Background
Scrub typhus, caused by Orientia tsutsugamushi, involves infiltration of a mixture of perivascular lymphocytes and macrophages into affected organs. We investigated if this is characterized by chemokine dysregulation.
Conclusions
Our findings suggest that CCL7 could represent a hitherto unknown pathogenic mediator in O tsutsugamushi infection, contributing to local and systemic inflammation.
Methods
mRNA expression of chemokines and receptors was screened in whole blood by cDNA microarray in a subgroup of patients and controls. Regulated transcripts were analyzed in plasma by enzyme immunoassays (chemokines) and in whole blood by quantitative polymerase chain reaction (receptors) from patients with scrub typhus (n = 129), patients with similar febrile illness without O tsutsugamushi infection (n = 31), and healthy controls (n = 31).
Results
cDNA microarray identified dysregulation of the chemokines CCL18 and CCL23 and the receptor CCR3 in severe scrub typhus. Plasma CCL7 (a ligand for CCR3), CCL18, and CCL23 were higher in patients with scrub typhus, with a decline during follow-up. Conversely, mRNA levels of CCR3 and CCR8 (the receptor for CCL18) were decreased in whole blood at hospital admission, followed by an increase during follow-up. CCL7 was independently associated with disease severity. Admission CCL7 levels were associated with short-time mortality. Conclusions: Our findings suggest that CCL7 could represent a hitherto unknown pathogenic mediator in O tsutsugamushi infection, contributing to local and systemic inflammation.