Recombinant AMA1 Virus-like Particle Antigen for Serodiagnosis of Toxoplasma gondii Infection

Abstract

Toxoplasmosis diagnosis predominantly relies on serology testing via enzyme-linked immunosorbent assay (ELISA), but these results are highly variable. Consequently, various antigens are being evaluated to improve the sensitivity and specificity of toxoplasmosis serological diagnosis. Here, we generated Toxoplasma gondii virus-like particles displaying AMA1 of T. gondii and evaluated their diagnostic potential. We found that AMA1 VLPs were highly sensitive and reacted with the sera acquired from mice infected with either T. gondii ME49 or RH strains. The overall IgG and IgM antibody responses elicited by AMA1 VLPs were substantially higher than those induced by the conventionally used T. gondii lysate antigen (TLA). Importantly, AMA1 VLPs were capable of detecting parasitic infection with T. gondii RH and ME49 as early as 1 week post-infection, even when mice were exposed to low infectious doses (5 × 103 and 10 cysts, respectively). AMA1 VLPs also did not cross-react with the immune sera acquired from Plasmodium berghei-infected mice. Compared to TLA, stronger antibody responses were induced by AMA1 VLPs when tested using T. gondii-infected human sera. The sensitivities and specificities of the two antigens were substantially different, with AMA1 VLPs demonstrating over 90% sensitivity and specificity, whereas these values were in the 70% range for the TLA. These results indicated that AMA1 VLPs can detect infections of both T. gondii ME49 and RH at an early stage of infection caused by very low infection doses in mice, and these could be used for serological diagnosis of human toxoplasmosis.

Application of gold immunochromatographic assay strip combined with digital evaluation for early detection of Toxoplasma gondii infection in multiple species

“…Several different Toxoplasma antigens, including toxoplasma surface antigen 2 (SAG2) [ 30 ], surface antigen 3 (SAG3) [ 31 ], dense granule antigen protein 7 (GRA7) [ 32 – 34 ], and rhoptry protein 14 (ROP14), are used for detecting T. gondii infection using GICA [ 26 ]. In our previous study, we identified AMA1 as a potential antigen for ELISA, but the high cutoff value and different form of this protein may lead to false positives when applied to GICA [ 20 , 35 ]. By truncating AMA1, we found that AMA1C was more specific than full-length AMA1 and AMA1N.…”

Identification of novel biomarkers for anti-Toxoplasma gondii IgM detection and the potential application in rapid diagnostic fluorescent tests

“…In a recent study ( Ferra et al, 2020 ), based on the parasite surface receptor protein AMA1, which is correlated with host cell entry, ELISA assays exhibited a sensitivity of 99.4% for IgG and 80% for IgM when testing T. gondii -infected human sera. Furthermore, the utilization of AMA1 virus-like particles (VLPs) by other research groups also demonstrated over 90% sensitivity and specificity, highlighting the potential of AMA1 as a valuable component in serological tests ( Kim et al, 2022 ).…”