Immunoglobulins to group A streptococcal surface molecules decrease adherence to and invasion of human pharyngeal...

Area of Science:

• Microbiology
• Immunology
• Infectious Diseases

Background:

• Group A Streptococcus (Streptococcus pyogenes) M protein is a key virulence factor in initial infection stages.
• Acute pharyngitis, a common infection, is caused by Streptococcus pyogenes.
• Understanding antibody roles in preventing streptococcal adherence and internalization to pharyngeal cells is crucial.

Purpose of the Study:

• To investigate the inhibitory effects of secretory immunoglobulin A (sIgA) and immunoglobulin G (IgG) on Streptococcus pyogenes adherence and internalization to human pharyngeal cells.
• To determine the specific roles of whole sIgA, M6 protein-specific sIgA, and M6 protein-specific serum IgG in these processes.

Main Methods:

• Utilized Streptococcus pyogenes strains: D471 (M protein-positive) and JRS75 (M protein-negative).
• Tested purified whole sIgA, M6 protein-specific sIgA, and M6 protein-specific IgG for their effects on streptococcal adherence and internalization to cultured human pharyngeal cells.
• Employed sIgA preabsorbed with M protein to assess specificity.

Main Results:

• Purified whole sIgA and M6 protein-specific sIgA significantly reduced streptococcal adherence to pharyngeal cells.
• sIgA preabsorbed with M protein also decreased bacterial adherence, indicating M protein's role in this interaction.
• M6 protein-specific IgG antibodies did not affect bacterial attachment but significantly reduced internalization.

Conclusions:

• Secretory IgA plays a critical role in preventing Streptococcus pyogenes infection at mucosal surfaces by inhibiting bacterial adherence.
• M protein-specific IgG antibodies are important for blocking bacterial invasion by targeting specific epitopes involved in internalization.