Comparison of three ELISA protocols to measure antibody responses elicited against serogroup C meningococcal polysaccharide in mouse, monkey and human sera

Protein transduction domain of transactivating transcriptional activator fused to outer membrane protein K of Vibrio parahaemolyticus to vaccinate marbled eels (Anguilla marmorata) confers protection against mortality caused by V. parahaemolyticus

Although immersion and oral vaccination are the most practical methods for fish farmers, their applications are very limited due to low immune stimulation effect. We used the protein transduction domain (PTD) of transactivating transcriptional factor (TAT) derived from HIV TAT protein to increase the delivery efficiency of aquatic protein vaccines. Vibrio parahaemolyticus outer membrane protein K (ompK), a reported vaccine candidate for the prevention of V. parahaemolyticus infection, was fused with TAT-PTD expressed in Escherichia coli. We found that PTD-ompK fusion protein effectively penetrated into marbled eel bodies. Analysis of ompK antibody titres demonstrated that immersion vaccination with PTD-ompK was superior to ompK alone and induced robust immune stimulation in marbled eels. Both active and passive protection analyses against immersive challenge with V. parahaemolyticus strains demonstrated that marbled eels immunized with PTD-ompK survived significantly longer than those immunized with ompK alone. Our results indicated that TAT-PTD could be served as is an efficient delivery system for aquatic immersion vaccinations against various infectious diseases commonly seen in aquatic farm industry.

Characterization of size, structure and purity of serogroup X Neisseria meningitidis polysaccharide, and development of an assay for quantification of human antibodies

Serogroup X Neisseria meningitidis (MenX) has recently emerged as a cause of localized disease outbreaks in sub-Saharan Africa. In order to prepare for vaccine development, MenX polysaccharide (MenX PS) was purified by standard methods and analyzed for identity and structure by NMR spectroscopy. This study presents the first full assignment of the structure of the MenX PS using (13)C, (1)H and (31)P NMR spectroscopy and total correlation spectroscopy (TOCSY) and (1)H-(13)C heteronuclear single quantum coherence (HSQC). Molecular size distribution analysis using HPLC-SEC with multi-angle laser light scattering (MALLS) found the single peak of MenX PS to have a weight-average molar mass of 247,000g/mol, slightly higher than a reference preparation of purified serogroup C meningococcal polysaccharide. MenX PS tended to be more thermostable than serogroup A PS. A method for the quantification of MenX PS was developed by use of high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). A novel and specific ELISA assay for quantification of human anti-MenX PS IgG based on covalent linkage of the MenX PS to functionally modified microtitre plates was developed and found valid for the assessment of the specific antibody concentrations produced in response to MenX vaccination or natural infection. The current work thus provides the necessary background for the development of a MenX PS-based vaccine to prevent meningococcal infection caused by bacteria bearing this capsule.

Purified capsular polysaccharide of Neisseria meningitidis serogroup A as immune potentiator for antibody production

The development of new immune potentiators for human vaccines is an important and expanding field of research. In the present study, the ability of the capsular polysaccharide from Neisseria meningitidis serogroup A (CPS-A), a mannose-containing carbohydrate, to enhance the antibody production against a co-administered model vaccine antigen, is examined. A protein-meningococcal serogroup C capsular polysaccharide (CPS-C) conjugate was selected as the model antigen for this study. After subcutaneous immunization of Balb/C mice, the conjugate mixed with CPS-A induced higher anti-CPS-C IgG and IgG(2a) antibody levels and higher anti-meningococcal serogroup C bactericidal titers than the conjugate alone or mixed with CPS-C. The immuno-stimulatory properties exhibited by CPS-A and the fact that vaccines based on purified CPS-A has been safely used during decades to fight the serogroup A meningococcal disease, support the proposal to use CPS-A as immune potentiator for human vaccination studies.

Effects of a chemically derived homo zwitterionic polysaccharide on immune activation in mice

In this study, a chemically modified homo zwitterionic polysaccharide (ZPS), sulfated chitosan, was used to examine its effects on murine immune response. The results showed that homoZPS could markedly promote the proliferation of both splenic T/B cells and adhesive cells. In particular, flow cytometry assay demonstrated that the sulfated chitosan could non-specifically activate CD3(+) and CD8(+) T cells proliferation in vitro. The effectiveness of sulfated chitosan as adjuvant was tested using bovine serum albumin (BSA) and diphtheria toxin (DT) as antigens and compared with that of aluminum hydroxide. The levels of specific antibodies to BSA and DT significantly increased after homoZPS vaccination. Both homoZPS and aluminum hydroxide adjuvants could protect mice against the attack of DT from edemas of spleen and tail. The present findings demonstrated the chemically derived homoZPS could be a potential candidate in the development of T-lymphocyte dependent vaccine adjuvants.

Development of 5-valent conjugate pneumococcal protein A - Capsular polysaccharide pneumococcal vaccine against invasive pneumococcal disease

In this study, we synthesized a 5-valent pneumococcal conjugate vaccine, which was prepared with the pneumococcal capsular polysaccharides (PCPs) (from Streptococcus pneumoniae 1, 5, 6B, 19F, 23F) and pneumococcal surface protein A (PspA) mediated by 1,4-butanediol diglycidyl ether. The PspA cloned from serotype 19 strain showed good cross-immune response to 1, 5, 6B, and 23F serotypes of Streptococcus pneumonia (S. pneumoniae). Analysis of the maturation process of conjugate polyclonal antibody showed that conjugation with the protein carrier converted the polysaccharide from a weak T cell-independent (TI) antigen to a T cell-dependent (TD) antigen, although antibodies affinity to polysaccharide was not as strong as it to PspA in conjugate. We used an invasive disease mouse model to evaluate the protective efficacy of this conjugate vaccine. Active and passive protection against intraperitoneal challenge with virulent type 6B strain showed that the median survival times for mice immunized with conjugate were significantly longer than that of mice treated with capsular polysaccharides or PspA alone. Our study's results showed that immunization of the 5-valent PspA-capsular polysaccharides conjugate vaccine could afford strong protection to mice against the invasion of 1, 5, 6B, 19F, 23F serotypes S. pneumoniae.