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Paper of the Month December 2011

A mechanism for glycoconjugate vaccine activation of the adaptive immune system and its implications for vaccine design

Nature Medicine, Vol. 17, No. 12, 1602-1609


Fikri Y Avci, Xiangming Li, Moriya Tsuji & Dennis L Kasper


Glycoconjugate vaccines have provided enormous health benefits globally, but they have been less successful in some populations at high risk for developing disease. To identify new approaches to enhancing glycoconjugate effectiveness, we investigated molecular and cellular mechanisms governing the immune response to a prototypical glycoconjugate vaccine. We found that in antigen-presenting cells a carbohydrate epitope is generated upon endolysosomal processing of group B streptococcal type III polysaccharide coupled to a carrier protein. In conjunction with a carrier protein–derived peptide, this carbohydrate epitope binds major histocompatibility class II (MHCII) and stimulates carbohydrate- specific CD4+ T cell clones to produce interleukins 2 and 4—cytokines essential for providing T cell help to antibody-producing B cells. An archetypical glycoconjugate vaccine that we constructed to maximize the presentation of carbohydrate-specific T cell epitopes is 50–100 times more potent and substantially more protective in a neonatal mouse model of group B Streptococcus infection than a vaccine constructed by methods currently used by the vaccine industry. Our discovery of how glycoconjugates are processed resulting in presentation of carbohydrate epitopes that stimulate CD4+ T cells has key implications for glycoconjugate vaccine design that could result in greatly enhanced vaccine efficacy.

Also see a related N&V article:

A sweet T cell response

Rino Rappuoli & Ennio De Gregorio

Nature Medicine, Vol. 17, No. 12, 1551-1552

Although protein-polysaccharide conjugate vaccines provide notable clinical benefits, it is still not fully understood how they work. A new mechanism of action for these vaccines has been identified in which T cells can recognize sugar epitopes in the context of the major histocompatibility complex (MHC) provided they are bound to a protein ‘anchor’, which allows binding of the sugar epitope to the MHC~