Enzyme-linked immunosorbent assay for detection of human antibodies to Salmonella typhi Vi antigen

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Abstract
An enzyme-linked immunosorbent assay (ELISA) was developed to detect antibodies to S. typhi Vi antigen in human serum; the results were compared with those from a previously described hemagglutination assay (HA). The ELISA detected Vi antibodies at a titer of .gtoreq. 20 in 40 (52%) of 77 sera from typhoid fever patients; the HA gave titers of .gtoreq. 20 in 35 (47%). Determination of titers of serum specimens from 170 persons without typhoid fever revealed Vi antibody titers of .gtoreq. 20 in 4 (2.3%) by the ELISA and 3 (1.7%) by the HA. Unlike the sensitized erythrocytes used in the HA, the ELISA reagents have a shelf life of .gtoreq. 1 yr. The ELISA may be preferred by some laboratories, especially those already performing other ELISA tests.