Diagnosis of congenital toxoplasmosis using whole-blood interferon-{gamma} release assay

J Clin Microbiol. 2009 Nov 18. [Epub ahead of print]

Diagnosis of congenital toxoplasmosis using whole-blood interferon-{gamma} release assay

Chapey E, Wallon M, Debize G, Rabilloud M, Peyron F.

Hospices Civils de Lyon, Service de Parasitologie, Hôpital de la Croix Rousse, F-69317 Lyon, France; Université Claude Bernard Lyon 1, Service de Parasitologie, Faculté de Médecine Lyon Sud, F-69372 Lyon, France; Hospices Civils de Lyon, Laboratoire d'Hématologie, Hôpital de la Croix Rousse, F-69317 Lyon, France; Hospices Civils de Lyon, Service de Biostatistique, F-69424 Lyon, France; Université Claude Bernard Lyon 1, F-69622 Villeurbanne, France; CNRS, UMR 5558, Laboratoire Biostatistique Santé, F-69495 Pierre-Bénite, France.

Congenital toxoplasmosis at birth is generally subclinical but infected infants are at risk of developing ocular lesions. Diagnosis at birth relies mainly on serological tests. Cell- mediated immunity plays the major role in resistance to infection but is not routinely investigated for diagnostic purposes. Here we describe a simple test based on the response to interferon-gamma (IFN-gamma) after stimulation of whole blood by crude parasitic antigens. One millilitre of heparinized blood was centrifuged; plasma was kept for routine serological tests and pellets were resuspended in culture medium. After 24 h of culture in the presence of crude Toxoplasma gondii antigen, the cells were centrifuged and IFN-gamma was assayed in the supernatant. In 62 infants under 1 year of age born to mothers who were infected during pregnancy, the sensitivity and specificity were 94% (16/17) and 98% (44/45), respectively. The false negative was in a treated baby who turned positive after withdrawal of treatment. The false positive was observed in 3-month-old baby. In a cohort of 124 congenitally infected patients aged between 1 and 30 years, the sensitivity of the test was 100%. We present a simple test based on IFN-gamma secretion to assess cell-mediated immunity in toxoplasmosis. As only 1 mL of blood is required to investigate humoral and cellular immunity, our assay is well adapted for the study of congenital toxoplasmosis in infants. Using purified antigens or recombinant peptides might improve the test performances.

PMID: 19923492 [PubMed - as supplied by publisher]