Streptococcus pneumoniae PspC Subgroup Prevalence in Invasive Disease and Differences in Contribution to Complement...

Area of Science:

• Microbiology
• Immunology
• Infectious Diseases

Background:

• Pneumococcal capsular serotype influences complement resistance and disease potential.
• Pneumococcal surface protein C (PspC) binds complement factor H, aiding evasion of C3 opsonization.
• PspC is divided into two subgroups: choline-bound subgroup I and LPxTG-anchored subgroup II.

Purpose of the Study:

• To determine the prevalence of PspC subgroups in invasive pneumococcal disease (IPD) isolates.
• To investigate functional differences in complement evasion between PspC subgroups.
• To assess the impact of PspC variation on factor H binding and complement resistance.

Main Methods:

• Analysis of 349 sequenced *Streptococcus pneumoniae* strains from adult IPD patients.
• Construction of *pspC* deletion and switch mutants.
• Assessment of factor H binding and complement opsonization in relation to capsule thickness.

Main Results:

• Subgroup I *pspC* was significantly more prevalent in IPD isolates than subgroup II *pspC*.
• Subgroup I PspC bound more factor H and demonstrated more effective complement evasion than subgroup II PspC.
• Capsule presence enhanced factor H's ability to reduce complement opsonization.

Conclusions:

• PspC subgroup variation, independent of capsule serotype, influences pneumococcal factor H binding.
• PspC subgroups differentially affect the ability of *Streptococcus pneumoniae* to evade complement deposition.
• Subgroup I PspC confers a potential advantage in invasive pneumococcal disease due to enhanced complement evasion.