Antibody response to Shigella sonnei infection determined by an enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) was developed for determination of the IgA, IgM and IgG antibody responses against a lipopolysaccharide antigen representing Shigella sonnei phase I bacteria. Two or more sera from 33 patients infected with Shigella sonnei were collected during a 12 month period after onset of the disease. Convalescent sera from 56 patients with other enteric infections (salmonellosis, yersiniosis, campylobacteriosis) and sera drawn from 40 healthy blood donors served as controls. Twenty-eight of the 33 patients (85%) had at least one serum specimen where two or three of the immunoglobulin titres were classified as positive (greater than + 2SD above mean titres seen in healthy blood donors), whereas only ten of 56 patients (18%) with other enteric infections had similarly elevated titres (p less than 0.001). The Shigella sonnei ELISA using purified lipopolysaccharide as antigen is considered more sensitive and specific than the formerly used agglutination tests.