title: Immunogenicity of bacterial-expressed recombinant Plasmodium knowlesi merozoite surface protein-142 (MSP-142).
abstract: BACKGROUND
  Plasmodium knowlesi is the fifth Plasmodium species that can infect humans. The Plasmodium merozoite surface protein-1(42) (MSP-1(42)) is a potential candidate for malaria vaccine. However, limited studies have focused on P. knowlesi MSP-1(42).
  
  
  METHODS
  A ~42 kDa recombinant P. knowlesi MSP-1(42) (pkMSP-1(42)) was expressed using an Escherichia coli system. The purified pkMSP-1(42) was evaluated with malaria and non-malaria human patient sera (n = 189) using Western blots and ELISA. The immunogenicity of pkMSP-1(42) was evaluated in mouse model.
  
  
  RESULTS
  The purified pkMSP-1(42) had a sensitivity of 91.0% for detection of human malaria in both assays. Specificity was 97.5 and 92.6% in Western blots and ELISA, respectively. Levels of cytokine interferon-gamma, interleukin-2, interleukin-4, and interleukin-10 significantly increased in pkMSP-1(42)-immunized mice as compared to the negative control mice. pkMSP-1(42)-raised antibody had high endpoint titres, and the IgG isotype distribution was IgG1 > IgG2b > IgG3 > IgG2a.
  
  
  CONCLUSIONS
  pkMSP-1(42) was highly immunogenic and able to detect human malaria. Hence, pkMSP-1(42) would be a useful candidate for malaria vaccine development and seroprevalence studies.
authors.forename: Fei Wen
authors.initials: FW
authors.lastname: Cheong
authors.affiliation: Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia. fongmy@um.edu.my.
authors.forename: Mun Yik
authors.initials: MY
authors.lastname: Fong
authors.forename: Yee Ling
authors.initials: YL
authors.lastname: Lau
authors.forename: Rohela
authors.initials: R
authors.lastname: Mahmud
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D015153:Blotting, Western; D003001:Cloning, Molecular; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D017780:Malaria Vaccines / Q000235:genetics / Q000276:immunology; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D052940:Merozoites / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D016790:Plasmodium knowlesi / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D012698:Serologic Tests / Q000379:methods
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D017780:Malaria Vaccines; D008565:Membrane Proteins; D011994:Recombinant Proteins