Uses and limitations in the demonstration of specific circulating immune complexes in patients with amoebiasis

Abstract

Summary.A micro-enzyme linked immuaosorbent assay (micro-ELISA) has been evaluated as a diagnostic test to detect amoebic antigen in polyethylene glycol (PEG) precipitated circulating immune complexes (CIC) in sera from patients with amoebiasis. The immune complexes were captured on rabbit anti-amoebic IgGcoated wells of microtitration plates and the complexed antigen was detected by enzyme linked antihuman immunoglobulins. A titre of > 160 for the immune complexes was considered to be of clinical significance. The immunoassay detected amoebic, antigen-specific CIC in 35 (94.5%) of 37 patients with confirmed amoebic liver abscess. Twenty (55.5%) of 36 clinically suspected cases of amoebic liver abscess had amoebic antigen-specific CIC and responded favourably to anti-amoebic chemotherapy. Only two (20%) of 10 cases of non-dysenteric symptomatic intestinal amoebic infection had amoebic antigen-specific CIC. One (10%) of 10 patients with non-amoebic intestinal disorders also had amoebic antigen in CIC. However, none of 15 cases of non-amoebic hepatic disorders that included hydatid disease, metastatic adenocarcinoma, hepatocellular carcinoma, cholecystitis and choledocal cyst, 13 cases of rheumatoid arthritis and 25 apparently healthy subjects had amoebic antigen in CIC. The levels of the amoebic antigen-specific CIC did not correlate (p>O-O5) with either the number of abscess(es) or lobe(s) of the liver involved. However, the levels of antigen-specific CIC were higher (p < 0.01) in patients with a liver size of more than 5 cm below the right costal margin. Antigen-specific CIC levels tended to decline or disappear during 3-6 months following completion of therapy. In spite of the limitations for diagnosing symptomatic intestinal amoebic disease, the demonstration of specific CIC is recommended as an immuno-diagnostic procedure for patients with suspected amoebic liver abscess.

Significance of detection of immune-complexed 8 kDa hydatid-specific antigen for immunodiagnosis of hydatidosis

“…The CICs were prepared by the method as described elsewhere [17]. The optimal dilutions of IgG antibodies and PEG-precipitated CICs were determined by checker-board titration in a micro-ELISA.…”

The plasma membrane of Entamoeba histolytica: structure and dynamics*

“…There seems to be some degree of protection that develops after invasive amebiasis, since recurrence of amebic liver abscess is very rare. Antibody titers in these patients remain high for months after recovery of the amebic episode, but circulating immune complexes tend to decline or disappear 3-6 months following completion of therapy [32,33,43,100].…”

“…To st,ldy the role of the immune response in the rejection of amebic infection, it is necessary to identify the antigens that elicit a humeral response and determine if they are important in protection. Several authors have analysed the main antigens recognized by sera from patients with invasive amebiasis [3,5,22,28,34,45,49,61,72,80,85,100]. It has been reported that the number of antigens is larger and the level of immunogenicity higher in cytoplasmic vesicles than in the plasma membrane [95].…”