Plasmodium falciparum Merozoite Vaccine in Aotus Monkeys: An Evaluation of the Tolerableness of Three Types of Adjuvants

Abstract

Eight Aotus trivirgatus monkeys were included in a comparative study of adverse reactions caused by 3 types of malarial vaccine. The antigen consisted of late schizonts and merozoites combined with each of 3 adjuvants, a lipoidal amine CP-20,961, a muramvl dipeptide derivative [B30]-MDP, or Freund's complete adjuvant (FCA); 3 monkeys received CP-20,961 and 3 [B30]-MDP, whereas the FCA vaccine was given to 2 animals. All the vaccine combinations caused some adverse reactions, but their nature and intensity varied. Oedema, petechiae and/or ecchymosis, induration, and formation of fluctuating masses at the injection site were the local reactions observed, but except for the FCA group, all reactions disappeared without notable sequelae. Fever was the commonest general reaction, being mildest in the [B30]-MDP group. A transient increase (about 50%) in leukocyte count and a decrease (15-20%) in red blood cell count were observed in all animals, regardless of the type of adjuvant or whether it was a primary or booster injection in question. However, because the vaccine using [B30]-MDP evoked the mildest reactions, this may be the one most promising for future human studies if its protective efficacy is proven.