Antigenicity and immunogenicity of PvRALP1, a novel Plasmodium vivax rhoptry neck protein

Yang Cheng, Jian Li, Daisuke Ito, Deok Hoon Kong, Kwon Soo Ha, Feng Lu, Bo Wang, Jetsumon Sattabongkot, Chae Seung Lim, Takafumi Tsuboi, Eun Taek Han

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Background: Proteins secreted from the rhoptry in Plasmodium merozoites are associated with the formation of tight junctions and parasitophorous vacuoles during invasion of erythrocytes and are sorted within the rhoptry neck or bulb. Very little information has been obtained to date about Plasmodium vivax rhoptry-associated leucine (Leu) zipper-like protein 1 (PvRALP1; PVX-096245), a putative rhoptry protein. PvRALP1 contains a signal peptide, a glycine (Gly)/glutamate (Glu)-rich domain, and a Leu-rich domain, all of which are conserved in other Plasmodium species. Methods: Recombinant PvRALP1s were expressed as full-length protein without the signal peptide (PvRALP1-Ecto) and as truncated protein consisting of the Gly/Glu- and Leu-rich domains (PvRALP1-Tr) using the wheat germ cell-free expression system. The immunoreactivity to these two fragments of recombinant PvRALP1 protein in serum samples from P. vivax-infected patients and immunized mice, including analysis of immunoglobulin G (IgG) subclasses, was evaluated by enzyme-linked immunosorbent assay or protein microarray technology. The subcellular localization of PvRALP1 in blood stage parasites was also determined. Results: Recombinant PvRALP1-Ecto and PvRALP1-Tr proteins were successfully expressed, and in serum samples from P. vivax patients from the Republic of Korea, the observed immunoreactivities to these proteins had 58.9% and 55.4% sensitivity and 95.0% and 92.5% specificity, respectively. The response to PvRALP1 in humans was predominantly cytophilic antibodies (IgG1 and IgG3), but a balanced Th1/Th2 response was observed in mice. Unexpectedly, there was no significant inverse correlation between levels of parasitaemia and levels of antibody against either PvRALP1-Ecto (R 2∈=∈0.11) or PvRALP1-Tr (R 2∈=∈0.14) antigens. PvRALP1 was localized in the rhoptry neck of merozoites, and this was the first demonstration of the localization of this protein in P. vivax. Conclusions: This study analysed the antigenicity and immunogenicity of PvRALP1 and suggested that PvRALP1 may be immunogenic in humans during parasite infection and might play an important role during invasion of P. vivax parasites.

Original languageEnglish
Article number186
JournalMalaria Journal
Issue number1
Publication statusPublished - 2015 Apr 29

Bibliographical note

Funding Information:
This work was supported by National Research Foundation (NRF) of Korea Grant funded by the Korea government (MEST) (2011–0016401) and a grant from the Korea Health technology R&D Project, Ministry of Health &Welfare, Republic of Korea (A121180). This work was also supported in part by MEXT KAKENHI (23117008) and JSPS KAKENHI (23406007) in Japan.

Publisher Copyright:
© 2015 Cheng et al.; licensee BioMed Central.


  • Antigenicity
  • Immunogenicity
  • Plasmodium vivax
  • RALP1
  • Rhoptry neck protein

ASJC Scopus subject areas

  • Parasitology
  • Infectious Diseases


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