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Clinical and Diagnostic Laboratory Immunology, November 2002, p. 1343-1347, Vol. 9, No. 6
1071-412X/02/$04.00+0     DOI: 10.1128/CDLI.9.6.1343-1347.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Characterization of Toxoplasma gondii SAG2 Expressed in Insect Cells by Recombinant Baculovirus and Evaluation of Its Diagnostic Potential in an Enzyme-Linked Immunosorbent Assay

Xiaohong Huang,1 Xuenan Xuan,1 Hiroshi Suzuki,1 Chihiro Sugimoto,1 Hideyuki Nagasawa,1 Kozo Fujisaki,1 Takeshi Mikami,2 and Ikuo Igarashi1*

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555,1 College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-8510, Japan2

Received 29 April 2002/ Returned for modification 20 June 2002/ Accepted 22 July 2002

A baculovirus carrying the SAG2 gene of Toxoplasma gondii was constructed, and recombinant SAG2 protein (S-rSAG2) was expressed in insect cells. S-rSAG2 was recognized by sera from cats and pigs infected with T. gondii. Mice immunized with S-rSAG2 produced high titers of specific immunoglobulin G2a (IgG2a) and IgG1 antibodies. In an indirect fluorescent antibody test, all mouse antisera against S-rSAG2 reacted strongly to the natural parasites, but those against rSAG2 expressed in Escherichia coli (E-rSAG2) only showed very weak reaction, although no markedly difference was found in the reaction to denatured antigen, T. gondii lysate, in Western blot analysis. The results suggest that S-rSAG2 is better than E-rSAG2 in both antigenicity and immunogenicity. Enzyme-linked immunosorbent assay (ELISA) with S-rSAG2 could differentiate clearly between sera from 30 specific-pathogen-free cats and 4 experimentally infected cats. Serum samples from domestic cats in Japan were tested by the ELISA and compared with a latex agglutination test (LAT) and ELISA with E-rSAG2. Of 187 samples, all 35 LAT-positive sera had strong reactions to S-rSAG2 and E-rSAG2. Of the 152 LAT-negative sera, 18 were positive in the ELISA with S-rSAG2, whereas only 2 were positive in the ELISA with E-rSAG2. Although there were significant correlations among the three methods, the ELISA with S-rSAG2 was more sensitive than the others, which could be attributed to the fact that S-rSAG2 shares some common conformational structure with the native antigen. The results suggest that S-rSAG2 would be a useful reagent for the detection of T. gondii infection in cats.

* Corresponding author. Mailing address: National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan. Phone: 81-155-49-5641. Fax: 81-155-49-5643. E-mail: igarcpmi{at}obihiro.ac.jp.

Clinical and Diagnostic Laboratory Immunology, November 2002, p. 1343-1347, Vol. 9, No. 6
1071-412X/02/$04.00+0     DOI: 10.1128/CDLI.9.6.1343-1347.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Huang, X., Xuan, X., Hirata, H., Yokoyama, N., Xu, L., Suzuki, N., Igarashi, I. (2004). Rapid Immunochromatographic Test Using Recombinant SAG2 for Detection of Antibodies against Toxoplasma gondii in Cats. J. Clin. Microbiol. 42: 351-353 [Abstract] [Full Text]  


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