Glycan-specific IgM is critical for human immunity to Staphylococcus aureus

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Staphylococcus aureus is a significant human pathogen, but protective immune factors are not fully understood.
• Previous attempts using high IgG antibody titers for protection against S. aureus have been unsuccessful in humans.

Purpose of the Study:

• To investigate antibody responses against the conserved S. aureus surface glycan, wall teichoic acid (WTA).
• To evaluate the functional capacity of WTA-specific IgM and IgG antibodies in combating S. aureus infections.

Main Methods:

• Detection of WTA-specific IgM and IgG antibodies in healthy individuals.
• Assessment of opsonophagocytic killing activity of WTA-specific IgM and IgG.
• Passive immunization studies in a mouse model of S. aureus bacteremia.
• Comparison of WTA-specific antibody levels in patients with S. aureus bacteremia versus healthy controls.

Main Results:

• WTA-specific IgM and IgG antibodies are present in healthy individuals.
• WTA-specific IgM demonstrates superior opsonophagocytic killing of S. aureus compared to IgG.
• Passive immunization with WTA-specific IgM protects against disseminated S. aureus bacteremia.
• Patients with S. aureus bacteremia exhibit lower WTA-specific IgM levels and similar IgG levels compared to controls.
• Low WTA-specific IgM levels correlate with increased disease mortality and impaired bacterial opsonization.

Conclusions:

• WTA-specific IgM is a critical protective antibody against S. aureus infection, outperforming IgG.
• Reduced WTA-specific IgM levels in patients indicate a poorer prognosis and are linked to mortality.
• These findings support the use of WTA-specific IgM for risk stratification and the development of novel antibody-based therapies and vaccines against S. aureus.