A major antigenic domain for the human humoral response to Puumala virus nucleocapsid protein is located at the amino-terminus.

Nephropathia epidemica (NE), the major form of hemorrhagic fever with renal syndrome in Europe, is caused by the hantavirus serotype Puumala (PUU). The PUU virus nucleocapsid protein (N) has been shown to be highly immunogenic both in laboratory animals and in man. We aimed to locate domains important in humoral immune reactivity and to use this information to develop a specific and sensitive enzyme-linked immunosorbent assay (ELISA) for serological diagnosis of NE. Escherichia coli poly-histidine fusion protein expression vectors containing over-lapping gene segments encoding the PUU virus N (PUU rN) were constructed. The resulting gene products were examined by immunoblots and ELISA with polyclonal and monoclonal antibodies. The dominating antigenic region of PUU rN was located between amino acids (aa) 7 and 94. A recombinant fusion protein containing aa 7-137 of PUU virus N (PUU rN delta 5) was used for the detection of specific IgG and IgM responses in NE. ELISA based on PUU rN delta 5 was found to have equal sensitivity and specificity as compared to the full length recombinant PUU rN by ELISA, for both acute serological diagnosis of NE and for seroepidemiological screening purposes. Furthermore, this protein is easier to handle than full length PUU rN due to its higher solubility in aqueous solutions.