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Clinical and Vaccine Immunology, August 2009, p. 1158-1169, Vol. 16, No. 8
1071-412X/09/$08.00+0     doi:10.1128/CVI.00092-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Selection of Polymorphic Peptides from GRA6 and GRA7 Sequences of Toxoplasma gondii Strains To Be Used in Serotyping{triangledown}

Susana Sousa,1,2 Daniel Ajzenberg,2,4 Maggy Marle,3 Dominique Aubert,3,4 Isabelle Villena,3,4 José Correia da Costa,1 and Marie-Laure Dardé2,4*

Center for Parasite Immunology and Biology, INSA, Porto 4000-055, Portugal,1 Laboratoire de Parasitologie-Mycologie, EA 3174-NETEC, Faculté de Médecine, Université de Limoges, Limoges 87025, France,2 Laboratoire Parasitologie-Mycologie, EA 3800, CHU Reims, 51 rue Cognacq-Jay, Reims 51095 Cedex, France,3 Centre National de Référence Toxoplasmose/Toxoplasma Biological Resource Center, Limoges, Reims, France4

Received 2 March 2009/ Returned for modification 15 April 2009/ Accepted 27 May 2009

The evaluation of Toxoplasma gondii isolates obtained from geographical environments other than Europe and North America revealed the existence of atypical strains that are not included in the three archetypal clonal lineages (lineages I, II, and III). GRA6 and GRA7 are polymorphic genes that have been used for the genotyping of Toxoplasma. The coding regions of GRA6 and GRA7 from 49 nonarchetypal strains were sequenced and compared with the sequences of type I, II, and III reference strains. Eighteen and 10 different amino acid sequences were found for GRA6 and GRA7, respectively. The polymorphisms found between the different sequences were analyzed, with the objective of defining peptides to be used for the serotyping of Toxoplasma infections. Two peptides specific for clonal lineages I and III (peptides GRA7I and GRA7III, respectively) were selected from the GRA7 locus. Three peptides specific for some atypical strains (peptides Am6, Af6, and Am7) were selected from both the GRA6 and the GRA7 loci. Serum samples from humans infected with Toxoplasma strains of known genotypes were serotyped with the selected peptides. Peptide GRA7III seems to be a good candidate for the serotyping of infections caused by type III strains. Peptide GRA7I had a very low sensitivity. Peptides Am6 and Af6 had low specificities, since they reacted with serum samples from patients infected with strains belonging to the three archetypal lineages. Although peptide Am7 was specific, it had low sensitivity.

* Corresponding author. Mailing address: Laboratoire de Parasitologie-Mycologie, CHRU Dupuytren, 2, Av. Martin Luther King, Limoges 87042 Cedex, France. Phone: 33 555 056 160. Fax: 33 555 056 177. E-mail: darde{at}unilim.fr

{triangledown} Published ahead of print on 3 June 2009.

Clinical and Vaccine Immunology, August 2009, p. 1158-1169, Vol. 16, No. 8
1071-412X/09/$08.00+0     doi:10.1128/CVI.00092-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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