Epitope clustering analysis for vaccine-induced human antibodies in relationship to a panel of murine monoclonal antibodies against HPV16 viral capsid

Application of Pseudotyped Viruses

Highly pathogenic emerging and reemerging viruses have serious public health and socioeconomic implications. Although conventional live virus research methods can more reliably investigate disease pathogenicity and evaluate antiviral products, they usually depend on high-level biosafety laboratories and skilled researchers; these requirements hinder in vitro assessments of efficacy, as well as efforts to test vaccines and antibody drugs. In contrast, pseudotyped viruses (i.e., single-round infectious viruses that mimic the membrane structures of various live viruses) are widely used in studies of highly pathogenic viruses because they can be handled in biosafety level 2 facilities. This chapter provides a concise overview of various aspects of pseudotyped virus technologies, including (1) exploration of the mechanisms of viral infection; (2) evaluation of the efficacies of vaccines and monoclonal antibodies based on pseudovirion-based neutralization assay; (3) assessment of antiviral agents (i.e., antibody-based drugs and inhibitors); (4) establishment of animal models of pseudotyped virus infection in vivo; (5) investigation of the evolution, infectivity, and antigenicity of viral variants and viral glycosylation; and (6) prediction of antibody-dependent cell-mediated cytotoxic activity.

Monoclonal antibodies in cervical malignancy-related HPV

Despite many efforts to treat HPV infection, cervical cancer survival is still poor for several reasons, including resistance to chemotherapy and relapse. Numerous treatments such as surgery, radiation therapy, immune cell-based therapies, siRNA combined with various drugs, and immunotherapy are being studied and performed to provide the best treatment. Depending on the stage and size of the tumor, methods such as radical hysterectomy, pelvic lymphadenectomy, or chemotherapy can be utilized to treat cervical cancer. While accepted, these treatments lead to interruptions in cellular pathways and immune system homeostasis. In addition to a low survival rate, cervical neoplasm incidence has been rising significantly. However, new strategies have been proposed to increase patient survival while reducing the toxicity of chemotherapy, including targeted therapy and monoclonal antibodies. In this article, we discuss the types and potential therapeutic roles of monoclonal antibodies in cervical cancer.

Generation and characterization of mouse monoclonal antibodies against the VP4 protein of group A human rotaviruses

Human rotaviruses (RVs) are the leading cause of severe diarrhea in infants and young children worldwide. Among the structural proteins, as a spike protein, rotavirus VP4 plays a key role in both viral attachment and penetration. Currently, studies on monoclonal antibodies (mAbs) against VP4 are limited. In this study, mice were immunized with truncated VP4* to produce murine mAbs. In total, 50 mAbs were produced and characterized. Twenty-four mAbs were genotype-specific and 20 mAbs recognized the common VP4 epitopes shared by P[8], P[4], and P[6] viruses. Thirty-five of the 50 mAbs were neutralizing mAbs, among which nine mAbs could neutralize all three P-genotype RVs, and 10 neutralizing mAbs exhibited conformational sensitivity. Ten mAbs recognized dominant neutralizing epitopes, including the broadly neutralizing mAb 9C4 recognized conformational epitope. Further investigation shows that S376 and S464 are key amino acids for 9C4 binding, however, the exact binding sites of 9C4 remain to be fully defined. Overall, this panel of mAbs has demonstrated utility as immunodiagnostic and research reagents, and could potentially serve as crucial tools for exploring the neutralizing mechanisms and quality control of VP4* protein-based RV subunit vaccines. Further evaluation of cross-neutralizing mAbs could not only improve the understanding of the heterotypic protection conferred by RV vaccines, but also facilitate the development of broadly protective RV vaccines.

Development and characterisation of anti-HPV16 monoclonal antibodies for assembly of an HPV16 detection kit

Quality control is very important during the development of 3-valent (16/18/58), 9-valent (6/11/16/18/31/33/45/52/58), and 15-valent human papillomavirus (HPV) vaccines (6/11/16/18/31/33/35/39/45/52/56/58/59/68). All 3-valent, 9-valent, and 15-valent HPV vaccines contain the HPV16 antigen; therefore, a detection method that can specifically identify HPV16 in vaccines is urgently required. This study aimed to develop and characterise monoclonal antibodies to assemble a highly specific HPV16 detection kit. The HPV16 L1 pentameric protein developed as an immunogen was used to prepare monoclonal antibodies. From the pool of prepared monoclonal antibodies, we selected 4G12 and 5A6 to screen and evaluate their subtypes, specificity, neutralising activity, serum competition, binding affinity, and gene sequencing. After these characterisations, an enzyme-linked immunosorbent assay kit for these monoclonal antibodies was developed, and excellent quality was demonstrated in the assessment of linearity, repeatability, and specificity. The developed detection kit has great potential for wide use in clinical testing and quality control in vaccine production processes. This article is protected by copyright. All rights reserved.

Capsid destabilization and epitope alterations of human papillomavirus 18 in the presence of thimerosal

Thimerosal has been widely used as a preservative in drug and vaccine products for decades. Due to the strong propensity to modify thiols in proteins, conformational changes could occur due to covalent bond formation between ethylmercury (a degradant of thimerosal) and thiols. Such a conformational change could lead to partial or even complete loss of desirable protein function. This study aims to investigate the effects of thimerosal on the capsid stability and antigenicity of recombinant human papillomavirus (HPV) 18 virus-like particles (VLPs). Dramatic destabilization of the recombinant viral capsid upon thimerosal treatment was observed. Such a negative effect on the thermal stability of VLPs preserved with thimerosal was shown to be dependent on the thimerosal concentration. Two highly neutralizing antibodies, 13H12 and 3C3, were found to be the most sensitive to thimerosal treatment. The kinetics of antigenicity loss, when monitored with 13H12 or 3C3 as probes, yielded two distinctly different sets of kinetic parameters, while the data from both monoclonal antibodies (mAbs) followed a biphasic exponential decay model. The potential effect of thimerosal on protein function, particularly for thiol-containing proteinaceous active components, needs to be comprehensively characterized during formulation development when a preservative is necessary.

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Altered antigenicity of thimerosal-treated HPV VLPs was observed with antibodies.

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Antigenicity reduction and capsid destabilization were concentration dependent.

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The kinetics of epitope-specific antigenicity loss were monitored in real time.

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The reduced antigenicity of adjuvant-adsorbed antigens was visualized.

Identification of the mimotopes within the major capsid protein L1 of human papillomavirus types 18 and 45, using neutralizing monoclonal antibodies

Persistent infection with high-risk mucosal human papillomavirus (HPV) types has much association with the development of cervical cancer. The major capsid protein L1 has been confirmed to be a major candidate antigen for the development of vaccines. Here, the HPV18 L1 protein was successfully expressed and purified, then nine anti-HPV18 L1 monoclonal antibodies were prepared. Four neutralizing monoclonal antibodies (NmAbs) were identified by using hemagglutination inhibition assay and pseudovirus based neutralization assay. The results of Dot-ELISA, Western blot and indirect immunofluorescence assay showed that the neutralizing antibodies could cross-react with HPV16/18/45/31/33/58/35/39 L1. The mimotopes on HPV18/45 L1 proteins were identified and analyzed by using both phage display and Bioinformatics tool. The B cell epitopes 43-54 aa and 116-126 aa of HPV18 L1 protein, the B cell epitope 381-389 aa of HPV45 L1 protein, and the mimotopes epitope of HPV45 L1 protein were identified by peptide-ELISA and competitive ELISA. The results of PyMOL and Pepitope server analysis indicated that epitopes recognized by NmAbs 7F4, 5A6, 3G11, and 2F5 are located on the surface of L1 VLPs. The results of this study enriched the library of HPV neutralizing antibodies, revealed the mechanism of antibody neutralization, might open new perspectives on the antibody-antigen reaction and have important implications for the development of novel HPV vaccines.

Comprehensive Assessment of the Antigenic Impact of Human Papillomavirus Lineage Variation on Recognition by Neutralizing Monoclonal Antibodies Raised against Lineage A Major Capsid Proteins of Vaccine-Related Genotypes

Human papillomavirus (HPV) is the causative agent of cervical and other epithelial cancers. Naturally occurring variants of HPV have been classified into lineages and sublineages based on their whole-genome sequences, but little is known about the impact of this diversity on the structure and function of viral gene products. The HPV capsid is an icosahedral lattice comprising 72 pentamers of the major capsid protein (L1) and the associated minor capsid protein (L2). We investigated the potential impact of this genome variation on the capsid antigenicity of lineage and sublineage variants of seven vaccine-relevant, oncogenic HPV genotypes by using a large panel of monoclonal antibodies (MAbs) raised against the L1 proteins of lineage A antigens. Each genotype had at least one variant that displayed a ≥4-fold reduced neutralizing antibody sensitivity against at least one MAb, demonstrating that naturally occurring variation can affect one or more functional antigenic determinants on the HPV capsid. For HPV16, HPV18, HPV31, and HPV45, the overall impact was of a low magnitude. For HPV33 (sublineages A2 and A3 and lineages B and C), HPV52 (lineage D), and HPV58 (lineage C), however, variant residues in the indicated lineages and sublineages reduced their sensitivity to neutralization by all MAbs by up to 1,000-fold, suggesting the presence of key antigenic determinants on the surface of these capsids. These determinants were resolved further by site-directed mutagenesis. These data improve our understanding of the impact of naturally occurring variation on the antigenicity of the HPV capsid of vaccine-relevant oncogenic HPV genotypes.IMPORTANCE Human papillomavirus (HPV) is the causative agent of cervical and some other epithelial cancers. HPV vaccines generate functional (neutralizing) antibodies that target the virus particles (or capsids) of the most common HPV cancer-causing genotypes. Each genotype comprises variant forms that have arisen over millennia and which include changes within the capsid proteins. In this study, we explored the potential for these naturally occurring variant capsids to impact recognition by neutralizing monoclonal antibodies. All genotypes included at least one variant form that exhibited reduced recognition by at least one antibody, with some genotypes affected more than others. These data highlight the impact of naturally occurring variation on the structure of the HPV capsid proteins of vaccine-relevant oncogenic HPV genotypes.

Structural characterization of a neutralizing mAb H16.001, a potent candidate for a common potency assay for various HPV16 VLPs

With more human papillomavirus (HPV) virus-like particle (VLP) vaccines to hit the market in future, a monoclonal antibody (mAb) with preferably comparable reactivity against vaccines from different expression systems and bioprocesses is urgently needed for the potency characterization. Among all mAbs against HPV16 collected, rabbit mAb H16.001 is potently neutralizing with the highest affinity, recognizes an immune-dominant epitope, and can comparably react with HPV16 vaccines from various sources. Cryo-electron microscopic (cryo-EM) structure demonstrated that 360 H16.001 Fabs could bind to HPV16 capsid in preferable binding manner without steric hindrance between neighboring Fabs, potentially supporting its identification for VLP structural integrity and utility in monitoring VLP structural probity. This structural analysis indicated that mAb H16.001 afforded unbiased potency characterization for various HPV16 vaccines and was potential for use in vaccine regulation practice. This study also showed a model process for selecting suitable mAbs for potency assays of other vaccines.

Development and validation of a multiplex immunoassay for the simultaneous quantification of type-specific IgG antibodies to E6/E7 oncoproteins of HPV16 and HPV18

More than 170 types of human papilloma viruses (HPV) exist with many causing proliferative diseases linked to malignancy in indications such as cervical cancer and head and neck squamous cell carcinoma. Characterization of antibody levels toward HPV serology is challenging due to complex biology of oncoproteins, pre-existing titers to multiple HPV types, cross-reactivity, and low affinity, polyclonal responses. Using multiplex technology from MSD, we have developed an assay that simultaneously characterizes antibodies against E6 and E7 oncoproteins of HPV16 and 18, the primary drivers of HPV-associated oncogenesis. We fusion tagged our E6 and E7 proteins with MBP via two-step purification, spot-printed an optimized concentration of protein into wells of MSD 96-well plates, and assayed various cynomolgus monkey, human and HPV+ cervical cancer patient serum to validate the assay. The dynamic range of the assay covered 4-orders of magnitude and antibodies were detected in serum at a dilution up to 100,000-fold. The assay was very precise (n = 5 assay runs) with median CV of human serum samples ~ 5.3% and inter-run variability of 11.4%. The multiplex serology method has strong cross-reactivity between E6 oncoproteins from human serum samples as HPV18 E6 antigens neutralized 5 of 6 serum samples as strongly as HPV16 E6. Moderate concordance (Spearman’s Rank = 0.775) was found between antibody responses against HPV16 E7 in the multiplex assay compared to standard ELISA serology methods. These results demonstrate the development of a high-throughput, multi-plex assay that requires lower sample quantity input with greater dynamic range to detect type-specific anti-HPV concentrations to E6 and E7 oncoproteins of HPV16 and 18.

Evaluation of Immunogenicity, Protective Immunity on Aquaculture Pathogenic Vibrio and Fermentation of Vibrio alginolyticus Flagellin FlaC Protein

Background:

Vibrio are the main pathogenic bacteria in aquaculture. The flagellin protein C (FlaC) of Vibrio alginolyticus has good immunogenicity and the prospect of potential application in a vaccine.

Objectives:

We aimed to evaluate the immunogenicity, protective immunity, and prokaryotic expression fermentation of V. alginolyticus FlaC protein for the vaccine in aquaculture.

Material and Methods:

A molecular cloning method was used to construct the expression strain of FlaC protein, and the protein was purified with Ni-affinity chromatography. Polyclonal antiserum was prepared via mice immunized with the FlaC protein. The Western blot and enzyme-linked immunosorbent assay (ELISA) were used to check the specificity and titre of the antiserum. ELISA and pull-down assay detected the interaction between FlaC protein antiserum and Vibrio. The immune protection function of FlaC protein was detected with mice actively immunized with FlaC protein and challenged by V. alginolyticus and V. parahaemolyticus. The optimal expression conditions for FlaC protein were detected using an L₉(3⁴) orthogonal design model.

Results:

The expression strain of FlaC protein was obtained successfully, and purified FlaC protein was prepared using a mice polyclonal antibody. The FlaC protein antiserum held a high specificity, and the titre was 13200. The antiserum directly interacted with V. alginolyticus and V. parahaemolyticus, and the FlaC protein demonstrated a significant immune protection function (50%) against V. alginolyticus infection and some immune protection function (41.66%) against V. parahaemolyticus. The optimal expression conditions for FlaC protein included a strain OD₆₀₀ value of 0.8, final isopropyl-β-d-thiogalactoside (IPTG) concentration of 0.1 mmol/L, an inducing time of 8 hours, and an inducing temperature of 28°C.

Conclusions:

This study showed that the FlaC protein possesses a significant immunogenicity and immune protection effect and obtained the optimal fermentation conditions. It is expected to be a potential vaccine against V. alginolyticus and V. parahaemolyticus.