Combination conjugate vaccines

NMR characterization of a multi-valent conjugate vaccine against Neisseria meningitidis A, C, W, Y and Haemophilus influenzae b infections

Physicochemical technologies are a powerful tool for the structural characterization of vaccine antigens both at bulk level as well as on the final formulation. High-field Nuclear Magnetic Resonance (NMR) spectroscopy has been found to be an extremely and robust tool for tracking the industrial process manufacturing of carbohydrate-based vaccines. I have applied NMR spectroscopy to the characterization of a penta-valent conjugate vaccine against Neisseria meninigitidis group A, C, W, Y (MenACWY) and Haemophilus influenzae type b (Hib) infections, constituted of capsule derived polysaccharide fragments independently conjugated to CRM₁₉₇ protein carrier (CRM-MenA, CRM-MenC, CRM-MenW, CRM-MenY, CRM-Hib). ¹H NMR has been used for the identity testing of the carbohydrate antigens and of the vaccine formulation. The application of NMR-based assays on multivalent conjugate vaccines looks to be a promising approach for identity and stability analyses useful for future vaccines development.

Protein glycosylation: Sweet or bitter for bacterial pathogens?

Protein glycosylation systems in many bacteria are often associated with crucial biological processes like pathogenicity, immune evasion and host-pathogen interactions, implying the significance of protein-glycan linkage. Similarly, host protein glycosylation has been implicated in antimicrobial activity as well as in promoting growth of beneficial strains. In fact, few pathogens notably modulate host glycosylation machineries to facilitate their survival. To date, diverse chemical and biological strategies have been developed for conjugate vaccine production for disease control. Bioconjugate vaccines, largely being produced by glycoengineering using PglB (the N-oligosaccharyltransferase from Campylobacter jejuni) in suitable bacterial hosts, have been highly promising with respect to their effectiveness in providing protective immunity and ease of production. Recently, a novel method of glycoconjugate vaccine production involving an O-oligosaccharyltransferase, PglL from Neisseria meningitidis, has been optimized. Nevertheless, many questions on defining antigenic determinants, glycosylation markers, species-specific differences in glycosylation machineries, etc. still remain unanswered, necessitating further exploration of the glycosylation systems of important pathogens. Hence, in this review, we will discuss the impact of bacterial protein glycosylation on its pathogenesis and the interaction of pathogens with host protein glycosylation, followed by a discussion on strategies used for bioconjugate vaccine development.

Immunogenicity of a Glycoconjugate from Hydrazine-Detoxified Lipopolysaccharide of Vibrio cholerae O139

A glycoconjugate (dLPS-CBSA) from hydrazine-detoxified lipopolysaccharide (LPS) of Vibrio cholerae O139 and BSA was used for immunization of BALB/c mice. The immunogenicity (concentration of induced IgG antibodies) of the conjugate was determined by enzyme-linked immunosorbent assay. The highest level of LPS-specific IgGs was found in sera collected 2 weeks after the third immunization. Both IgM and IgG antibodies present in the anti-V. cholerae O139-specific sera showed long-lasting vibriocidal activity. The glycoconjugate also stimulated production of IL-4, IL-6, IFNγ, TNFα and IL-10. Immunization with the conjugate induced significant production of both Th1 and Th2 cytokine sets, indicating balanced Th1/Th2 immune response polarization. The quantitative analysis of total and LPS-specific IgM and IgG antibodies production by B lymphocytes (from both the spleen and the bone marrow) was performed by ELISPOT assay. From the analysis of antibodies produced directly by B lymphocytes in the bone marrow (of dLPS-CBSA immunized mice), we were able to identify the IgM-IgG switch in the antibodies produced.

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.