Specific IgG and IgA Antibody Reactivities in Sera of Children by Enzyme-Linked Immunoassay and Comparison With Giardia duodenalis Diagnosis in Feces

Abstract

Background: Giardia duodenalis is conventionally diagnosed in fecal samples using parasitological methods. However, sensitivity is poor when only a single sample is analyzed, due to intermittent excretion of cysts in feces. Alternatively, the serum antibodies to G. duodenalis can be used for parasite diagnosis and epidemiological studies to determine previous exposure. We compared the rate of G. duodenalis infection between serum anti-Giardia IgG and IgA antibodies and fecal examination in Brazilian children. Methods: Fecal and serum samples were tested from 287 children at a clinical laboratory and from 187 children at daycare centers. Fecal samples were processed using conventional parasitological methods and coproantigen detection for Giardia diagnosis. Serum samples were tested using an in-house ELISA for detection of anti-Giardia IgG and IgA. Results: G. duodenalis was found in 8.2% (N = 39) of the 474 children analyzed. The sensitivity and specificity of ELISA were 80.0% and 90.0% for IgG and 80.0% and 83.3% for IgA, respectively. The total positivity rate of anti-Giardia IgG and IgA in the sera was 13.9% (N = 66) and 23.6% (N = 112). The agreement between the positivity of specific antibodies and the detection of G. duodenalis in feces was moderate for ELISA-IgG, kappa index (95% CI) = 0.543 (0.422-0.664), and mild for ELISA-IgA, kappa index (95% CI) = 0.283 (0.162-0.404). Among the children infected with other enteroparasites, 11.6% (N = 10) and 24.4% (N = 21) showed reactivity to anti-Giardia IgG and to IgA, respectively. This cross-reactivity was more frequent in samples from children infected with Endolimax nana and Entamoeba coli. Conclusions: The higher frequency of specific antibody reactivity compared with G. duodenalis diagnosis in feces could reflect continuous exposure of children to G. duodenalis infection, resulting in long-lasting immunological memory and/or cross-reactivity with other intestinal amoebas.

Role of anti-Giardia recombinant cyst wall protein IgG polyclonal antibodies in diagnosis and protection

“…ELISA assesses soluble antigens and offers greater sensitivity compared to light microscopy (Ali et al 1999 ). ELISA has also been regarded as a cost-effective diagnostic approach that can identify small amounts of parasite coproantigens, even in moderate infections, and diagnose the disease effectively even when the live parasite is not present in the stool sample (Bride et al 1995 ; Yang and Harrison, 1996 ; Boone et al 1999 ; Duque-Beltrán et al 2002 ; Barazesh et al 2010 , and Barazesh et al 2011 ; Silva et al 2016 ; Pacheco et al 2020 ). Nash and Keister ( 1985 ) categorized nineteen G. duodenalis isolates into three groups based on the reactivity of antibodies produced against excretory-secretory components generated in vitro in the growth media by each group.…”

“…The diagnosis through immunological techniques is accomplished either by detecting antibodies (IgG and/or IgM) or antigens by enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), and western blot (Gutiérrez-Cisneros et al 2011 ; Júlio et al 2012 ). However, one of the drawbacks of antibodies screening test is the probability of a false-positive result due to: 1- IgG remains in the serum for approximately eighteen months after infection, 2- levels of IgM decline after two or three weeks after infection because IgM is regarded as a useful detector in acute infection (Heyworth, 2014 ) and 3- Cross-reactivity against other protozoan antigens (Pacheco et al 2020 ). Researchers reported that 11.6% and 24.4% of the patients (infected with Endolimax nana or Escherichia coli, respectively) showed high reactivity for anti- G. duodenalis IgA and IgG; they explained this cross-reactivity with the similarity of protozoans’ antigens and immunological memory due to the previous giardiasis.…”

Foodborne Parasites Dominate Current Parasitic Infections in Hunan Province, China

“…The examination of etiology is mainly used to observe whether there are worms, eggs, or trophozoite of protozoa in specimens through a microscope, but the detection rate of this method is very low ( Lin et al., 2011 ). In recent decades, the immunological technology in the medical industry has been more and more mature, with a higher sensitivity and positive rate than that of etiological examination, and the detection of parasitosis is also more and more inseparable from immunological examination ( Pacheco et al., 2020 ). That is why sometimes the positive result by immunological examination is negative by etiological examination.…”

Utility of an Automatic Vision-Based Examination System (AVE-562) for the Detection of Clonorchis sinensis Eggs in Stool

“…Serological analysis using enzyme-linked immunosorbent assay (ELISA) is useful for diagnosing clonorchiasis, but it is insensitive for low-burden infection. Although molecular diagnostic techniques are sensitive, they are associated with issues concerning contamination and high cost, which hindered their application in large-scale field surveys [ 6 - 9 ]. Stool examination for C. sinensis eggs is the gold standard for clonorchiasis diagnosis [ 10 , 11 ], but it is labor-intensive, requires a high level of technical expertise, and can be insensitive for low-burden infection [ 12 ].…”