A protein A based Staphylococcus aureus vaccine with improved safety

Area of Science:

• Immunology
• Microbiology
• Vaccine Development

Background:

• Staphylococcus aureus evades host immunity through factors like Staphylococcal protein A (SpA).
• SpA binds to immunoglobulin (Ig) domains, interfering with immune responses and causing B cell expansion and anaphylaxis.
• A previous SpA variant (SpA_KKAA) showed promise in animal models but retained some problematic activities.

Purpose of the Study:

• To design and test novel SpA variants with reduced V H3 binding and anaphylactic activities.
• To identify SpA variants that elicit neutralizing antibodies against S. aureus.
• To evaluate the potential of these detoxified SpA variants as vaccine candidates.

Main Methods:

• Rational design and synthesis of 67 new SpA variants with modified Immunoglobulin Binding Domains (IgBDs).
• Assays to assess V H3 binding, crosslinking activity, and anaphylaxis induction.
• Testing of lead candidates in animal models for antibody induction, protection against S. aureus colonization, and bloodstream infection.

Main Results:

• Two detoxified SpA candidates with three amino acid substitutions were identified, showing reduced V H3 binding and anaphylactic activity.
• These candidates successfully elicited SpA-neutralizing antibodies in animal models.
• The detoxified SpA variants provided protection against S. aureus colonization and bloodstream infection.

Conclusions:

• Detoxified SpA variants, with reduced V H3-idiotypic immunoglobulin crosslinking, can elicit protective immune responses.
• These variants represent promising candidates for developing safe and effective clinical-grade vaccines against S. aureus infections.