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Infect. Immun. doi:10.1128/IAI.00327-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Characterization of the antibody response against Plasmodium falciparum erythrocyte membrane protein-1 in human volunteers

Malaria Drug Resistance and Chemotherapy, Infectious Diseases and Immunology Division, The Queensland Institute of Medical Research, Post Office Royal Brisbane Hospital, Qld 4029, Australia; Drug Resistance and Diagnostics, Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, Qld 4051, Australia. Department of Biochemistry, La Trobe University, Melbourne, 3086, Australia. Victorian Infectious Disease Service, Royal Melbourne Hospital, Victoria, Australia. Molecular Immunology, Infectious Diseases and Immunology Division, The Queensland Institute of Medical Research, Post Office Royal Brisbane Hospital, Qld 4029, Australia

^* To whom correspondence should be addressed. Email: qin.cheng{at}defence.gov.au.

	Abstract

The immune response against the Plasmodium falciparum variant surface antigen PfEMP1 is a key component of clinical immunity against falciparum malaria. In this study we used sera from human volunteers who had been infected with the P. falciparum 3D7 strain to investigate the development, specificity and dynamics of anti-PfEMP1 antibodies measured against six different 3D7 DBL1 fusion proteins. We observed that a parasitemia of 20 to 200 infected erythrocytes per µL was required to trigger an antibody response to DBL1 and that antibodies against one DBL1 variant cross-react with other DBL1 variants. Both the serum and purified IgGs were able to agglutinate infected erythrocytes and purified anti-DBL1 IgGs bound to the live infected red blood cell surface in a punctate surface pattern, confirming that the IgGs recognise native PfEMP1. Analysis of sera from tourists naturally infected with P. falciparum suggests that the anti-PfEMP1 antibodies often persisted more than 100 days after a single infection. These results help to further understand the development of acquired immunity to P. falciparum infections.