LONGITUDINAL-STUDY OF THE ANTIBODY-RESPONSE TO RECOMBINANT ENTAMOEBA-HISTOLYTICA ANTIGENS IN PATIENTS WITH AMEBIC LIVER-ABSCESS

Serology is a critical component in the diagnosis of amebic liver absc ess. However, in areas endemic for amebiasis there is a high backgroun d level of seropositivity for amebiasis (owing to previous infection w ith Entamoeba histolytica), which may complicate the interpretation of a positive serologic test result. Recently, we reported that serologi c tests based on recombinant E. histolytica antigens might offer impro ved diagnosis of current invasive amebiasis because they apparently di fferentiated active infection from past exposure to the parasite. To c onfirm this finding, we have performed a longitudinal study on 20 pati ents with amebic liver abscess by examining their seroreactivity over time with recombinant versions of two major E. histolytica proteins, t he serine rich E. histolytica protein (SREHP), and the 170-kD subunit of the galactose-specific adhesin. We found that more than 50% of the patients examined had become seronegative by one or both recombinant t ests within 180 days of their diagnosis of amebic liver abscess. In th e case of the recombinant SREHP-based tests, 12 patients had become se ronegative 90 days after presentation. In contrast, all patients remai ned seropositive by a standard conventional test, an indirect hemagglu tination test, at more than six months after presentation. Our study s hows that patients lose seroreactivity with the recombinant SREHP or 1 70-kD antigen-based tests more rapidly than with a conventional serolo gic test; this may make them useful for the serologic diagnosis of ame biasis in endemic areas.