Scientific challenges for the quality control and production of group C meningococcal conjugate vaccines

Comparative Analysis of Antigenic Strength and In vivo Serum Antibodies Concentration of Tetanus Toxoid Vaccine Adsorbed in Pakistan

Clostridium tetani produce tetanospasmin, a potent exotoxin; that causes tetanus or lockjaw disease. Scientists developed an anti-tetanus toxoid to protect the body from the spasm's neurotoxic effect. In Pakistan recently, 478 cases of neonatal tetanus were reported. The study was carried out at The National Control Laboratory for Biologicals Islamabad, aiming to decipher the effectiveness of the most frequently used tetanus toxoid vaccine adsorbed in Pakistan in comparison to standard reference vaccine having earlier known consistent values. The vaccines included domestic public sector, domestic private sector, imported private sector I, and imported private sector II. The triplicate experiments on purebred Swiss albino mice were performed by immunizing with Tetanus toxoid and then tested parallel with standard reference vaccine. Various analytical tests were performed on the test organism that included flocculation test/identity test, antibody quantification using enzyme-linked immunosorbent assay (ELISA), potency test, abnormal toxicity test, osmolality, pH test, liquid sub-visible particle test, and sterility test. Results of all the vaccines were compared in comparison with the standard reference vaccine. Absorbances of test vaccines were recorded at the lowest dilution by ELISA. The domestic private sector, imported private sector I, imported private sector II and standard reference vaccine were flocculated at mean dilution (Mean: 0.24, 95% CI: 0.1903–0.2897), and the domestic public sector was flocculated at mean dilution (Mean: 0.23, 95% CI: 0.2052–0.2548). All the products were found within the normal ranges where it was concluded that the maximum average titer of 2.81 was observed at dilution 10^−1.6, indicating that these vaccines were adequate/suitable for the prevention of tetanus.

Combined vaccines for prophylaxis of infectious conditions

In recent years, the application of vaccines shows limitations, including the high number of vaccine administrations and the fear of safety and effectiveness. In this regard, advanced vaccine products have been developed, like the combined vaccines, or are under development, such as nucleic acid vaccines (DNA and RNA), polymer-based vaccines, etc. Moreover, the possible use of traditional, like aluminium hydroxide and aluminium phosphate, or innovative adjuvants, like monophosphoryl lipid A, polysaccharides and nanoparticulate system, may further increase vaccine effectiveness. This review article focuses on the combined vaccines, which, especially when they are associated with adjuvants, reduce the dosing frequency, and prolong the duration of action, thus providing better vaccine coverage. Marketed preparations, like Typhim Vi, Peda typh and Boostrix showed better vaccine coverage for diseases like typhoid, tetanus, diphtheria and acellular pertussis. The future aspect for the development of combined vaccines will protect not only against infectious diseases but likely even against various infectious conditions, like pneumonia, meningococcal infection and respiratory syncytial virus infection.

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.

Carbohydrate-Based Polymers for Immune Modulation

Carbohydrates play prominent roles in immune surveillance and response to infection. Multivalency, molecular weight control, and molecular architecture control are properties that polymer science is well suited to address. Each of these properties has been demonstrated to impact the biological interaction of carbohydrate-bearing chains with their binding partners. This viewpoint highlights synthetic advances and potential applications of carbohydrate-based polymers for immune modulation. It also offers future directions in polymer science necessary for carbohydrate polymers to fulfill their potential as immune modulators.

Antibody persistence and response to a booster dose of a quadrivalent conjugate vaccine for meningococcal disease in adolescents

BACKGROUND

In a previous randomized phase 2 study in adolescents, a CRM197 meningococcal conjugate vaccine against serogroups A, C, W-135 and Y (MenACWY-CRM) was well tolerated and immunogenic, compared with a plain polysaccharide vaccine (MenACWY-PS).

METHODS

This extension study assessed antibody persistence 5 years after primary vaccination with MenACWY-CRM (n = 50) or MenACWY-PS (n = 51), and the immunogenicity and reactogenicity of a dose of MenACWY-CRM given 5 years after primary vaccination; antibody response was also compared with vaccine-naive controls (n = 54). The primary endpoints were the percentage of subjects with titers ≥8 by serum bactericidal activity assay using human complement (hSBA) 5 years after primary vaccination and hSBA geometric mean titers 1 month after the MenACWY-CRM dose given in the current study.

RESULTS

Five years after primary vaccination, over 70% of subjects who had received MenACWY-CRM were seropositive (hSBA titers ≥8) for serogroups C, W-135 and Y; for serogroups C and Y, the percentages of seropositive subjects were significantly higher in subjects previously vaccinated with MenACWY-CRM than in subjects previously vaccinated with MenACWY-PS. The MenACWY-CRM dose given 5 years postprimary vaccination elicited an anamnestic response across serogroups in those previously vaccinated with MenACWY-CRM. Responses in those previously vaccinated with MenACWY-PS were less robust but adequate and similar to that seen in the vaccine-naive group, both in magnitude and kinetics. MenACWY-CRM was well tolerated in all 3 groups.

CONCLUSION

MenACWY-CRM provided a broad and persistent immune response in adolescents. A subsequent dose of MenACWY-CRM elicited an adequate antibody response, regardless of vaccine history.

Assignment of quantities to biological medicines: an old problem re-discovered

A distinction exists between 'chemical' and 'biological' medicines. While, from antiquity, both organic and inorganic substances had been used in therapy, developing chemical sciences were inapplicable to materials extracted from natural sources, and the active principles could be neither identified nor characterized. The distinction between biological medicines or 'biologicals' grew out of this realization. Such 'biologicals' in clinical use were, however, variable in efficacy and in safety, and controlling the strength or quality was necessary. Without information on what biological medicines are, it was necessary to quantify what they do, and such medicines were quantified using systems based on biological responses (bioassays) in animals, organs or cells. Bioassays are defined in terms of an external standard rather than in absolute terms, and depend on a number of key assumptions: the need to assay 'like against like', the desirability of making the assay principle relevant to the intended clinical effect in man, and the importance of appropriate statistical models of design and analysis. The science of 'biological standardization' has kept pace with developments in medicine and continues to allow the use of biological medicines in man to be controlled on the basis of common measurement systems.

WITHDRAWN: Conjugate vaccines for preventing meningococcal C meningitis and septicaemia

BACKGROUND

Meningococcal polysaccharide (MPLS) vaccines protect against Serogroup C disease, but do not produce an immune response in infants less than two years of age. This limitation can be overcome by linking C polysaccharide to carrier proteins ('conjugating'), to create meningococcal serogroup C conjugate (MCC) vaccines. In the absence of trial data, the immune response to vaccination has been considered to be a reasonable surrogate for vaccine protection.

OBJECTIVES

To assess the immunogenicity, safety and efficacy of MCC vaccines for preventing meningitis and septicaemia.

SEARCH STRATEGY

We searched the Cochrane Central Register Controlled Trials (CENTRAL) (The Cochrane Library 2005, issue 3); MEDLINE (1966 to September, Week 1 2005); and EMBASE (1990 to June 2005) and references of studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and controlled clinical trials (CCTs) in humans comparing MCC vaccines against a control vaccine or none. In the absence of any trials on vaccine efficacy, population-based observational studies about effectiveness were included.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the results of the literature searches, selected eligible studies, extracted the data and evaluated the quality of them.

MAIN RESULTS

The studies showed that MCC vaccine was highly immunogenic in infants after two and three doses, in toddlers after one and two doses and in older age groups after one dose. In general higher titres were generated after MCC than after MPLS vaccines. Immunological hypo-responsiveness seen after repeated doses of MPLS vaccine may be overcome with MCC. Observational studies have documented a significant decline in meningococcal C disease in countries where MCC vaccines have been widely used. The timing of the vaccinations schedules, the specific conjugate used, and the vaccines given concomitantly or combined, may be important.

AUTHORS' CONCLUSIONS

The MCC vaccine appears to be safe, immunogenic and able to induce immunological memory in all age groups. Observational studies strongly suggest that MCC is clinically effective.

Characterization and immunogenicity of meningococcal group C conjugate vaccine prepared using hydrazide-activated tetanus toxoid

The steps to produce, purify and control an immunogenic Brazilian conjugate vaccine against group C meningococcus (MenCPS-TT) using hydrazide-activated tetanus toxoid were developed. The conjugation methodology reduced the reaction time easily allowing scale-up. One freeze-dried pilot vaccine lot purified by tangential filtration, showed satisfactory quality control results including safety and stability. The pilot vaccine was immunogenic in mice in a dose-dependent fashion generating a 10-20-fold rise in IgG response in mice. The vaccine also induced high bactericidal titers. Vaccine concentrations of 1 and 0.1 microg showed higher avidity indices, suggesting induction of immunologic memory. These results support initiation of Phase I clinical studies with the MenCPS-TT conjugate vaccine.

Serum bactericidal antibody response to serogroup C polysaccharide meningococcal vaccination in children with primary antibody deficiencies

Primary antibody deficiencies are characterized by decreased serum levels of immunoglobulin isotypes and increased susceptibility to infection by various microorganisms including encapsulated bacteria. This study was performed in order to evaluate bactericidal antibody response of these patients to polysaccharide meningococcal vaccine. Twenty-four antibody deficient children of mean age 11.2+/-3.5 years, and 15 sex and age-matched healthy volunteers were enrolled. All subjects received meningococcal polysaccharide vaccine A+C; blood samples were collected before vaccination and 3 weeks after vaccination. Following vaccination, the serum bactericidal antibody (SBA) geometric mean titre was significantly increased compared to the prevaccination level in the patient group (8.98 versus 1.63, P<0.001) and the control group (12.13 versus 1.26, P<0.001). All controls had a protective SBA response (SBA titre of >or=8 post-vaccination or rise of >or=4-fold from pre- to post-vaccination), whereas only 16 of 24 patients (66.6%) had a protective response (P=0.014). The non-responder patients included 5 cases with common variable immunodeficiency, two cases with hyper IgM syndrome, and one case with IgG subclass deficiency. This study indicates that some patients with primary antibody deficiencies can produce protective post-vaccination titres similar to the normal population, despite the common perception that patients with primary antibody deficiencies respond poorly to vaccination. This supports the use of polysaccharide-containing vaccines in these patients.

Conjugate vaccines for preventing meningococcal C meningitis and septicaemia

BACKGROUND

Meningococcal polysaccharide (MPLS) vaccines protect against Serogroup C disease, but do not produce an immune response in infants less than two years of age. This limitation can be overcome by linking C polysaccharide to carrier proteins ('conjugating'), to create meningococcal serogroup C conjugate (MCC) vaccines. In the absence of trial data, the immune response to vaccination has been considered to be a reasonable surrogate for vaccine protection.

OBJECTIVES

To assess the immunogenicity, safety and efficacy of MCC vaccines for preventing meningitis and septicaemia.

SEARCH STRATEGY

We searched the Cochrane Central Register Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2005); MEDLINE (1966 to September, Week 1 2005); and EMBASE (1990 to June 2005) and references of studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and controlled clinical trials (CCTs) in humans comparing MCC vaccines against a control vaccine or none. In the absence of any trials on vaccine efficacy, population-based observational studies about effectiveness were included.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the results of the literature searches, selected eligible studies, extracted the data and evaluated the quality of them.

MAIN RESULTS

The studies showed that MCC vaccine was highly immunogenic in infants after two and three doses, in toddlers after one and two doses and in older age groups after one dose. In general higher titres were generated after MCC than after MPLS vaccines. Immunological hypo-responsiveness seen after repeated doses of MPLS vaccine may be overcome with MCC. Observational studies have documented a significant decline in meningococcal C disease in countries where MCC vaccines have been widely used. The timing of the vaccinations schedules, the specific conjugate used, and the vaccines given concomitantly or combined, may be important.

AUTHORS' CONCLUSIONS

The MCC vaccine appears to be safe, immunogenic and able to induce immunological memory in all age groups. Observational studies strongly suggest that MCC is clinically effective.

Immunogenicity of an investigational quadrivalent Neisseria meningitidis-diphtheria toxoid conjugate vaccine in 2-year old children

BACKGROUND

One dose of a quadrivalent meningococcal conjugate (MC-4) vaccine elicits higher group C bactericidal responses in 2-year olds than a U.S.-licensed quadrivalent polysaccharide (MPS-4) vaccine [Granoff DM, Harris SL. Protective activity of group C anticapsular antibodies elicited in 2-year olds by an investigational quadrivalent Neisseria meningitidis-diptheria toxoid conjugate vaccine. Pediatr Infect Dis J, 2004;23:490-7].

OBJECTIVE

Assess immunogenicity and persistence of serum antibody to capsular groups A, Y and W-135 in 2-year old children immunized with MC-4 vaccine.

DESIGN

Measurement of antibody responses in sera from a multicenter randomized trial comparing MC-4 and MPS-4 vaccines.

RESULTS

At 1 month, the group A serum bactericidal GMT was higher in the MC-4 than the MPS-4 group (P < 0.001) but there were no significant differences at 6 months. At 6 months, the respective Y and W-135 GMTs were higher in the MC-4 group (P < 0.05) but there were no differences at 1 month. The higher W-135 bactericidal titers reflected higher antibody avidity in the MC-4 group (P < 0.0001) and avidity maturation between 1 and 6 months (P < 0.05). At 2-year post-vaccination, the proportion of MC-4 immunized children with bactericidal titers > or =1:4 (presumed to be protective) was 15.0% (group A), 32.5% (group Y) and 45% (group W-135), as compared with 2.5, 15.4 and 17.5%, respectively, in unvaccinated children (P < 0.01 for group W-135; P < 0.05 for group A, and P = 0.07 for Y).

CONCLUSIONS

One dose of the MC-4 vaccine in 2-year olds elicits higher A, Y and W-135 bactericidal titers than MPS-4 vaccine. Compared with unvaccinated children, serum antibody titers remain elevated for 2 years after MC-4 vaccination. However, many vaccinated children have titers <1:4 and may require a booster dose for sustained protection.

Prevention and control of meningococcal disease: recommendations for use of meningococcal vaccines in pediatric patients

Two peaks in the incidence of invasive meningococcal disease (IMD) occur in pediatric patients: infants younger than 1 year and adolescents 15 to 18 years of age. Although the incidence of IMD is highest in infants, the case-fatality rate is highest in adolescents (approximately 20%). Epidemiologic studies also have demonstrated increased risk of IMD among college freshman living in dormitories compared with other college students and similarly aged persons in the general population. At least 75% of cases of IMD in 11- to 18-year-olds are caused by serogroups A, C, Y, and W-135; thus, IMD potentially is preventable by immunization with quadrivalent meningococcal vaccines. Meningococcal A, C, Y, W-135 conjugate vaccine (MCV4) was licensed in 2005 for use in people 11 to 55 years of age. On the basis of data indicating increased risk of meningococcal disease and fatality among certain adolescents and college students, the American Academy of Pediatrics recommends administration of MCV4 to young adolescents (at the 11- to 12-year visit), students entering high school or 15-year-olds, and college freshmen who will be living in dormitories. For pediatric patients 11 years and older who are at increased risk of meningococcal disease, MCV4 also is recommended. The purposes of this statement are to provide the rationale for routine use of MCV4 in adolescents and to update recommendations for use of the meningococcal polysaccharide vaccine in pediatric patients.