Humoral and mucosal IgA antibody response to a recombinant 52-kDa cysteine-rich portion of the Entamoeba histolytica galactose-inhibitable lectin correlates with detection of native 170-kDa lectin antigen in serum of patients with amebic colitis

Humoral and mucosal IgA responses to a recombinant cysteine-rich portion (designated LC3) of the Entamoeba histolytica galactose-inhibitable lectin's 170-kDa subunit were determined in patients with amebic colitis. All patients had 170-kDa amebic antigen in serum, compared with 1 of 50 cyst passers and 1 of 31 controls (P <.01). Seven days after treatment, serum and fecal 170-kDa antigen became undetectable in 12 of the 13 patients (P <.001). Serum anti-LC3 IgA was found in 83.8% of colitis patients, compared with 2% of controls and 12% of asymptomatic cyst passers (P <.001). Salivary and fecal anti-LC3 IgA levels were higher in patients than in cyst passers (P <.001). In conclusion, in amebic colitis, development of humoral and mucosal IgA responses to the recombinant LC3-encoded protein correlates with detection of amebic 170-kDa antigen in serum and feces.