Development and Immunogenicity of a Brazilian Glycoconjugate vaccine against Meningococcal W in a Pilot Scale.

Recent changes in the epidemiology of meningococcal have been reported and meningococcal group W (MenW) has become the third most prevalent group isolated in Brazil in the last 10 years. In this study we have developed a conjugate vaccine for MenW using a modified reductive amination conjugation method through a covalent linkage between periodate-oxidized MenW non-O-acetylated polysaccharide and hydrazide-activated monomeric tetanus toxoid. Process control of bulks was done by physicochemical analysis including polysaccharide and protein quantification, high performance liquid chromatography - size exclusion chromatography, capillary electrophoresis, and hydrogen nuclear magnetic resonance. Conjugate bulks were best produced with concentration of polysaccharide twice as high as protein, at room temperature, and pH approximately 6.0. A scaled-up bulk (100 mg scale) was formulated and inoculated intramuscularly in mice in a dose-response study (0.1, 0.5, 1.0 and 10.0 µg of polysaccharide/dose). The immunogenicity of conjugate bulks was determined by serum bactericidal assay and ELISA assays of serum from immunized mice. ELISA and SBA titers revealed high titers of IgG and demonstrated the functionality of the antibodies produced in all doses studied 15 days after the third dose. However, significant differences were observed among them by ELISA. In conclusion, this study established the best conditions to produce MenW conjugate bulks and showed the efficacy of the obtained conjugate bulk in induce a good immune response in mice. Further experiments will need to be done to scale up the conjugation reaction and then allow the use of this conjugate in clinical trials.

Brazilian meningococcal C conjugate vaccine: physicochemical, immunological, and thermal stability characteristics.

High temperature is known to cause some instability in polysaccharide-protein conjugated vaccines and studies under stress conditions may be useful in determining whether short-term accidental exposure to undesired conditions can compromise product quality. In this study, we examined the structural stability of three industrial batches of Brazilian Meningococcal C conjugate bulk (MPCT) incubated at 4, 37, and 55 °C for 5 weeks. The effect of exposure to the storage temperatures was monitored by HPLC-SEC, CZE, CD and NMR techniques. The immunological significance of any physicochemical changes observed in MPCT was determined by SBA and ELISA assays of serum from immunized mice. Fluorescence emission spectra at 4 and 37 °C were similar among all samples and compatible with the native fold of the carrier protein. Fluorescence spectra of MPCT stored at 55 °C decreased in intensity and had a significant red-shift, indicating conformational changes. Far-UV CD spectra revealed a trend toward loss of structural conformation as storage temperature was increased to 55 °C. The NMR data showed modified signal intensity of the aromatic and aliphatic residues, mainly for samples incubated at 55 °C, suggesting a partial loss of tertiary structure. About 50% free saccharide content was found in bulks stored at 55 °C, but no difference was observed in the IgG or SBA titers. The present study showed physicochemical methods alone are insufficient to predict the biological activity of a MPCT conjugate vaccine without extensive validation against immunological data. However, they provide a sensitive means of detecting changes induced in a vaccine exposed to adverse environmental condition.

Brazilian meningococcal C conjugate vaccine: Scaling up studies.

Several outbreaks caused by Neisseria meningitidis group C have been occurred in different regions of Brazil. A conjugate vaccine for Neisseria meningitidis was produced by chemical linkage between periodate-oxidized meningococcal C polysaccharide and hydrazide-activated monomeric tetanus toxoid via a modified reductive amination conjugation method. Vaccine safety and immunogenicity tested in Phase I and II trials showed satisfactory results. Before starting Phase III trials, vaccine production was scaled up to obtain industrial lots under Good Manufacture Practices (GMP). Comparative analysis between data obtained from industrial and pilot scales of the meningococcal C conjugate bulk showed similar execution times in the scaling up production process without significant losses or alterations in the quality attributes of purified compounds. In conclusion, scale up was considered satisfactory and the Brazilian meningococcal conjugate vaccine production aiming to perform Phase III trials is feasible.

Single validation of CE method for determining free polysaccharide content in a Brazilian meningococcal C conjugate vaccine.

Neisseria meningitidis group C is an encapsulated bacterium that causes several diseases and is associated with high mortality rates, thereby constituting a serious public health problem. Bio-Manguinhos/Fiocruz is developing a conjugate vaccine by covalent attachment of capsular polysaccharide to hydrazide-activated tetanus toxoid through reductive amination. It is necessary to quantify free components as a quality control process to prevent exacerbated adverse reactions and/or attenuation of vaccine immunogenicity. Thus, this study aimed to develop and validate a quality control method appropriate for the separation and quantification of free polysaccharide present in this conjugate N. meningitidis group C vaccine using CE. CZE was used to remove unbound polysaccharide, and the electrophoretic conditions were varied to optimize resolution. We were able to develop and validate the proposed method, which was linear and showed a matrix effect. Repeatability and partial reproducibility of the method were also evaluated. The robustness results showed that control of temperature is required for reliable results. The validated method will be used to evaluate the conjugate batches submitted for Phase III clinical studies and for routine quality control of the conjugate vaccine.

Investigation of cultivation conditions for capsular polysaccharide production by Streptococcus pneumoniae serotype 14

Streptococcus pneumoniae (pneumococcus) is among the most significant causes of bacterial disease in humans. Capsular polysaccharide (CPS) production is essential for pneumococcal virulence. Pneumococcal CPS has been widely used as vaccine antigen. This study is focused on the influence of culture conditions of Streptococcus pneumoniae serotype 14 as for developing an industrial method for polysaccharide production. The pH proved to be a highly important variable in batchwise culture. Using the pH control all glucose added was consumed resulting in a four-fold increase in polysaccharide productivity relative to cultivation without pH control. S. pneumoniae is a lactic acid bacterium, so named for its primary metabolic byproduct (lactate), which has an inhibitory effect on cell growth in concentrations ranging from 4 to 5 g/L. An increase of 30 percent in polysaccharide productivity was observed using glucose pulses with 5.5 hrs of growth, resulting in a maximum polysaccharide concentration of 185.2 mg/L. Our data suggest the possibility of using a medium of non-animal origin and employing pH control for the cultivation of pneumococcus to produce a polysaccharide vaccine.

Outer membrane vesicles (OMVs) and detoxified lipooligosaccharide (dLOS) obtained from Brazilian prevalent N. meningitidis serogroup B strains protect mice against homologous and heterologous meningococcal infection and septic shock.

Neisseria meningitidis (N. meningitidis) is a serious bacterial pathogen that causes life-threatening invasive bacterial infections especially in children below 2 years of age, teenagers and young adults. We have investigated the protective potential of outer membrane vesicles (OMVs) and detoxified lipooligosaccharide (dLOS) obtained from Brazilian prevalent N. meningitidis serogroup B strains. Swiss mice were immunized with different combinations of OMV and dLOS from N. meningitidis serogroup B strains compared to a reference vaccine (VA-MENGOC-BC), Cuba). The OMVs + dLOS from Brazilian prevalent strains induced higher bactericidal antibody titers against homologous and heterologous target strains and stronger inhibition of thrombocytopenia as compared to the reference vaccine. When the challenge was performed with the B strain, all immunogens tested showed similar survival rates (80%) significantly higher than the control group. Bacterial clearance against the group B strain was comparable for animals immunized with the tested immunogen and the reference vaccine. Inclusion of dLOS from the B strain with the OMV, induced a similar clearance of C strain bacteria as compared to VA-MENGOC-BC. The immunogens, as well as the reference vaccine drastically inhibited increases in TNF-alpha and IL-6 plasma levels after challenge. In conclusion, the OMV/dLOS formulation obtained from Brazilian prevalent strains of N. meningitidis has a remarkable performance protecting mice against the lethal effects of meningococcal challenge showing a good potential as a vaccine and should be considered for clinical evaluation.