Clostridium difficile vaccine and serum immunoglobulin G antibody response to toxin A

Abstract

There is a strong association between serum antibody responses to toxin A and protection against Clostridium difficile diarrhea. A parenteral C. difficile toxoid vaccine induced very-high-level responses to anti-toxin A immunoglobulin G (IgG) in the sera of healthy volunteers. After vaccination, the concentrations of anti-toxin A IgG in the sera of all 30 recipients exceeded the concentrations that were associated with protection in previous clinical studies. Furthermore, the median concentration of serum anti-toxin A IgG in the test group was 50-fold higher than the previous threshold. These findings support the feasibility of using a vaccine to protect high-risk individuals against C. difficile-associated diarrhea and colitis.

FIG. 1.

Serum anti-toxin A IgG concentrations following natural infection with C. difficile (left panel) or following vaccination with C. difficile toxoid (right panel). Results, expressed as ELISA units, are shown for control patients not infected with C. difficile (Control; n = 187), symptom-free carriers of C. difficile (CD carrier; n = 19), patients with recurrent C. difficile-associated diarrhea (Recurrent CDAD; n = 9), patients with a single episode of C. difficile-associated diarrhea (Single CDAD; n = 7), and healthy volunteers at various time points during vaccination with C. difficile toxoid (n = 30). The median values are depicted as bold horizontal lines, the boxes indicate the 25th and 75th percentiles, and the I bars indicate the 10th and 90th percentiles.