Figure 1.

Labile toxin B subunit (LTB) significantly enhanced the immunogenicity of enterovirus 71 VP1 subunit (EVP1) vaccine. Balb/c mice of 3–4 weeks (male) were divided into four groups (6 mice in each group) as LTB, EVP1, LTB+EVP1, and PBS (phosphate buffer saline). After anesthetizing with chloral hydrate, the mice were vaccinated intranasally three times on day 0, 7, and 14 with 10–20 µL of LTB (10 µg/mL each mouse), EVP1 (10 µg/mL each mouse), LTB + EVP1 (20 µg/mL each mouse), and PBS, respectively. Samples were individually collected from immunized mice on day 21. Endpoint titers were determined as the dilution of each sample from groups of EVP1, LTB+EVP1, and PBS which showed a 2.1-fold higher absorbance level of 450 nm as compared to that of the negative control samples. Average OD₄₅₀ values for the animals were calculated. The specific antibodies of EVP1 were significantly increased in LTB+EVP1 treatment (* p < 0.05).