[The immunogenic properties of the endotoxin protein: serum antibodies in animals and man]

Abstract

Endotoxin protein or lipid A-associated protein (LAP) from Shigella sonnei was isolated and characterized earlier (Zh. mikrobiol. epidemiol. immunobiol., 1991, No. 4, pp. 47-50). In this investigation serum antibodies against LAP were studied in ELISA Anti-LAP antibodies were detected in high titers in the sera of nonimmunized mice, guinea pigs, rabbits, monkeys and healthy adults. We suppose that normal anti-LAP antibodies resulted from interaction between the immune system and environmental endotoxin. Parenteral injections of LAP to different animals induced intensive antibody response with a 100- to 1000-fold increase in the serum anti-LAP antibody level and a significant rise in the serum O-antibody level. The latter is seemingly due to the contamination of LAP with minute amounts of O-antigen (0.12% or less) and to the amplification of its immunogenicity by LAP. Both antigenic and amplifying activity of LAP was destroyed by proteinase K. The biological function of LAP and its possible use as a component of bacterial vaccines are briefly discussed.