Comparison of immunogenicity of the bivalent or tetravalent vaccine in hamster vaccinated.
Sera from immunized hamsters (Fig 3) were assayed for functional antibody titers to TcdA, TcdB and binary toxin in a cell based assay. The ED50 was calculated as the serum dose that reduced cytotoxicity by 50%. There was no significant difference in TcdA and TcdB neutralizing antibody titers at day 56 in (A) the VPI10463 challenge, (B) the BI17 challenge, and (C) the 8864 challenge. Data was analyzed by two tailed t-test. (D) Pooled serum samples from the BI17 challenged animals were used to measure neutralizing antibody responses to TcdA, TcdB and binary toxin at days 0, 7, 28, 42 and 56. (E) ELISA binding titers were measured in pooled sera from B17 challenged hamsters for TcdA and TcdB. (F) Strong neutralizing antibodies were also generated to binary toxin by the tetravalent and binary toxin vaccines in the VPI10463, BI17 and 8864 challenges at day 56. One way ANOVA and Tukey's multiple comparisons tests were used to compared binary toxin titers. (G) Pooled serum samples from the BI17 challenged animals were also tested for binary toxin binding antibodies. Similar kinetics were observed in the VPI10463 and 8864 studies for neutralizing and binding antibody titers. * = p<0.05, ** = p<0.01, *** = p<0.001, ns = no significant differences.