THE INHIBITION OF NUCLEIC ACID AND PROTEIN SYNTHESIS IN TRYPANOSOMA LEWISI BY THE ANTIBODY ABLASTIN

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Abstract
The rate of protein synthesis in infections started with adult Trypanosoma lewisi was highest, during the course of infection, within a few hours after washed ablastin-inhibited parasites were placed in ablastin-free rats. It decreased rapidly during the first 3 days of the infection before the appearance of appreciable amounts of ablastin. The same is probably true for nucleic acid synthesis although our earlier observations were only made at 2 days. The rates of nucleic acid and protein synthesis observed on day 3, when trypanosomes were rapidly dividing, markedly decreased thereafter as ablastin was formed. Thus, on the 10th day of the infection, nucleic acid synthesis had virtually stopped and protein synthesis was inhibited by more than 50% as compared to the 3-day rate. Protein synthesis continued at a low grade for several weeks although at a gradually decreasing rate. These conclusions were reached by injecting rats once with S35-amino acids or adenine-8-C14 from 0 to 19 or 22 days after infection and killing the rats from 1 to 3 hours later to obtain trypanosomes for radioassay. The foregoing conclusion were corroborated by experiments with passively transferred ablastin and by in vitro experiments. Following a single injection of S35-amino acids into rats with 3-day or with 6- to 12-day infections, the rate of protein incorporation was faster and reached a higher peak in dividing than in adult trypanosomes. The loss in radioactivity was also faster, especially at first, in the dividing forms. Radioassay determinations were made from 20 minutes to 48 hours.