Gonococcal infection in a nonhuman host is determined by human complement C1q

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Neisseria gonorrhoeae (GC) is a significant human pathogen.
• The complement system, including C1q, is crucial for innate immunity against bacterial infections.
• The role of human C1q in GC pathogenesis is not fully understood.

Purpose of the Study:

• To investigate the effect of human C1q on the in vivo virulence of Neisseria gonorrhoeae.
• To determine if human C1q can protect GC from host immune responses.
• To explore the potential of C1q as a factor in GC dissemination.

Main Methods:

• GC were preincubated with varying concentrations of human C1q.
• Preincubated GC were injected into newborn rats to assess bacteremia and organ infection.
• The effect of C1q from different species and complement components was evaluated.
• Inhibition studies using anti-C1q antibodies were performed.

Main Results:

• Human C1q dose-dependently protected GC from serum bactericidal effects.
• Rats injected with C1q-preincubated GC developed bacteremia and persistent infection in organs.
• Higher C1q concentrations correlated with increased GC virulence and host morbidity.
• C1q from other species, heat-inactivated C1q, and complement C3 did not confer similar protection.

Conclusions:

• Human C1q unexpectedly enhances Neisseria gonorrhoeae virulence and promotes disseminated infection in a nonhuman host.
• This finding challenges the traditional view of C1q as solely protective against infection.
• C1q's role in bacterial pathogenesis warrants further investigation, particularly in the context of host-pathogen interactions.