Rhoptry-associated protein 1-binding monoclonal antibody raised against a heterologous peptide sequence inhibits Plasmodium falciparum growth in vitro.
Monoclonal antibodies (MAbs) specific for Plasmodium falciparum rhoptry-associated protein 1 (RAP-1) were generated and tested for inhibition of parasite growth in vitro. The majority of indirect immunofluorescence assay (IFA)-positive MAbs raised against recombinant RAP-1 positions 23 to 711 (rRAP-1(23-711)) recognized epitopes located in the immunodominant N-terminal third of RAP-1. MAbs specific for the building block 35.1 of the synthetic peptide malaria vaccine SPf66 also yielded an IFA staining pattern characteristic for rhoptry-associated proteins and reacted specifically with rRAP-1 and parasite-derived RAP-1 molecules p67 and p82. Cross-reactivity with RAP-1 was blocked by the 35.1 peptide. Epitope mapping with truncated rRAP-1 molecules and overlapping peptides identified the linear RAP-1 sequence Y218KYSL222 as a target of the anti-35.1 MAbs. This sequence lacks primary sequence similarity with the 35.1 peptide (YGGPANKKNAG). Cross-reactivity of the anti-35.1 MAbs thus appears to be associated with conformational rather than sequence homology. While the anti-35.1 MAb SP8.18 exhibited parasite growth-inhibitory activity, none of the tested anti-rRAP-1(23-711) MAbs inhibited parasite growth, independently of their fine specificity for the RAP-1 sequences at positions 33 to 42, 213 to 222, 243 to 247, 280 to 287, or 405 to 446. The growth-inhibitory activity of MAb SP8.18 was, however, accelerated by noninhibitory anti-RAP-1 MAbs. Results demonstrate that in addition to fine specificity, other binding parameters are also crucial for the inhibitory potential of an antibody.
Swiss Tropical Institute, CH-4002 Basel, Switzerland.
R
R
Moreno
F
F
Pöltl-Frank
D
D
Stüber
H
H
Matile
M
M
Mutz
N A
NA
Weiss
G
G
Pluschke
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000953:Antigens, Protozoan / Q000276:immunology*; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology*; D010963:Plasmodium falciparum / Q000254:growth & development / Q000276:immunology*; D015800:Protozoan Proteins / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology
D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; D010446:Peptide Fragments; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C066269:SPf66 protein, Plasmodium; C065352:rhoptry associated protein, Plasmodium