Synthesis of Plasmodium knowlesi polypeptides in a cell-free system.

Preliminary results are presented concerning the characterization of Plasmodium knowlesi antigens. RNA with messenger activity has been extracted from P. knowlesi and translated in a rabbit reticulocyte cell-free system. The products of this system have been analysed both before and after precipitation with specific P. knowlesi antiserum and many polypeptides ranging in molecular weight from over 100 000 to approximately 20 000 have been found. A good correlation was found between these results and those obtained by McColin with in vitro labelling of P. knowlesi with ((3)H)-isoleucine. The major polypeptide in both systems had a molecular weight of about 50 000-55 000. These results indicate the parasite origin of the antigens.