Long term studies on rhesus monkeys (Macaca mulatta) immunized against Plasmodium knowlesi

Abstract

Studies carried out on 4 rhesus monkeys (macaca mulatta) vaccinated against Plasmodium knowlesi, showed that the immunized animals were protected against a challenge with a heterologous strain of P. knowlesi. This protection was shown to be present even 4 years after the immunization schedule had been completed. The effect could not be attributed to previous infections with the parasite, since 4 control rhesus monkeys that had recovered from 1 to 4 challenges with P. knowlesi died when exposed to the heterologous strain. Data obtained from the lymphocyte transformation test and the radioimmunoassay are also presented.