Evaluation of the human immune response to outer membrane proteins of Vibrio cholerae

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Abstract
The immune response of 114 volunteers with diarrhea after experimental challenge with four strains of Vibrio cholerae O1 was characterized in a microtiter enzyme-linked immunosorbent assay antibody detection system by using a partially purified outer membrane preparation (OMP) from these strains as an antigen. Analysis of paired sera from 29 persons with noncholera diarrhea (negative control population), demonstrated that a rise in net optical density greater than 0.10 was significant. A total of 50% of the 79 cholera volunteers challenged with El Tor biotype and 54% of the 35 volunteers challenged with classical biotype had significant rises in immunoglobulin G anti-OMP. Paired sera that showed significant rises when tested against homologous OMP all manifested significant rises when also tested against a serotype-heterologous OMP. Immunoblotting techniques showed that the antigens to which antibodies were reacting were mainly protein in nature, not lipopolysaccharide. Furthermore, absorption with lipopolysaccharide decreased the optical density by a mean of only 12% (0 to 30%), corroborating that antibody was mainly directed against OMP and not lipopolysaccharide. This study indicates that there is a human immunoglobulin G response to OMP during clinical cholera infection and that this response is constant among bio- and serotypes.