Cell-free vaccines induced humoral immune responses; anti-38C13 Ab levels were comparable to that of the Id-KLH standard. The concentration of anti-38C13 IgG antibodies in mouse serum 10 days after the third vaccination was determined by ELISA. Data plotted is combined from 3 independent experiments (n = 29 mice for mGM-Im9-VL-VH, 20 mice for VL-VH-IL1β9 and DsbC, 19 mice for Id-KLH and scFv (VH-VL), and 10 mice for A20 VH-VL and IL1β9aa-VH-VL). Variations in group sizes are due to groups being tested in 1, 2, or 3 experiments and to the loss of serum samples in a few cases. Data shown are means with SEM; *P < .05 compared with scFv (VH-VL); **P < .05 compared with mGM-Im9-VL-VH and VH-VL-IL1β9aa using a 2-tailed Student t test. Exact P values are stated in the text.
