Human neutrophil-like cells demonstrate antimicrobial responses to the
chronic cyst form of Toxoplasma gondii
Abstract
The protozoan parasite Toxoplasma gondii infects approximately
2.5 billion people worldwide. Infection induces a rapid dissemination of
parasites throughout the body followed by the formation of lifelong
cysts within neurons of the host brain. Both stages require a dynamic
immune response comprised of both innate and adaptive cells. Neutrophils
are a primary responding cell to acute infection and have been observed
in the brain during murine chronic infection. Previous studies
investigating human neutrophils found that invasion by Toxoplasma
tachyzoites inhibits apoptosis of neutrophils, prolonging their survival
under inflammatory conditions. Here, we demonstrate the differentiation
of two distinct subsets following exposure of human
neutrophil-like-cells (HNLC) to Toxoplasma cysts. In vitro
stimulation and imaging studies show cyst-specific induction of
cytokines and cyst clearance by HNLCs. Further testing demonstrates that
aged HNLCs perform less phagocytosis of cysts compared to non-aged
HNLCs. In conclusion, this study identifies a novel response of HNLCs to
Toxoplasma cysts and may indicate a role for neutrophils in the
clearance of cysts during human infection with Toxoplasma.