Multivalent pneumococcal capsular polysaccharide conjugate vaccines employing genetically detoxified pneumolysin as a carrier protein

Michon, Francis; Fusco, Peter C.; Minetti, Conceição A.S.A.; Laude-Sharp, Maryline; Uitz, Catherine; Huang, Chung‐Ming; D’Ambra, Anello J.; Moore, Samuel L.; Remeta, David P.; Heron, Iver; Blake, M. S.

doi:10.1016/s0264-410x(98)00225-4

Cited by 45 publications

(20 citation statements)

References 29 publications

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“…The functional activity of the sera was determined in an opsonophagocytic assay using the HL-60 cell line as described previously (10,19,22). Briefly, 200 CFU of GBS type II strain 18RS21 cells or type III strain M781 cells were mixed in an equal volume with serum antibodies, and samples were shaken for 15 min at 35°C in an incubator in 5% CO 2 .…”

Section: Gbsp-iii ([O]/[h]-gbsp-iii) Identical Conditions Were Usedmentioning

confidence: 99%

Group B Streptococcal Type II and III Conjugate Vaccines: Physicochemical Properties That Influence Immunogenicity

Michon¹,

Uitz²,

Sarkar³

et al. 2006

Clin Vaccine Immunol

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Recent efforts toward developing vaccines against group B streptococci (GBS) have focused on increasing the immunogenicity of GBS polysaccharides by conjugation to carrier proteins. However, partial depolymerization of GBS polysaccharides for the production of vaccines is a difficult task because of their acid-labile, antigenically critical sialic acids. Here we report a method for the partial depolymerization of type II and III polysaccharides by mild deaminative cleavage to antigenic fragments with reducing-terminal 2,5-anhydro-Dmannose residues. Through the free aldehydes of their newly formed end groups, the fragments were conjugated to tetanus toxoid by reductive amination. The resulting conjugates stimulated the production in animals of high-titer type II-and III-specific antibodies which induced opsonophagocytic killing of type II and III strains of group B streptococci. For the type II conjugates, immunogenicity increased as oligosaccharide size decreased, whereas for type III conjugates, the size of the oligosaccharides did not significantly influence immunogenicity. When oligosaccharides of defined size were conjugated through sialic acid residues, the resulting cross-linkages were shown to affect immunogenicity. When oligosaccharides were conjugated through terminal aldehyde groups generated by deamination, modification of the exocyclic chain of sialic acid did not influence immunogenicity.Group B streptococci (GBS) are an important cause of neonatal sepsis and meningitis and of invasive infections in nonpregnant adults with underlying illnesses (7). Although antibodies directed to the capsular polysaccharide (CPS) antigens are protective, these antigens are variably immunogenic (6). The immunogenicity of GBS CPS antigens has been increased by covalent coupling to proteins to form CPS-protein conjugate vaccines (1-5, 18, 21, 23, 25, 29). Experimental GBS type III polysaccharide (GBSP-III)-and oligosaccharide-tetanus toxoid conjugate vaccines of different designs have been developed and their immunogenicity tested in animals (21, 29). (The term "oligosaccharide" is generally used to designate carbohydrates containing between 2 and 10 monosaccharide units per molecule [12]. For convenience and consistency with related published material [12,15,23,25,29], the term oligosaccharide is used in this paper to indicate a fragment obtained by chemical or enzymatic cleavage of a native polysaccharide.) Generating GBS oligosaccharides is a difficult task because of the acid-labile, antigenically critical sialic acid residues present at the termini of the side chains of all GBS CPS serotypes. Enzymatic digestion of the type III CPS with endo-␤-galactosidase allowed the production of oligosaccharide-tetanus toxoid (TT) conjugates which proved to be immunogenic in animals (21). Unfortunately, the specificity of the endo-␤-galactosidase is restricted to type III CPS. We sought a facile chemical degradation for the type III polysaccharide (PS) and possibly those of other CPS serotypes, keeping in mind the acid labilit...

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Section: Gbsp-iii ([O]/[h]-gbsp-iii) Identical Conditions Were Usedmentioning

confidence: 99%

Group B Streptococcal Type II and III Conjugate Vaccines: Physicochemical Properties That Influence Immunogenicity

Michon¹,

Uitz²,

Sarkar³

et al. 2006

Clin Vaccine Immunol

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“…Although 9-valent and 11-valent formulations of conjugate vaccines including serotype 1 capsule polysaccharide have undergone trials (38,55), capsule polysaccharide from all 90 pneumococcal serotypes cannot be included in one vaccine (37). As a result of this, research is focusing on alternatives such as using common immunogenic pneumococcal proteins to be included in future vaccines (1,9,51,56).…”

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confidence: 99%

“…Pneumolysin, a cytoplasmic cholesterol-dependent cytolysin, is of particular interest as a vaccine candidate as it is produced by all strains of S. pneumoniae (33) and is protective in animal models of vaccination (1,42,51,59). The cholesterol-dependent cytolysins form large pores in cholesterol-containing membranes and are therefore cytotoxic to mammalian cells (23,58).…”

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Identification of Invasive Serotype 1 Pneumococcal Isolates That Express Nonhemolytic Pneumolysin

et al. 2006

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Recently, there has been an increase in invasive pneumococcal disease (IPD) caused by serotype 1 Streptococcus pneumoniae throughout Europe. Serotype 1 IPD is associated with bacteremia and pneumonia in Europe and North America, especially in neonates, and is ranked among the top five most prevalent pneumococcal serotypes in at least 10 countries. The currently licensed pediatric pneumococcal vaccine does not afford protection to this serotype. Upon screening of 252 clinical isolates of S. pneumoniae, we discovered mutations in the pneumolysin gene of two out of the four serotype 1 strains present in the study group. Analysis of an additional 28 serotype 1 isolates from patients with IPD from various Scottish Health Boards, revealed that >50% had mutations in their pneumolysin genes. This resulted in the expression of nonhemolytic forms of pneumolysin. All of the strains producing nonhemolytic pneumolysin were sequence type 306 (ST306), whereas those producing "wild-type" pneumolysin were ST227. The mutations were in a region of pneumolysin involved in pore formation. These mutations can be made in vitro to give the nonhemolytic phenotype. Pneumolysin is generally conserved throughout all serotypes of S. pneumoniae and is essential for full invasive disease; however, it appears that serotype 1 ST306 does not require hemolytically active pneumolysin to cause IPD.

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“…Ply could be used alone (1,33) or as a carrier protein to the polysaccharides in current vaccine preparations (21,26,34), conferring increased protection against pneumococcal disease. Ply belongs to the cholesterol-dependent cytolysin (CDC) family of toxins that bind to the cholesterol of eukaryotic membranes.…”

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Construction and Immunological Characterization of a Novel Nontoxic Protective Pneumolysin Mutant for Use in Future Pneumococcal Vaccines

et al. 2006

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Pneumolysin, the pore-forming toxin produced by Streptococcus pneumoniae, may have an application as an immunogenic carrier protein in future pneumococcal conjugate vaccines. Most of the 90 S. pneumoniae serotypes identified produce pneumolysin; therefore, this protein may confer non-serotype-specific protection against pneumococcal infections such as pneumonia, meningitis, and otitis media. However, as pneumolysin is highly toxic, a nontoxic form of pneumolysin would be a more desirable starting point in terms of vaccine production. Previous pneumolysin mutants have reduced activity but retain residual toxicity. We have found a single amino acid deletion that blocks pore formation, resulting in a form of pneumolysin that is unable to form large oligomeric ring structures. This mutant is nontoxic at concentrations greater than 1,000 times that of the native toxin. We have demonstrated that this mutant is as immunogenic as native pneumolysin without the associated effects such as production of the inflammatory mediators interleukin-6 and cytokine-induced neutrophil chemoattractant KC, damage to lung integrity, and hypothermia in mice. Vaccination with this mutant protects mice from challenge with S. pneumoniae. Incorporation of this mutant pneumolysin into current pneumococcal vaccines may increase their efficacy.

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Multivalent pneumococcal capsular polysaccharide conjugate vaccines employing genetically detoxified pneumolysin as a carrier protein

Cited by 45 publications

References 29 publications

Group B Streptococcal Type II and III Conjugate Vaccines: Physicochemical Properties That Influence Immunogenicity

Group B Streptococcal Type II and III Conjugate Vaccines: Physicochemical Properties That Influence Immunogenicity

Identification of Invasive Serotype 1 Pneumococcal Isolates That Express Nonhemolytic Pneumolysin

Construction and Immunological Characterization of a Novel Nontoxic Protective Pneumolysin Mutant for Use in Future Pneumococcal Vaccines

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