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In vivo expression and distribution of dense granule protein 7 (GRA7) in the exoenteric (tachyzoite, bradyzoite) and enteric (coccidian) forms of Toxoplasma gondii

Published online by Cambridge University Press:  01 September 1999

D. J. P. FERGUSON
Affiliation:
Nuffield Department of Pathology, Oxford University, John Radcliffe Hospital, Oxford OX3 9DU, UK
D. JACOBS
Affiliation:
Innogenetics N.V., Industriepark 7, B-9052, Gent, Belgium
E. SAMAN
Affiliation:
Innogenetics N.V., Industriepark 7, B-9052, Gent, Belgium
J-F. DUBREMETZ
Affiliation:
Laboratoire de Pathogenèse des Sporozoaires, Institut Pasteur, 1 rue du Professeur Calmette, 59021 Lille, France
S. E. WRIGHT
Affiliation:
Moredun Research Institute, Pentland Science Park, Bush Loan, Penicuik EH26 0PZ, Scotland
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Abstract

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The in vivo expression and distribution of the dense granule protein GRA7 was examined in both the exoenteric (tachyzoite and bradyzoite) and enteric (coccidian) forms of Toxoplasma gondii by immunocytochemistry. There was strong staining of GRA7 in granules within all the infectious stages (tachyzoite, bradyzoite, merozoite and sporozoite). During tachyzoite development, GRA7 was secreted and was associated with the parasitophorous vacuole. In contrast, although there was staining of granules within the bradyzoites of more mature cysts, there appeared to be little staining of the tissue cyst wall or host cell. The apparent stage-specific variation in secretion of GRA7 between tachyzoites and bradyzoites was confirmed by double labelling using stage-specific markers (SAG1 and BAG1). In the enteric forms in the cat gut there was strong labelling of the PV containing early asexual and sexual stages and staining of a few granules in the apical cytoplasm of the merozoite. The positive enteric staining pattern differentiates GRA7 from the other GRA proteins (GRA1–6) which were absent in the merozoites and enteric stages. The staining pattern of GRA7 with strong staining during tachyzoite and enteric development and reduced staining in the tissue cysts is similar to that seen for NTPases. The function of GRA7 is unknown but it is unique among the dense granule proteins in being expressed in all the infectious forms of T. gondii which would point to a basic role in the vacuolar adaptations required for active parasite development.

Type
Research Article
Copyright
1999 Cambridge University Press

Footnotes

Dedicated to the memory of Professor W. M. Hutchison who died 28 December 1998.