Detection of bovine leukaemia virus proviral DNA in paraffin sections, tissue smears, and peripheral blood leucocytes by in situ PCR

In situ PCR was developed for the detection of proviral DNA of bovine leukaemia virus in paraffin embedded tissues, tissue smears of experimentally inoculated sheep, as well in peripheral blood leukocytes of naturally infected cattle. The liver, spleen, lung, heart, kidney, and lymph node were collected from two infected sheep, which died or were euthanized due to lymphosarcoma and persistent lymphocytosis, respectively. Peripheral blood leukocytes (PBLs) were isolated from eleven cattle serologically positive for BLV. The presence of proviral DNA was confirmed in all paraffin embedded tissue sections and tissue smears as well in all PBLs preparations. In situ PCR results agreed 100% with those of provirus detection using conventional PCR. Newly developed in situ PCR would be recommended as a method to differentiate between EBL and other lymphosarcomas of unknown aetiology.