Bank vole monoclonal antibodies against Puumala virus envelope glycoproteins: identification of epitopes involved in neutralization

Lung tissues from 73 rodents (Apodemus agrarius coreae) gave specific immunofluorescent reactions when they reacted with sera from patients convalescing from Korean hemorrhagic fever. Similar staaining was observed in the lungs of A. agrarius inoculated with acute-phase sera obtained from two patients with this disease. The unidentified agent was successfully propagated in adult A. agrarius through eight passages representing a cumulative dilution of greater than 10(-17). Experimentally inoculated rodents developed specific fluorescent antigen in the lung, kidney, liver, parotid glands, and bladder. Organs, especially lungs, were positive beginning 10 days and continuing through 69 days after inoculation. The agent could not be cultivated in several types of cell cultures nor in laboratory animals. No fluorescence was observed when infected A. agrarius lung tissues were reacted with antisera to Marburg virus, Ebola virus, and serval arenaviruses. Diagnostic increases in immunofluorescent antibodies occurred in 113 of 116 severe and 11 of 34 milder cases of clinically suspected Korean hemorrhagic fever. Antibodies were present during the first week of symptoms, reached a peak at the end of the second week, and persisted for up to 14 years. Convalescent-phase sera from four persons suffering a similar disease in the Soviet Union were also positive for antibodies.

An indirect immunofluorescence test for detection of serum antibodies specific for nephropathia epidemica (NE) has been developed with use of acetone-fixed cryostat sections of the lungs of bank voles (Clethrionomys glareolus) that had been trapped from the NE-endemic area in Finland as antigen. NE antigen was detected as distinct fluorescence in the cytoplasm of alveolar and macrophage-like cells. The 16 patients studied included typical cases from an endemic area, cases from a family outbreak, and cases in a laboratory staff which had had close contact with infected bank voles. Antibodies reacting with antigen in the lung sections developed in all of the patients but they were not found in the preimmune sera of the patients, in the sera of patients with other renal diseases, or in the sera of healthy individuals, with the exception of a member of the laboratory staff who had lived in the endemic area for 20 years. No specific IgM antibodies to NE could be detected. The rise in titer of antibodies to NE was characteristically prolonged, and elevated antibody levels persisted for many years.