Limits...
Cellular responses to Plasmodium falciparum erythrocyte membrane protein-1: use of relatively conserved synthetic peptide pools to determine CD4 T cell responses in malaria-exposed individuals in Benin, West Africa.

Sanni LA, Allsopp CE, Reubsaet L, Sanni A, Newbold C, Chauhan VS, Langhorne J - Malar. J. (2002)

Bottom Line: CD4 T cell proliferation occurs at a relatively higher magnitude to peptide pools from the DBLalpha and EXON 2 in the malaria-exposed donors living in Benin than in the UK malaria-unexposed donors.These findings suggest that an immunological recall response to conserved peptides of a variant antigen can be measured.These types of assays may provide information on conserved peptides of PfEMP1 which could be useful for stimulating T cells to provide help to P. falciparum specific B cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Parasitology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK. lsanni@nimr.mrc.ac.uk

ABSTRACT

Background: Plasmodium falciparum erythrocyte membrane protein-1, a variant antigen of the malaria parasite, is potentially a target for the immune response. It would be important to determine whether there are CD4 T cells that recognise conserved regions. However, within the relatively conserved region, there is variation. It is not possible to test T cell responses from small field samples with all possible peptides.

Methods: We have aligned sequences that are relatively conserved between several PfEMP1 molecules, and chosen a representative sequence similar to most of the PfEMP1 variants. Using these peptides as pools representing CIDRalpha, CIDRbeta and DBLbeta-delta domains, DBLalpha domain, and EXON 2 domain of PfEMP1, we measured the CD4 T cell responses of malaria-exposed donors from Benin, West Africa by a FACS based assay.

Results: All the three peptide pools elicited a CD4 T cell response in a proportion of malaria-exposed and non-exposed donors. CD4 T cell proliferation occurs at a relatively higher magnitude to peptide pools from the DBLalpha and EXON 2 in the malaria-exposed donors living in Benin than in the UK malaria-unexposed donors.

Conclusions: These findings suggest that an immunological recall response to conserved peptides of a variant antigen can be measured. Further testing of individual peptides in a positive pool will allow us to determine those conserved sequences recognised by many individuals. These types of assays may provide information on conserved peptides of PfEMP1 which could be useful for stimulating T cells to provide help to P. falciparum specific B cells.

Show MeSH

Related in: MedlinePlus

Three pools of the relatively conserved peptides from PfEMP1. Pool 1 is from the DBLα domain, pool 2 contains two peptides from CIDRα and ten from DBLβ-δ and CIDRβ domains and pool 3 contains conserved peptides from the intracellular EXON 2 domain. The peptides were selected as representative of 15 var gene sequences as described in the Materials and Methods Section. TM stands for transmembrane region.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC111505&req=5

Figure 1: Three pools of the relatively conserved peptides from PfEMP1. Pool 1 is from the DBLα domain, pool 2 contains two peptides from CIDRα and ten from DBLβ-δ and CIDRβ domains and pool 3 contains conserved peptides from the intracellular EXON 2 domain. The peptides were selected as representative of 15 var gene sequences as described in the Materials and Methods Section. TM stands for transmembrane region.

Mentions: PfEMP1 is a highly variant antigen, with the variable domains within the extra-cellular region coded for by EXON 1 and a relatively conserved intracellular region coded for by EXON 2 (Figure 1). PfEMP1 has been identified as the molecule responsible for intra-vascular sequestration of P. falciparum-infected red blood cells [3,4], a factor which has been associated with the pathogenesis of a severe malaria syndrome (cerebral malaria) [5]. The role of PfEMP1 in cytoadherence, when considered together with the fact, that antibodies to variants of PfEMP1 have been reported to occur in people living in malaria-endemic regions, buttresses the notion that PfEMP1 is indeed an important target for malaria immunity. Furthermore, the number of parasite variants recognised by the sera of these people increases with age and hence, exposure to many parasite variants [2,6]. This indicates that sequential accumulation of antibodies to the different variant molecules present in the local malaria parasite population contributes to the partial immunity that develops to malaria infection. Variant specific antibody responses are likely to require CD4 T cell help. CD4 T cells recognising conserved peptides of a malarial antigen would be potentially more beneficial in malaria immunity, as a memory response from such T cells could provide a rapid help for the variant specific antibody responses. However, it is impractical to determine if a recall response occurs to the conserved portions of a variant antigen by producing recombinant proteins or synthetic peptides of the conserved regions of all known or published sequence of the molecule.


Cellular responses to Plasmodium falciparum erythrocyte membrane protein-1: use of relatively conserved synthetic peptide pools to determine CD4 T cell responses in malaria-exposed individuals in Benin, West Africa.

Sanni LA, Allsopp CE, Reubsaet L, Sanni A, Newbold C, Chauhan VS, Langhorne J - Malar. J. (2002)

Three pools of the relatively conserved peptides from PfEMP1. Pool 1 is from the DBLα domain, pool 2 contains two peptides from CIDRα and ten from DBLβ-δ and CIDRβ domains and pool 3 contains conserved peptides from the intracellular EXON 2 domain. The peptides were selected as representative of 15 var gene sequences as described in the Materials and Methods Section. TM stands for transmembrane region.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC111505&req=5

Figure 1: Three pools of the relatively conserved peptides from PfEMP1. Pool 1 is from the DBLα domain, pool 2 contains two peptides from CIDRα and ten from DBLβ-δ and CIDRβ domains and pool 3 contains conserved peptides from the intracellular EXON 2 domain. The peptides were selected as representative of 15 var gene sequences as described in the Materials and Methods Section. TM stands for transmembrane region.
Mentions: PfEMP1 is a highly variant antigen, with the variable domains within the extra-cellular region coded for by EXON 1 and a relatively conserved intracellular region coded for by EXON 2 (Figure 1). PfEMP1 has been identified as the molecule responsible for intra-vascular sequestration of P. falciparum-infected red blood cells [3,4], a factor which has been associated with the pathogenesis of a severe malaria syndrome (cerebral malaria) [5]. The role of PfEMP1 in cytoadherence, when considered together with the fact, that antibodies to variants of PfEMP1 have been reported to occur in people living in malaria-endemic regions, buttresses the notion that PfEMP1 is indeed an important target for malaria immunity. Furthermore, the number of parasite variants recognised by the sera of these people increases with age and hence, exposure to many parasite variants [2,6]. This indicates that sequential accumulation of antibodies to the different variant molecules present in the local malaria parasite population contributes to the partial immunity that develops to malaria infection. Variant specific antibody responses are likely to require CD4 T cell help. CD4 T cells recognising conserved peptides of a malarial antigen would be potentially more beneficial in malaria immunity, as a memory response from such T cells could provide a rapid help for the variant specific antibody responses. However, it is impractical to determine if a recall response occurs to the conserved portions of a variant antigen by producing recombinant proteins or synthetic peptides of the conserved regions of all known or published sequence of the molecule.

Bottom Line: CD4 T cell proliferation occurs at a relatively higher magnitude to peptide pools from the DBLalpha and EXON 2 in the malaria-exposed donors living in Benin than in the UK malaria-unexposed donors.These findings suggest that an immunological recall response to conserved peptides of a variant antigen can be measured.These types of assays may provide information on conserved peptides of PfEMP1 which could be useful for stimulating T cells to provide help to P. falciparum specific B cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Parasitology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK. lsanni@nimr.mrc.ac.uk

ABSTRACT

Background: Plasmodium falciparum erythrocyte membrane protein-1, a variant antigen of the malaria parasite, is potentially a target for the immune response. It would be important to determine whether there are CD4 T cells that recognise conserved regions. However, within the relatively conserved region, there is variation. It is not possible to test T cell responses from small field samples with all possible peptides.

Methods: We have aligned sequences that are relatively conserved between several PfEMP1 molecules, and chosen a representative sequence similar to most of the PfEMP1 variants. Using these peptides as pools representing CIDRalpha, CIDRbeta and DBLbeta-delta domains, DBLalpha domain, and EXON 2 domain of PfEMP1, we measured the CD4 T cell responses of malaria-exposed donors from Benin, West Africa by a FACS based assay.

Results: All the three peptide pools elicited a CD4 T cell response in a proportion of malaria-exposed and non-exposed donors. CD4 T cell proliferation occurs at a relatively higher magnitude to peptide pools from the DBLalpha and EXON 2 in the malaria-exposed donors living in Benin than in the UK malaria-unexposed donors.

Conclusions: These findings suggest that an immunological recall response to conserved peptides of a variant antigen can be measured. Further testing of individual peptides in a positive pool will allow us to determine those conserved sequences recognised by many individuals. These types of assays may provide information on conserved peptides of PfEMP1 which could be useful for stimulating T cells to provide help to P. falciparum specific B cells.

Show MeSH
Related in: MedlinePlus