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Journal of Clinical Microbiology, March 2003, p. 1147-1151, Vol. 41, No. 3
0095-1137/03/$08.00+0     DOI: 10.1128/JCM.41.3.1147-1151.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

High-Level Expression and Purification of a Truncated Merozoite Antigen-2 of Babesia equi in Escherichia coli and Its Potential for Immunodiagnosis

Xiaohong Huang,^1,2 Xuenan Xuan,¹ Naoaki Yokoyama,¹ Longshan Xu,¹ Hiroshi Suzuki,¹ Chihiro Sugimoto,¹ Hideyuki Nagasawa,¹ Kozo Fujisaki,¹ and Ikuo Igarashi^1*

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan,¹ Fujian Provincial Centers for Disease Control, Fuzhou 350001, China²

Received 7 October 2002/ Returned for modification 24 November 2002/ Accepted 15 December 2002

The gene encoding a truncated merozoite antigen-2 (EMA-2t) of Babesia equi was cloned and highly expressed in Escherichia coli as a glutathione S-transferase fusion protein (G-rEMA-2t). Both G-rEMA-2t and rEMA-2t (after the removal of glutathione S-transferase) had good antigenicity. Either Western blot analysis with rEMA-2t or enzyme-linked immunosorbent assay (ELISA) with G-rEMA-2t clearly discriminated the sera of horses experimentally infected with B. equi from sera of horses infected with Babesia caballi and healthy horses, although rEMA-2t was not suitable for ELISA, probably owing to its poor absorbability to the plates. The specific antibodies in B. equi-infected horses were detectable during both acute and latent infection (6 to 244 days postinfection). Horse sera from Jilin Province, China, were examined by the two tests. The seroprevalence of B. equi was 49.2% (31 of 63 sera) by Western blot analysis with rEMA-2t and 47.6% (30 of 63 sera) by ELISA with G-rEMA-2t. The correspondence was 98.4% (62 of 63 sera) between the two tests. The results indicate that G-rEMA-2t and rEMA-2t proteins should be suitable antigens for the development of an effective immunodiagnostic assay due to their high sensitivity, specificity, and great yield.

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* 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.

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Journal of Clinical Microbiology, March 2003, p. 1147-1151, Vol. 41, No. 3
0095-1137/03/$08.00+0     DOI: 10.1128/JCM.41.3.1147-1151.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

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