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Infection and Immunity, December 2008, p. 5565-5580, Vol. 76, No. 12
0019-9567/08/$08.00+0 doi:10.1128/IAI.00901-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
An In Vivo and In Vitro Model of Plasmodium falciparum Rosetting and Autoagglutination Mediated by varO, a Group A var Gene Encoding a Frequent Serotype
Inès Vigan-Womas,1*
Micheline Guillotte,1
Cécile Le Scanf,2
Sébastien Igonet,3
Stéphane Petres,4
Alexandre Juillerat,3
Cyril Badaut,3
Farida Nato,4
Achim Schneider,1
Anne Lavergne,2
Hugues Contamin,2
Adama Tall,5
Laurence Baril,5
Graham A. Bentley,3 and
Odile Mercereau-Puijalon1
Institut Pasteur, Unité d'Immunologie Moléculaire des Parasites, URA CNRS 2581, F-75015 Paris, France,1 Institut Pasteur de la Guyane, BP 6010, 97306 Cayenne Cedex, French Guiana,2 Institut Pasteur, Unité d'Immunologie Structurale, CNRS URA 2185, F-75015 Paris, France,3 Institut Pasteur, Plate-forme de Production de Protéines recombinantes et d'Anticorps, F-75015 Paris, France,4 Institut Pasteur de Dakar, Unité d'Epidémiologie des Maladies Infectieuses, BP 220, Dakar, Sénégal5
Received 22 July 2008/ Returned for modification 7 September 2008/ Accepted 11 September 2008
In the Saimiri sciureus monkey, erythrocytes infected with the varO antigenic variant of the Plasmodium falciparum Palo Alto 89F5 clone bind uninfected red blood cells (rosetting), form autoagglutinates, and have a high multiplication rate, three phenotypic characteristics that are associated with severe malaria in human patients. We report here that varO parasites express a var gene having the characteristics of group A var genes, and we show that the varO Duffy binding-like 1
1 (DBL11) domain is implicated in the rosetting of both S. sciureus and human erythrocytes. The soluble varO N-terminal sequence (NTS)-DBL11 recombinant domain, produced in a baculovirus-insect cell system, induced high titers of antibodies that reacted with varO-infected red blood cells and disrupted varO rosettes. varO parasites were culture adapted in vitro using human erythrocytes. They formed rosettes and autoagglutinates, and they had the same surface serotype and expressed the same varO gene as the monkey-propagated parasites. To develop an in vitro model with highly homogeneous varO parasites, rosette purification was combined with positive selection by panning with a varO NTS-DBL11-specific mouse monoclonal antibody. The single-variant, clonal parasites were used to analyze seroprevalence for varO at the village level in a setting where malaria is holoendemic (Dielmo, Senegal). We found 93.6% (95% confidence interval, 89.7 to 96.4%) seroprevalence for varO surface-reacting antibodies and 86.7% (95% confidence interval, 82.8 to 91.6%) seroprevalence for the recombinant NTS-DBL11 domain, and virtually all permanent residents had seroconverted by the age of 5 years. These data imply that the varO model is a relevant in vivo and in vitro model for rosetting and autoagglutination that can be used for rational development of vaccine candidates and therapeutic strategies aimed at preventing malaria pathology.
* Corresponding author. Mailing address: Institut Pasteur, Unité d'Immunologie Moléculaire des Parasites, CNRS URA 2581, 25 rue du Dr Roux, F-75724 Paris, France. Phone: 33 1 45 68 82 19. Fax: 33 1 45 68 85 88. E-mail: ines.vigan-womas{at}pasteur.fr
Published ahead of print on 22 September 2008.
Infection and Immunity, December 2008, p. 5565-5580, Vol. 76, No. 12
0019-9567/08/$08.00+0 doi:10.1128/IAI.00901-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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