IMMUNOAFFINITY PURIFICATION, STABILIZATION AND COMPARATIVE CHARACTERIZATION OF LISTERIOLYSIN-O FROM LISTERIA-MONOCYTOGENES SEROTYPE-1/2A AND SEROTYPE-4B

We developed a simple and highly effective procedure for stabilizing the haemolytic activity of listeriolysin O (LLO) from Listeria monocytogenes after immunoaffinity purification. The haemolytic activity of LLO was stabilized by eluting it directly into tubes containing an alkaline buffer (5 mM lysine, 140 mM KCl, 50 % ethylene glycol, pH 11.5). The purified LLO retained 100 % of its haemolytic activity after 6 weeks of storage at - 20-degrees-C. LLO purified from a strain of L. monocytogenes serotype 1/2a (ATCC 43249) and LLO purified from a strain of L. monocytogenes serotype 4b (F 2365) isolated from a Mexican-style cheese, showed no significant differences in pH and temperature stability. When incubated in buffers at pH values from 4 to 12 at 4-degrees-C and 25-degrees-C, LLO from serotypes 1/2a and 4b retained maximal haemolytic activity at pH 8 after 4 h of incubation. LLO from both serotypes lost their haemolytic activity after incubation at 50-degrees-C for 25 min.