Understanding glycoconjugate vaccines

T cells can recognize polysaccharides when coupled to a peptide presented by Major Histocompatibility Complex (MHC) molecules of the immune system, reports a paper published online this week in Nature Medicine. This finding changes previous assumptions that T cells recognize only peptides presented by MHC molecules, and could have implications for current glycoconjugate vaccine design. Glycoconjugate vaccines have been successfully developed to protect against important bacterial pathogens, such as Streptococcus pneumoniae, which can cause pneumonia. These vaccines conjugate polysaccharides from the bacterial surface to a carrier protein. The protein portion is recognized by T cells, which provide help to B cells to enhance the antibody response to the polysaccharide. While investigating how to improve upon current glycoconjugate vaccine design, Dennis Kasper and colleagues discovered that T cells can recognize the polysaccharide portion of a glycoconjugate. The researchers used this finding to optimize the design of a glyconcjugate vaccine and show its efficacy in protecting newborn mice from lethal infection with B Streptococcus. Their results suggest that harnessing the ability of T cells to recognize carbohydrates — and not just peptides — may increase vaccine success.