Indirect immunofluorescence tests in Korean hemorrhagic fever and epidemic (endemic) nephropathia: treatment at low pH for removal of 'nonspecific' fluorescence in tissues from immunocompetent hosts.

A 'nonspecific' fluorescence probably caused by immunocomplexes appears in the lung tissue of immunocompetent hosts infected with Korean hemorrhagic fever (KHF) or epidemic nephropathy (EN) viruses. Indirect immunofluorescence tests with such KHF- or EN-infected tissue as antigen are unsatisfactory for the detection of low-titer antibody or the reading of titer endpoints. Treatment of acetone-fixed lung sections at pH 3.0 followed by washing with 0.01 M phosphate-buffered saline and distilled water apparently dissolves the immunocomplexes, resulting in an effective removal of the 'nonspecific' fluorescence while the viral antigens are not significantly impaired. Lung sections of KHF-infected Apodemus agrarius coreae and EN-infected Clethrionomys glareolus, acetone-fixed and treated at pH 3.0, were used for the antigenic differentiation of the EN and KHF viruses.