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Membrane localization and demonstration of isoforms of nucleoside triphosphate hydrolase from Toxoplasma gondii

Published online by Cambridge University Press:  11 January 2002

T. KIKUCHI
Affiliation:
Department of Parasitology, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
T. FURUTA
Affiliation:
Department of Parasitology, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
S. KOJIMA
Affiliation:
Department of Parasitology, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan

Abstract

Toxoplasma gondii has a unique enzyme, a NTPase, which has a wide specificity toward NTP. In the present study, we produced a monoclonal antibody (IgG1, 6C6) against the enzyme which could recognize NTPase isozymes among several strains of T. gondii. Three avirulent strains of T. gondii, ME49, Beverley and Nakayama, were found to have 1 NTPase (63kDa, pI 6·0), while a virulent strain RH and an avirulent strain Fukaya had 2 isozymes (63kDa) with different pIs (pIs 6·0 and 6·5 for the former, and pIs 6·2 and 6·4 for the latter, respectively), suggesting that this monoclonal antibody recognizes a common epitope of NTPase among T. gondii strains. Furthermore, 6C6 could inhibit NTPase activity in the presence of dithiothreitol in a dose-dependent manner, and immuno-EM study of NTPase revealed that this molecule is located on the surface membrane of T. gondii tachyzoites. When Vero cells were co-cultured with tachyzoites pre-treated with 6C6, the number of infected cells significantly decreased, suggesting that 6C6 inhibits invasion of the parasites to host cells. These data suggest that the molecule recognized by 6C6 might be considered a potential candidate antigen for vaccines against T. gondii tachyzoites.

Type
Research article
Copyright
© 2001 Cambridge University Press

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