An integrity assay for a meningococcal type B conjugate vaccine

Vaccine Quality Ensured by High-Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection

Many important vaccines use bacterial capsular polysaccharides, or shorter polysaccharides or oligosaccharides, derived from the capsular polysaccharides, conjugated to protein. It is imperative that manufacturers understand the carbohydrate composition of these vaccines and deliver a product with a consistent polysaccharide or polysaccharide conjugate composition and content. High-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) is a major technique used to understand the carbohydrate composition of these vaccines and ensure product quality. HPAE-PAD separates and detects carbohydrates without analyte derivatization. This paper describes the basics of the HPAE-PAD technique and then reviews how it has been applied to Haemophilus influenzae type b, pneumococcal, meningococcal, group B streptococcal, and Salmonella polysaccharide and corresponding conjugate vaccines.

Development and evaluation of a novel vaccine against prevalent invasive multi-drug resistant strains of Streptococcus pneumoniae

Streptococcus pneumoniae is a pathogen that causes serious invasive infections, such as septicemia, meningitis and pneumonia in addition to mild upper respiratory tract infections. Protection from pneumococcal diseases is thought to be mediated mainly by serotype-specific antibodies to capsular antigens. Pneumococcal conjugate vaccine consists of sugars (polysaccharides) from the capsule of the bacterium S. pneumoniae that are conjugated to a carrier protein. Three pneumococcal conjugated vaccines, each directed against a group of serotypes, are registered in Egypt; however, local vaccine production is required to cover the most prevalent serotypes. In this work, capsular polysaccharide from the most current and prevalent serotypes in Egypt were extracted, purified and conjugated to bovine serum albumin (BSA). The polysaccharide protein conjugate was purified through ultrafiltration technique and molecular size distribution was compared to an available vaccine. The immunogenicity of the prepared vaccine was examined via two methods: First, by measuring the levels of the elicited antibodies in the sera of the vaccinated mice; second, by challenging the vaccinated groups of mice with approximately 107 CFU of each specific serotype and determining the degree of protection the developled vaccine offers. Our results show that the developed conjugated capsular polysaccharide vaccine is highly immunogenic and protective in mice. This finding illustrates the importance of tracking the most recent and predominant peneumococcal serotypes to generate effective vaccines, instead of using expensive imported vaccines with large number of serotypes which might not be even present in the community.

Liquid chromatography/tandem mass spectrometry with fluorous derivatization method for selective analysis of sialyl oligosaccharides

RATIONALE

A separation-oriented derivatization method using a specific fluorous affinity between perfluoroalkyl-containing compounds was applied to selective liquid chromatography/tandem mass spectrometric (LC/MS/MS) analysis of sialyl oligosaccharides. The perfluoroalkyl-labeled sialyl oligosaccharides could be selectively retained on an LC column with the perfluoroalkyl-modified stationary phase and effectively distinguished from non-derivatized species.

METHODS

Sialyl oligosaccharides (3'-sialyllactose, 6'-sialyllactose, sialyllacto-N-tetraose a, sialyllacto-N-tetraose b, sialyllacto-N-tetraose c, and disialyllacto-N-tetraose) were derivatized with 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecylamine via amidation in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (condensation reagent). The obtained derivatives were directly injected onto the fluorous LC column without any pretreatments and then detected by positive electrospray ionization MS/MS.

RESULTS

The method enabled accurate determination of the sialyl oligosaccharides in biological samples such as human urine and human milk, because there was no interference with matrix-induced effects during LC/MS/MS analysis. The limits of detection of the examined sialyl oligosaccharides, defined as signal-to-noise (S/N) = 3, were in the range 0.033-0.13 nM. Accuracy in the range 95.6-108% was achieved, and the precision (relative standard deviation) was within 9.4%.

CONCLUSIONS

This method enabled highly selective and sensitive analysis of sialyl oligosaccharides, enabling accurate measurement of even their trace amounts in biological matrices. The proposed method may prove to be a powerful tool for the analysis of various sialyl oligosaccharides.

Determination of saccharide content in pneumococcal polysaccharides and conjugate vaccines by GC-MSD

A simple and sensitive gas chromatographic method was designed for quantitative analysis of Streptococcus pneumoniae capsular polysaccharides, activated polysaccharides, and polysaccharide conjugates. Pneumococcal serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F polysaccharide or conjugate were subjected to methanolysis in 3N hydrochloric acid in methanol followed by re-N-acetylation and trimethylsilylation. Derivatized samples were chromatographed and detected using gas chromatography with mass selective detector. Gas chromatographic results were compared with colorimetric values with agreement of 92 to 123% over the range of all samples tested. Monosaccharides released during methanolysis included hexoses, uronic acids, 6-deoxy-hexoses, amino sugars, and alditols. Quantitative recovery of monosaccharides was achieved for all serotypes by the use of a single methanolysis, derivatization, and chromatography procedure. Response factors generated from authentic monosaccharide standards were used for quantitation of pneumococcal polysaccharides and conjugates with confirmation of peak assignments by retention time and mass spectral analysis. This method allows saccharide quantitation in multivalent pneumococcal vaccine intermediates and final drug products with low-level detection (10 pg) and peak purity.

Meningococcal disease in international travel: vaccine strategies

International travel and migration facilitate the rapid intercontinental spread of meningococcal disease. Serogroup A, and to a lesser extent serogroup C, have been responsible for pandemics in the past (mainly in Africa), but in recent years there was an international outbreak due to W135 related to the Hajj pilgrimage. The high carriage rates, persistence and transmissibility, in combination with the high case fatality rate of the Hajj-associated W135 outbreak clone, certainly raise considerable concern about the public health consequences of widespread dissemination of this organism and the potential for future epidemics. Indeed, the now evolving W135 epidemic in Africa mandates that the bivalent meningococcal vaccine should be replaced by the tetravalent meningococcal vaccine, covering A, C, Y and W135 serogroups. The currently available polysaccharide tetravalent meningococcal vaccine, albeit associated with high seroconversion and efficacy rates, has several shortcomings: it is not immunogenic in young children, duration of protective immunity is short, and it has minimal or no effect on nasopharyngeal carriage and therefore transmission of the organism. Immunogenicity of polysaccharide vaccines can be improved by chemical conjugation to a protein carrier, thereby eliciting a T-cell-dependent antibody response. In contrast to polysaccharide vaccines, conjugate vaccines are immunogenic in young infants, induce long-term protection, and reduce nasopharyngeal carriage. The tetravalent conjugate vaccine will be a leap forward in the control of meningococcal epidemics in affected countries. It will also boost the uptake of meningococcal vaccines in travelers, because the duration of protection is longer and it eliminates the problem of immune hyporesponsiveness of serogroup C with repeated dosing. The small risk of travel-associated disease for the general traveler and the unpredictable nature of epidemics make it difficult to provide evidence-based vaccine recommendations. The current recommendation is to vaccinate all Hajj pilgrims, travelers to areas with current outbreaks, travelers to the sub-Saharan meningitis belt, and high-risk individuals (i.e., those with immunodeficiencies).