Immunohistochemical and in situ hybridization studies of the liver and kidney in human leptospirosis.

An in situ hybridization (ISH) assay for the detection of leptospiral DNA in tissues was described and its diagnostic and pathogenetic usefulness in combination with immunohistochemistry (IHC) was evaluated in formalin-fixed, paraffin-embedded liver and kidney samples from human fatal cases of leptospirosis. IHC assays with anti-E-cadherin antibodies assessed the liver-plate disarray frequently observed in leptospirosis. Immunohistochemistry detected leptospiral antigen (LAg) in macrophages, both in human liver and kidney. In guinea pigs, in addition to these findings, staining on cell membranes of hepatocytes and, occasionally, in apical membrane of kidney tubular cells was demonstrated. Positive ISH signal was observed chiefly in the nuclei of human hepatocytes and in the cytoplasm and nuclei of liver cells of experimentally infected guinea pigs. Loss of E-cadherin membrane expression is associated with liver-plate disarray. These findings were discussed in the contention that, in leptospirosis, cell membrane damage might be important for the pathogenesis of the disease. Finally, it was suggested that both IHC and/or ISH might be used for both diagnostic and research purposes.