Abstract:
The study was designed to perform Dot-blot ELISA for detection of Entamoeba
histolytica antigen from stools and serum antibody of amoebic patients. The crude
antigen was extracted from axenic culture of Entamoeba histolytica, HK-9 strain, to
detect serum IgG antibodies against Entamoeba histolytica and polyclonal antibody
was used to detect Entamoeba histolytica antigen in the stools from amoebic
patients, by dot-blot ELISA. The assays were applied to detect both antibody and
antigen in serum and stool samples of 220 individuals, respectively. The samples
were divided into three groups: group 1 comprised 120 confirmed individuals
whose stools were positive only for Entamoeba histolytica cysts and/or trophozoite;
group 2 was comprised of 50 individuals whose stools were negative for
Entamoeba histolytica but contained other intestinal parasites such as Entamoeba
coli, Entamoeba hartmanni, Endolimax nana, Giardia lamblia, Strongyloides
stercoralis and Ascaris lumbricoides; and group 3 consisted of 50 healthy
individuals whose stools were free from other intestinal parasites.
The results of Dot-blot ELISA assay were detected based on colors of the
reaction which were recorded as follows: three plus positive (+++), two plus
positive (++), one plus positive (+) and negative (-). In group 1, serum antibody of
amoebic patients found positive as three plus positive (+++), two plus positive
(++) and one plus positive (+) were 10, 22, and 15 of 120 cases, respectively.
Among 50 cases in group 2 (other intestinal parasitic infection), there were two
plus positive (++) in 4 out of 50. The two plus positive (++) and the one plus
positive (+) were detected in 1 and 4 out of 50 for group 3. For the Dot-blot ELISA
assays using polyclonal antibody to detect Entamoeba histolytica antigen in the
stool specimens, the three plus positive (+++), the two plus positive (++) and the
one plus positive (+) were found in 7, 43 and 24 out of 120 cases in group 1. The
one plus positive (+) was found in 2 and 6 out of 50 cases in group 2. The two plus
positive (++) and the one plus positive (+) were detected in 2 and 1 out of 50 cases
in group 3. This Dot-blot ELISA showed that the sensitivity in serum antibody of
amoebic patients was 38.29%, which was higher than in using polyclonal antibody
to detect Entamoeba histolytica antigen in the stools (22.97%). The specificity in
serum antibody of amoebic patients was 61.70%, which was lower than in using
polyclonal antibody to detect Entamoeba histolytica antigen in the stools (77.03%).