Multiplexed Anti-Toxoplasma IgG, IgM, and IgA Assay on Plasmonic Gold Chips: towards Making Mass Screening Possible with Dye Test Precision

Abstract

Toxoplasmosis is an infection caused by the protozoan parasite Toxoplasma gondii that can lead to severe sequelae in the fetus during pregnancy. Definitive serologic diagnosis of the infection during gestation is made mostly by detecting T. gondii-specific antibodies, including IgG and IgM, individually in a single serum sample by using commercially available kits. The IgA test is used by some laboratories as an additional marker of acute infection. Most of the commercial tests have failed to reach 100% correlation with the reference method, the Sabin-Feldman dye test for the detection of Toxoplasma IgG antibodies. For Toxoplasma IgM and IgA antibodies, there is no reference method and their evaluation is done by comparing the results of one assay to those of another. There is a need for multiplexed assay platforms, as the serological diagnosis of T. gondii infection does not rely on the detection of a single Ig subtype. Here we describe the development of a plasmonic gold chip with vast fluorescence enhancement in the near-infrared region for simultaneous detection of IgG, IgM, and IgA antibodies against T. gondii in an ϳ1-l serum or whole-blood sample. When 168 samples were tested on this platform, IgG antibody detection sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were all 100%. IgM antibody detection achieved 97.6% sensitivity and 96.9% specificity with a 90.9% PPV and a 99.2% NPV. Thus, the nanoscience-based plasmonic gold platform enables a high-performance, low-cost, multiplexed assay requiring ultrasmall blood volumes, paving the way for the implementation of universal screening for toxoplasmosis infection during gestation.

Serological and molecular rapid diagnostic tests for Toxoplasma infection in humans and animals

“…The multicolor detection scheme has the potential to differentiate between patients with acute and chronic infections. The sensitivity and specificity of the method were reported to be similar to those of well-established assays used in the USA National Reference Laboratories for Toxoplasma infection [74]. The potential of the plasmonic gold chips to detect Toxoplasma IgG was similar to that of the IgG dye test [75,76].…”

“…The potential of the plasmonic gold chips to detect Toxoplasma IgG was similar to that of the IgG dye test [75,76]. Also, the plasmonic gold chip can detect IgG, IgM, and IgA antibodies in serum or whole blood in a single run [74] and is comparable to the commercial multiplexed test using the BioPlex 2200 system (Bio-Rad) which is based on Luminex technology [22]. The approximate time for the detection of IgG, IgM, and IgA antibodies with a plasmonic gold chip is about 2 h at USD10 per patient [74].…”

“…Also, the plasmonic gold chip can detect IgG, IgM, and IgA antibodies in serum or whole blood in a single run [74] and is comparable to the commercial multiplexed test using the BioPlex 2200 system (Bio-Rad) which is based on Luminex technology [22]. The approximate time for the detection of IgG, IgM, and IgA antibodies with a plasmonic gold chip is about 2 h at USD10 per patient [74]. With~1 μl serum sample, the multiplex plasmonic gold platform has been used for the detection of IgG/IgM in seroconverted, chronically infected, non-infected, and newborns in Nice, France [77].…”

Diagnosis, Treatment, and Prevention of Congenital Toxoplasmosis in the United States

“…7, 96, 131, 222 -226 A study limitation that was acknowledged by Stillwaggon et al 7 Moreover, the following changes in the future may make the universal screening strategy even more costeffective: (1) "point-of-care test" technologies for serologic screening, (2) screening with the use of saliva specimens, and (3) multiplex screening 227 (multiplex IgG/IgM, which already are under evaluation and will soon provide further costsaving alternatives for screening). In addition, screening for >1 congenital disease at the same time will provide further cost savings.…”

Commentary: Towards Universal Screening for Toxoplasmosis: Rapid, Cost-Effective, and Simultaneous Detection of Anti-Toxoplasma IgG, IgM, and IgA Antibodies by Use of Very Small Serum Volumes

“…ity, positive predictive value, and negative predictive value in as little as 5 l of patient serum (18).…”