CHARACTERIZATION OF PUUMALA VIRUS NUCLEOCAPSID PROTEIN - IDENTIFICATION OF B-CELL EPITOPES AND DOMAINS INVOLVED IN PROTECTIVE IMMUNITY

B-cell epitopes in the nucleocapsid protein (N) of Puumala (PUU) virus were investigated by use of truncated recombinant proteins and overla pping peptides. Six of seven epitopes, recognized by bank vole monoclo nal antibodies, were localized within the amino-terminal region of the protein (aa 1-79). Polyclonal antibodies from wild-trapped or experim entally infected bank voles identified epitopes located over the entir e protein. Antibody end-point titers to different N fragments indicate d that the amino-terminal region is the major antigenic target in PUU virus-infected bank voles. To investigate the role of PUU virus N in p rotective immunity, we analyzed the immunogenicity of truncated recomb inant N and developed an animal model based on colonized bank voles. N o PUU virus N antigen, nor any glycoprotein-specific antibodies, could be detected after virus challenge in animals immunized with an amino- terminal fragment (aa 1-118), a fragment covering two thirds of the pr otein (aa 1-267), or total N, indicating that a complete protection wa s evoked by the recombinant proteins. Two of eight animals immunized w ith shorter N fragments displayed either N antigen, or glycoprotein-sp ecific antibodies, suggestive of partial protection. Prechallenge sera from all groups of immunized animals were found negative or only weak ly positive for neutralizing antibodies when assayed by focus reductio n neutralization test, which indicated an important role for cell-medi ated immunity in protection. (C) 1996 Academic Press, Inc.