Truncated recombinant Dobrava hantavirus nucleocapsid proteins induce strong, long-lasting immune responses in mice

We describe the cloning and expression of Dobrava hantavirus (DOBV) nucleocapsid proteins and a truncated form consisting of the first 118 N-terminal amino acids, and the capacity of these E. coli ICONE 200-expressed recombinant proteins (rNp) to induce a protective immune response against DOBV in mice. As an alternative carrier protein, the outer membrane protein A derived from Klebsiella pneumoniae (rP40) has been coupled to different rNp constructs. All recombinant proteins were found to be highly immunogenic after three immunizations of rNp. The immunizations resulted in the induction of a strong Np-specific IgG response with a predominance of IgG1 over IgG2b and IgG2a, suggesting a mixed Th1/Th2 cell involvement. A specific IgG3 response could not be detected. Mice immunized with recombinant DOBV rNp without rP40 showed lower nucleocapsid-specific antibody responses in comparison with the rP40-conjugated constructs, but all mice were found to be protected against DOBV challenge. Our results indicate that the rNp constructs coupled to rP40, represent promising vaccine candidates.