Typhax is an investigational typhoid fever vaccine candidate that is comprised of Vi polysaccharide from Salmonella enterica serovar typhi (S. Typhi) non-covalently entrapped in a glutaraldehyde catalyzed, cross-linked α-poly-L-lysine and CRM protein matrix. A previous Phase 1 trial of an aluminum phosphate adjuvanted Typhax formulation showed it induced Vi IgG after a single dose but that subsequent doses failed to further boost Vi IgG levels.
View Article and Find Full Text PDFPneumolysin is a highly conserved, cholesterol-dependent cytolysin that is an important Streptococcus pneumoniae virulence factor and an attractive target for vaccine development. To attenuate pneumolysin toxicity, a genetic toxoid was constructed with two amino acid changes, G293S and L460D, termed PLY-D, that reduced cytolytic activity > 125,000-fold. In mice, PLY-D elicited high anti-PLY IgG antibody titers that neutralized the cytolytic activity of the wild-type toxin in vitro.
View Article and Find Full Text PDFBackground: Typhoid fever remains a significant cause of morbidity and mortality in developing countries especially in children ≤5 years old. Although the widely available unconjugated Vi polysaccharide vaccines are efficacious, they confer limited, short-term protection and are not approved for young children or infants. Vi conjugate vaccines, however, are now licensed in several typhoid endemic countries for use in children >6 months of age.
View Article and Find Full Text PDFTyphax is an investigational typhoid fever vaccine candidate that was GMP manufactured applying Protein Capsular Matrix Vaccine (PCMV) technology. It consists of Vi polysaccharide antigen, derived from . Typhi, non-covalently entrapped in a glutaraldehyde catalyzed cross-linked α-poly-L-lysine and CRM197 protein matrix.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
March 2015
Capsular polysaccharides are the primary antigenic components involved in protective immunity against encapsulated bacterial pathogens. Although immunization of adolescents and adults with polysaccharide antigens has reduced pathogen disease burden, pure polysaccharide vaccines have proved ineffective at conferring protective immunity to infants and the elderly, age cohorts that are deficient in their adaptive immune responses to such antigens. However, T-cell-independent polysaccharide antigens can be converted into more potent immunogens by chemically coupling to a "carrier protein" antigen.
View Article and Find Full Text PDFBackground: Altered levels of inositol phosphate in the central nervous system (CNS) are hypothesized to produce distorted brain signaling and lead to numerous neurologic maladies. Little is known of mechanisms controlling the complex metabolic flux of inositol phosphate. Less is known of controls that regulate inositol-phosphate biosynthesis in the mammalian brain.
View Article and Find Full Text PDFThe chain length of Streptococcus pneumoniae type 3 capsular polysaccharide (cellubiuronic acid) is tightly regulated by the cellubiuronic acid synthase through an assembly process involving a catalytic motif that is potentially conserved over a wide range of related processive beta-glucan synthases. Cellubiuronic acid is initiated on a lipid and is composed of alternating beta-1,3-Glc and beta-1,4-glucuronic acid (GlcUA) linkages. The entire assembly process is carried out by a polypeptide synthase thought to contain a single active site, suggesting that the donor specificity is controlled by the terminal nonreducing sugar in the acceptor subsite.
View Article and Find Full Text PDFThe processive reaction mechanisms of beta-glycosyl-polymerases are poorly understood. The cellubiuronan synthase of Streptococcus pneumoniae catalyzes the synthesis of the type 3 capsular polysaccharide through the alternate additions of beta-1,3-Glc and beta-1,4-GlcUA. The processive multistep reaction involves the sequential binding of two nucleotide sugar donors in coordination with the extension of a polysaccharide chain associated with the carbohydrate acceptor recognition site.
View Article and Find Full Text PDFLipoteichoic acid (LTA) is an essential bacterial membrane polysaccharide (cell wall component) that is attached to the membrane via a lipid anchor. According to the currently accepted structure of pneumococcal LTA, the polysaccharide is comprised of several repeating units, each of which starts with glucose and ends with ribitol, with the lipid anchor predicted to be Glc(beta1-->3)AATGal(beta1-->3)Glc(alpha1-->3)-acyl(2)Gro, where AATGal is 2-acetamido-4-amino-2,4,6-trideoxy-D-galactose. However, this lipid anchor has not been detected in pneumococcal membranes.
View Article and Find Full Text PDFAppl Environ Microbiol
November 2007
Putative N-acetylmuramyl-l-alanine amidase genes from LambdaSa1 and LambdaSa2 prophages of Streptococcus agalactiae were cloned and expressed in Escherichia coli. The purified enzymes lysed the cell walls of Streptococcus agalactiae, Streptococcus pneumoniae, and Staphylococcus aureus. The peptidoglycan digestion products in the cell wall lysates were not consistent with amidase activity.
View Article and Find Full Text PDFRegulation of chain length is essential to the proper functioning of prokaryotic and eukaryotic polysaccharides. Modulation of polymer size by substrate concentration is an attractive but unexplored control mechanism that has been suggested for many polysaccharides. The Streptococcus pneumoniae capsular polysaccharide is essential for virulence, and regulation of its size is critical for survival in different host environments.
View Article and Find Full Text PDFThe type 3 synthase catalyzes the formation of the Streptococcus pneumoniae type 3 capsular polysaccharide [-3)-beta-D-GlcUA-(1, 4)-beta-D-Glc-(1-]n. Synthesis is comprised of two distinct catalytic phases separated by a transition step whereby an oligosaccharylphosphatidylglycerol primer becomes tightly bound to the carbohydrate acceptor recognition site of the synthase. Using the recombinant synthase in Escherichia coli membranes, we determined that a critical oligosaccharide length of approximately 8 monosaccharides was required for recognition of the growing chain by the synthase.
View Article and Find Full Text PDFThe majority of the 90 capsule types made by the gram-positive pathogen Streptococcus pneumoniae are assembled by a block-type mechanism similar to that utilized by the Wzy-dependent O antigens and capsules of gram-negative bacteria. In this mechanism, initiation of repeat unit formation occurs by the transfer of a sugar to a lipid acceptor. In S.
View Article and Find Full Text PDFThe type 3 synthase from Streptococcus pneumoniae is a processive beta-glycosyltransferase that assembles the type 3 polysaccharide [3)-beta-D-GlcUA-(1-->4)-beta-D-Glc-(1-->] by a multicatalytic process. Polymer synthesis occurs via alternate additions of Glc and GlcUA onto the nonreducing end of the growing polysaccharide chain. In the presence of a single nucleotide sugar substrate, the type 3 synthase ejects its nascent polymer and also adds a single sugar onto a lipid acceptor.
View Article and Find Full Text PDFCpsA, CpsB, CpsC, and CpsD are part of a tyrosine phosphorylation regulatory system involved in modulation of capsule synthesis in Streptococcus pneumoniae and many other gram-positive and gram-negative bacteria. Using an immunoblotting technique, we observed distinct laddering patterns of S. pneumoniae capsular polysaccharides of various serotypes and found that transfer of the polymer from the membrane to the cell wall was independent of size.
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