Table 4.

Immune response to C. difficile toxoid vaccine

AssayNo. of subjects with response/total (geometric mean peak postvaccination assay result)
6.25 μg of toxoid25 μg of toxoid100 μg of toxoid
ToxoidToxoid-alumToxoidToxoid-alumToxoidToxoid-alum
Neutralizing antibody
 Anti-toxin A4/5 (80)a 5/5 (269)5/5 (134)5/5 (604)5/5 (339)5/5 (243)
 Anti-toxin B4/5 (368)4/5 (80)5/5 (368)5/5 (1,513)5/5 (485)5/5 (2,560)
Serum antibody ELISA
 Anti-toxin A
  IgA4/5 (238)b 5/5 (785)5/5 (1,622)5/5 (5,272)5/5 (6,369)5/5 (1,548)
  IgG5/5 (275)5/5 (1,217)5/5 (422)5/5 (2,345)5/5 (1,060)5/5 (1,260)
 Anti-toxin B
  IgA4/5 (13)3/5 (4)3/5 (13)5/5 (39)5/5 (29)5/5 (23)
  IgG4/5 (56)5/5 (64)3/5 (161)5/5 (488)5/5 (183)5/5 (342)
ASC ELISPOT
 Anti-toxin A
  IgA4/5 (12)c 3/5 (6.7)5/5 (23)5/5 (84)5/5 (179)5/5 (89)
  IgG4/5 (5.2)2/5 (2.8)5/5 (30)4/5 (79)4/5 (38)5/5 (63)
 Anti-toxin B
  IgA3/5 (6.6)5/5 (5.7)5/5 (60)5/5 (86)5/5 (134)5/5 (115)
  IgG5/5 (5.4)5/5 (1.8)5/5 (54)5/5 (170)5/5 (42)5/5 (123)
Fecal antibody ELISA
 Anti-toxin A IgA5/5 (2,219)d 4/5 (5,275)1/4 (907)0/5 (779)2/4 (329)2/3 (210)
 Anti-toxin B IgA2/5 (43)3/5 (60)2/4 (170)2/5 (127)3/4 (157)3/3 (95)
  • a Reciprocal titer.

  • b 103 EU/ml.

  • c Number of ASC per 106 PBMC.

  • d Nanograms per milliliter.