Evidence for differences in erythrocyte surface receptors for the malarial parasites, Plasmodium falciparum and Plasmodium knowlesi.

Abstract

The asexual erythrocytic cycle responsible for the clinical manifestations of malaria is perpetuated by merozoites which rupture out of infected erythrocytes and invade uninfected ones. Interaction between the merozoites and receptors on the erythrocyte surface initiate invasion (1-3). Chemical or immunologic interference between the merozoite and its receptor could block the infection at this point in the life cycle. Previously, we studied the characteristics of the erythroycte surface that are required for interaction and subsequent invasion by Plasmodium knowlesi merozoites (3, 4). Erythrocytes which lacked Duffy blood group determinants (Duffy negative erythrocytes) (3) or had been treated with chymotrypsin (4) were resistant to invasion. With the recent advances in in vitro cultivation ofPlasmodium falciparum (5, 6), it was possible to compare the erythrocyte surface determinants required for invasion by P. falciparum, the major malaria of man, and P. knowlesi, a monkey malaria that infects man. Materials and MethodsHuman erythrocytes (test cells) which either lacked a blood group determinant (Table I) or had been treated with various enzymes (Table II) were exposed to P. falciparum and P. knowlesi merozoites in vitro, and the percentage of test cells infected was determined. Chimpanzee erythrocytes infected with P. falciparum (Camp strain) and frozen in liquid nitrogen were thawed (7) on the day of the experiment. They contained approximately 50% infected erythroeytes and varied in viability from experiment to experiment. The infected cells were centrifuged in microhematocrit tubes. Cells from the upper half of the tubes, containing about 90% infected erythrocytes were mixed with test erythrocytes in a ratio of 1 to 25 and cultured as previously described (6). Erythrocytes were removed from culture 48 h later, spread in a thin film on a slide, stained with Giemsa, and the percent of erythrocytes infected with young trophozoites (ring forms) determined.Rhesus erythrocytes that are refractory to invasion by P. falciparum were included in each experiment (Table I). In parallel experiments, samples of test erythrocytes were cultured with P.knowlesi-infected cells (3). Since P. falciparum merozoites were released after 48 h in culture and P. knowlesi within 1 h, test erythrocytes were incubated at 35°C for 48 h before addition of P. knowlesi-infected cells.

Plasmodium vivax clinical malaria is commonly observed in Duffy-negative Malagasy people

“…Following on observations that vivax malaria was rare in Africa (6), Miller et al performed definitive in vivo studies to show that Duffy-negative people resisted, whereas Duffy-positive people were susceptible, to experimental P. vivax blood-stage infection following exposure to infected mosquitoes (7). This seminal work, and related Plasmodium knowlesi in vitro studies (7)(8)(9), established the paradigm that malaria parasites invade erythrocytes through specific "receptor"-based interactions and that the Duffy blood group was the receptor for P. vivax.…”

Primary structure of the 175K Plasmodium falciparum erythrocyte binding antigen and identification of a peptide which elicits antibodies that inhibit malaria merozoite invasion.

“…Merozoite recognition and invasion of erythrocytes is probably a multi-step process and depends on the ability of the merozoite to recognize ligands on the erythrocyte membrane (Miller et al, 1977;Pasvol and Jungery, 1984;Perkins, 1984;Okoye and Bennet, 1985;. Several studies of P. falciparum merozoite-erythrocyte interaction have identified erythrocyte membrane glycophorins and sialic acid as ligands important for invasion (Miller et al, 1977;Pasvol et al, 1982;Pasvol and Jungery, 1984;.…”

Detection and quantification of Duffy antigen on bovine red blood cell membranes using a polyclonal antibody

“…In human beings the Duffy antigen aminoacid shifting G44D deϐines two phenotypes (Fy a and Fy b ) (Iwamoto et al, 1996) but does not confer any Plasmodium vivax resistance (Miller et al 1976); however, a single aminoacid substitution (R89C) reduces by 90% the level of Duffy protein detected on the erythrocytes (Olsson et al 1998, Tournamille et al 1998 which reduces it ability to bind to chemokines and therefore possibly might confer certain resistance to P. vivax infection (López et al 2010). The alignment of Bos taurus taurus and Bos taurus indicus Duffy protein sequences deposited at the GeneBank shows 99% identity and just the changes at the aminoacid 22 (F22L) are exclusive of Bos taurus indicus which could have a role in babesiosis resistance.…”

“…Cattle infected with B. bigemina and B. bovis present clinical signs very similar to those of human beings infected with Plasmodium vivax and Plasmodium falciparum (Cooke et al 2005). The glycoprotein Duffy is the only human erythrocyte receptor for Plasmodium vivax (Horuk et al 1993) and the majority of people originating from the indigenous populations of West Africa are resistant to vivax malaria (Miller et al 1976, Tournamille et al 1995 because of a mutation which prevents expression of the Duffy antigen on their erythrocytes' surfaces (Tournamille et al 1995, Iwamoto et al 1996.…”