Promotion of tick cell growth by proline and fractions from tick eggs

Tick cell lines representing three genera (Rhipicephalus appendiculatus, Dermacentor variabilis and Boophilus microplus) were grown in basal medium containing different supplements. Their effect on cell growth was measured by determining the rate at which cultures were transferred. The optimal concentration of the foetal bovine serum was 5% for the Boophilus line and 10% for the other two. Addition.of tick egg extract (TEE) increased the splitting rate 1.5-2.4 times during a period of 30 days, and changed the morphology of some cells. The crude TEE was delipidized and the protein and lipid fractions were analyzed for biological activity. The delipidized protein fraction of the TEE improved the splitting rate to about the same degree as the crude TEE. Adding l-proline to the basal medium increased the splitting rate 1.2-1.9-fold, or nearly to the same degree as did the crude TEE. The addition of the lipid and aqueous polar fractions of TEE did not improve cell growth.