Viral load and cytokines in the pathogenesis of severe fever with thrombocytopenia syndrome / 中华传染病杂志

ABSTRACT

Objective To observe the relationship of viral load,serum cytokines and tissue damage after severe fever with thrombocytopenia syndrome virus (SFTSV)infection,and to explore the impact of SFTSV levels on tissue injury and prognosis.Methods Twenty-four ambulatory and hospitalized patients who were infected with SFTSV were enrolled between May 2011 and July 2012 at Department of Infectious Disease, First Affiliated Hospital with Nanjiang Medical University. According to their prognosis,they were divided into cure and death group,while 32 healthy blood donators were also enrolled from center blood station in Nanjing as control.The serum SFTSV load was detected using fluorescence quantitative polymerase chain reaction (PCR).The serum T helper (Th)1/Th2/Th17 cytokines in patients with severe fever with thrombocytopenia syndrome (SFTS)were determined dynamically and quantitatively by flow cytometry.The relationships between viral load,cytokines and serum enzymes, white blood cell (WBC),platelet (PLT)counts were analyzed.Comparisons among groups were achieved by rank sum test and correlation analysis among serum cytokines,blood cell counts and tissue damage was done by Spearman correlation test.Results All of the 24 patients showed a positive reaction to SFTSV RNA.The SFTSV loads of 21 cured cases,those of 2 were > 7.0 lg copy/mL,and those of 3 death patients were 6.7 lg copy/mL,8.8 lg copy/mL and 9.8 lg copy/mL,respectively.Serum level of interleukin (IL)-6 (21 .76 pg/mL in day 5 and 7.12 pg/mL in day 7)and IL-10 (14.33 pg/mL in day 5 , 14.13 pg/mL in day 7 and 3.01 pg/mL in day 9)of cured patients were significantly higher than those of healthy controls (IL-62.82 pg/mL and IL-101 .56 pg/mL)(P <0.05 ).At day 7 and day 9,serum levels of IL-6 of death cases were 137.61 pg/mL and 1 450.83 pg/mL,respectively and serum levels of IL-10 were 50.26 pg/mL and 49.43 pg/mL,respectively.Both of the indicators in the death group were significantly higher than those of cure group (P <0.05 ).However,serum levels of IL-2 and IL-4 were significantly lower than those in healthy control group (P <0.05 ).In the cure group,WBC and PLT counts were lowest during the early course of the disease,and serum alamine aminotransferase (ALT), aspartate aminotransferase (AST ), lactic dehydrogenase (LDH ) and creatine kinase (CK ) were significantly higher than their upper limits of normal.The correlation analysis showed that serum IL-6, IL-10 levels were negatively correlated with PLT count (r=-0.390 and -0.608,respectively;both P <0.01),and positively correlated with SFTSV load (r=0.560 and 0.758,respectively),ALT (r=0.412 and 0.390,respectively),AST (r = 0.686 and 0.764,respectively),LDH (r = 0.633 and 0.677, respectively)and CK (r =0.527 and 0.636,respectively)(all P <0.01 ).Conclusions SFTSV load, IL-6,IL-10 and serum enzyme levels are closely related to the severity of the disease.The inflammatory and anti-inflammatory cytokine storm after SFTSV infection may be involved in the immune pathological injury in patients with SFTS.