Serum anti-rTsSP IgG titers determined by ELISA.

<p>Microtiter plates were coated with 2 μg rTsSP /ml and incubated overnight at 4°C. After being blocked with 5% nonfat milk, the plates were incubated at 37°C for 1 h with different dilutions of immune sera. Normal mouse sera (n = 20) diluted at 1:100 were assayed as negative controls. HRP-conjugated IgG was utilized as the second antibodies. The coloration was developed by incubation with the substrate OPD. The absorbance at 490 nm was assayed following adding 2 M H₂SO₄. The cut-off values (0.202) are expressed with a dotted line.