Detection of anti-lipopolysaccharide antibodies to Vibrio cholerae O1 and O139 using a novel microtiter limulus amebocyte lysate (LAL) assay

This paper describes a new assay for measuring antibodies to lipopolysaccha ride (LPS) of Vibrio cholerae using blocking of the limulus amebocyte lysat e (LAL) reaction in a microtiter place. When cholerae LPS was coated onto a microtiter plate, and then LAL reagent was added, a typical gel reaction o ccurred. However, when the LPS-coated plates were first incubated with seru m containing anti-cholera antibodies, the gel reaction did not occur. Block ing of the gel reaction was serotype specific, in that anti-O1 serum blocke d the O1 LAL reaction but not the O139 LAL reaction, and anti-O139 serum ne utralized the O139 reaction but not the Of reaction, Preliminary data sugge sted that the LAL titers were comparable to the vibriocidal titers but that titers using the LAL assay may have been slightly higher. This study showe d that antibodies to V. cholerae blocked the LAL reaction and suggested tha t the LAL blocking assay could be applicable for determining antibodies to other endotoxin-containing bacteria and microorganisms. (C) 2001 Elsevier S cience BN. All rights reserved.