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Infection and Immunity, August 2003, p. 4472-4486, Vol. 71, No. 8
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.8.4472-4486.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Stress-Dependent Expression of a Polymorphic, Charged Antigen in the Protozoan Parasite Entamoeba histolytica

S. Satish,^1, Abhijeet A. Bakre,² Sudha Bhattacharya,² and Alok Bhattacharya^1,3*

School of Life Sciences,¹ School of Environmental Sciences,² Bioinformatics Centre, Jawaharlal Nehru University, New Delhi-110067, India³

Received 21 March 2003/ Returned for modification 15 April 2003/ Accepted 12 May 2003

We have identified a novel stress inducible gene, Ehssp1 in Entamoeba histolytica, the causative agent of amebiasis. Ehssp1 belongs to a polymorphic, multigene family and is present on multiple chromosomes. No homologue of this gene was found in the NCBI database. Sequence alignment of the multiple copies, and genomic PCR data restricted the polymorphism to the central region of the gene. This region contains a polypurine stretch that encodes a domain rich in acidic and basic amino acids. Under normal culture conditions only one copy of this multigene family is expressed, as observed by Northern blot and RT-PCR analysis. The size of this copy of the gene is 1,077 nucleotides, encoding a protein of 359 amino acids. The polymorphic domain in this copy is 64 nucleotides long. However, on exposure of cells to stress conditions such as heat shock or oxidative stress, multiple polymorphic copies of the gene are expressed, suggesting a possible role of this gene in adaptation of cells to stress conditions. The gene copy expressed under normal conditions, and the expression profile of cells under heat stress was identical in two different strains of E. histolytica tested. Interestingly, the extent of polymorphism in this gene was very less in E. dispar, a nonpathogenic sibling species of E. histolytica. Ehssp1 was found to be antigenic in invasive amebiasis patients.

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* Corresponding author. Mailing address: School of Life Sciences, Jawaharlal Nehru University, New Delhi-110067, India. Phone: 91-011-26704516. Fax: 91-11-6165886. E-mail: alok0200{at}mail.jnu.ac.in.

Editor: W. A. Petri, Jr.

Present address: Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass.

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Infection and Immunity, August 2003, p. 4472-4486, Vol. 71, No. 8
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.8.4472-4486.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

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