Polysaccharide immunogenicity

Each dose of pneumococcal vaccine contains 25 micrograms of polysaccharide immunogens. How many doses of the vaccine can be obtained with two grams of the polysaccharide immunogens ... 

Release profiles of these immunogens ean be improved through their formulation with adjuvants (Chapters 14, 15), and the immunogenieity of certain purified baeterial eomponents such as polysaccharides ean be improved by their conjugation to a carrier. 

Polysaccharide vaccines are poorly immunogenic in children younger than 2 years of age. 

The 23-valent pneumococcal polysaccharide vaccine contains 23 serotypes that are responsible for causing more than 80% of invasive S. pneumoniae infections in adults. The vaccine includes those serotypes that are associated with drug resistance. Use of the vaccine will not prevent the development of antibiotic-resistant S. pneumoniae, but is likely to prevent infection from drug-resistant strains. The 23-valent pneumococcal polysaccharide vaccine has demonstrated good immunogenicity in adults, but an individual will not develop immunity to all 23 serotypes following vaccination.10... 

Bacterial polysaccharides were activated with CDI and then coupled via spacers to immunogenic membrane proteins.[133],[134]... 

Lett E, et al. Immunogenicity of polysaccharides conjugated to peptides containing T- and B-cell epitopes. Infect Immun 1994 62 785. 

In preparation for use as a surrogate vaccine, these peptides were synthesized as conjugates to tetanus toxoid, and in this form also competed with the 0-antigen polysaccharide for binding [104]. Whether these peptides will function as effective immunogenic mimics will likely depend on their propensity to adopt the bioactive conformation in solution. A certain amount... 

Clearly, further studies will be necessary to sort out the multiple factors involved in the in vivo immune response to C. neoformans carbohydrate-mimetic peptides. Several conclusions may be drawn from the results to date. Peptides that mimic the cryptococcal capsular polysaccharide show specificity, in that each peptide binds with differing affinity to closely related mAbs [140,149]. The pattern of binding to protective and nonprotective mAbs differs between the mimetic peptides and the polysaccharide [140]. Protective efficacy is related to the location of carbohydrate epitopes recognized by these mAbs, within the polysaccharide capsule, but hkely also depends on interactions between mAbs and cellular responses [149]. Peptides have been shown to be functional, immunogenic mimics, but their protective efficacy depends on multiple factors, including the type of Abs elicited and interactions with the cellular immune system. Protective efficacy does not correlate with binding affinity to representative mAbs, but rather depends on the nature of these interactions. 

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