title: Alteration in host cell tropism limits the efficacy of immunization with a surface protein of malaria merozoites.
abstract: Immunization with Plasmodium yoelii merozoite surface protein-8 (PyMSP-8) has been shown to protect mice against lethal P. yoelii 17XL malaria. Here we demonstrate that PyMSP-8-specific antibodies preferentially suppress P. yoelii 17XL growth in mature erythrocytes compared to growth in reticulocytes and do not suppress the growth of nonlethal P. yoelii 17X, a parasite that primarily replicates in reticulocytes. The protection against normocyte-associated P. yoelii malaria parasites is mediated by antibodies that recognize conformational epitopes of PyMSP-8 that are nonpolymorphic. We examined changes in gene expression in reticulocyte-restricted P. yoelii 17XL parasites that escaped neutralization by PyMSP-8-specific antibodies using P. yoelii DNA microarrays. Of interest, Pymsp-8 gene expression decreased, while the expression of msp-1, msp-7, and several rhoptry protein genes increased. Breakthrough parasites also exhibited increases in the expression of a subset of yir and Pyst-a genes that are predicted to encode polymorphic antigens expressed on the surface of infected erythrocytes. These data suggest that changes in the expression of parasite proteins expressed on the merozoite surface, as well as the surface of infected erythrocytes, may alter host cell tropism and contribute to the ability of malaria parasites to evade merozoite-specific, neutralizing antibodies.
authors.affiliation: Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA.
authors.forename: Qifang
authors.initials: Q
authors.lastname: Shi
authors.forename: Amy
authors.initials: A
authors.lastname: Cernetich
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Daly
authors.forename: Gina
authors.initials: G
authors.lastname: Galvan
authors.forename: Akhil B
authors.initials: AB
authors.lastname: Vaidya
authors.forename: Lawrence W
authors.initials: LW
authors.lastname: Bergman
authors.forename: James M
authors.initials: JM
authors.lastname: Burns
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology*; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology; D018985:Epitopes, B-Lymphocyte / Q000276:immunology; D004912:Erythrocytes / Q000469:parasitology; D015870:Gene Expression; D020869:Gene Expression Profiling; D017125:Genes, Protozoan; D007116:Immunization, Passive; D008288:Malaria / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010967:Plasmodium yoelii / Q000235:genetics / Q000254:growth & development / Q000276:immunology*; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D012156:Reticulocytes / Q000469:parasitology
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D018985:Epitopes, B-Lymphocyte; D015800:Protozoan Proteins; C431669:merozoite surface protein 8, Plasmodium