Eur J Clin Microbiol Infect Dis (2003) 22:181–184 DOI 10.1007/s10096-003-0903-9 ARTICLE A. F. Fatoohi · G. J. N. Cozon · M. Wallon · S. Kahi · F. Gay-Andrieu · T. Greenland · F. Peyron Cellular Immunity to Toxoplasma gondii in Congenitally Infected Newborns and Immunocompetent Infected Hosts Published online: 4 March 2003 # Springer-Verlag 2003 Abstract The aim of this study was to determine the frequency of anergy to Toxoplasma gondii in congenitally infected newborns and immunocompetent infected indi- viduals. Specific anergy to Toxoplasma has been reported previously, especially in cases of congenital toxoplasmo- sis. Whole blood from 592 immunocompetent patients with suspected toxoplasmosis was cultured in the pres- ence of soluble Toxoplasma antigen for 7 days. Activated T lymphocytes were detected by flow cytometry. In patients over 1 year of age, the percentage of soluble Toxoplasma antigen-stimulated T cells expressing the interleukin-2 receptor CD25 was higher in infected patients than in uninfected subjects (40.0€18.3% vs. 1.8€2.0%, P<0.0001). No differences were detected between seroconverters, i.e. those with recent rises in IgM and IgG antibodies, and those with acquired or congenital toxoplasmosis. Similar results were observed when congenitally infected (n=38) and uninfected (n=89) children under 1 year of age were compared (17.6€9.2% vs. 3.0€4.9%, P<0.0001). The sensitivity and specificity values of CD25 detection for diagnosis of congenital toxoplasmosis in infants were 95% and 89%, respectively, at a threshold value of 7% above control culture. The results show that specific cellular immunity is detectable in virtually all Toxoplasma-infected patients, including newborns. Detection of CD25 constitutes a simple, sensitive and specific test for diagnosis of congenital toxoplasmosis. Introduction Toxoplasmosis is an opportunistic infection that induces a strong cellular immune response in the normal host. Cell- mediated immunity is essential for host resistance to the parasite [1]. In immunocompetent individuals, toxoplas- mosis is usually either asymptomatic or paucisymptomat- ic. In immunodeficient subjects such as HIV-infected patients, infection with Toxoplasma gondii may induce severe, even lethal, cerebral or pulmonary toxoplasmosis [2]. In congenitally infected infants, infection with Toxoplasma gondii may result in other sequelae such as fibrous or calcified cerebral lesions or acute ocular lesions that threaten vision [3]. Systemic or diffuse infection is very rare in immunocompetent individuals, even in congenitally infected patients. Nevertheless, previous studies using [ 3 H] thymidine incorporation methods have reported lymphocyte anergy to Toxoplasma gondii in a newborn [4] and in patients with congenital toxoplasmo- sis [5]. Using rapid flow-cytometric detection of CD25, the interleukin-2 receptor, after culture with soluble Toxo- plasma gondii antigen [6], we showed previously that cellular immunity was present in all 15 congenitally infected patients tested [7]. In the present study, in order to appreciate the occurrence of specific anergy in a larger group of immunocompetent patients, we reviewed the cellular immune status of all immunocompetent individ- uals tested for suspected toxoplasmosis in our service during the past 5 years. The results show that cellular A. F. Fatoohi E.A. 3087 Parasitologie, FacultØ de MØdecine Lyon Nord, Laboratoire d’Immunologie, Hôpital de la Croix-Rousse, Lyon, France G. J. N. Cozon ( ) ) Laboratoire d’Immunologie, Hôpital de la Croix-Rousse, 93 Grande Rue de la Croix-Rousse, 69317 Lyon, France e-mail: gregoire.cozon@chu-lyon.fr Tel.: +33-4-72071952 Fax: +33-4-72071848 M. Wallon E.A. 3087 Parasitologie, FacultØ de MØdecine Lyon Nord, Service de Parasitologie, Hôpital de la Croix-Rousse, Lyon, France S. Kahi · F. Gay-Andrieu · F. Peyron E.A. 3087 Parasitologie, FacultØ de MØdecine Lyon Nord, Lyon, France T. Greenland UMR INRA 754, Universite Claude Bernard Lyon, Lyon, France