Vaccination with <i>Plasmodium vivax</i> Duffy-binding protein inhibits parasite growth during controlled human malaria infection.

Abstract

There are no licensed vaccines against <i>Plasmodium vivax</i>. We conducted two phase 1/2a clinical trials to assess two vaccines targeting <i>P. vivax</i> Duffy-binding protein region II (PvDBPII). Recombinant viral vaccines using chimpanzee adenovirus 63 (ChAd63) and modified vaccinia virus Ankara (MVA) vectors as well as a protein and adjuvant formulation (PvDBPII/Matrix-M) were tested in both a standard and a delayed dosing regimen. Volunteers underwent controlled human malaria infection (CHMI) after their last vaccination, alongside unvaccinated controls. Efficacy was assessed by comparisons of parasite multiplication rates in the blood. PvDBPII/Matrix-M, given in a delayed dosing regimen, elicited the highest antibody responses and reduced the mean parasite multiplication rate after CHMI by 51% (<i>n</i> = 6) compared with unvaccinated controls (<i>n</i> = 13), whereas no other vaccine or regimen affected parasite growth. Both viral-vectored and protein vaccines were well tolerated and elicited expected, short-lived adverse events. Together, these results support further clinical evaluation of the PvDBPII/Matrix-M <i>P. vivax</i> vaccine.