Complement activation in nephropathia epidemica caused by Puumala hantavirus

Background and aim: Nephropathia epidemics (NE) is a hemorrhagic fever with renal syndrome caused by Puumala hantavirus. There is considerable variabi lity in the clinical severity of NE. Its pathogenesis is largely unknown an d data on complement activation in NE are scant. We sought here to establis h how the complement system behaves during NE and whether the variation in the clinical outcome is related to the activation of complement. Patients a nd methods: The complement component levels and complement activation produ cts and the clinical course of 25 hospital-treated acutely ill NE patients were studied. Results: Complement activation was observed in 23 patients. T n 10 patients the complement system was activated mainly through the altern ative route, in 6 mainly through the classical route and in 5 through both the alternative and the classical route. Arm elevated soluble terminal comp lex SC5b-9 was the most sensitive indicator of complement activation (17 ou t of 25 patients). Two patients had only an elevated SC5b-9 value and 2 had no complement activation. The C4d/C4 maximal ratio was significantly highe r in patients with clinically severe NE compared to the mild or moderate di sease groups. Conclusion: Our results show that complement activation is co mmon in NE. Although both pathways are usually activated, the classical pat hway activation by immune complexes or directly by viral components is asso ciated with a severe clinical course of NE.