Immunogenicity and Protective Efficacy of Recombinant Vaccine Based on the Receptor-Binding Domain of the Plasmodium Vivax Duffy Binding Protein in Aotus Monkeys

Abstract

Invasion of human erythrocytes by Plasmodium vivax requires interaction between Duffy binding protein (PvDBP) and the Duffy blood group antigen. The receptor-binding domain of PvDBP lies in a conserved N-terminal, cysteine-rich region, region II (PvRII). PvRII is a valuable malaria subunit vaccine candidate for asexual blood stages. We have evaluated in Aotus monkeys the immunogenicity and protective efficacy of recombinant PvRII formulated in Freund's and Montanide ISA720 adjuvants. Specific antibody titers were determined by an enzyme-linked immunosorbent assay after each of three doses of 50 microg of protein administered by the subcutaneous route. Immunization with PvRII formulated in Freund's adjuvant yielded higher antibody titers than immunization with the Montanide ISA720 formulation and offered partial protection. Although the Montanide ISA720 formulation was immunogenic, it did not provide any protection. Given the immunogenicity and partial protection observed, further studies are needed to optimize the PvRII vaccine formulation with adjuvants suitable for human use.

Phase I Safety and Immunogenicity Trial of Plasmodium vivax CS Derived Long Synthetic Peptides Adjuvanted with Montanide ISA 720 or Montanide ISA 51

“…These adjuvants were selected because they form stable water-in-oil emulsions and induced high antibody levels that lasted for up to 1 year in mice, rabbits, and monkeys in previous studies using recombinant malaria proteins. 23,[26][27][28][29][30][31][32] More recently, a recombinant P. vivax CS protein produced in Escherichia coli and formulated in Montanide ISA 720 showed to be highly immunogenic in mice. 33 Several phase I clinical trials have been conducted using different malaria vaccine antigens in which these two adjuvants have been able to stimulate both humoral and cellular immune responses.…”

Plasmodium vivax thrombospondin related adhesion protein: immunogenicity and protective efficacy in rodents and Aotus monkeys

“…The peptide proved to be immunogenic in both animal species when formulated in Freund's adjuvant not acceptable for human use, as well as in Montanide ISA 720 currently being used in human vaccine trials. Although, mice developed a steadily increasing antibody pattern since the first immunization and those antibodies cross reacted with et al 2005aet al ,b, Herrera et al 2005. Furthermore, T cell responses appear to be the most efficient mechanisms of protection against malaria pre-erythrocytic forms; however in this study the production of IFN-γ specifically in response to stimulation with PvTRAP peptide was not demonstrated most probably due to ineffective stimulation of CD4 + and/or CD8 + T-cells by the vaccine formulation used.…”

Immune Responses and Protection of Aotus Monkeys Immunized with Irradiated Plasmodium vivax Sporozoites

“…Next, the blood was transported at 37 ± 1°C to the Immunology Institute at Universidad del Valle in Cali and used for mosquito feeding, using an artificial membrane system. 28 On Day 14 before sporozoite isolation, batches of infected mosquitoes were placed in an acrylic box and irradiated for 1 hour using a 60 Co source at the Radiotherapy Unit of the Hospital Universitario del Valle -a time calculated to deliver 150 Gy (15K Rad).…”

“…In addition, parasitemia results were confirmed by PCR using DNA extracted from glass slides previously used for thin blood smears, using QIAamp DNA mini-kit (Qiagen, Carlsbad, CA). 28 The sensitivity of this DNA nested PCR was 10 parasites/μL of blood.…”

“…28 Briefly, ELISA was performed as follows: microplates (Nunc-Immuno Plate, Maxisorp, RoskildeDenmark) were coated overnight at 4°C with the CS peptides at a concentration of 1 μg/mL in PBS. Plates were then blocked with 5% skim milk in PBS, pH 7.4, for 2 hrs at room temperature.…”