Introduction: Plasmodium vivax causes approximately 80-100
million clinical cases every year. It is the most prevalent human
malaria parasite in the American continent and its prevalence is second
only to P. falciparum worldwide. Due to the emergence of
medication-resistant parasites and an increase in insecticide-resistant
mosquitoes, research to find a vaccine that could prevent or limit the
clinical manifestations of the disease has increased greatly. During
the last two decades, significant progress has been achieved in this
attempt; however, the development of a P. vivax vaccine has been
hampered due to the lack of sustainable in vitro parasite cultures.
Objectives: We describe the development and testing of a vaccine to P.
vivax pre-erythrocytic stages. We selected the circumsporozoite (CS)
protein, an antigen abundantly expressed on the parasite surface.
Methodology: After extensive immunological characterization in vitro,
three long peptides (N, R and C) were synthesized, and the toxicity and
immunogenicity of these peptides were thoroughly assessed in animals.
To determine the safety and immunogenicity in humans, a randomized,
double blind clinical trial was conducted. The trial included 23
healthy volunteers who received 100 μg of N, R and C of each
peptide formulated in Montanide ISA-720 adjuvant. Conclusions: The
vaccination was well tolerated and proven to be safe in both animals
and volunteers; thus, additional clinical trials utilizing this vaccine
candidate are indicated
