Clonality analysis of various hematopoietic disorders in cats naturally infected with feline leukemia virus

The clonality analysis of the bone marrow cells was carried out by detecting the integrated proviruses of feline leukemia virus (FeLV) to understand the pathogenesis of FeLV-associated hematopoietic disorders in cats. Bone marrow cells from 4 cases with acute myeloid leukemia (AML), 9 cases with myelodysplastic syndromes (MDS), 2 cases with pure red cell aplasia (PRCA) and 3 healthy carriers infected with FeLV were subjected to Southern blot analyses using an exogenous FeLV probe. Clonal hematopoiesis was found in all the cases with AML and in 6 of the 9 cases with MDS, but not in the cases with both PRCA and healthy carriers infected with FeLV. In the 2 cases with MDS, it was thought that the same clones of the hematopoietic cells might proliferate before and after the progression of the disease irrespective of the changes of the hematological diagnoses by cytological examination. This study indicates that MDS in cats is a disease manifestation as a result of clonal proliferation of hematopoietic cells and can be recognized as a pre-leukemic state of AML.