CHARACTERIZATION OF TULA VIRUS ANTIGENIC DETERMINANTS DEFINED BY MONOCLONAL-ANTIBODIES RAISED AGAINST BACULOVIRUS-EXPRESSED NUCLEOCAPSID PROTEIN

Tula virus was recently discovered by RT-PCR in lung samples from Euro pean common voles (Microtus arvalis and M. rossiaemeridionalis). Since virus isolation attempts had been unsuccessful, no antigen was availa ble for analysis or for use in immunoassays. To circumvent this, compl ete Tula virus nucleocapsid protein (bac-TUL-N) was expressed in recom binant baculovirus. Rodent antibody end-point titers to bac-TUL-N and to truncated N fragments indicated that the NH2-terminal region is the major antigenic target and revealed a high cross-reactivity to Puumal a virus N. Immunizations with crude bac-TUL-N preparations evoked high antibody responses to native hantavirus N in Balb/c mice and six mono clonal antibodies (Mabs) were generated. Epitope mapping of the Mabs, based on a competitive assay, reactivities to truncated recombinant N fragments, and reactivity patterns to different hantavirus strains, id entified five recognition sites on Tula virus N. One epitope, which wa s identified as specific for Tula virus, was located in a region of N which is highly variable among the hantaviruses (aa 226-293), and four epitopes were mapped to the NH2-terminal region of the protein (aa 1- 61). One epitope was expressed only in Tula and Prospect Hill viruses, one epitope in Tula, Prospect Hill, Khabarovsk, and Sin Nombre viruse s, while two epitopes were conserved in all examined hantaviruses carr ied by rodents within the subfamily Arvicolinae of the Muridae family.