Differences in immune damage between patients with severe fever with thrombocytopenia syndrome and patients with tsutsugamushi disease

Abstract

To analyze the difference of immune damage between patients with severe fever with thrombocytopenia syndrome (SFTS) and patients with tsutsugamushi disease. A prospective case-control study was conducted. Thirty-one patients with SFTS and 16 patients with tsutsugamushi disease admitted to the First Affiliated Hospital of Anhui Medical University from October 2014 to June 2017 were enrolled, and another 10 healthy people were enrolled as control. The counts of CD4+ and CD8+ T lymphocytes, and the proportion of CD3+ T lymphocytes, natural kill cells (NK cells), B lymphocytes and plasma cells were detected by flow cytometry. Thirty-four inflammatory mediators were determined by a multiplex Luminex® system synchronously. The differences of lymphocytes and cytokines between the two groups were compared. The proportion of CD3+ T lymphocytes, the counts of CD4+ and CD8+ T lymphocytes in SFTS patients were significantly lower than those in patients with tsutsugamushi disease (t values were 4.860, 9.411 and 5.030, respectively, all P < 0.01), and the proportion of NK cells and B lymphocytes were significantly higher than those in patients with tsutsugamushi disease (t values were 2.344 and 5.896, respectively, both P < 0.05). The proportion of plasma cells in peripheral blood of SFTS patients was (7.7±1.2)%, the highest proportion of plasma cells in severe SFTS patients was up to 30%, and all patients showed λ monoclonal cell group in plasma cells. No plasma cells were detected in tsutsugamushi disease patients. The abnormal expressions of interleukin-1 receptor antibody (IL-1RA), interleukin (IL-6, IL-15, IL-10, IL-8), tumor necrosis factor-α (TNF-α), γ-interferon (IFN-γ), granulocyte colony-stimulating factor (G-CSF), eosinophil chemotactic factor (Eotaxin), IFN-γ-inducible protein-10 (IP-10), monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein (MIP-1α, MIP-1β), platelet-derived growth factor (PDGF-AA, PDGF-AB/BB), activated regulatory normal T cells and secretion factors (RANTES) were found in patients with SFTS and tsutsugamushi disease. The levels of IL-1RA, IL-6, IL-15, IL-10, TNF-α, IFN-γ, G-CSF, Eotaxin, IL-8, IP-10, MCP-1 and MIP-1α in SFTS patients were significantly higher than those in patients with tsutsugamushi disease (Z values were 2.312, 2.447, 3.660, 5.444, 1.965, 2.402, 2.402, 2.997, 3.525, 2.481, 3.817, and 2.211, respectively, all P < 0.05), while PDGF-AA, PDGF-AB/BB and RANTES were significantly lower than those in patients with tsutsugamushi disease (Z values were 3.728, 2.514, 2.649, respectively, all P < 0.05). Correlation analysis showed that RANTES, PDGF-AA and PDGF-AB/BB levels were significantly positively correlated with the level of platelet in patients with SFTS and tsutsugamushi disease (SFTS: r values were 0.223, 0.365, 0.330; tsutsugamushi disease: r values were 0.263, 0.632, 0.407, respectively, all P < 0.05). In SFTS patients, compared with the survival group (n = 21), the CD3+ and CD4+ T lymphocytes in the death group (n = 10) significantly decreased, while the plasma cells significantly increased (t values were 3.980, 3.314 and 26.692, respectively, all P < 0.01); IL-1RA, IL-6, IL-15, IL-10, TNF-α, IFN-γ, G-CSF, Eotaxin, IL-8, IP-10, MCP-1, MIP-1α and MIP-1β significantly increased, while PDGF-AA, PDGF-AB/BB and RANTES significantly decreased (Z values were 3.930, 4.014, 2.832, 3.592, 2.958, 3.508, 2.578, 3.254, 4.270, 3.465, 2.663, 3.085, 3.107, 3.639, 3.043 and 3.825, respectively, all P < 0.05). The immune function was impaired more seriously in SFTS patients than that in tsutsugamushi disease patients. Excessive humoral immunity and apoptosis of T lymphocytes are closely related to the death in SFTS patients. The detection of CD4 cells, plasma cells and proinflammatory and anti-inflammatory cytokines (e.g. IL-6, IL-10) had great clinical significance for the differentiation and illness evaluation in disease with SFTS or tsutsugamushi disease.