Abstract
Toxoplasma gondii is an important zoonotic protozoan that infects a wide variety of vertebrates as intermediate hosts. For this reason, the diagnosis of this disease is very important and requires continuous improvement. One possibility is to use recombinant antigens in serological tests. Apical membrane antigen 1 (AMA1), a protein located in specific secretory organelles (micronemes) of T. gondii, is very interesting in regard to its potential diagnostic utility. In the present study, we attempted to identify a fragment of the AMA1 protein with a high sensitivity and specificity for the serological diagnosis of human toxoplasmosis. The full-length AMA1 and two different fragments (AMA1N and AMA1C) were produced using an Escherichia coli expression system. After purification by metal affinity chromatography, recombinant proteins were tested for their utility as antigens in enzyme-linked immunosorbent assays (ELISAs) for the detection of IgG and IgM anti-T. gondii antibodies in human and mouse immune sera. Our data demonstrate that the full-length AMA1 recombinant antigen (corresponding to amino acid residues 67–569 of the native protein) has a better diagnostic potential than its N- or C-terminal fragments. This recombinant protein strongly interacts with specific anti-T. gondii IgG (99.4%) and IgM (80.0%) antibodies, and may be used for developing new tools for diagnostics of toxoplasmosis.
Highlights
Toxoplasma gondii is an obligate intracellular protozoan parasite and an important zoonotic pathogen that is capable of invading and replicating within a wide variety of nucleated host cells.This parasite infects up to 80% of the population in some regions of the world
The diagnosis of T. gondii invasion is mainly based on the use of native antigens in Currently, the diagnosis of T. gondii invasion is mainly based on the use of native antigens in enzyme-linked immunosorbent assays, which can detect IgG, IgM, and IgA antibody classes
Many research groups are working on new diagnostic tools, mainly involving recombinant proteins
Summary
Toxoplasma gondii is an obligate intracellular protozoan parasite and an important zoonotic pathogen that is capable of invading and replicating within a wide variety of nucleated host cells. This parasite infects up to 80% of the population in some regions of the world. Immunocompetent individuals are protected by both cell-mediated and humoral immune mechanisms, and, for this reason, T. gondii infection does not cause severe illness These individuals remain chronically infected for the rest of their lives, with the parasites encysted in their brain and muscles, and develop life-long protective immunity against reinfection.
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