Annemarie M Voorberg - van der Wel

Publications (24) View all

• Article: Molecular characterisation of Plasmodium reichenowi apical membrane antigen-1 (AMA-1), comparison with P. falciparum AMA-1, and antibody-mediated inhibition of red cell invasion.

  C H Kocken, D L Narum, A Massougbodji, B Ayivi, M A Dubbeld, A van der Wel, D J Conway, A Sanni, A W Thomas
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  ABSTRACT: Apical membrane antigen 1 is a candidate vaccine component for malaria. It is encoded by a single copy gene and has been characterised in a number of malaria species as either an 83-kDa de novo product (Plasmodium falciparum; Pf AMA-1) or a 66-kDa product (all other species). All members of the AMA-1 family are expressed during merozoite formation in maturing schizonts and are initially routed to the rhoptries. Processed forms may subsequently be associated with the merozoite surface. Because of the unique occurrence of the 83-kDa form in P. falciparum we were interested to determine whether the phylogenetically closely related chimpanzee malaria Plasmodium reichenowi shared characteristics with Pf AMA-1. Here we show that the molecular structure, the localisation and processing are similar to that of Pf AMA-1 and that in vitro growth inhibitory mAbs reactive with Pf AMA-1 also inhibit P. reichenowi growth in an in vitro assay. Polymorphism in the 83-kDa AMA-1 family was analysed through comparison of Pr ama-1 with Pf ama-1 alleles, which showed the most significant evidence for selection maintaining polymorphism in Domains I-III of AMA-1 in P. falciparum. The most substantial divergence between Pr AMA-1 and Pf AMA-1 sequences was in the N-terminal region unique to the 83-kDa form of AMA-1. It was confirmed that the specific Pr ama-1-type allele was not present among P. falciparum parasites in an African population, and an allele coding for lysine at amino acid 187 was uniquely associated with field isolates in this population.
  Molecular and Biochemical Parasitology 08/2000; 109(2):147-56. · 2.55 Impact Factor
• Article: Plasmodium cynomolgi: transfection of blood-stage parasites using heterologous DNA constructs.

  C H Kocken, A van der Wel, A W Thomas
  Experimental Parasitology 10/1999; 93(1):58-60. · 2.12 Impact Factor
• Article: High-level expression of Plasmodium vivax apical membrane antigen 1 (AMA-1) in Pichia pastoris: strong immunogenicity in Macaca mulatta immunized with P. vivax AMA-1 and adjuvant SBAS2.

  C H Kocken, M A Dubbeld, A Van Der Wel, J T Pronk, A P Waters, J A Langermans, A W Thomas
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  ABSTRACT: The apical membrane antigen 1 (AMA-1) family is a promising family of malaria blood-stage vaccine candidates that have induced protection in rodent and nonhuman primate models of malaria. Correct conformation of the protein appears to be essential for the induction of parasite-inhibitory responses, and these responses appear to be primarily antibody mediated. Here we describe for the first time high-level secreted expression (over 50 mg/liter) of the Plasmodium vivax AMA-1 (PV66/AMA-1) ectodomain by using the methylotrophic yeast Pichia pastoris. To prevent nonnative glycosylation, a conservatively mutagenized PV66/AMA-1 gene (PV66Deltaglyc) lacking N-glycosylation sites was also developed. Expression of the PV66Deltaglyc ectodomain yielded similar levels of a homogeneous product that was nonglycosylated and was readily purified by ion-exchange and gel filtration chromatographies. Recombinant PV66Deltaglyc43-487 was reactive with conformation-dependent monoclonal antibodies. With the SBAS2 adjuvant, Pichia-expressed PV66Deltaglyc43-487 was highly immunogenic in five rhesus monkeys, inducing immunoglobulin G enzyme-linked immunosorbent assay titers in excess of 1:200,000. This group of monkeys had a weak trend showing lower cumulative parasite loads following a Plasmodium cynomolgi infection than in the control group.
  Infection and Immunity 02/1999; 67(1):43-9. · 4.16 Impact Factor
• Article: Transfection systems for animal models of malaria.

  A M Tomas, A M van der Wel, A W Thomas, C J Janse, A P Waters
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  ABSTRACT: Transfection of malaria parasites is a rapidly emerging technology that offers great promise for the investigation of many aspects of infection. Animal models of malaria have always played an important role in the investigation of the disease. In this article, two of the Dutch groups that have been involved in combining transfection with animal models describe the relevant techniques and recent vector developments for the expression of transgenes, giving examples of their application.
  Parasitology Today 01/1999; 14(6):245-9.
• Article: Erratum.

  A M Tomas, A M van der Wel, A W Thomas, C J Janse, A P Waters
  Parasitology Today 09/1998; 14(8):336.