Measurement of naturally acquired humoral immune responses against the C-terminal region of the Plasmodium vivax MSP1 protein using protein arrays.

Protein arrays are powerful tools for antibody profiling and vaccine development against infectious agents. In the previous report, we successfully applied an antibody-based protein array for immunoprofiling of Plasmodium vivax infection. Herein, we developed a Ni-NTA surface based protein array to detect immune responses against the recombinant C-terminal region (19 and 42 kDa) of the P. vivax merozoite surface protein 1 (PvMSP1-19 and -42) from sera of vivax malaria patients. The PvMSP1-19 arrays detected P. vivax in 112 of 130 (86.2%; 95% CI, 83.2-89.2%) microscopically positive samples and 2 false positives were obtained among 100 sera samples from healthy subjects (2.0%; 95% CI, 0.6-3.4%). These results were in concordance with results of enzyme-linked immunosorbent assays (ELISA). Kappa values represented excellent agreement for the recombinant PvMSP1-19 protein against sera samples as measured by protein arrays and ELISA (Kappa=0.904, 95% CI: 0.849-0.960). The PvMSP1-42 protein arrays detected antibody response in 100 of 130 microscopically positive samples (76.9%; 95% CI, 72.4-86.8%) and 8 false positives were obtained in 100 healthy subjects (8.0%; 95% CI, 2.7-13.3%). There is no significant difference between the fluorescent intensity of antibody response to PvMSP1-19 and PvMSP1-42 in the positive sera samples (P>0.05). The novel protein array platform may be used for profiling naturally acquired humoral immune responses to P. vivax infection.