The Plasmodium yoelii yoelli genome contains around 35 genes encoding 235 kD rhoptry proteins (Py235) that are involved in erythrocyte invasion and parasite virulence. In the January 11 issue of Science, Preiser et al. describe the transcription pattern of py235 genes during the parasite's life cycle and their role in cell invasion (Science 2002, 295:342-345).

Immunofluorescence analysis using antibodies recognizing distinct Py235 proteins revealed differences between pre-erythrocytic and erythrocytic parasites. Antibodies to Py235 expressed in the sporozoite were found to inhibit invasion, whereas those to the blood stage proteins were not. They analyzed stage-specific expression of py235 transcripts by RT-PCR, and found that genes transcribed in the sporozoite and hepatic forms differed from those in the erythrocytic parasite. Non-overlapping sets of py235 genes are associated with the sporozoite, hepatic schizont and erythrocytic schizont developmental stages.

The distinct rhoptry proteins in the sporozoites and liver stages, may offer...

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