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Clinical and Diagnostic Laboratory Immunology, November 2004, p. 1016-1021, Vol. 11, No. 6
1071-412X/04/$08.00+0     DOI: 10.1128/CDLI.11.6.1016-1021.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Limited Value of Assays Using Detection of Immunoglobulin G Antibodies to the Two Recombinant Dense Granule Antigens, GRA1 and GRA6 Nt of Toxoplasma gondii, for Distinguishing between Acute and Chronic Infections in Pregnant Women

Josette Ferrandiz,1 Corinne Mercier,2 Martine Wallon,1,3 Stéphane Picot,1 Marie-France Cesbron-Delauw,2 and François Peyron1,3*

Laboratoire de Parasitologie, Mycologie Médicale et Pathologie Exotique, Equipe d'Accueil E.A 3732, Faculté de Médecine de Lyon Service de Parasitologie et Pathologie Exotique, Hôpital de la Croix-Rousse, Lyon,3 CNRS UMR 5163—Université Joseph Fourier, Grenoble, France2

Received 28 January 2004/ Returned for modification 8 April 2004/ Accepted 26 August 2004

An enzyme-linked immunosorbent assay (ELISA) using two recombinant antigens of Toxoplasma gondii (GRA1 and GRA6 Nt) was developed in order to differentiate between pregnant women with a serological profile of recently acquired infection and those with chronic infection. Both proteins were expressed in Escherichia coli as glutathione S-transferase fusion proteins. Thirty-two serum samples from subjects who presented seroconversion within 3 months before sampling (group 1; acute profile), 46 serum samples from women who had a positive serology at least 1 year before sampling (group 2; chronic profile), and 100 serum samples from pregnant women who were not infected by T. gondii (group 3) were examined for immunoglobulin G (IgG) reactivity. For both antigens, the specificity reached 98%. In both groups of infected patients, the overall sensitivity scored was 60% for GRA1 and 83% for GRA6 Nt. In group 1, 34% of sera reacted with GRA1 whereas 84% of sera reacted with GRA6 Nt; in group 2, however, sensitivities were 78.2 and 82.6%, respectively. Combination of the readings obtained with both antigens yielded a sensitivity of 91%. A serological follow-up of 10 women who seroconverted during pregnancy displayed three different serological patterns: (i) a GRA profile paralleling the IgG curve, as detected by the commercial kit, (ii) a GRA1 profile, or (iii) GRA1 and GRA6 Nt profiles remaining negative for at least 8 weeks after the reference test gave positive results. Taken together, these results suggest that neither GRA1 nor GRA6 Nt is sensitive enough to be used routinely to differentiate between acute and chronic toxoplasmic infections.

* Corresponding author. Mailing address: Service de Parasitologie et Pathologie Exotique, Hôpital de la Croix-Rousse, 103 grande rue de la Croix-Rousse, 69317 Lyon, France. Phone: (33) 4 72 07 18 69. Fax: (33) 4 72 07 18 73. E-mail: francois.peyron{at}chu-lyon.fr.

Clinical and Diagnostic Laboratory Immunology, November 2004, p. 1016-1021, Vol. 11, No. 6
1071-412X/04/$08.00+0     DOI: 10.1128/CDLI.11.6.1016-1021.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.





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