Cysteine proteinases are important virulence factors, which are encoded by at least six genes. Noninvasive E. dispar has at least four of the same genes, but releases significantly less cysteine proteinase activity. We are investigated differences in the synthesis and release of cysteine proteinases in E. histolytica and noninvasive E. dispar. We have developed the first vector which will integrate into the E. histolytica genome using pseudotyped retroviruses. We can now take advantage of transgenic amebae expressing different cysteine proteinase genes or antisense RNA as well as novel new cysteine proteinase inhibitors to further our understanding of a key virulence factor of E. histolytica.
Toxoplasmosis is one of the most common parasitic infections of man.
Although a number of drug regimens have been used effectively, all are limited by toxic side effects and life-long suppression is required. Thus, the identification of potential new drug targets is critically important. We have cloned a cysteine proteinase gene in T. gondii and have purified the native enzyme using cross-reactive antibodies. We can now localize the proteinase, evaluate its release, and determine the effect of specific cysteine proteinase inhibitors on parasite survival. We will also develop proteinase gene knock-outs which can be tested in animal models.