Immune parameters in hemorrhagic fever with renal syndrome during the incubation and acute disease: Case report

We describe immune parameters in a Croatian soldier who presented with mild flu-like symptoms and interstitial inflammatory infiltrate in the lungs on an X-ray during the incubation phase of hemorrhagic fever with renal syndrome (HFRS). Enzyme-linked immunosorbent assay (ELISA) IgM and polymerase chain reaction (PCR) were negative. Two weeks later, he developed HFRS caused by the Puumala virus. We performed two-color immunofluorescence cytometry with monoclonal antibodies identifying the activation markers on T cells. Serum samples were also examined by enzyme immunoassay (EIA) for the presence of interleukins IL-2 and IL-6 and their soluble receptors (sR). The analysis of early and late activation markers during the period of incubation revealed a small increase in the percentage of helper (CD4⁺CD25⁺) T cells and no significant increase in total activated (HLA-DR⁺TCR⁺) and cytotoxic (CD8⁺CD71⁺) T cells as compared with healthy controls. In the serum, only the concentration of soluble IL-6 receptor was increased. However, when the patient developed HFRS, all activation markers on T cells increased. Concentrations of sIL-2Rα and IL-6 remained increased two and six days after HFRS onset, respectively, whereas sIL-6R increased six days after HFRS onset. IL-2 concentration did not change. Our case indicates that rapid, modern diagnostic tools are necessary in the diagnosis of infectious diseases and their differential diagnosis. Immunological tests, which provide information on the patient immune status and especially on early changes in immune parameters, may contribute to the improvement of the diagnosis, prognosis, and therapy of HFRS.