E. coli cells. For control experiments, we included PVY VLPs chemically coupled with Fel d 1. All constructed PVY-Fel d 1 variants were well expressed and soluble, formed PVY-like filamentous particles, and were recognized by monoclonal Fel d 1 antibodies. Our results indicate that all vaccine variants induced high titers of anti-Fel d 1 antibodies in murine models. Mice that were immunized with the chemically coupled Fel d 1 antigen exhibited the highest antibody titers and antibody-antigen interaction specificity, as detected by binding avidity and recognition of native Fel d 1. IgG1 subclass antibodies were found to be the dominant IgG class against PVY-Fel d 1. PVY CP-derived VLPs represent an efficient platform for the comparison of various antigen presentation systems to help evaluate different vaccine designs.

Induction of Broadly Cross-Reactive Antibodies by Displaying Receptor Binding Domains of SARS-CoV-2 on Virus-like Particles

The impact of the COVID-19 pandemic has been reduced since the application of vaccination programs, mostly shown in the reduction of hospitalized patients. However, the emerging variants, in particular Omicron, have caused a steep increase in the number of infections; this increase is, nevertheless, not matched by an increase in hospitalization. Therefore, a vaccine that induces cross-reactive antibodies against most or all variants is a potential solution for the issue of emerging new variants. Here, we present a vaccine candidate which displays receptor-binding domain (RBD) of SARS-CoV-2 on virus-like particles (VLP) that, in mice, not only induce strong antibody responses against RBD but also bind RBDs from other variants of concern (VOCs). The antibodies induced by wild-type (wt) RBD displayed on immunologically optimized Cucumber mosaic virus incorporated tetanus toxin (CuMVTT) VLPs bind to wt as well as RBDs of VOCs with high avidities, indicating induction of strongly cross-reactive IgG antibodies. Interestingly, similar cross-reactive IgA antibodies were induced in immunized mice. Furthermore, these cross-reactive antibodies demonstrated efficacy in neutralizing wt (Wuhan) as well as SARS-CoV-2 VOCs (Beta, Delta, and Gamma). In summary, RBDs displayed on VLPs are capable of inducing protective cross-reactive IgG and IgA antibodies in mice, indicating that it may be possible to cover emerging VOCs with a single vaccine based on wt RBD.

TLR7 Signaling Shapes and Maintains Antibody Diversity Upon Virus-Like Particle Immunization

Virus-like particles (VLPs) are used in different marketed vaccines and are able to induce potent antibody responses. The innate pattern recognition receptors TLR7/8 recognize single stranded (ss) RNA naturally packaged into some VLPs and have been shown to enhance the production of IgG antibodies upon immunization. Here we demonstrate that, upon immunization with RNA-loaded bacteriophage-derived VLP Qβ, TLR7 signaling accelerates germinal center formation, promotes affinity/avidity maturation of VLP-specific IgG and isotype switching to IgG2b/2c. These findings extrapolated to antigens displayed on Qβ; as Fel d 1, the major cat allergen, chemically attached to Qβ also induced higher affinity/avidity IgG2b/2c antibodies in a TLR7-dependent fashion. Chimeric mice lacking TLR7-expression exclusively in B cells demonstrated that the enhanced IgG responses were driven by a B cell intrinsic mechanism. Importantly, deep sequencing of the BCR repertoire of antigen-specific B cells demonstrated higher diversity in mice with TLR7 signaling in B cells, suggesting that TLR7-signaling drives BCR repertoire development and diversity. Furthermore, the current data demonstrate that high levels of clonal diversity are reached early in the response and maintained by TLR7 signaling. In conclusion, TLR7 signaling enhances levels and quality of IgG antibodies, and this finding has major implications for vaccine design.

Bedside formulation of a personalized multi-neoantigen vaccine against mammary carcinoma

Background

Harnessing the immune system to purposely recognize and destroy tumors represents a significant breakthrough in clinical oncology. Non-synonymous mutations (neoantigenic peptides) were identified as powerful cancer targets. This knowledge can be exploited for further improvements of active immunotherapies, including cancer vaccines, as T cells specific for neoantigens are not attenuated by immune tolerance mechanism and do not harm healthy tissues. The current study aimed at developing an optimized multitarget vaccine using short or long neoantigenic peptides utilizing virus-like particles (VLPs) as an efficient vaccine platform.

Methods

Mutations of murine mammary carcinoma cells were identified by integrating mass spectrometry-based immunopeptidomics and whole exome sequencing. Neoantigenic peptides were synthesized and covalently linked to virus-like nanoparticles using a Cu-free click chemistry method for easy preparation of vaccines against mouse mammary carcinoma.

Results

As compared with short peptides, vaccination with long peptides was superior in the generation of neoantigen-specific CD4⁺ and CD8⁺ T cells, which readily produced interferon gamma (IFN-γ) and tumor-necrosis factor α (TNF-α). The resulting anti-tumor effect was associated with favorable immune re-polarization in the tumor microenvironment through reduction of myeloid-derived suppressor cells. Vaccination with long neoantigenic peptides also decreased post-surgical tumor recurrence and metastases, and prolonged mouse survival, despite the tumor’s low mutational burden.

Conclusion

Integrating mass spectrometry-based immunopeptidomics and whole exome sequencing is an efficient approach for identifying neoantigenic peptides. Our multitarget VLP-based vaccine shows a promising anti-tumor effect in an aggressive murine mammary carcinoma model. Future clinical application using this strategy is readily feasible and practical, as click chemistry coupling of personalized synthetic peptides to the nanoparticles can be done at the bedside directly before injection.

A scalable and highly immunogenic virus-like particle-based vaccine against SARS-CoV-2

BACKGROUND

SARS-CoV-2 caused one of the most devastating pandemics in the recent history of mankind. Due to various countermeasures, including lock-downs, wearing masks, and increased hygiene, the virus has been controlled in some parts of the world. More recently, the availability of vaccines, based on RNA or adenoviruses, has greatly added to our ability to keep the virus at bay; again, however, in some parts of the world only. While available vaccines are effective, it would be desirable to also have more classical vaccines at hand for the future. Key feature of vaccines for long-term control of SARS-CoV-2 would be inexpensive production at large scale, ability to make multiple booster injections, and long-term stability at 4℃.

METHODS

Here, we describe such a vaccine candidate, consisting of the SARS-CoV-2 receptor-binding motif (RBM) grafted genetically onto the surface of the immunologically optimized cucumber mosaic virus, called CuMVTT -RBM.

RESULTS

Using bacterial fermentation and continuous flow centrifugation for purification, the yield of the production process is estimated to be >2.5 million doses per 1000-litre fermenter run. We demonstrate that the candidate vaccine is highly immunogenic in mice and rabbits and induces more high avidity antibodies compared to convalescent human sera. The induced antibodies are more cross-reactive to mutant RBDs of variants of concern (VoC). Furthermore, antibody responses are neutralizing and long-lived. In addition, the vaccine candidate was stable for at least 14 months at 4℃.

CONCLUSION

Thus, the here presented VLP-based vaccine may be a good candidate for use as conventional vaccine in the long term.

In vitro data suggest that Indian delta variant B.1.617 of SARS-CoV-2 escapes neutralization by both receptor affinity and immune evasion

BACKGROUND

Emerged mutations can be attributed to increased transmissibility of the B.1.617 and B.1.36 Indian delta variants of SARS-CoV-2, most notably substitutions L452R/E484Q and N440K, respectively, which occur in the receptor-binding domain (RBD) of the Spike (S) fusion glycoprotein.

OBJECTIVE

We aimed to assess the effects of mutations L452R/E484Q and N440K (as well as the previously studied mutation E484K present in variants B.1.351 and P.1) on the affinity of RBD for ACE2, SARS-CoV-2 main receptor. We also aimed to assess the ability of antibodies induced by natural infection or by immunization with BNT162b2 mRNA vaccine to recognize the mutated versions of the RBD, as well as blocking the interaction RBD-ACE2, an important surrogate readout for virus neutralization.

METHODS

To this end, we produced recombinant wild-type RBD, as well as RBD containing each of the mutations L452R/E484Q, N440K, or E484K (the latest present in variants of concern B.1.351 and P.1), as well as the ectodomain of ACE2. Using Biolayer Interferometry (BLI), we measured the binding affinity of RBD for ACE2 and the ability of sera from COVID-19 convalescent donors or subjects immunized with BNT162b2 mRNA vaccine to block this interaction. Finally, we correlated these results with total anti-RBD IgG titers measured from the same sera by direct ELISA.

RESULTS

The binding assays showed L452R/E484Q double-mutant RBD to interact with ACE2 with higher affinity (KD  = 4.6 nM) than wild-type (KD  = 21.3 nM) or single mutants N440K (KD  = 9.9 nM) and E484K (KD  = 19.7 nM) RBDs. Meanwhile, the anti-RBD IgG titration resulted in lower recognition of mutants E484K and L452R/E484Q by infection-induced antibodies, whereas only mutant E484K was recognized less by antibodies induced by vaccination. More interestingly, sera from convalescent as well as immunized subjects showed reduced ability to block the interaction between ACE2 and RBD mutants E484K and L452R/E484Q, as shown by the inhibition assays.

CONCLUSION

Our data suggest that the newly emerged SARS-CoV-2 variant B.1.617, as well as the better-studied variants B.1.351 and P.1 (all containing a mutation at position E484) display increased transmissibility both due to their higher affinity for the cell receptor ACE2 and their ability to partially bypass immunity generated against the wild-type virus. For variant B.1.36 (with a point mutation at position N440), only increased affinity seems to play a role.

Molecular definition of severe acute respiratory syndrome coronavirus 2 receptor-binding domain mutations: Receptor affinity versus neutralization of receptor interaction

Background

Several new variants of SARS‐CoV‐2 have emerged since fall 2020 which have multiple mutations in the receptor‐binding domain (RBD) of the spike protein. It is unclear which mutations affect receptor affinity versus immune recognition.

Methods

We produced wild type RBD, RBD with single mutations (E484K, K417N, or N501Y) or with all three mutations combined and tested their binding to ACE2 by biolayer interferometry (BLI). The ability of convalescent sera to recognize RBDs and block their interaction with ACE2 was tested as well.

Results

We demonstrated that single mutation N501Y increased binding affinity to ACE2 but did not strongly affect its recognition by convalescent sera. In contrast, single mutation E484K had almost no impact on the binding kinetics, but essentially abolished recognition of RBD by convalescent sera. Interestingly, combining mutations E484K, K417N, and N501Y resulted in a RBD with both features: enhanced receptor binding and abolished immune recognition.

Conclusions

Our data demonstrate that single mutations either affect receptor affinity or immune recognition while triple mutant RBDs combine both features.

A Novel Double Mosaic Virus-like Particle-Based Vaccine against SARS-CoV-2 Incorporates Both Receptor Binding Motif (RBM) and Fusion Domain

COVID-19 has emerged, and has rapidly become a major health problem worldwide, causing millions of mortalities. Vaccination against COVID-19 is the most efficient way to stop the pandemic. The goal of vaccines is to induce neutralizing antibodies against SARS-CoV-2 virus. Here, we present a novel double mosaic virus-like particle (VLP) displaying two independent neutralizing epitopes, namely the receptor binding motif (RBM) located in S1 and the fusion peptide (AA 817-855) located in S2. CuMVTT virus-like particles were used as VLP scaffold and both domains were genetically fused in the middle of CuMVTT subunits, which co-assembled into double mosaic particles (CuMVTT-DF). A single fusion mosaic particle (CuMVTT-FP) containing the fusion peptide only was used for comparison. The vaccines were produced in E. coli, and electron microscopy and dynamic light scattering confirmed their integrity and homogeneity. In addition, the CuMVTT-DF vaccine was well recognized by ACE2 receptor, indicating that the RBM was in native conformation. Both CuMVTT-FP and CuMVTT-DF vaccines induced high levels of high avidity IgG antibodies as well as IgA recognizing spike and RBD in the case of CuMVTT-DF. Both vaccine candidates induced virus-neutralizing antibodies indicating that the fusion peptide can independently induce virus-neutralizing antibodies. In contrast, CuMVTT-DF containing both RBM and fusion peptide induced a higher level of neutralizing antibodies suggesting that the new double mosaic vaccine candidate CuMVTT-DF consisting of two antigens in one VLP maybe an attractive candidate for scale-up in a bacterial fermentation process for clinical development.

Low-affinity but high-avidity interactions may offer an explanation for IgE-mediated allergen cross-reactivity

Background

Allergy is a global disease with overall frequencies of >20%. Symptoms vary from irritating local itching to life‐threatening systemic anaphylaxis. Even though allergies are allergen‐specific, there is a wide range of cross‐reactivities (eg apple and latex) that remain largely unexplained. Given the abilities of low‐affinity IgG antibodies to inhibit mast cells activation, here we elucidate the minimal affinity of IgE antibodies to induce type I hypersensitivity.

Methods

Three mature (high‐affinity) IgE antibodies recognizing three distinct epitopes on Fel d 1, the major cat allergen, were back‐mutated to germline conformation, resulting in binding to Fel d 1 with low affinity. The ability of these IgE antibodies to activate mast cells in vitro and in vivo was tested.

Results

We demonstrate that affinities as low as 10⁻⁷ M are sufficient to activate mast cells in vitro and drive allergic reactions in vivo. Low‐affinity IgE antibodies are able to do so, since they bind allergens bivalently on the surface of mast cells, leading to high‐avidity interactions.

Conclusions

These results suggest that the underlying mechanism of allergen cross‐reactivity may be low‐affinity but high‐avidity binding between IgE antibodies and cross‐reactive allergen.

Augmenting the Immune Response against a Stabilized HIV-1 Clade C Envelope Trimer by Silica Nanoparticle Delivery

The delivery of HIV-1 envelope (Env) trimer-based immunogens on the surface of nanoparticles holds promise to promote immunogenicity with the aim of inducing a potent, durable and broad neutralizing antibody (bnAb) response. Towards that goal, we examined the covalent conjugation of Env to 100 nm and 200 nm silica nanoparticles (SiNPs) to optimize conjugation density and attachment stability. Env was redesigned to enable site-specific cysteine-mediated covalent conjugation while maintaining its structural integrity and antigenicity. Env was anchored to different sized SiNPs with a calculated spacing of 15 nm between adjacent trimers. Both particle sizes exhibited high in vitro stability over a seven-day period. After attachment, 100 nm particles showed better colloidal stability compared to 200 nm particles. Importantly, the antigenic profile of Env was not impaired by surface attachment, indicating that the quaternary structure was maintained. In vitro Env uptake by dendritic cells was significantly enhanced when Env was delivered on the surface of nanoparticles compared to soluble Env. Furthermore, multivalent Env displayed efficiently activated B cells even at Env concentrations in the low nanomolar range. In mice, antibody responses to nanoparticle-coupled Env were stronger compared to the free protein and had equivalent effects at lower doses and without adjuvant.

Glycan-specific IgG anti-IgE autoantibodies are protective against allergic anaphylaxis in a murine model

BACKGROUND

IgE causes anaphylaxis in type I hypersensitivity diseases by activating degranulation of effector cells such as mast cells and basophils. The mechanisms that control IgE activity and prevent anaphylaxis under normal conditions are still enigmatic.

OBJECTIVE

We aimed to unravel how anti-IgE autoantibodies are induced and we aimed to understand their role in regulating serum IgE level and allergic anaphylaxis.

METHODS

We immunized mice with different forms of IgE and tested anti-IgE autoantibody responses and their specificities. We then analyzed the effect of those antibodies on serum kinetics and their in vitro and in vivo impact on anaphylaxis. Finally, we investigated anti-IgE autoantibodies in human sera.

RESULTS

Immunization of mice with IgE-immune complexes induced glycan-specific anti-IgE autoantibodies. The anti-IgE autoantibodies prevented effector cell sensitization, reduced total IgE serum levels, protected mice from passive and active IgE sensitization, and resulted in cross-protection against different allergens. Furthermore, glycan-specific anti-IgE autoantibodies were present in sera from subjects with allergy and subjects without allergy.

CONCLUSION

In conclusion, this study provided the first evidence that in the murine model, the serum level and anaphylactic activity of IgE may be downregulated by glycan-specific IgG anti-IgE autoantibodies.

Accuracy of serological testing for SARS-CoV-2 antibodies: First results of a large mixed-method evaluation study

BACKGROUND

Serological immunoassays that can identify protective immunity against SARS-CoV-2 are needed to adapt quarantine measures, assess vaccination responses, and evaluate donor plasma. To date, however, the utility of such immunoassays remains unclear. In a mixed-design evaluation study, we compared the diagnostic accuracy of serological immunoassays that are based on various SARS-CoV-2 proteins and assessed the neutralizing activity of antibodies in patient sera.

METHODS

Consecutive patients admitted with confirmed SARS-CoV-2 infection were prospectively followed alongside medical staff and biobank samples from winter 2018/2019. An in-house enzyme-linked immunosorbent assay utilizing recombinant receptor-binding domain (RBD) of the SARS-CoV-2 spike protein was developed and compared to three commercially available enzyme-linked immunosorbent assays (ELISAs) targeting the nucleoprotein (N), the S1 domain of the spike protein (S1), and a lateral flow immunoassay (LFI) based on full-length spike protein. Neutralization assays with live SARS-CoV-2 were performed.

RESULTS

One thousand four hundred and seventy-seven individuals were included comprising 112 SARS-CoV-2 positives (defined as a positive real-time PCR result; prevalence 7.6%). IgG seroconversion occurred between day 0 and day 21. While the ELISAs showed sensitivities of 88.4% for RBD, 89.3% for S1, and 72.9% for N protein, the specificity was above 94% for all tests. Out of 54 SARS-CoV-2 positive individuals, 96.3% showed full neutralization of live SARS-CoV-2 at serum dilutions ≥ 1:16, while none of the 6 SARS-CoV-2-negative sera revealed neutralizing activity.

CONCLUSIONS

ELISAs targeting RBD and S1 protein of SARS-CoV-2 are promising immunoassays which shall be further evaluated in studies verifying diagnostic accuracy and protective immunity against SARS-CoV-2.

The impact of size on particle drainage dynamics and antibody response

Vaccine-induced immune response can be greatly enhanced by mimicking pathogen properties. The size and the repetitive geometric shape of virus-like particles (VLPs) influence their immunogenicity by facilitating drainage to secondary lymphoid organs and enhancing interaction with and activation of B cells and innate humoral immune components. VLPs derived from the plant Bromovirus genus, specifically cowpea chlorotic mottle virus (CCMV), are T = 3 icosahedral particles. (T) is the triangulation number that refers to the number and arrangements of the subunits (pentamers and hexamers) of the VLPs. CCMV-VLPs can be easily expressed in an E. coli host system and package ssRNA during the expression process. Recently, we have engineered CCMV-VLPs by incorporating the universal tetanus toxin (TT) epitope at the N-terminus. The modified CCMV_TT-VLPs successfully form icosahedral particles T = 3, with a diameter of ~30 nm analogous to the parental VLPs. Interestingly, incorporating TT epitope at the C-terminus of CCMV_TT-VLPs results in the formation of Rod-shaped VLPs, ~1 μm in length and ~ 30 nm in width. In this study, we have investigated the draining kinetics and immunogenicity of both engineered forms (termed as Round-shaped CCMV_TT-VLPs and Rod-shaped CCMV_TT-VLPs) as potential B cell immunogens using different in vitro and in vivo assays. Our results reveal that Round-shaped CCMV_TT-VLPs are more efficient in draining to secondary lymphoid organs to charge professional antigen-presenting cells as well as B cells. Furthermore, compared to Rod-shaped CCMV_TT-VLPs, Round-shaped CCMV_TT-VLPs led to more than 100-fold increased systemic IgG and IgA responses accompanied by prominent formation of splenic germinal centers. Round-shaped CCMV_TT-VLPs could also polarize the induced T cell response toward Th1. To our knowledge, this is the first study investigating and comparing the draining kinetics and immunogenicity of one and the same VLP monomer forming nano-sized icosahedra or rods in the micrometer size.

SARS-CoV-2 structural features may explain limited neutralizing-antibody responses

Neutralizing antibody responses of SARS-CoV-2-infected patients may be low and of short duration. We propose here that coronaviruses employ a structural strategy to avoid strong and enduring antibody responses. Other viruses induce optimal and long-lived neutralizing antibody responses, thanks to 20 or more repetitive, rigid antigenic epitopes, spaced by 5–10 nm, present on the viral surface. Such arrays of repetitive and highly organized structures are recognized by the immune system as pathogen-associated structural patterns (PASPs), which are characteristic for pathogen surfaces. In contrast, coronaviruses are large particles with long spikes (S protein) embedded in a fluid membrane. Therefore, the neutralizing epitopes (which are on the S protein) are loosely “floating” and widely spaced by an average of about 25 nm. Consequently, recruitment of complement is poor and stimulation of B cells remains suboptimal, offering an explanation for the inefficient and short-lived neutralizing antibody responses.

Shaping Modern Vaccines: Adjuvant Systems Using MicroCrystalline Tyrosine (MCT®)

The concept of adjuvants or adjuvant systems, used in vaccines, exploit evolutionary relationships associated with how the immune system may initially respond to a foreign antigen or pathogen, thus mimicking natural exposure. This is particularly relevant during the non-specific innate stage of the immune response; as such, the quality of this response may dictate specific adaptive responses and conferred memory/protection to that specific antigen or pathogen. Therefore, adjuvants may optimise this response in the most appropriate way for a specific disease. The most commonly used traditional adjuvants are aluminium salts; however, a biodegradable adjuvant, MCT®, was developed for application in the niche area of allergy immunotherapy (AIT), also in combination with a TLR-4 adjuvant-Monophosphoryl Lipid A (MPL®)-producing the first adjuvant system approach for AIT in the clinic. In the last decade, the use and effectiveness of MCT® across a variety of disease models in the preclinical setting highlight it as a promising platform for adjuvant systems, to help overcome the challenges of modern vaccines. A consequence of bringing together, for the first time, a unified view of MCT® mode-of-action from multiple experiments and adjuvant systems will help facilitate future rational design of vaccines while shaping their success.

COVID-19: Mechanisms of Vaccination and Immunity

Vaccines are needed to protect from SARS-CoV-2, the virus causing COVID-19. Vaccines that induce large quantities of high affinity virus-neutralizing antibodies may optimally prevent infection and avoid unfavorable effects. Vaccination trials require precise clinical management, complemented with detailed evaluation of safety and immune responses. Here, we review the pros and cons of available vaccine platforms and options to accelerate vaccine development towards the safe immunization of the world's population against SARS-CoV-2. Favorable vaccines, used in well-designed vaccination strategies, may be critical for limiting harm and promoting trust and a long-term return to normal public life and economy.

Strategies to Prevent SARS-CoV-2-Mediated Eosinophilic Disease in Association with COVID-19 Vaccination and Infection

A vaccine to protect against COVID-19 is urgently needed. Such a vaccine should efficiently induce high-affinity neutralizing antibodies which neutralize SARS-CoV-2, the cause of COVID-19. However, there is a concern regarding both vaccine-induced eosinophilic lung disease and eosinophil-associated Th2 immunopotentiation following infection after vaccination. Here, we review the anticipated characteristics of a COVID-19 vaccine to avoid vaccine-associated eosinophil immunopathology.

The 3Ds in virus-like particle based-vaccines: "Design, Delivery and Dynamics"

Vaccines need to be rationally designed in order be delivered to the immune system for maximizing induction of dynamic immune responses. Virus‐like particles (VLPs) are ideal platforms for such 3D vaccines, as they allow the display of complex and native antigens in a highly repetitive form on their surface and can easily reach lymphoid organs in intact form for optimal activation of B and T cells. Adjusting size and zeta potential may allow investigators to further fine‐tune delivery to lymphoid organs. An additional way to alter vaccine transfer to lymph nodes and spleen may be the formulation with micron‐sized adjuvants that creates a local depot and results in a slow release of antigen and adjuvant. Ideally, the adjuvant in addition stimulates the innate immune system. The dynamics of the immune response may be further enhanced by inclusion of Toll‐like receptor ligands, which many VLPs naturally package. Hence, considering the 3Ds in vaccine development may allow for enhancement of their attributes to tackle complex diseases, not usually amenable to conventional vaccine strategies.

Safety Profile of a Virus-Like Particle-Based Vaccine Targeting Self-Protein Interleukin-5 in Horses

Background: Insect bite hypersensitivity (IBH) is an eosinophilic allergic dermatitis of horses caused by type I/IVb reactions against mainly Culicoides bites. The vaccination of IBH-affected horses with equine IL-5 coupled to the Cucumber mosaic virus-like particle (eIL-5-CuMV_TT) induces IL-5-specific auto-antibodies, resulting in a significant reduction in eosinophil levels in blood and clinical signs. Objective: the preclinical and clinical safety of the eIL-5-CuMV_TT vaccine. Methods: The B cell responses were assessed by longitudinal measurement of IL-5- and CuMV_TT-specific IgG in the serum and plasma of vaccinated and unvaccinated horses. Further, peripheral blood mononuclear cells (PBMCs) from the same horses were re-stimulated in vitro for the proliferation and IFN-γ production of specific T cells. In addition, we evaluated longitudinal kidney and liver parameters and the general blood status. An endogenous protein challenge was performed in murine IL-5-vaccinated mice. Results: The vaccine was well tolerated as assessed by serum and cellular biomarkers and also induced reversible and neutralizing antibody titers in horses and mice. Endogenous IL-5 stimulation was unable to re-induce anti-IL-5 production. The CD4⁺ T cells of vaccinated horses produced significantly more IFN-γ and showed a stronger proliferation following stimulation with CuMV_TT as compared to the unvaccinated controls. Re-stimulation using E. coli-derived proteins induced low levels of IFNγ⁺CD4⁺ cells in vaccinated horses; however, no IFN-γ and proliferation were induced following the HEK-eIL-5 re-stimulation. Conclusions: Vaccination using eIL-5-CuMV_TT induces a strong B-cell as well as CuMV_TT-specific T cell response without the induction of IL-5-specific T cell responses. Hence, B-cell unresponsiveness against self-IL-5 can be bypassed by inducing CuMV_TT carrier-specific T cells, making the vaccine a safe therapeutic option for IBH-affected horses.

Vaccine against peanut allergy based on engineered virus-like particles displaying single major peanut allergens

BACKGROUND

Peanut allergy is a severe and increasingly frequent disease with high medical, psychosocial, and economic burden for affected patients and wider society. A causal, safe, and effective therapy is not yet available.

OBJECTIVE

We sought to develop an immunogenic, protective, and nonreactogenic vaccine candidate against peanut allergy based on virus-like particles (VLPs) coupled to single peanut allergens.

METHODS

To generate vaccine candidates, extracts of roasted peanut (Ara R) or the single allergens Ara h 1 or Ara h 2 were coupled to immunologically optimized Cucumber Mosaic Virus-derived VLPs (CuMVtt). BALB/c mice were sensitized intraperitoneally with peanut extract absorbed to alum. Immunotherapy consisted of a single subcutaneous injection of CuMVtt coupled to Ara R, Ara h 1, or Ara h 2.

RESULTS

The vaccines CuMVtt-Ara R, CuMVtt-Ara h 1, and CuMVtt-Ara h 2 protected peanut-sensitized mice against anaphylaxis after intravenous challenge with the whole peanut extract. Vaccines did not cause allergic reactions in sensitized mice. CuMVtt-Ara h 1 was able to induce specific IgG antibodies, diminished local reactions after skin prick tests, and reduced the infiltration of the gastrointestinal tract by eosinophils and mast cells after oral challenge with peanut. The ability of CuMVtt-Ara h 1 to protect against challenge with the whole extract was mediated by IgG, as shown via passive IgG transfer. FcγRIIb was required for protection, indicating that immune complexes with single allergens were able to block the allergic response against the whole extract, consisting of a complex allergen mixture.

CONCLUSIONS

Our data suggest that vaccination using single peanut allergens displayed on CuMVtt may represent a novel therapy against peanut allergy with a favorable safety profile.

Interleukin 31 in insect bite hypersensitivity-Alleviating clinical symptoms by active vaccination against itch

BACKGROUND

Insect bite hypersensitivity (IBH) is the most common seasonal pruritic allergic dermatitis of horses occurring upon insect bites. In recent years, a major role for IL-31 in allergic pruritus of humans, monkeys, dogs, and mice was acknowledged. Here, we investigate the role of IL-31 in IBH of horses and developed a therapeutic vaccine against equine IL-31 (eIL-31).

METHODS

IL-31 levels were quantified in allergen-stimulated peripheral blood mononuclear cells (PBMCs) and skin punch biopsies of IBH lesions and healthy skin from IBH-affected and healthy horses. The vaccine consisted of eIL-31 covalently coupled to a virus-like particle (VLP) derived from cucumber mosaic virus containing a tetanus toxoid universal T-cell epitope (CuMVTT). Eighteen IBH-affected horses were recruited and immunized with 300 μg of eIL-31-CuMVTT vaccine or placebo and IBH severity score was recorded.

RESULTS

IL-31 was increased in PBMCs and exclusively detectable in skin lesions of IBH-affected horses. Vaccination against eIL-31 reduced delta clinical scores when compared to previous untreated IBH season of the same horses and to placebo-treated horses in the same year. The vaccine was well tolerated without safety concerns throughout the study.

CONCLUSION

TH2-derived IL-31 is involved in IBH pathology and accordingly the immunotherapeutic vaccination approach targeting IL-31 alleviated clinical scores in affected horses.

State-of-the-art in marketed adjuvants and formulations in Allergen Immunotherapy: A position paper of the European Academy of Allergy and Clinical Immunology (EAACI)

Since the introduction of allergen immunotherapy (AIT) over 100 years ago, focus has been on standardization of allergen extracts, with reliable molecular composition of allergens receiving the highest attention. While adjuvants play a major role in European AIT, they have been less well studied. In this Position Paper, we summarize current unmet needs of adjuvants in AIT citing current evidence. Four adjuvants are used in products marketed in Europe: aluminium hydroxide (Al(OH)₃ ) is the most frequently used adjuvant, with microcrystalline tyrosine (MCT), monophosphoryl lipid A (MPLA) and calcium phosphate (CaP) used less frequently. Recent studies on humans, and using mouse models, have characterized in part the mechanisms of action of adjuvants on pre-existing immune responses. AIT differs from prophylactic vaccines that provoke immunity to infectious agents, as in allergy the patient is presensitized to the antigen. The intended mode of action of adjuvants is to simultaneously enhance the immunogenicity of the allergen, while precipitating the allergen at the injection site to reduce the risk of anaphylaxis. Contrasting immune effects are seen with different adjuvants. Aluminium hydroxide initially boosts Th2 responses, while the other adjuvants utilized in AIT redirect the Th2 immune response towards Th1 immunity. After varying lengths of time, each of the adjuvants supports tolerance. Further studies of the mechanisms of action of adjuvants may advise shorter treatment periods than the current three-to-five-year regimens, enhancing patient adherence. Improved lead compounds from the adjuvant pipeline are under development and are explored for their capacity to fill this unmet need.

A Single Monoclonal Antibody against the Peanut Allergen Ara h 2 Protects against Systemic and Local Peanut Allergy

BACKGROUND

Peanut allergy is the most prevalent and dangerous food allergy. Peanuts consist of a large number of different allergens and peanut-allergic patients are frequently sensitized to multiple allergens. Hence, conventional desensitization approaches aim at targeting as many allergens as possible.

METHODS

The monoclonal anti-Ara h 2 antibody (mAb) was produced by hybridoma cells derived from WT BALB/c mice after immunization with a vaccine based on virus-like particles coupled to Ara h 2. BALB/c mice were sensitized intraperitoneally with peanut extract absorbed to alum and mAbs were applied i.v. Challenge was performed the next day with the whole peanut extract intravenously and via skin prick test.

RESULTS

Here we show in peanut-allergic mice that a single high-affinity mAb specific for Ara h 2 is able to block systemic and local allergic reactions induced by the complex peanut extract. We confirm in vitro binding of the mAb to the inhibitory low-affinity FcγRIIb receptor using a sensitive biosensor and demonstrate in vivo that protection was dependent on FcγRIIb.

CONCLUSION

A single mAb specific for Ara h 2 is able to improve local and systemic allergic symptoms induced by the whole allergen mixture.

Immunization of Cats against Fel d 1 Results in Reduced Allergic Symptoms of Owners

An innovative approach was tested to treat cat allergy in humans by vaccinating cats with Fel-CuMV (HypoCat^TM), a vaccine against the major cat allergen Fel d 1 based on virus-like particles derived from cucumber mosaic virus (CuMV-VLPs). Upon vaccination, cats develop neutralizing antibodies against the allergen Fel d 1, which reduces the level of reactive allergen, thus lowering the symptoms or even preventing allergic reactions in humans. The combined methodological field study included ten cat-allergic participants who lived together with their cats (n = 13), that were immunized with Fel-CuMV. The aim was to determine methods for measuring a change in allergic symptoms. A home-based provocation test (petting time and organ specific symptom score (OSSS)) and a general weekly (or monthly) symptom score (G(W)SS) were used to assess changes in allergic symptoms. The petting time until a pre-defined level of allergic symptoms was reached increased already early after vaccination of the cats and was apparent over the course of the study. In addition, the OSSS after provocation and G(W)SS recorded a persistent reduction in symptoms over the study period and could serve for long-term assessment. Hence, the immunization of cats with HypoCat^TM (Fel-CuMV) may have a positive impact on the cat allergy of the owner, and changes could be assessed by the provocation test as well as G(W)SS.