Figure 5.

Fluorimetric determination of culture fluid sialidase activity. Cell-free supernatant of C. chauvoei strain JF4135 was pre-incubated with different dilutions of anti-sialidase 40 kDa peptide serum or pre-immune serum from the same rabbit. Liberated 4-methylumbelliferone (MU) obtained upon cleavage of substrate MU-Neu5Ac with sialidase in culture fluids of 5 × 10⁷ C. chauvoei cells was recorded at 30 sec intervals. Black circles, no pre-incubation with antibodies; white triangles, pre-incubation with pre-immune serum (diluted 1:10); squares, pre-incubation with anti-sialidase serum (white, diluted 1:1000; gray, diluted 1:100; black, diluted 1:10). Plots are the mean of three kinetic measurements of sialidase activity.