Bovine babesiosis is a tick-borne disease caused by protozoan parasites of the Babesia genus that affects livestock production worldwide, being B. bovis the most virulent species. The definition of the proteins involved in the parasite’s virulence is essential to understand the host-pathogen interaction and develop novel strategies to control the disease. The characterization of the Perforin-like protein (PLP) family of B. bovis is of special interest since these pore-forming proteins are critical for pathogenesis and cell invasion in closely related parasites but have not been characterized in Babesia sp. so far. B. bovis PLP1 protein was selected as an initial candidate for the functional characterization of the PLP family. Previous studies show that plp1, one of the six plp genes in B. bovis, is ortholog to Plasmodium and Toxoplasma plps that were proven to be essential for pathogenesis, and also it is highly expressed. The aim of this project is to perform a functional characterization of the PLP1 protein of B. bovis through the generation of plp1 knock out (KO) parasites, followed by phenotypic analysis to evaluate its capability of replication and virulence in comparison to the wild type (WT) virulent strain. To perform these studies, molecular tools for the genetic manipulation of B. bovis that are not available in Argentina are required. Dr. Suarez's laboratory (Washington State University) was the first to develop the methodology for the genetic manipulation of B. bovis, thus the possibility of carrying out this project at his lab and is invaluable. This project will provide information to improve our understanding of the biology of Babesia sp., to investigate and define virulence mechanisms, and to better characterize key parasite-host interactions. Also, it will contribute to the development of novel therapeutic and preventive strategies against babesiosis. Advances in the control of babesiosis will bring about a significant increase in the livestock production of Argentina.