Saeij LabUC Davis · School of Veterinary Medicine

Host–parasite interactions

How Toxoplasma takes over a cell, and how the host fights back.

Toxoplasma gondii infects about a third of humanity and nearly every warm-blooded animal. We find the parasite genes that let it spread, hide from the immune system and persist, and the host genes that decide who gets sick.

Our research
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Fluorescence micrograph of a dendritic cell infected with Toxoplasma parasites lacking TgWIP: F-actin in green, nucleus in blue, parasites in red.
A dendritic cell infected with Toxoplasma lacking the secreted effector TgWIP. F-actin green, nucleus blue, parasites red. Without TgWIP, the cell keeps its podosomes and loses the hypermotility that spreads the parasite.

What we study

Four questions, one parasite

Read about our research

Spreading through the host

In vivo CRISPR screens map the parasite genes needed to cross barriers and reach distant organs. The secreted effector TgWIP rewires dendritic cell actin and motility, and GRA28 and other GRAs turn infected macrophages hypermigratory.

Surviving interferon-γ

Genome-wide screens in naive and IFNγ-activated mouse and human cells reveal how the parasite withstands the host’s main antiparasitic cytokine, from GRA45’s chaperone-like role to TgIST’s silencing of STAT1 targets.

Life inside the vacuole

The parasite grows inside a vacuole it must feed through. We study the pores (GRA17, GRA23, GRA47, GRA72) and the lipid machinery (GRA38, TgSEC14-LTP1) that move small molecules and lipids across its membrane.

Host and parasite genetics

Why do some strains blind and others go unnoticed? Why do rats resist and mice succumb? We trace outcomes to strain-specific effectors such as ROP16 and GRA15 and to host pathways such as the NLRP1 inflammasome.

Recent papers

Latest from the lab

All 99 publications

Funding

Supported by the NIH

Our research is funded by the National Institute of Allergy and Infectious Diseases, and our training by the NIH Office of the Director. The full award history is on the research page.

  • Mechanisms of host leukocyte-mediated Toxoplasma dissemination in its hostNIH/NIAID R01 AI166715 · 2022–2027 · with Baoyu Chen
  • Restriction of Toxoplasma growth in human cellsNIH/NIAID R01 AI173803 · 2023–2028
  • Comparative Medical Science Training ProgramNIH/OD T32 OD011147 · since 2023 · with Sara Michelle Thomasy
Nine members of the Saeij lab posing outdoors in 2021.

The lab

A small, international group

We are postdocs, graduate students and undergraduates in the Department of Pathology, Microbiology & Immunology at the UC Davis School of Veterinary Medicine, working side by side on the same parasite from very different angles.

“A lab with people from different backgrounds and countries is what keeps our research innovative.”

Everyone who is excited about host–parasite interactions is welcome here, regardless of background, nationality or immigration status.

Meet the lab