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Analysis of var genes from p. vivax and p. falciparum

Objective

* to determine the genomic organization of var genes in P. falciparum
* to examine the mechanism of differential var gene expression in P. falciparum
* to examine the adhesive phenotypes of specific var gene variants
* to clone var gene homologous genes from P. vivax
* to study the genomic organization of var gene homologues in P.vivax
Expected Outcome

* The study will provide a better understanding of the mechanisms of differential var gene expression.
* The study will correlate defined adhesive properties with particular var gene variants
* The study will show the diversity of var gene variants in the field.
* The study will provide tools, such as YAC libraries and chromosomal contig maps, that will be useful in other areas of malaria research.
* The study will explore the existence of var genes in P. vivax.
* Production of a P. vivax YAC library and the assortment into contigs. A representative YAC library for P. vivax will be constructed. The DNA material will be obtained from patients and from primates infected with an Indian isolate of P. vivax.

* Assortment of P. vivax YAC clones into chromosomal contig maps. Chromosomal YAC contig maps will be generated using a 'top down' approach based on advanced filter hybridization strategies. YAC filters will be screened with random cDNA clones from P. vivax.

* Isolation of P. vivax var genes. The UNIEBP primers developed to amplify P. falciparum var genes will be used to identify and clone homologous genes from P. vivax. The production of full-length gene sequences from P. vivax will be useful for comparison to the P. falciparum var genes, particularly for functional comparison as it is believed that P. vivax-infected erythrocytes do not adhere to host endothelium.

* Production of a 3D7 clone tree and cloning of expressed var genes. To study the mechanism of var gene switching in P. falciparum, a clone tree from the P. falciparum isolate 3D7 will be generated by limiting dilution. The resulting clones will be analyzed for antigenic similarity using the mixed agglutination reaction with hyperimmune sera. Using RT-PCR, the expressed var gene will be identified and sequenced. The sequence will be correlated with the adhesive properties of this variant.

* Mapping a rosetting locus in P. falciparum. Using the existing progeny from the genetic cross between the rosetting clone Dd2 and the non-rosetting clone HB3 we will follow the segregation of the rosetting phenotype in this cross and determine a candidate locus. This candidate locus will be screened for the possible expression of var genes, to explore the possibility that rossetting is mediated by a particular var gene variant.

* Genomic analysis of var genes. Using existing, and yet to be constructed, YAC contig maps of P. falciparum and P. vivax chromosomes, the genomic location and organization of the var gene family will be studied in both P. vivax and P. falciparum.

* Analysis of var genes in field samples (P. vivax and P. falciparum). To determine the degree of var gene variability in field populations, longitudinal studies will be carried out in Brazil and India. The expressed var gene variants will be determined by RT/PCR amplification using the UNIEBP oligonucleotides as primers. The resulting fragments will be cloned and sequenced. This will generate a data set of expressed var genes within given spatial and temporal locations.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Bayerische Julius-Maximilians-Universität Würzburg
Address
11,Röntgenring 11
97070 Würzburg
Germany

Participants (4)

International Centre for Genetic Engineering and Biotechnology
India
Address
Aruna Asaf Ali Marg
110067 New Delhi
THE CHANCELLOR, MASTERS AND SCHOLARS OF THE UNIVERSITY OF OXFORD
United Kingdom
Address
John Radcliffe Hospital - Oxfordshire 5802
OX3 9DU Oxford/headington
UNIVERSIDADE DE SAO PAULO
Brazil
Address
Avenida Prof. Lineu Prestes 1374, Edificio Biomedi
05508-900 Sao Paulo
UNIVERSITAETSKLINIKUM HEIDELBERG
Germany
Address
Im Neuenheimer Feld 324
69120 Heidelberg