C-C Motif Ligand 7 (CCL7) and C-C Motif Chemokine Receptor 3 (CCR3) dysregulation in patients with scrub typhus and association with mortality.

ABSTRACT

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. METHODS: mRNA expression of chemokines and receptors were 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 qPCR (receptors) from scrub typhus patients (n=129), patients with similar febrile illness without Orentia tsutsugamushi infection (n=31) and healthy controls (n=31). RESULTS: (i) cDNA microarray identified dysregulation of the chemokines CCL18 and CCL23 and CCR3 receptor, in severe scrub typhus. (ii) Plasma CCL7, a ligand for CCR3, CCL18 and CCL23 were higher in scrub typhus patients, with a decline during follow-up. (iii) 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. (iv) CCL7 was independently associated with disease severity. (v) Admission CCL7 levels were associated with short-time mortality. CONCLUSION: Our findings suggest CCL7 could represent a hitherto unknown pathogenic mediator in Orentia tsutsugamushi infection contributing to local and systemic inflammation.