An adjuvant strategy enabled by modulation of the physical properties of microbial ligands expands antigen immunogenicity

Activation of the innate immune system via pattern recognition receptors (PRRs) is key to generate lasting adaptive immunity. PRRs detect unique chemical patterns associated with invading microorganisms, but whether and how the physical properties of PRR ligands influence the development of the immune response remains unknown. Through the study of fungal mannans, we show that the physical form of PRR ligands dictates the immune response. Soluble mannans are immunosilent in the periphery but elicit a potent pro-inflammatory response in the draining lymph node (dLN). By modulating the physical form of mannans, we developed a formulation that targets both the periphery and the dLN. When combined with viral glycoprotein antigens, this mannan formulation broadens epitope recognition, elicits potent antigen-specific neutralizing antibodies, and confers protection against viral infections of the lung. Thus, the physical properties of microbial ligands determine the outcome of the immune response and can be harnessed for vaccine development.

Balanced T and B cell responses are required for immune protection against Powassan virus in virus-like particle vaccination

Powassan virus (POWV) is a tick-borne pathogen for which humans are an incidental host. POWV infection can be fatal or result in long-term neurological sequelae; however, there are no approved vaccinations for POWV. Integral to efficacious vaccine development is the identification of correlates of protection, which we accomplished in this study by utilizing a murine model of POWV infection. Using POWV lethal and sub-lethal challenge models, we show that (1) robust B and T cell responses are necessary for immune protection, (2) POWV lethality can be attributed to both viral- and host-mediated drivers of disease, and (3) knowledge of the immune correlates of protection against POWV can be applied in a virus-like particle (VLP)-based vaccination approach that provides protection from lethal POWV challenge. Identification of these immune protection factors is significant as it will aid in the rational design of POWV vaccines.

A functional spleen contributes to afucosylated IgG in humans

As a lymphoid organ, the spleen hosts a wide range of immune cell populations, which not only remove blood-borne antigens, but also generate and regulate antigen-specific immune responses. In particular, the splenic microenvironment has been demonstrated to play a prominent role in adaptive immune responses to enveloped viral infections and alloantigens. During both types of immunizations, antigen-specific immunoglobulins G (IgGs) have been characterized by the reduced amount of fucose present on N-linked glycans of the fragment crystallizable (Fc) region. These glycans are essential for mediating the induction of immune effector functions. Therefore, we hypothesized that a spleen may modulate humoral responses and serve as a preferential site for afucosylated IgG responses, which potentially play a role in immune thrombocytopenia (ITP) pathogenesis. To determine the role of the spleen in IgG-Fc glycosylation, we performed IgG subclass-specific liquid chromatography-mass spectrometry (LC-MS) analysis of Fc glycosylation in a large cohort of individuals splenectomized due to trauma, due to ITP, or spherocytosis. IgG-Fc fucosylation was consistently increased after splenectomy, while no effects for IgG-Fc galactosylation and sialylation were observed. An increase in IgG1- and IgG2/3-Fc fucosylation level upon splenectomy has been reported here for the first time, suggesting that immune responses occurring in the spleen may be particularly prone to generate afucosylated IgG responses. Surprisingly, the level of total IgG-Fc fucosylation was decreased in ITP patients compared to healthy controls. Overall, our results suggest a yet unrecognized role of the spleen in either the induction or maintenance of afucosylated IgG responses by B cells.

Immunohistochemical Evaluation of Adaptor Protein FAM159B Expression in Normal and Neoplastic Human Tissues

FAM159B is a so-called adaptor protein. These proteins are essential components in numerous cell signalling pathways. However, little is known regarding FAM159B expression in normal and neoplastic human tissues. The commercially available rabbit polyclonal anti-human FAM159B antibody HPA011778 was initially characterised for its specificity using Western blot analyses and immunocytochemistry and then applied to a large series of formalin-fixed, paraffin-embedded normal and neoplastic human tissue samples. Confirmation of FAM159B's predicted size and antibody specificity was achieved in BON-1 cells, a neuroendocrine tumour cell line endogenously expressing FAM159B, using targeted siRNA. Immunocytochemical experiments additionally revealed cytoplasmic expression of the adaptor protein. Immunohistochemical staining detected FAM159B expression in neuronal and neuroendocrine tissues such as the cortex, the trigeminal ganglia, dorsal root and intestinal ganglia, the pancreatic islets and the neuroendocrine cells of the bronchopulmonary and gastrointestinal tract, but also in the syncytiotrophoblasts of the placenta. FAM159B was also expressed in many of the 28 tumour entities investigated, with high levels in medullary and anaplastic thyroid carcinomas, parathyroid adenomas, lung and ovarian carcinomas, lymphomas and neuroendocrine tumours of different origins. The antibody HPA011778 can act as a useful tool for basic research and identifying FAM159B expression in tissue samples.

A novel linear epitope at the C-terminal region of the classical swine fever virus E2 protein elicits neutralizing activity

Classical swine fever virus (CSFV) is a member of the genus Pestivirus, which causes serious economic losses. The re-emergence of the disease in Japan in 2018 has increased awareness of CSFV. In this study, Balb/c mice were immunized with plant-derived E2 protein, and four monoclonal antibodies (mAbs) 4B11, 7B3, 11A5 and 6F3 were generated. Two of these mAbs, 4B11 and 7B3, effectively blocked CSFV infection of PK-15 cells. Both mAbs recognized a novel linear epitope, 256CLIGNTTVKVHASDER271. The neutralizing ability of anti-CSFV serum decreased 63%, when pre-incubated with the linear peptide at 200 μg/mL. Structural analysis showed that this linear epitope is present at the border of Domain C and Domain D on the surface of the E2 protein. Alignment of amino acid sequences showed that the epitope was conserved in different subgroups of CSFV but not in other members of the Pestivirus genus. Consistently with the analysis above, this epitope distinguished antibodies against CSFV from those against bovine viral diarrhea virus (BVDV). Our study provides an ideal candidate peptide for new vaccine design and differential diagnosis of CSFV. These findings will contribute to the control and eradication of classical swine fever.

Lrp1 is a host entry factor for Rift Valley fever virus

Rift Valley fever virus (RVFV) is a zoonotic pathogen with pandemic potential. RVFV entry is mediated by the viral glycoprotein (Gn), but host entry factors remain poorly defined. Our genome-wide CRISPR screen identified low-density lipoprotein receptor-related protein 1 (mouse Lrp1/human LRP1), heat shock protein (Grp94), and receptor-associated protein (RAP) as critical host factors for RVFV infection. RVFV Gn directly binds to specific Lrp1 clusters and is glycosylation independent. Exogenous addition of murine RAP domain 3 (mRAP_D3) and anti-Lrp1 antibodies neutralizes RVFV infection in taxonomically diverse cell lines. Mice treated with mRAP_D3 and infected with pathogenic RVFV are protected from disease and death. A mutant mRAPD3 that binds Lrp1 weakly failed to protect from RVFV infection. Together, these data support Lrp1 as a host entry factor for RVFV infection and define a new target to limit RVFV infections.

Anisakis pegreffii Extract Induces Airway Inflammation with Airway Remodeling in a Murine Model System

Exposure of the respiratory system to the Anisakis pegreffii L3 crude extract (AE) induces airway inflammation; however, the mechanism underlying this inflammatory response remains unknown. AE contains allergens that promote allergic inflammation; exposure to AE may potentially lead to asthma. In this study, we aimed to establish a murine model to assess the effects of AE on characteristic features of chronic asthma, including airway hypersensitivity (AHR), airway inflammation, and airway remodeling. Mice were sensitized for five consecutive days each week for 4 weeks. AHR, lung inflammation, and airway remodeling were evaluated 24 h after the last exposure. Lung inflammation and airway remodeling were assessed from the bronchoalveolar lavage fluid (BALF). To confirm the immune response in the lungs, changes in gene expression in the lung tissue were assessed with reverse transcription-quantitative PCR. The levels of IgE, IgG1, and IgG2a in blood and cytokine levels in the BALF, splenocyte, and lung lymph node (LLN) culture supernatant were measured with ELISA. An increase in AHR was prominently observed in AE-exposed mice. Epithelial proliferation and infiltration of inflammatory cells were observed in the BALF and lung tissue sections. Collagen deposition was detected in lung tissues. AE exposure increased IL-4, IL-5, and IL-13 expression in the lung, as well as the levels of antibodies specific to AE. IL-4, IL-5, and IL-13 were upregulated only in LLN. These findings indicate that an increase in IL-4+ CD4+ T cells in the LLN and splenocyte resulted in increased Th2 response to AE exposure. Exposure of the respiratory system to AE resulted in an increased allergen-induced Th2 inflammatory response and AHR through accumulation of inflammatory and IL-4+ CD4+ T cells and collagen deposition. It was confirmed that A. pegreffii plays an essential role in causing asthma in mouse models and has the potential to cause similar effects in humans.

Epitope-specific antibody responses differentiate COVID-19 outcomes and variants of concern

BACKGROUNDThe role of humoral immunity in COVID-19 is not fully understood, owing, in large part, to the complexity of antibodies produced in response to the SARS-CoV-2 infection. There is a pressing need for serology tests to assess patient-specific antibody response and predict clinical outcome.METHODSUsing SARS-CoV-2 proteome and peptide microarrays, we screened 146 COVID-19 patients' plasma samples to identify antigens and epitopes. This enabled us to develop a master epitope array and an epitope-specific agglutination assay to gauge antibody responses systematically and with high resolution.RESULTSWe identified linear epitopes from the spike (S) and nucleocapsid (N) proteins and showed that the epitopes enabled higher resolution antibody profiling than the S or N protein antigen. Specifically, we found that antibody responses to the S-811-825, S-881-895, and N-156-170 epitopes negatively or positively correlated with clinical severity or patient survival. Moreover, we found that the P681H and S235F mutations associated with the coronavirus variant of concern B.1.1.7 altered the specificity of the corresponding epitopes.CONCLUSIONEpitope-resolved antibody testing not only affords a high-resolution alternative to conventional immunoassays to delineate the complex humoral immunity to SARS-CoV-2 and differentiate between neutralizing and non-neutralizing antibodies, but it also may potentially be used to predict clinical outcome. The epitope peptides can be readily modified to detect antibodies against variants of concern in both the peptide array and latex agglutination formats.FUNDINGOntario Research Fund (ORF) COVID-19 Rapid Research Fund, Toronto COVID-19 Action Fund, Western University, Lawson Health Research Institute, London Health Sciences Foundation, and Academic Medical Organization of Southwestern Ontario (AMOSO) Innovation Fund.

Immune response characterization in a human challenge study with a Shigella flexneri 2a bioconjugate vaccine

BACKGROUND

Diarrheal diseases are a leading cause of global morbidity and mortality affecting all ages, but especially children under the age of five in resource-limited settings. Shigella is a leading contributor to diarrheal diseases caused by bacterial pathogens and is considered a significant antimicrobial resistance threat. While improvements in hygiene, and access to clean water help as control measures, vaccination remains one of the most viable options for significantly reducing morbidity and mortality.

METHODS

Flexyn2a is a bioconjugate vaccine manufactured using novel conjugation methodologies enzymatically linking the O-polysaccharide of S. flexneri 2a to exotoxin A of Pseudomonas aeruginosa. The protective capacity of Flexyn2a was assessed in a controlled human infection model after two intramuscular immunizations. Immune responses pre- and post-immunization and/or infection were investigated and are described here.

FINDINGS

Flexyn2a induced lipopolysaccharide (LPS)-specific serum IgG responses post-immunization which were associated with protection against shigellosis. Additionally, several other immune parameters, including memory B cell responses, bactericidal antibodies and serum IgA, were also elevated in vaccinees protected against shigellosis. Immunization with Flexyn2a also induced gut-homing, LPS-specific IgG and IgA secreting B cells, indicating the vaccine induced immune effectors functioning at the site of intestinal infection.

INTERPRETATION

Collectively, the results of these immunological investigations provide insights into protective immune mechanisms post-immunization with Flexyn2a which can be used to further guide vaccine development and may have applicability to the larger Shigella vaccine field.

FUNDING

Funding for this study was provided through a Wellcome Trust grant.

Effects of early nutrition and sanitary conditions on antibody levels in early and later life of broiler chickens

Immune maturation of broiler chickens may be affected by management, such as early life feeding strategy (early versus delayed nutrition) or by low or high sanitary conditions (LSC versus HSC). We compared systemic maternal (MAb), natural (NAb), natural auto- (NAAb), and antigen specific antibody (SpAb) levels (IgM, IgY) between broilers (n = 48 per treatment) that received early (EN) or delayed nutrition for 72 h (DN) housed in either low (LSC) or high sanitary conditions (HSC) between 7 and 35 d of age. We found minimal interactions between feeding strategy and sanitary conditions. At 7 d of age, broilers receiving EN compared with DN, had elevated levels of IgM binding keyhole limpet hemocyanin (KLH), phosphoryl-conjugated ovalbumin (PC-OVA), and muramyl dipeptide (MDP), whereas effects of feeding strategy diminished at later ages. In LSC compared with HSC broilers, levels of NAb agglutinating RRBC and sheep red blood cells (SRBC) were already elevated from 14 d of age onwards. At 33 d of age, antibody levels (NAb, NAAb, anti-LPS, anti-MDP) were all elevated in LSC, compared with HSC broilers, for both IgM and IgY, but not IgM against KLH. Western blotting revealed different binding patterns of NAAb against chicken liver homogenate, which may indicate that the NAAb repertoire is affected by antigenic pressure. Our data suggest that antibody levels are affected for an important part by environmental conditions (feeding strategy and sanitary conditions), but minimally by their interaction. However, it remains to be further studied whether the enhanced levels of antibodies as initiated by EN and LSC contribute to enhanced resistance to infectious diseases.

One or two injections of MVA-vectored vaccine shields hACE2 transgenic mice from SARS-CoV-2 upper and lower respiratory tract infection

Modified vaccinia virus Ankara (MVA) is a replication-restricted smallpox vaccine, and numerous clinical studies of recombinant MVAs (rMVAs) as vectors for prevention of other infectious diseases, including COVID-19, are in progress. Here, we characterize rMVAs expressing the S protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Modifications of full-length S individually or in combination included two proline substitutions, mutations of the furin recognition site, and deletion of the endoplasmic retrieval signal. Another rMVA in which the receptor binding domain (RBD) is flanked by the signal peptide and transmembrane domains of S was also constructed. Each modified S protein was displayed on the surface of rMVA-infected cells and was recognized by anti-RBD antibody and soluble hACE2 receptor. Intramuscular injection of mice with the rMVAs induced antibodies, which neutralized a pseudovirus in vitro and, upon passive transfer, protected hACE2 transgenic mice from lethal infection with SARS-CoV-2, as well as S-specific CD3+CD8+IFNγ+ T cells. Antibody boosting occurred following a second rMVA or adjuvanted purified RBD protein. Immunity conferred by a single vaccination of hACE2 mice prevented morbidity and weight loss upon intranasal infection with SARS-CoV-2 3 wk or 7 wk later. One or two rMVA vaccinations also prevented detection of infectious SARS-CoV-2 and subgenomic viral mRNAs in the lungs and greatly reduced induction of cytokine and chemokine mRNAs. A low amount of virus was found in the nasal turbinates of only one of eight rMVA-vaccinated mice on day 2 and none later. Detection of low levels of subgenomic mRNAs in turbinates indicated that replication was aborted in immunized animals.

Rapid and reliable hybridoma screening method that is suitable for production of functional structure-recognizing monoclonal antibody

Monoclonal antibodies are extremely valuable functional biomaterials that are widely used not only in life science research but also in antibody drugs and test drugs. There is also a strong need to develop high-quality neutralizing antibodies as soon as possible in order to stop the rapid spread of new infectious diseases such as the SARS-CoV-2 virus. This study has developed a membrane-type immunoglobulin-directed hybridoma screening (MIHS) method for obtaining high-quality monoclonal antibodies with high efficiency and high speed. In addition to these advantages, this paper demonstrates that the MIHS method can selectively obtain monoclonal antibodies that specifically recognize the functional structure of proteins. The MIHS method is a useful technology that greatly contributes to the research community because it can be easily introduced in any laboratory that uses a flow cytometer.

EDTA-K2 Improves the Detection Sensitivity of SARS-CoV-2 IgM and IgG Antibodies by Chelating Colloidal Gold in the Immunochromatographic Assay

OBJECTIVE

The coronavirus disease (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is now rapidly spreading globally. Serological tests are an important method to assist in the diagnosis of COVID-19, used for epidemiological investigations. In this study, we aimed to investigate the impact of different types of vacuum collection tubes on the detection of SARS-CoV-2 IgM and IgG antibodies, using the colloidal gold immunochromatographic assay (GICA).

PATIENTS AND METHODS

A total of 112 patients with COVID-19 and 200 healthy control subjects with no infection were enrolled in this study. Their serum and plasma were collected into four different types of vacuum blood collection tubes. SARS-CoV-2 IgM and IgG specific antibodies in the plasma and serum were then detected by GICA and chemiluminescence assay (CA), respectively. In addition, the particle sizes of different colloidal gold solutions in the presence of different anticoagulants and coagulants were evaluated by both laser diffraction (Malvern) and confocal laser microscope, respectively.

RESULTS

Our results revealed that anticoagulated plasma with EDTA-K2 improved the positive detection rate of SARS-CoV-2 IgM antibodies. Furthermore, our results shown that the detection results by GICA and CA were highly consistent, especially, the results of EDTA-K2 anticoagulated plasma detected by GICA was more consistent with CA results. We confirmed that EDTA-K2 could improve the detection sensitivity of SARS-CoV-2 IgG antibodies by chelating excessive colloidal gold compared with sodium citrate or lithium heparin, these methodologies did not appear to cause false positives. Colloidal gold particles could be chelated and aggregated by EDTA-K2, but not by sodium citrate, lithium heparin and coagulants.

CONCLUSION

GICA is widely used to detect antibodies for the advantages of convenient, fast, low cost, suitable for screening large sample and require minimal equipment. In this study, we found that EDTA-K2 amplified the positive antibody signal by chelating colloidal gold and improved the detection sensitivity of SARS-CoV-2 IgM and IgG antibodies when using the GICA. Therefore, we suggested that EDTA-K2 anticoagulated plasma was more suitable for the detection of SARS-CoV-2 antibodies.

Latent 1,3-β-D-glucan acts as an adjuvant for allergen-specific IgE production induced by Japanese cedar pollen exposure

BACKGROUND

The pollen grains of several plant species contain 1,3-β-D-glucan (BG). BG activates dendritic cells (DCs) and subsequently regulates the innate immune responses. Within Japan, the most common disease associated with type-I hypersensitivity is Japanese cedar pollinosis. However, the role of BG in Japanese cedar pollen (JCP) remains unclear. This study examined the localization and immunological effects of BG in JCP.

METHODS

The localization of BG in JCP grain was determined by immunohistochemical staining using a soluble dectin-1 protein probe and a BG recognition protein (BGRP). The content of BG extracted from JCP was measured by a BGRP-based ELISA-like assay. The cytokine production by bone marrow-derived DCs (BMDCs) obtained from wild-type and BG receptor (dectin-1) knock-out mice was examined in vitro. The mice were intranasally administered JCP grains and the specific serum Ig levels were then quantified.

RESULTS

BG was detected in the exine and cell wall of the generative cell and tube cell of the JCP grain. Moreover, BG in the exine stimulated production of TNF-α and IL-6 in the BMDCs via a dectin-1-dependent mechanism. Meanwhile, JCP-specific IgE and IgG were detected in the serum of wild-type mice that had been intranasally administered with JCP grains. These mice also exhibited significantly enhanced sneezing behavior. However, dectin-1 knock-out mice exhibited significantly lower JCP-specific IgE and IgG levels compared to wild-type mice.

CONCLUSIONS

Latent BG in JCP can act as an adjuvant to induce JCP-specific antibody production via dectin-1.

Recombinant antibody against Trypanosoma cruzi from patients with chronic Chagas heart disease recognizes mammalian nervous system

BACKGROUND

To deeply understand the role of antibodies in the context of Trypanosoma cruzi infection, we decided to characterize A2R1, a parasite antibody selected from single-chain variable fragment (scFv) phage display libraries constructed from B cells of chronic Chagas heart disease patients.

METHODS

Immunoblot, ELISA, cytometry, immunofluorescence and immunohistochemical assays were used to characterize A2R1 reactivity. To identify the antibody target, we performed an immunoprecipitation and two-dimensional electrophoresis coupled to mass spectrometry and confirmed A2R1 specific interaction by producing the antigen in different expression systems. Based on these data, we carried out a comparative in silico analysis of the protein target´s orthologues, focusing mainly on post-translational modifications.

FINDINGS

A2R1 recognizes a parasite protein of ~50 kDa present in all life cycle stages of T. cruzi, as well as in other members of the kinetoplastid family, showing a defined immunofluorescence labeling pattern consistent with the cytoskeleton. A2R1 binds to tubulin, but this interaction relies on its post-translational modifications. Interestingly, this antibody also targets mammalian tubulin only present in brain, staining in and around cell bodies of the human peripheral and central nervous system.

INTERPRETATION

Our findings demonstrate for the first time the existence of a human antibody against T. cruzi tubulin capable of cross-reacting with a human neural protein. This work re-emphasizes the role of molecular mimicry between host and parasitic antigens in the development of pathological manifestations of T. cruzi infection.

Live Attenuated African Swine Fever Viruses as Ideal Tools to Dissect the Mechanisms Involved in Cross-Protection

African swine fever (ASF) has become the major threat for the global swine industry. Furthermore, the epidemiological situation of African swine fever virus (ASFV) in some endemic regions of Sub-Saharan Africa is worse than ever, with multiple virus strains and genotypes currently circulating in a given area. Despite the recent advances on ASF vaccine development, there are no commercial vaccines yet, and most of the promising vaccine prototypes available today have been specifically designed to fight the genotype II strains currently circulating in Europe, Asia, and Oceania. Previous results from our laboratory have demonstrated the ability of BA71∆CD2, a recombinant LAV lacking CD2v, to confer protection against homologous (BA71) and heterologous genotype I (E75) and genotype II (Georgia2007/01) ASFV strains, both belonging to same clade (clade C). Here, we extend these results using BA71∆CD2 as a tool trying to understand ASFV cross-protection, using phylogenetically distant ASFV strains. We first observed that five out of six (83.3%) of the pigs immunized once with 10⁶ PFU of BA71∆CD2 survived the tick-bite challenge using Ornithodoros sp. soft ticks naturally infected with RSA/11/2017 strain (genotype XIX, clade D). Second, only two out of six (33.3%) survived the challenge with Ken06.Bus (genotype IX, clade A), which is phylogenetically more distant to BA71∆CD2 than the RSA/11/2017 strain. On the other hand, homologous prime-boosting with BA71∆CD2 only improved the survival rate to 50% after Ken06.Bus challenge, all suffering mild ASF-compatible clinical signs, while 100% of the pigs immunized with BA71∆CD2 and boosted with the parental BA71 virulent strain survived the lethal challenge with Ken06.Bus, without almost no clinical signs of the disease. Our results confirm that cross-protection is a multifactorial phenomenon that not only depends on sequence similarity. We believe that understanding this complex phenomenon will be useful for designing future vaccines for ASF-endemic areas.

Development of Genotype-Specific Anti-Bovine Rotavirus A Immunoglobulin Yolk Based on a Current Molecular Epidemiological Analysis of Bovine Rotaviruses A Collected in Japan during 2017-2020

Bovine rotavirus A (RVA), a major causative pathogen of diarrhea in dairy and Japanese beef calves, has led to severe economic losses in numerous countries. A dual genotyping system based on genomic segments encoding VP7 (G genotype) and VP4 (P genotype), comprising the outer layer of the virion, has been used to understand the epidemiological dynamics of RVAs at the national and global levels. This study aimed to investigate occurrence frequency of G and P genotypes for multiple bovine RVAs from calf diarrheic samples collected in Japan from 2017 to 2020. After we produced anti-bovine RVA immunoglobulin yolks (IgYs) from hens immunized with the two RVAs with different genotypes (G6P[5] and G10P[11]) selected on the basis of the current epidemiological survey, we investigated cross-reactivity against bovine RVAs with different G and P combinations owing to establish a useful strategy to protect calves from RVA infections using the two IgYs. Consequently, the two produced anti-bovine IgYs showed strong cross-reactivity against bovine RVAs with the same G and/or P genotypes in neutralization assay, respectively. Therefore, our data suggest the possibility of a passive immunization to protect calves from a bovine RVA infections epidemic in Japan via oral administration of the two IgYs into calves. The findings presented herein will provide important information that IgY is one of the effective tools to prevent infections of various pathogens.

Differential distribution and potential regulatory roles of estrogen receptor 2a and 2b in the pituitary of ricefield eel Monopterus albus

Estrogens play important regulatory roles in the pituitary of vertebrates. Two forms of estrogen receptor 2 (Esr2), namely Esr2a and Esr2b, are identified in teleosts, but their differential roles remain to be fully elucidated. In the present study, expression and potential functional roles of Esr2a and Esr2b were characterized in ricefield eels. esr2a and esr2b mRNA were broadly distributed in tissues, with high levels observed in the brain, pituitary, and gonads. In order to examine the cellular localization of Esr2a and Esr2b in the pituitary, specific antisera against ricefield eel Esr2a and Esr2b were generated, respectively. Interestingly, immunohistochemistry and Western blot analysis revealed that Esr2a and Esr2b were differentially distributed in the pituitary, with the former localized to the adenohypophysis while the latter to the neurohypophysis. Dual fluorescent immunostaining showed that immunoreactive Esr2a was present in Gh and Prl cells, but not in Lh and Fsh cells. Estradiol (E₂) stimulated lhb and prl gene expression in dispersed pituitary cells of intersexual ricefield eels, but had no effects on gh, fshb, and gnrhr2 gene expression and Gh release. Results of the present study are helpful for further understanding the roles and mechanisms of estrogen signals in the pituitary.

Structure-Based Design with Tag-Based Purification and In-Process Biotinylation Enable Streamlined Development of SARS-CoV-2 Spike Molecular Probes

Biotin-labeled molecular probes, comprising specific regions of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike, would be helpful in the isolation and characterization of antibodies targeting this recently emerged pathogen. Here, we design constructs incorporating an N-terminal purification tag, a site-specific protease-cleavage site, the probe region of interest, and a C-terminal sequence targeted by biotin ligase. Probe regions include full-length spike ectodomain as well as various subregions, and we also design mutants that eliminate recognition of the angiotensin-converting enzyme 2 (ACE2) receptor. Yields of biotin-labeled probes from transient transfection range from ∼0.5 mg/L for the complete ectodomain to >5 mg/L for several subregions. Probes are characterized for antigenicity and ACE2 recognition, and the structure of the spike ectodomain probe is determined by cryoelectron microscopy. We also characterize antibody-binding specificities and cell-sorting capabilities of the biotinylated probes. Altogether, structure-based design coupled to efficient purification and biotinylation processes can thus enable streamlined development of SARS-CoV-2 spike ectodomain probes.

Toward Drug-Like Multispecific Antibodies by Design

The success of antibody therapeutics is strongly influenced by their multifunctional nature that couples antigen recognition mediated by their variable regions with effector functions and half-life extension mediated by a subset of their constant regions. Nevertheless, the monospecific IgG format is not optimal for many therapeutic applications, and this has led to the design of a vast number of unique multispecific antibody formats that enable targeting of multiple antigens or multiple epitopes on the same antigen. Despite the diversity of these formats, a common challenge in generating multispecific antibodies is that they display suboptimal physical and chemical properties relative to conventional IgGs and are more difficult to develop into therapeutics. Here we review advances in the design and engineering of multispecific antibodies with drug-like properties, including favorable stability, solubility, viscosity, specificity and pharmacokinetic properties. We also highlight emerging experimental and computational methods for improving the next generation of multispecific antibodies, as well as their constituent antibody fragments, with natural IgG-like properties. Finally, we identify several outstanding challenges that need to be addressed to increase the success of multispecific antibodies in the clinic.

Cross-Reactivity between Chemical Antibodies Formed to Serum Proteins and Thyroid Axis Target Sites

In some instances, when chemicals bind to proteins, they have the potential to induce a conformational change in the macromolecule that may misfold in such a way that makes it similar to the various target sites or act as a neoantigen without conformational change. Cross-reactivity then can occur if epitopes of the protein share surface topology to similar binding sites. Alteration of peptides that share topological equivalence with alternating side chains can lead to the formation of binding surfaces that may mimic the antigenic structure of a variant peptide or protein. We investigated how antibodies made against thyroid target sites may bind to various chemical–albumin compounds where binding of the chemical has induced human serum albumin (HSA) misfolding. We found that specific monoclonal or polyclonal antibodies developed against thyroid-stimulating hormone (TSH) receptor, 5′-deiodinase, thyroid peroxidase, thyroglobulin, thyroxine-binding globulin (TBG), thyroxine (T4), and triiodothyronine (T3) bound to various chemical HSA compounds. Our study identified a new mechanism through which chemicals bound to circulating serum proteins lead to structural protein misfolding that creates neoantigens, resulting in the development of antibodies that bind to key target proteins of the thyroid axis through protein misfolding. For demonstration of specificity of thyroid antibody binding to various haptenic chemicals bound to HSA, both serial dilution and inhibition studies were performed and proportioned to the dilution. A significant decline in these reactions was observed. This laboratory analysis of immune reactivity between thyroid target sites and chemicals bound to HSA antibodies identifies a new mechanism by which chemicals can disrupt thyroid function.

Direct kinetic fingerprinting and digital counting of single protein molecules

The sensitive and accurate quantification of protein biomarkers plays important roles in clinical diagnostics and biomedical research. Sandwich ELISA and its variants accomplish the capture and detection of a target protein via two antibodies that tightly bind at least two distinct epitopes of the same antigen and have been the gold standard for sensitive protein quantitation for decades. However, existing antibody-based assays cannot distinguish between signal arising from specific binding to the protein of interest and nonspecific binding to assay surfaces or matrix components, resulting in significant background signal even in the absence of the analyte. As a result, they generally do not achieve single-molecule sensitivity, and they require two high-affinity antibodies as well as stringent washing to maximize sensitivity and reproducibility. Here, we show that surface capture with a high-affinity antibody combined with kinetic fingerprinting using a dynamically binding, low-affinity fluorescent antibody fragment differentiates between specific and nonspecific binding at the single-molecule level, permitting the direct, digital counting of single protein molecules with femtomolar-to-attomolar limits of detection (LODs). We apply this approach to four exemplary antigens spiked into serum, demonstrating LODs 55- to 383-fold lower than commercially available ELISA. As a real-world application, we establish that endogenous interleukin-6 (IL-6) can be quantified in 2-µL serum samples from chimeric antigen receptor T cell (CAR-T cell) therapy patients without washing away excess serum or detection probes, as is required in ELISA-based approaches. This kinetic fingerprinting thus exhibits great potential for the ultrasensitive, rapid, and streamlined detection of many clinically relevant proteins.

Filling the Antibody Pipeline in Allergy: PIPE Cloning of IgE, IgG1 and IgG4 against the Major Birch Pollen Allergen Bet v 1

Birch pollen allergy is among the most prevalent pollen allergies in Northern and Central Europe. This IgE-mediated disease can be treated with allergen immunotherapy (AIT), which typically gives rise to IgG antibodies inducing tolerance. Although the main mechanisms of allergen immunotherapy (AIT) are known, questions regarding possible Fc-mediated effects of IgG antibodies remain unanswered. This can mainly be attributed to the unavailability of appropriate tools, i.e., well-characterised recombinant antibodies (rAbs). We hereby aimed at providing human rAbs of several classes for mechanistic studies and as possible candidates for passive immunotherapy. We engineered IgE, IgG1, and IgG4 sharing the same variable region against the major birch pollen allergen Bet v 1 using Polymerase Incomplete Primer Extension (PIPE) cloning. We tested IgE functionality and IgG blocking capabilities using appropriate model cell lines. In vitro studies showed IgE engagement with FcεRI and CD23 and Bet v 1-dependent degranulation. Overall, we hereby present fully functional, human IgE, IgG1, and IgG4 sharing the same variable region against Bet v 1 and showcase possible applications in first mechanistic studies. Furthermore, our IgG antibodies might be useful candidates for passive immunotherapy of birch pollen allergy.

Quantitative evaluation of protective antibody response induced by hepatitis E vaccine in humans

Efficacy evaluation through human trials is crucial for advancing a vaccine candidate to clinics. Next-generation sequencing (NGS) can be used to quantify B cell repertoire response and trace antibody lineages during vaccination. Here, we demonstrate this application with a case study of Hecolin®, the licensed vaccine for hepatitis E virus (HEV). Four subjects are administered the vaccine following a standard three-dose schedule. Vaccine-induced antibodies exhibit a high degree of clonal diversity, recognize five conformational antigenic sites of the genotype 1 HEV p239 antigen, and cross-react with other genotypes. Unbiased repertoire sequencing is performed for seven time points over six months of vaccination, with maturation pathways characterize for a set of vaccine-induced antibodies. In addition to dynamic repertoire profiles, NGS analysis reveals differential patterns of HEV-specific antibody lineages and highlights the necessity of the long vaccine boost. Together, our study presents a quantitative strategy for vaccine evaluation in small-scale human studies.

Tuning environmental timescales to evolve and maintain generalists

Natural environments can present diverse challenges, but some genotypes remain fit across many environments. Such "generalists" can be hard to evolve, outcompeted by specialists fitter in any particular environment. Here, inspired by the search for broadly neutralizing antibodies during B cell affinity maturation, we demonstrate that environmental changes on an intermediate timescale can reliably evolve generalists, even when faster or slower environmental changes are unable to do so. We find that changing environments on timescales comparable with evolutionary transients in a population enhance the rate of evolving generalists from specialists, without enhancing the reverse process. The yield of generalists is further increased in more complex dynamic environments, such as a "chirp" of increasing frequency. Our work offers design principles for how nonequilibrium fitness "seascapes" can dynamically funnel populations to genotypes unobtainable in static environments.

Immunoblotting

Immunoblotting allows detection of a protein antigen immobilized on the protein-retaining membrane support such as nitrocellulose or polyvinylidene fluoride (PVDF). The detection of the protein of interest relies on the binding of an antibody that specifically recognizes the protein of interest exposed on the membrane. The protein of interest can be purified or mixed with other proteins as in cell or tissue extracts. Usually immunoblotting combines the resolution of proteins by gel electrophoresis with immunochemical detection and is referred to as "western blotting." Immunoblotting can be used to determine the presence and the steady-state level of the protein of interest in the sample, its relative molecular weight, and the distribution of the protein between cellular fractions. Immunoblotting can be performed using the antibodies raised against synthetic peptide antigens modified to mimic posttranslational modifications of proteins, such as phosphorylation and acetylation, to study these modifications in the protein of interest in vivo. When antibodies against the protein of interest are not available, immunoblotting can be performed using antibodies that specifically recognize the recombinant epitope tags (hemagglutinin [HA]-, Flag-, cMyc-, or glutathione-S-transferase [GST]) fused to the protein of interest using recombinant DNA techniques. Immunoblotting has a variety of research, clinical, and forensic medicine applications. It is also one of the standard techniques for characterization of antibodies from different samples of polyclonal sera or hybridoma supernatants.

Innate and adaptive immunity in wild rodents spontaneously and experimentally infected with the tick-borne encephalitis virus

Two dominant species of wild small rodents trapped in Novosibirsk region, South-Western Siberia, Russia differed in their susceptibility to the tick-borne encephalitis virus (TBEV) infection. TBEV RNA average detection rate for Northern red-backed vole Myodes rutilus (Pallas, 1779) (82.2 ± 5.8% blood samples and 63.1 ± 2.7% organ samples) significantly exceeded the corresponding values for the striped field mouse Apodemus agrarius (Pallas, 1771) (47.0 ± 8.7% blood and 24.5 ± 2.8% organ samples) (p <0.001). Innate immunity may be one of possible reasons of the differences. Th1 cytokine gene expression distinguished between M. rutilus (12.5 ± 8.5%) and A. agrarius (66.6 ± 11.4%), whereas Th2 cytokine frequencies were statistically similar (81.8 ± 12.2% and 100.0%, respectively). Polarization indexes (PI) of the innate immunity calculated as ratio of Th2 to Th1 cytokine RNA detection rates for both M. rutilus (6.5) and A. agrarius (1.5) suggested Th2 mainly humoral immune response against persistent TBEV in natural mammalian hosts. Therefore, the TBEV-induced antibodies were analyzed by ELISA and hemagglutination inhibition (HI) tests. The TBEV-specific antibodies were detected in 74.8 ± 4.3% sera of M. rutilus and 67.3 ± 6.8% of A. agrarius. Among them HI antibodies were found in 4.8 ± 2.1% of the same analyzed sera of M. rutilus and in 6.0 ± 3.4% blood samples of A. agrarius only. To model the TBEV persistence both M. rutilus and A. agrarius were infected with the suspensions of the TBEV-infected ticks with further observations during 4 subsequent months. Detection rate of the TBEV RNA and antigen E remained high during the whole period, however, pathogenic for laboratory suckling mice virus was isolated up to 8 days postinfection. At late stages of the persistent infection (1-4 months) the TBEV RNA detection rate in northern red-backed voles remained high 70.6 ± 7.9% whereas in striped field mice significantly declined to 26.7 ± 9.2% (p < .001). Comparative analysis of the innate immunity of the wild rodents in 2 months postinfection showed similar frequencies of Th2 cytokine gene expression for M. rutilus (77.8 ± 10.1%) and A. agrarius (71.4 ± 12.5%) (p > .05) but Th1 cytokine mRNA detection rates were different (44.4 ± 12.5% and 85.7 ± 9.7%, respectively) (p < .05). In 2 months PI decreased from 6.5 until 1.75 for M. rutilus and from 1.5 until 0.83 for A. agrarius. Nevertheless, Th2 mainly humoral immune response was confirmed by direct detection of the TBEV-specific antibodies. HI and neutralizing antibodies were revealed in blood sera of the small rodents of both studied species in 30 days postinfection and remained at detectable levels during 4 months of observations. Accordingly, Th2 polarized innate immunity of small rodents might facilitate the TBEV intracellular persistence in the presence of HI and neutralization antibodies.

Mechanisms of Wheat Allergenicity in Mice: Comparison of Adjuvant-Free vs. Alum-Adjuvant Models

Wheat protein is considered a major type of food allergen in many countries including the USA. The mechanisms of allergenicity of wheat proteins are not well understood at present. Both adjuvant-based and adjuvant-free mouse models are reported for this food allergy. However, it is unclear whether the mechanisms underlying wheat allergenicity in these two types of models are similar or different. Therefore, we compared the molecular mechanisms in a novel adjuvant-free (AF) model vs. a conventional alum-adjuvant (AA) model of wheat allergy using salt-soluble wheat protein (SSWP). In the AF model, Balb/cJ mice were sensitized with SSWP via skin exposure. In the AA model, mice were sensitized by an intraperitoneal injection of SSWP with alum. In both models, allergic reactions were elicited using an identical protocol. Robust IgE as well as mucosal mast cell protein-1 responses were elicited similarly in both models. However, an analysis of the spleen immune markers identified strikingly different molecular activation patterns in these two models. Furthermore, a number of immune markers associated with intrinsic allergenicity were also identified in both models. Since the AF model uses skin exposure without an adjuvant, the mechanisms in the AF model may more closely simulate the human wheat allergenicity mechanisms from skin exposure in occupational settings such as in the baking industry.

Molecular Characterization and Experimental Utility of Monoclonal Antibodies with Specificity for Aliphatic Di- and Polyisocyanates

Aliphatic di- and polyisocyanates are crucial chemical ingredients in many industrial processes and are a well-recognized cause of occupational asthma. Serologic detection of "chemical epitopes" in biological samples could serve as an exposure surveillance approach toward disease prevention, and thus we sought to generate aliphatic isocyanate-specific monoclonal antibodies (mAbs). Three hybridomas were generated from Balb/c mice immunized with a commercial product containing a combination of uretdione, homopolymer, and monomeric forms of hexamethylene diisocyanate (HDI). Three stable hybridomas were subcloned by limiting dilution, two secreting IgG1κ and one secreting IgMκ mAb that bind aliphatic di- and polyisocyanates (conjugated to albumin), but not aromatic toluene or methylene diphenyl diisocyanate (TDI or MDI). Each mAb demonstrates slight differences in epitope specificity, for example, recognition of hydrogenated MDI (HMDI) or different carrier proteins (transferrin, actin) reacted with vapor phase HDI, and is encoded by unique recombination of different germline antibody genes, with distinct complementary determining regions. By western blot, all three mAbs detect a molecule with characteristics of an albumin adduct uniquely in urine from mice skin exposed to a mixture of aliphatic di- and polyisocyanate. Together, the data define molecular determinants of humoral immune recognition of aliphatic di- and polyisocyanates through new mAbs, which will serve as useful research reagents and may be applicable to future exposure surveillance efforts.

IgE-blocking antibodies following SLIT with recombinant Mal d 1 accord with improved apple allergy

BACKGROUND

We recently reported that 16 weeks of sublingual immunotherapy (SLIT) with recombinant (r) Mal d 1, but not rBet v 1, significantly improved birch pollen-related apple allergy. Allergen-specific IgE-blocking IgG antibodies have been associated with clinical efficacy.

OBJECTIVE

We compared the quantity, quality, and IgE-blocking bioactivity of SLIT-induced Mal d 1-specific IgG antibodies in both treatment groups.

METHODS

Pre- and post-SLIT sera were assessed for rMal d 1-specific IgG antibodies in ELISA and for their ability to inhibit apple allergen-induced upregulation of CD63 on basophils from nontreated individuals with birch pollen-related apple allergy. Post-SLIT sera depleted of IgG1 or IgG4 were compared for their IgE-blocking activity. IgG1 binding to rMal d 1 was competed with rMal d 1 and rBet v 1 in ELISA.

RESULTS

SLIT with rMal d 1 and rBet v 1 induced comparable levels of rMal d 1-specific IgG1, IgG2, IgG3, and IgG4 antibodies. Only post-rMal d 1 SLIT sera displayed IgE-blocking activity, which was significantly reduced by depletion of IgG1 and less so by IgG4 depletion. In competition ELISA, IgG1 binding to Mal d 1 in post-rMal d 1 SLIT sera was fully inhibited with rMal d 1 but not with rBet v 1. Correspondingly, Bet v 1 was the more potent competitor for IgG1 binding to Mal d 1 in post-rBet v 1 SLIT sera.

CONCLUSION

rMal d 1 SLIT for 16 weeks induced functional, primarily Mal d 1-specific IgE-blocking antibodies, whereas rBet v 1 SLIT induced Bet v 1-specific, Mal d 1-cross-reactive IgG antibodies with limited cross-blocking activity. These results provide a possible explanation for the limited effectiveness of birch pollen immunotherapy in birch pollen-related food allergy and indicate a dominant protective role of functional IgE-blocking IgG1 antibodies in the early phase of allergy treatment.

Epitope Mapping of PMab-241, a Lymphatic Endothelial Cell-Specific Anti-Bear Podoplanin Monoclonal Antibody

Anti-bear podoplanin (bPDPN) monoclonal antibodies (mAbs), including PMab-247 and PMab-241, have been previously established. Although PMab-247 has shown positive immunostaining for lymphatic endothelial cells (LECs), type I alveolar cells of the lung, and podocytes of the kidney, PMab-241 stains LECs but does not react with lung type I alveolar cells. PDPN possesses three platelet aggregation-stimulating (PLAG) domains (PLAG1, PLAG2, and PLAG3) and the PLAG-like domain (PLD). The binding epitope of PMab-247 was previously determined to include bPDPN residues Asp76, Arg78, Glu80, and Arg82. Among these, Glu80 and Arg82 are included in PLD of bPDPN. The purpose of this study is to determine the binding epitope of PMab-241 and to clarify the difference between these two anti-bPDPN mAbs. Analysis of bPDPN deletion mutants revealed that the N-terminus of the PMab-241 epitope exists between amino acids (aa) 75 and 80 of bPDPN. In addition, analysis of bPDPN point mutants demonstrated that the critical epitope of PMab-241 includes Thr75, Asp76, and Arg78 of bPDPN. The binding epitopes of PMab-241 and PMab-247 seem to overlap, but this slight difference may be sufficient to provide the specificity of PMab-241 to discriminate LECs from type I alveolar cells of the lung.

Enhanced Immune Response Against the Thomsen-Friedenreich Tumor Antigen Using a Bivalent Entirely Carbohydrate Conjugate

The Thomsen-Friedenreich (TF) antigen is a key target for the development of anticancer vaccines, and this ongoing challenge remains relevant due to the poor immunogenicity of the TF antigen. To overcome this challenge, we adopted a bivalent conjugate design which introduced both the TF antigen and the Thomsen-nouveau (Tn) antigen onto the immunologically relevant polysaccharide A1 (PS A1). The immunological results in C57BL/6 mice revealed that the bivalent, Tn-TF-PS A1 conjugate increased the immune response towards the TF antigen as compared to the monovalent TF-PS A1. This phenomenon was first observed with enzyme-linked immunosorbent assay (ELISA) where the bivalent conjugate generated high titers of IgG antibodies where the monovalent conjugate generated an exclusive IgM response. Fluorescence-activated cell sorting (FACS) analysis also revealed increased binding events to the tumor cell lines MCF-7 and OVCAR-5, which are consistent with the enhanced tumor cell lysis observed in a complement dependent cytotoxicity (CDC) assay. The cytokine profile generated by the bivalent construct revealed increased pro-inflammatory cytokines IL-17 and IFN-γ. This increase in cytokine concentration was matched with an increase in cytokine producing cells as observed by ELISpot. We hypothesized the mechanisms for this phenomenon to involve the macrophage galactose N-acetylgalactosamine specific lectin 2 (MGL2). This hypothesis was supported by using biotinylated probes and recombinant MGL2 to measure carbohydrate-protein interactions.

An HIV-1 vaccine based on bacterium-like particles elicits Env-specific mucosal immune responses

Although many vaccines have been designed to induce effective mucosal immune responses against HIV-1, designing an effective HIV-1 vaccine remains a challenge. Bacterium-like particles (BLPs) are a new type of vector used to induce mucosal immune responses, and have already been used for some vaccines against respiratory tract viruses. In this study, we designed a mucosal vaccine against HIV-1 based on BLPs. The vaccine was used to immunize both mice and guinea pigs via intramuscular (i.m.) injection or intranasal (i.n.) drip. We found that gp120 trimers bound to BLPs delivered via i.n. drip successfully induced Env-specific secretory IgA (sIgA) at mucosal sites in mice. Furthermore, nasal washes from guinea pigs immunized via i.n. drip showed neutralizing activity against HIV-1 tier 1 pseudoviruses. Thus, gp120 trimers bound to BLPs may be an effective vaccine strategy against HIV-1.

Specific antibodies reacting to JC polyomavirus capsid protein mimotopes in sera from multiple sclerosis and other neurological diseases-affected patients

Published data support the hypothesis that viruses could be trigger agents of multiple sclerosis onset. This link is based on evidence of early exposure to viral agents in patients affected by this neurologic disease. JC (JC polyomavirus [JCPyV]), BK (BKPyV), and simian virus 40 (SV40) neurotropic polyomavirus footprints have been detected in brain tissue specimens and samples from patients affected by different neurological diseases. In this investigation, serum samples from patients affected by multiple sclerosis and other inflammatory and noninflammatory neurologic diseases, as well as healthy subjects representing the control, were investigated for immunoglobulin G (IgG) antibodies against JCPyV. To this end, an immunologic approach was employed, which consists of employing indirect enzyme-linked immunosorbent assay testing with synthetic peptides mimicking viral capsid protein 1 antigens. A significantly lower prevalence of IgG antibodies against JCPyV VP1 epitopes, with a low titer, was detected in serum samples from patients with multiple sclerosis (MS) and other neurologic diseases than in healthy subjects. Our study indicates that the prevalence of JCPyV antibodies from patients with multiple sclerosis is 50% lower than in healthy subjects, suggesting specific immune impairments. These results indicate that patients affected by neurological diseases, including MS, respond poorly to JCPyV VP1 antigens, suggesting specific immunologic dysfunctions.

Boosting with AIDSVAX B/E Enhances Env Constant Region 1 and 2 Antibody-Dependent Cellular Cytotoxicity Breadth and Potency

Induction of protective antibodies is a critical goal of HIV-1 vaccine development. One strategy is to induce nonneutralizing antibodies (NNAbs) that kill virus-infected cells, as these antibody specificities have been implicated in slowing HIV-1 disease progression and in protection. HIV-1 Env constant region 1 and 2 (C1C2) monoclonal antibodies (MAbs) frequently mediate potent antibody-dependent cellular cytotoxicity (ADCC), making them an important vaccine target. Here, we explore the effect of delayed and repetitive boosting of RV144 vaccine recipients with AIDSVAX B/E on the C1C2-specific MAb repertoire. It was found that boosting increased clonal lineage-specific ADCC breadth and potency. A ligand crystal structure of a vaccine-induced broad and potent ADCC-mediating C1C2-specific MAb showed that it bound a highly conserved Env gp120 epitope. Thus, boosting to affinity mature these types of IgG C1C2-specific antibody responses may be one method by which to make an improved HIV vaccine with higher efficacy than that seen in the RV144 trial.IMPORTANCE Over one million people become infected with HIV-1 each year, making the development of an efficacious HIV-1 vaccine an important unmet medical need. The RV144 human HIV-1 vaccine regimen is the only HIV-1 clinical trial to date to demonstrate vaccine efficacy. An area of focus has been on identifying ways by which to improve upon RV144 vaccine efficacy. The RV305 HIV-1 vaccine regimen was a follow-up boost of RV144 vaccine recipients that occurred 6 to 8 years after the conclusion of RV144. Our study focused on the effect of delayed boosting in humans on the vaccine-induced Env constant region 1 and 2 (C1C2)-specific antibody repertoire. It was found that boosting with an HIV-1 Env vaccine increased C1C2-specific antibody-dependent cellular cytotoxicity potency and breadth.

DuoBody-CD3xCD20 induces potent T-cell-mediated killing of malignant B cells in preclinical models and provides opportunities for subcutaneous dosing

Background

DuoBody®-CD3xCD20 (GEN3013) is a full-length human IgG1 bispecific antibody (bsAb) recognizing CD3 and CD20, generated by controlled Fab-arm exchange. Its Fc domain was silenced by introduction of mutations L234F L235E D265A.

Methods

T-cell activation and T-cell-mediated cytotoxicity were measured by flow cytometry following co-culture with tumour cells. Anti-tumour activity of DuoBody-CD3xCD20 was assessed in humanized mouse models in vivo. Non-clinical safety studies were performed in cynomolgus monkeys.

Findings

DuoBody-CD3xCD20 induced highly potent T-cell activation and T-cell-mediated cytotoxicity towards malignant B cells in vitro. Comparison of DuoBody-CD3xCD20 to CD3 bsAb targeting alternative B-cell antigens, or to CD3xCD20 bsAb generated using alternative CD20 Ab, emphasized its exceptional potency. In vitro comparison with other CD3xCD20 bsAb in clinical development showed that DuoBody-CD3xCD20 was significantly more potent than three other bsAb with single CD3 and CD20 binding regions and equally potent as a bsAb with a single CD3 and two CD20 binding regions. DuoBody-CD3xCD20 showed promising anti-tumour activity in vivo, also in the presence of excess levels of a CD20 Ab that competes for binding. In cynomolgus monkeys, DuoBody-CD3xCD20 demonstrated profound and long-lasting B-cell depletion from peripheral blood and lymphoid organs, which was comparable after subcutaneous and intravenous administration. Peak plasma levels of DuoBody-CD3xCD20 were lower and delayed after subcutaneous administration, which was associated with a reduction in plasma cytokine levels compared to intravenous administration, while bioavailability was comparable.

Interpretation

Based on these preclinical studies, a clinical trial was initiated to assess the clinical safety of subcutaneous DuoBody-CD3xCD20 in patients with B-cell malignancies.

Funding

Genmab

Phage Display Derived Monoclonal Antibodies: From Bench to Bedside

Monoclonal antibodies (mAbs) have become one of the most important classes of biopharmaceutical products, and they continue to dominate the universe of biopharmaceutical markets in terms of approval and sales. They are the most profitable single product class, where they represent six of the top ten selling drugs. At the beginning of the 1990s, an in vitro antibody selection technology known as antibody phage display was developed by John McCafferty and Sir. Gregory Winter that enabled the discovery of human antibodies for diverse applications, particularly antibody-based drugs. They created combinatorial antibody libraries on filamentous phage to be utilized for generating antigen specific antibodies in a matter of weeks. Since then, more than 70 phage-derived antibodies entered clinical studies and 14 of them have been approved. These antibodies are indicated for cancer, and non-cancer medical conditions, such as inflammatory, optical, infectious, or immunological diseases. This review will illustrate the utility of phage display as a powerful platform for therapeutic antibodies discovery and describe in detail all the approved mAbs derived from phage display.

Hemagglutination Inhibition Assay

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

Suggestive Serological Evidence of Infection with Shrew-Borne Imjin Virus (Hantaviridae) in Humans

The pathogenicity of the shrew-borne Imjin virus (MJNV) is unknown. The objective of our study was to find serological evidence of MJNV infection in humans. Partial MJNV nucleocapsid protein (NP) was cloned and expressed as an antigen for double-antigen sandwich ELISA, IgM capture ELISA, and dot blot to detect MJNV specific antibodies in hemorrhagic fever with renal syndrome (HFRS) patients’ and healthy persons’ sera from endemic areas in China. The purified recombinant NP reacted with neither the 90 healthy individuals’ sera from non-endemic areas of MJNV nor the 100 antisera to HFRS-causing virus, indicating that the MJNV NP had no cross-reaction with normal human sera and HFRS-causing viral antibodies. As determined by screening ELISA and dot blot analysis, IgG antibodies against MJNV NP were detected in sera from two of 385 healthy individuals from MJNV-endemic areas, suggesting infection with MJNV or MJNV-like thottimvirus. Based on the suggestive evidence, healthcare workers should be alert to febrile diseases occurring among individuals with exposure to shrew-infested habitats.

Affinity Maturation Enhances Antibody Specificity but Compromises Conformational Stability

Monoclonal antibodies (mAbs) have recently emerged as one of the most promising classes of biotherapeutics. A potential advantage of B cell-derived mAbs as therapeutic agents is that they have been subjected to natural filtering mechanisms, which may enrich for B cell receptors (BCRs) with favorable biophysical properties. Here, we evaluated 400 human mAbs for polyreactivity, hydrophobicity, and thermal stability using high-throughput screening assays. Overall, mAbs derived from memory B cells and long-lived plasma cells (LLPCs) display reduced levels of polyreactivity, hydrophobicity, and thermal stability compared with naive B cell-derived mAbs. Somatic hypermutation (SHM) is inversely associated with all three biophysical properties, as well as BCR expression levels. Finally, the developability profiles of the human B cell-derived mAbs are comparable with those observed for clinical mAbs, suggesting their high therapeutic potential. The results provide insight into the biophysical consequences of affinity maturation and have implications for therapeutic antibody engineering and development.

Nanovaccine Confers Dual Protection Against Influenza A Virus And Porcine Circovirus Type 2

BACKGROUND

The influenza A virus (IAV) is known for its high variability and poses a huge threat to the health of humans and animals. Pigs play a central role in the cross-species reassortment of IAV. Ectodomain of matrix protein 2 (M2e) is the most conserved protective antigen in IAV and can be used to develop nanovaccines through nanoparticles displaying to increase its immunogenicity. However, the high immunogenicity of nanoparticles can cause the risk of off-target immune response, and excess unwanted antibodies may interfere with the protective efficacy of M2e-specific antibodies. Therefore, it is necessary to select reasonable nanoparticles to make full use of antibodies against nanoparticles while increasing the level of M2e-specific antibodies. Porcine circovirus type 2 (PCV2) is the most susceptible virus in pigs and can promote IAV infection. It is meaningful to develop a vaccine that can simultaneously control swine influenza virus (SIV) and PCV2.

METHODS

In the present study, M2e of different copy numbers were inserted into the capsid (Cap) protein of PCV2 and expressed in Escherichia coli to form self-assembled chimeric virus-like particles (VLPs) nanovaccine. BALB/c mice and pigs were immunized with these nanovaccines to explore optimal anti-IAV and anti-PCV2 immunity.

RESULTS

Cap is capable of carrying at least 81 amino acid residues (three copies of M2e) at its C-terminal without impairing VLPs formation. Cap-3M2e VLPs induced the highest levels of M2e-specific immune responses, conferring protection against lethal challenge of IAVs from different species and induced specific immune responses consistent with PCV2 commercial vaccines in mice. In addition, Cap-3M2e VLPs induced high levels of M2e-specific antibodies and PCV2-specific neutralizing antibodies in pigs.

CONCLUSION

Cap-3M2e VLP is an economical and promising bivalent nanovaccine, which provides dual protection against IAV and PCV2.

Infection and vaccine-induced HPV-specific antibodies in cervicovaginal secretions. A review of the literature

Background

Human papillomavirus (HPV) infects and propagates in the cervical mucosal epithelium. Hence, in addition to assessing systemic immunity, the accurate measurement of cervical immunity is important to evaluate local immune responses to HPV infection and vaccination. This review discusses studies that investigated the presence of infection and vaccine-induced HPV-specific antibodies in cervicovaginal secretions (CVS).

Methods

We searched the two main health sciences databases, PubMed and the ISI Web of Science, from the earliest dates available to March 2019. From the eligible publications, information was extracted regarding: (i) study design, (ii) the reported HPV-specific antibody concentrations in CVS (and the associated serum levels, when provided), (iii) the CVS collection method, and (iv) the immunoassays used.

Results

The systematic search and selection process yielded 44 articles. The evidence of HPV-specific antibodies in CVS after natural infection (26/44) and HPV vaccination (18/44) is discussed. Many studies indicate that HPV-specific antibody detection in CVS is variable but feasible with a variety of collection methods and immunoassays. Most CVS samples were collected by cervicovaginal washing or wicks, and antibody presence was mostly determined by VLP-based ELISAs. The moderate to strong correlation between vaccine-induced antibody levels in serum and in CVS indicates that HPV vaccines generate antibodies that transudate through the cervical mucosal epithelium.

Conclusion

Although HPV-specific antibodies have lower titres in CVS than in serum samples, studies have shown that their detection in CVS is feasible. Nevertheless, the high variability of published observations and the lack of a strictly uniform, well-validated method for the collection, isolation and quantification of antibodies indicates a need for specific methods to improve and standardize the detection of HPV-specific antibodies in CVS.

IgM in human immunity to Plasmodium falciparum malaria

Most studies on human immunity to malaria have focused on the roles of immunoglobulin G (IgG), whereas the roles of IgM remain undefined. Analyzing multiple human cohorts to assess the dynamics of malaria-specific IgM during experimentally induced and naturally acquired malaria, we identified IgM activity against blood-stage parasites. We found that merozoite-specific IgM appears rapidly in Plasmodium falciparum infection and is prominent during malaria in children and adults with lifetime exposure, together with IgG. Unexpectedly, IgM persisted for extended periods of time; we found no difference in decay of merozoite-specific IgM over time compared to that of IgG. IgM blocked merozoite invasion of red blood cells in a complement-dependent manner. IgM was also associated with significantly reduced risk of clinical malaria in a longitudinal cohort of children. These findings suggest that merozoite-specific IgM is an important functional and long-lived antibody response targeting blood-stage malaria parasites that contributes to malaria immunity.

Species identification of Bombyx mori and Antheraea pernyi silk via immunology and proteomics

In recent years, increasing attention has been paid to the origin, transmission and communication of silk. However, this is still an unsolved mystery in archaeology. The identification of silk-producing species, especially silk produced by Bombyx mori (B. mori) and Antheraea pernyi (A. pernyi), is of key significance to address this challenge. In this study, two innovative methods, i.e. immunology and proteomics, were proposed and successfully established for the species identification of silks. ELISAs result demonstrated that the two prepared antibodies exhibited high sensitivity and specificity in distinguishing B. mori and A. pernyi silk. No cross-reactivity with each other was observed. Moreover, biomarkers were obtained for Bombyx and Antheraea through proteomic analysis. It was also confirmed that the biomarkers were suitable for identifying the species that produced a given silk sample. Compared with conventional methods for distinguishing silk species, immunological and proteomics techniques used in tandem can provide intact information and have the potential to provide accurate and reliable information for species identification.

Isolation of IgG Associated with Human Placenta

We optimized the method of isolation of antibodies from placental tissue of a conventionally healthy patient. Four protocols of antibody isolation were evaluated and a protocol with tissue grinding (without homogenization) and successive elution of the antibodies with acidic and alkaline buffers was recommended for use. The repertoire of the isolated antibodies was characterized using a glycan array. Partial coincidence of the specificity of the isolated antibodies with antibodies in the peripheral blood was demonstrated, which indicates their possible association with carbohydrate antigens in the placenta. Identification of potential molecular targets of resident antibodies in the placenta is necessary for understanding the mechanisms of formation of immunological tolerance to the fetus.

A Tumor-Selective Monoclonal Antibody from Immunization with a Tumor-Associated Mucin Glycopeptide

We have previously studied the generation of immune responses after vaccination with tumor-associated carbohydrate antigen (TACA)-containing glycopeptides from the tandem repeat (TR) sequence of MUC4, an aberrantly expressed mucin in pancreatic adenocarcinomas. A specific lead antigen from that study containing the Thomsen-Friedenreich TACA disaccharide facilitated the pursuit of a monoclonal antibody to this synthetic hapten. Initial evaluation of polyclonal antiserum resulting from immunization with a KLH conjugate of this glycopeptide into rabbits showed high titer antibodies by ELISA assays, and selective immunoreactivity with MUC4+ cells by western blot and flow cytometry techniques. Glycan microarray analysis showed an intriguing binding pattern where the antiserum showed near complete specificity for MUC4 TR glycopeptides and peptides, relative to all components on the array. Tissue staining also showed distinct tumor specificity to pancreatic tumor tissue in relation to normal pancreatic tissue, with a preference for more aggressive tumor foci. Based on this data, we produced a monoclonal antibody whose binding and reactivity profile was similar to that of the polyclonal serum, with the added benefit of being more specific for the N-terminal glycosylated peptide domain. This epitope represents a novel immunogen to potentially develop diagnostic antibodies or immunotherapies against various MUC4-positive cancers.

Detection of recombinant and endogenous mouse melatonin receptors by monoclonal antibodies targeting the C-terminal domain

Melatonin receptors play important roles in the regulation of circadian and seasonal rhythms, sleep, retinal functions, the immune system, depression, and type 2 diabetes development. Melatonin receptors are approved drug targets for insomnia, non-24-hour sleep-wake disorders, and major depressive disorders. In mammals, two melatonin receptors (MTRs) exist, MT₁ and MT₂ , belonging to the G protein-coupled receptor (GPCR) superfamily. Similar to most other GPCRs, reliable antibodies recognizing melatonin receptors proved to be difficult to obtain. Here, we describe the development of the first monoclonal antibodies (mABs) for mouse MT₁ and MT₂ . Purified antibodies were extensively characterized for specific reactivity with mouse, rat, and human MT₁ and MT₂ by Western blot, immunoprecipitation, immunofluorescence, and proximity ligation assay. Several mABs were specific for either mouse MT₁ or MT₂ . None of the mABs cross-reacted with rat MTRs, and some were able to react with human MTRs. The specificity of the selected mABs was validated by immunofluorescence microscopy in three established locations (retina, suprachiasmatic nuclei, pituitary gland) for MTR expression in mice using MTR-KO mice as control. MT₂ expression was not detected in mouse insulinoma MIN6 cells or pancreatic beta-cells. Collectively, we report the first monoclonal antibodies recognizing recombinant and native mouse melatonin receptors that will be valuable tools for future studies.

The Impact of Autoantibodies on IVF Treatment and Outcome: A Systematic Review

The role of autoantibodies in in vitro fertilization (IVF) has been discussed for almost three decades. Nonetheless, studies are still scarce and widely controversial. The aim of this study is to provide a comprehensive systematic review on the possible complications associated to autoantibodies (AA) impeding the chances of a successful IVF cycle. An Embase, PubMed/Medline and Cochrane Central Database search was performed on 1 December 2018, from 2006 until that date. From the 598 articles yielded in the search only 44 relevant articles ultimately fulfilled the inclusion criteria and were qualitatively analyzed. Five subsets of results were identified, namely, thyroid related AA, anti-phospholipid antibodies, anti-nuclear antibodies, AA affecting the reproductive system and AA related to celiac disease. It may be implied that the majority of auto-antibodies exert a statistically significant effect on miscarriage rates, whereas the effects on clinical pregnancy and live birth rates differ according to the type of auto-antibodies. While significant research is performed in the field, the quality of evidence provided is still low. The conduction of well-designed prospective cohort studies is an absolute necessity in order to define the impact of the different types of autoantibodies on IVF outcome.

A Method to Detect the Binding of Hyper-Glycosylated Fragment Crystallizable (Fc) Region of Human IgG1 to Glycan Receptors

Engineering the fragment crystallizable (Fc) of human IgG can bring improved effector functions to monoclonal antibodies and Fc-fusion-based medicines and vaccines. Such Fc-effector functions are largely controlled by posttranslational modifications (PTMs) within the Fc, including the addition of glycans that introduce structural and functional heterogeneity to this class of therapeutic. Here, we describe a detailed method to allow the detection of hyper-sialylated Fcs to glycan receptors that will facilitate the future development of new mAbs and Fc-fragment therapies and vaccines.