| Summary: | The protozoan parasite <i>Leishmania donovani</i> is a causative agent of the neglected tropical disease known as visceral leishmaniasis, which can be lethal when untreated. Studying <i>Leishmania</i> viru-lence factors is crucial in determining how the parasite causes disease and identifying new targets for treatment. One potential virulence factor is <i>L. donovani’s</i> abundantly secreted protein: secreted acid phosphatase (SAcP). Whole-genome analysis revealed that the <i>sacp</i> gene was present in three copies in wild type <i>L. donovani</i>. Using CRISPR-Cas9 gene editing; we generated a <i>sacp</i> gene knockout termed LdΔSAcP, which demonstrated a loss of both the SAcP protein and an associated reduction in secreted acid phosphatase activity. Genome sequencing confirmed the precise dele-tion of the <i>sacp</i> gene in LdΔSAcP and identified several changes in the genome. LdΔSAcP demonstrated no significant changes in promastigote proliferation or its ability to infect and survive in macrophages compared to the wildtype strain. LdΔSAcP also demonstrated no change in murine liver infection; however, survival was impaired in the spleen. Taken together these results show that SAcP is not necessary for the survival of promastigotes in culture but may support long-term survival in the spleen. These observations also show that the use of CRISPR gene editing and WGS together are effective to investigate the function and phenotype of complex potential drug targets such as multicopy genes.
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