Capture and Detection of Plasmodium vivax Lactate Dehydrogenase in a Bead-Based Multiplex Immunoassay

Abstract

Laboratory detection of malaria antigens has proved valuable for research and epidemiological purposes. We recently developed a bead-based multiplex antigen assay for pan-Plasmodium and Plasmodium falciparum targets. Here, we report integration of a Plasmodium vivax-specific target to this multiplex panel: P. vivax lactate dehydrogenase (PvLDH). Within the multiplex panel, assay signal for purified PvLDH antigen titrated into the single-digit picogram range. Against a panel of polymerase chain reaction (PCR)-confirmed samples from acute P. vivax infections (n = 36), sensitivity was 91.7% in using PvLDH detection for identifying the presence of parasites. Specificity against a panel of persons with no Plasmodium infection (n = 44) was 100%, and specificity against a panel of PCR-confirmed P. falciparum, Plasmodium malariae, or Plasmodium ovale infections (n = 164) was 90.2%. Addition of this PvLDH capture and detection system into the multiplex antigen panel will now allow for sensitive screening for species identification of both P. falciparum and P. vivax in the laboratory.

Figure 1.

Detection of Plasmodium falciparum and Plasmodium vivax lactate dehydrogenase (LDH) by multiplex bead assay. Panels displayed for serial dilution series of both isoforms of LDH from 20,480,000 to 2.4 pg/mL. Assay signal specific for pan-Plasmodium LDH (pLDH) capture/detection is shown in blue lines with circles, and assay signal specific for P. vivax LDH (PvLDH) capture/detection shown in black lines with squares. Titration curves show average of results from two independent runs with error bars indicating SD.

Figure 2.

Assay signal for Plasmodium lactate dehydrogenase (pLDH) and P. vivax LDH (PvLDH) detection when testing samples from persons with no detectable Plasmodium infection or infection with one of the four human malarias. Multiplex bead assay signal shown for U.S.–based blood donors with no detectable Plasmodium infection (n = 44) (A) or an infection with one of the human malarias (B) Plasmodium falciparum (n = 148, blue circles), P. malariae (n = 4, black circles), P. ovale (n = 12, green circles), or Plasmodium vivax (n = 36, red circles) as confirmed by PCR.