Rhamno-oligosaccharide-based glycoconjugates as promising vaccine candidates against Group A Streptococcus.

Area of Science:

• Microbiology
• Immunology
• Vaccine Development

Background:

• Group A Streptococcus (GAS) infections are a significant public health concern.
• Currently, no commercial vaccines are available for GAS infections.
• The group A carbohydrate (GAC) polyrhamnose backbone is a key target for anti-GAS vaccine development.

Purpose of the Study:

• To synthesize and evaluate novel bivalent glycoconjugate vaccine candidates targeting GAS.
• To assess the immunogenicity and efficacy of these candidates.
• To identify a promising GAS vaccine candidate for further development.

Main Methods:

• Synthesis of structurally defined oligosaccharide fragments (tri-, tetra-, penta-, and hexasaccharides).
• Conjugation of oligosaccharides with an inactive mutant of Group A streptococcal C5a peptidase (ScpA193).
• In vitro and in vivo immunological studies, including T-cell responses, binding to inactivated GAS (InGAS) cells, and assessment of toxicity and immunological memory.

Main Results:

• Semisynthetic glycoconjugates induced robust T-cell-dependent immune responses.
• Glycoconjugates effectively recognized and bound to InGAS cells in vitro.
• Glycoconjugate GA-II-2 demonstrated favorable results, eliciting long-term immunological memory and exhibiting low systemic toxicity.
• GA-II-2 showed good recognition against sera from anti-streptolysin O (ASO)-positive patients.

Conclusions:

• Glycoconjugate GA-II-2 is a highly promising candidate for a Group A Streptococcus vaccine.
• Further investigation and development of GA-II-2 are warranted.
• The study highlights the potential of GAC-based glycoconjugates for GAS vaccine development.