Impact of Parkinson’s Disease and Cytomegalovirus Serostatus on the Frequencies of Chemokine Receptor-Expressing Leukocytes

Persons with Parkinson’s Disease (pwPD) exhibit an underlying systemic inflammation which is thought to contribute to neurodegeneration. The root cause of this chronic inflammatory state is unclear. We hypothesised that one factor contributing to it is the accumulation of late-differentiated/senescent immune cells, exacerbated by infection with persistent pathogens, especially cytomegalovirus (CMV). To test whether CMV infection impacts pwPD differently than healthy matched controls, we determined the frequencies of peripheral blood immune cells (including late-differentiated/senescent T-cells, NK-cells, NKT-cells, B-cells and monocytes) of 75 CMV-seronegative (median, 68 years old) and 99 CMV-seropositive pwPD (69 yo) using flow cytometry. Further, we included a control group of 10 CMV-seronegative (67 yo) and 14 CMV-seropositive individuals (68 yo). Our analyses of blood immune cell phenotypes confirmed a strong impact of CMV infection in both controls and pwPD, but with very few differences attributable to disease state. However, independent of any confounding effects of CMV-serostatus, the levels of CXCR2 expression on NK-cells (p = 0.007), NKT-cells (p = 0.016) and T-cells (p = 0.015) of pwPD were higher compared to controls. The results are consistent with enhanced migration of immune cells into the brain, potentially contributing to disease pathology and offering actionable therapeutic targets.