MAPPING OF B-CELL DETERMINANTS IN THE NUCLEOCAPSID PROTEIN OF PUUMALA-VIRUS - DEFINITION OF EPITOPES SPECIFIC FOR ACUTE IMMUNOGLOBULIN-G RECOGNITION IN HUMANS

The complete amino acid sequence of the Puumala (PUU) virus nucleocaps id protein (N), deduced from the genome of the prototype strain Sotkam o, was synthesized as decapeptides with 5-amino-acid overlaps. By use of the PEPSCAN method, 86 peptides were examined for reactivity with s era from serologically confirmed nephropathia epidemica (NE) patients and 11 PUU virus N-specific bank vole monoclonal antibodies. The human sera showed reactivity with several different regions, while only one of the monoclonal antibodies reacted with one single peptide, Sequenc es were selected by this PEPSCAN analysis of human antibody reactiviti es, and five W-amino acid peptides were synthesized and evaluated as a ntigens by an enzyme-linked immunosorbent assay (ELISA). Peptide react ive antibodies of the immunoglobulin M (IgM) class were measured in se rum samples drawn from patients with acute NE. In comparison with the results of a mu-capture IgM ELISA using native PUU virus antigen, only a few serum samples were found positive (sensitivity, 2 to 10%), Inte restingly, when antibodies of the IgG class were measured, the sensiti vities of the five peptide ELISAs were found to be 79, 46, 2, 100, and 40%, respectively, as compared with the sensitivity of an IgG ELISA b ased on native viral antigen, The IgG reactivities of sequentially dra wn sera from NE patients with the two peptides giving the highest assa y sensitivities were analyzed and compared,vith their reactivities wit h native viral antigen, All patients had detectable anti-peptide IgG i n the acute-phase sample, which, however, had totally declined in samp les drawn after 2 years, The opposite pattern was seen with native vir al antigen, in which case all patients showed the highest levels of sp ecific IgG after 2 years. The results suggest the presence of epitopes specific for the acute IgG response.