Toxoplasma Gondii Pathogenesis and Immunology

Toxoplasma gondii is an obligate intracellular parasite of the phylum Apicomplexa that infects a broad range of warm-blooded hosts, including humans. Infection typically begins with the rapidly dividing tachyzoite form, which disseminates systemically and elicits a robust innate immune response driven by macrophages, dendritic cells and natural killer cells. Interferon-γ produced by T cells and natural killer cells is pivotal in controlling parasite replication and promoting conversion to the slow-growing bradyzoite stage within tissue cysts, which underpins chronic infection. Immune evasion strategies employed by the parasite include manipulation of host signalling pathways, secretion of effector proteins and modulation of antigen presentation. Pathogenesis arises both from direct tissue damage during acute replication and from immune-mediated inflammation, with particular impact on the central nervous system, retina and myocardium. Understanding the interplay between parasite developmental transitions, nutrient acquisition and host defences is critical for the development of new interventions against toxoplasmosis.

Research from Nature Portfolio

Recent studies have achieved the in vitro generation of pre-sexual stages of T. gondii that were once confined to the feline intestine. By depleting two ApiAP2 transcription factors simultaneously, researchers induced tachyzoites to convert into merozoites, revealing an epigenetic rewiring mechanism that governs developmental commitment. This breakthrough offers a platform for studying sexual development without relying on cat hosts. In parallel, ultrastructural and functional analyses have identified a specialised organelle, the micropore, as a key site for endocytic uptake of host-derived nutrients. The kelch-domain protein at its neck functions as a hub for cargo selection, and maximal activity of this machinery depends on the parasite’s own ceramide synthesis. This work sheds light on critical pathways for parasite growth and suggests new targets for therapeutic intervention.

Toxoplasma Gondii Pathogenesis and Immunology publication trend

The graph below shows the total number of articles in toxoplasma gondii pathogenesis and immunology across all publications each year (not limited to Nature Index journals).

Technical terms

Tachyzoite: The fast-replicating stage responsible for acute infection and tissue dissemination.

Bradyzoite: The slow-growing, encysted stage that establishes chronic infection in host tissues.

Merozoite: A developmental form in the feline intestine that gives rise to gametes during the parasite’s sexual cycle.

Micropore: A plasma membrane invagination on intracellular parasites that mediates selective endocytosis of host nutrients.

Effector protein: A parasite-secreted molecule that manipulates host cell signalling and immune responses to favour survival.

References

1. In vitro production of cat-restricted Toxoplasma pre-sexual stages. Nature (2023).
2. The Toxoplasma micropore mediates endocytosis for selective nutrient salvage from host cell compartments. Nature Communications (2023).
3. High-throughput identification of Toxoplasma gondii effector proteins that target host cell transcription. Cell Host & Microbe (2023).
4. Gut microbiota mediates anxiety-like behaviors induced by chronic infection of Toxoplasma gondii in mice. Gut Microbes (2024).