Analysis of lymphocyte subgroups in Crimean-Congo hemorrhagic fever

Objectives: This study examined the association between lymphocyte subgroups and mortality in patients with Crimean-Congo hemorrhagic fever (CCHF) in Turkey. Methods: During the spring and summer of 2007, peripheral blood was collected from hospitalized patients with suspected CCHF. Lymphocyte subgroups were characterized by fluorescence-activated cell sorting. CCHF cases were confirmed by detecting viral RNA by PCR and/or IgM antibodies by ELISA. Lymphocyte subgroups were compared between fatal and non-fatal cases. The correlation between lymphocyte subgroups and viral loads was also investigated. Results: Seventy-seven confirmed cases of CCHF were included in this study (five cases were fatal (6.5 %)). No differences in lymphocyte subgroups were found between fatal and non-fatal cases, except for significantly higher CD3+CD8+ T cells in the fatal cases (p = 0.017). A positive correlation between viral toad and CD3+CD8+ T cells was also detected (p = 0.044). There was no correlation between other lymphocyte subgroups and viral load. Conclusions: Higher levels of CD3+CD8+ T lymphocytes were detected in fatal compared to non-fatal CCHF cases. Despite this cytotoxic immune activation, a fatal outcome could not be prevented. We hypothesize that high viral load and other factors may influence this outcome, although more studies are required to explain the pathogenesis of CCHF. (C) 2008 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.