A clinical trial examining the effect of increased total CRM197 carrier protein dose on the antibody response to Haemophilus influenzae type b CRM197 conjugate vaccine

A Phase II/III, Multicenter, Observer-blinded, Randomized, Non-inferiority and Safety, study of typhoid conjugate vaccine (EuTCV) compared to Typbar-TCV® in healthy 6 Months-45 years aged participants

The typhoid conjugate vaccine (TCV) ensures a long-lasting protective immune response, requires fewer doses and is fit for children under 2 years of age. From Phase I study, EuTCV displayed considerable immunogenicity and reliable safety, thus endorsing further examination in Phase II/III trials. Therefore, a clinical Phase II/III study (NCT04830371) was conducted to evaluate its efficacy in healthy Filipino participants aged 6 months to 45 years through administration of the test vaccine (Arm A, B, and C) or comparator vaccine Typbar-TCV® (Arm D). Sera samples were collected pre-vaccination (Visit 1) and post-vaccination (Visit 4, Day 28) to assess the immunogenicity of EuTCV and Typbar-TCV®. During the study, participants were regularly monitored through scheduled visits to the clinic to report any adverse events associated with the vaccine. For vaccine safety, the proportion of solicited and unsolicited Treatment-Emergent Adverse Events was all comparable between EuTCV and Typbar-TCV® groups. A single dose of EuTCV produced seroconversion in 99.4% of treated participants, with seroconversion rates non-inferior to that of Typbar-TCV®. Batch-to-batch consistency was concluded based on the 90% Confidence Interval of the geometric mean ratio (EuTCV Arm A, B, and C) at Week 4, lying within the equivalence margin of 0.5 to 2.0 for all batches. Results from this Phase II/III clinical trial of EuTCV in healthy volunteers show comparable safety and considerable immunogenicity, compared to Typbar-TCV®, meeting the objectives of this pivotal study. ClinicalTrials.gov registration number: NCT04830371.

Fluorine-modified sialyl-Tn-CRM197 vaccine elicits a robust immune response

Even though a vaccine that targets tumor-associated carbohydrate antigens on epithelial carcinoma cells presents an attractive therapeutic approach, relatively poor immunogenicity limits its development. In this study, we investigated the immunological activity of a fluoro-substituted Sialyl-Tn (F-STn) analogue coupled to the non-toxic cross-reactive material of diphtheria toxin197 (CRM197). Our results indicate that F-STn-CRM197 promotes a greater immunogenicity than non-fluorinated STn-CRM197. In the presence or absence of adjuvant, F-STn-CRM197 remarkably enhances both cellular and humoral immunity against STn by increasing antigen-specific lymphocyte proliferation and inducing a mixed Th1/Th2 response leading to production of IFN-γ and IL-4 cytokines, as well as STn-specific antibodies. Furthermore, antisera produced from F-STn-CRM197 immunization significantly recognizes STn-positive tumor cells and increases cancer cell lysis induced by antibody-dependent cell-mediated cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC) pathways. Our data suggest that this F-STn vaccine may be useful for cancer immunotherapy and possibly for prophylactic prevention of cancer.

Factors contributing to the immunogenicity of meningococcal conjugate vaccines

Various glycoprotein conjugate vaccines have been developed for the prevention of invasive meningococcal disease, having significant advantages over pure polysaccharide vaccines. One of the most important features of the conjugate vaccines is the induction of a T-cell dependent immune response, which enables both the induction of immune memory and a booster response after repeated immunization. The nature of the carrier protein to which the polysaccharides are chemically linked, is often regarded as the main component of the vaccine in determining its immunogenicity. However, other factors can have a significant impact on the vaccine's profile. In this review, we explore the physico-chemical properties of meningococcal conjugate vaccines, which can significantly contribute to the vaccine's immunogenicity. We demonstrate that the carrier is not the sole determining factor of the vaccine's profile, but, moreover, that the conjugate vaccine's immunogenicity is the result of multiple physico-chemical structures and characteristics.

The design of semi-synthetic and synthetic glycoconjugate vaccines

INTRODUCTION

Glycoconjugate vaccines are among the safest and most efficacious vaccines developed during the last 30 years. They are a potent tool for prevention of life-threatening bacterial infectious diseases like meningitis and pneumonia. The concept of hapten-carrier conjugation is now being extended to other disease areas.

AREAS COVERED

This is an overview of the history and current status of glycoconjugate vaccines. The authors discuss the approaches for their preparation and quality control as well as those variables which might affect their product profile. The authors also look at the potential to develop fully synthetic conjugate vaccines based on the progress of organic chemistry. Additionally, new applications of conjugate vaccines technology in the field of non-infectious diseases are discussed. Through this review, the reader will have an insight regarding the issues and complexities involved in the preparation and characterization of conjugate vaccines, the variables that might affect their immunogenicity and the potential for future applications.

EXPERT OPINION

The immunogenicity of weak T-independent antigens can be increased in quantity and quality by conjugation to protein carriers, which provide T-cell help. Glycoconjugate vaccines are among the safest and most efficacious vaccines developed so far. Various conjugation procedures and carrier proteins can be used. Many variables impact on the immunogenicity of conjugate vaccines and a tight control through physicochemical tests is important to ensure manufacturing and clinical consistency. New and challenging targets for conjugate vaccines are represented by cancer and other non-infectious diseases.

Immunogenicity of a combination vaccine containing diphtheria toxoid, tetanus toxoid, three-component acellular pertussis, hepatitis B, inactivated polio virus, and Haemophilus influenzae type b when given concomitantly with 13-valent pneumococcal conjugate vaccine

Two randomized trials of 13-valent pneumococcal conjugate vaccine (PCV13) relative to PCV7 evaluated the immune responses of coadministered antigens comprising Infanrix(®) hexa/Infanrix(®)-IPV+Hib (diphtheria, tetanus, 3-component acellular pertussis, hepatitis B, inactivated poliovirus, and Haemophilus influenzae type b). After the 3-dose infant series, immunogenic noninferiority was demonstrated for all concomitantly administered antigens between the PCV13 and PCV7 groups. All antigens elicited good booster responses after the toddler dose except pertussis toxoid; however, 99.6% subjects achieved pertussis toxoid protective antibody level ≥5EU/mL in both groups. These results support the concomitant administration of PCV13 and Infanrix hexa/Infanrix-IPV+Hib as part of routine immunization schedules.

Pentapeptide commonality between Corynebacterium diphtheriae toxin and the Homo sapiens proteome

Cross-reactivity may affect diagnostic tests and cause harmful autoimmune reactions following immunotherapy. To predict potential cross-reactivity and search for safe immunotherapeutic approaches, we analyzed sequence identity between microbial antigens and the human proteome. Using diphtheria toxin (DT) as a model, we examined its patterns of identity with human proteins at the pentapeptide level. DT shares 503 pentapeptides with the human proteome, while only 31 pentapeptides are unique to the toxin. DT pentapeptide identity involves multiple/repeated matches in human proteins (a total of 4966 occurrences). Human proteins containing bacterial peptide matches include antigens linked to fundamental cellular functions, such as cell cycle control, proliferation, development and differentiation. The data presented in this article offer a rational basis for designing peptide-based vaccines that specifically target DT and thus eliminate the potential risk of cross-reactivity with human proteins. More generally, this study proposes a methodological approach for avoiding cross-reactivity in immune reactions.