TABLE 2.

Immunogenicity evaluation in mice for S. Typhi Vi-DT conjugatesa

ConjugateGM of IgG (95% CI) 2 wk after indicated injections
Anti-Vi IgGbAnti-DT IgGc
1st2nd1st2nd
C18.95 (4.67-17.20)18.74 (13.28-26.42)0.02 (0.02-0.02)0.20 (0.07-0.62)
C26.45 (3.95-10.53)16.85 (10.09-28.14)0.02 (0.02-0.03)1.89 (0.73-4.95)
C39.34 (5.53-15.79)17.39 (13.62-22.20)0.02 (0.02-0.02)0.04 (0.02-0.12)
C411.09 (7.06-17.41)17.38 (9.57-31.55)0.03 (0.02-0.07)0.73 (0.28-1.87)
C510.24 (6.73-15.56)18.05 (12.14-26.82)0.02 (0.02-0.03)0.63 (0.14-2.81)
Vi0.39 (0.24-0.64)0.40 (0.15-1.07)NDND
DTNDdND0.02 (0.02-0.02)0.44 (0.21-0.95)
Saline0.02 (0.02-0.02)ND0.02 (0.02-0.02)ND
  • a Female mice (6 weeks old; 10/group) were injected s.c. twice, 4 weeks apart, with 2.5 μg of Vi as a conjugate or Vi alone per injection. Serum samples were taken 2 weeks after each injection. IgG anti-Vi is expressed as EU with respect to reference Vi and DT sera.

  • b All conjugates versus the Vi group (for all injections), P < 0.001; within each conjugate group, 1st versus 2nd injection, C1, C2, C3, and C5, P < 0.05; C4, P = 0.19. There was no statistical difference among conjugates after the 1st and 2nd injections (P > 0.083 and P > 0.69, respectively).

  • c Conjugates induced anti-DT responses in mice similar to those with DT. Dosages of DT varied in different groups, so no statistical analysis was performed.

  • d ND, not done.