In vitro selective suppression of feline myeloid colony formation is attributable to molecularly cloned strain of feline leukemia virus with unique long terminal repeat

Molecularly cloned feline leukemia virus (FeLV)-clone 33 (C-33), derived from a cat with acute myelocytic leukemia (AML), was examined to assess its relation to the pathogenesis of AML and myelodysplastic syndrome (MDS). To evaluate in vitro pathogenicity of FeLV C-33, bone marrow colony-forming assay was performed on marrow cells infected with FeLV C-33 or an FeLV subgroup A strain (61E, a molecularly cloned strain with minimal pathogenicity). The myeloid colony-forming activity of feline bone marrow mononuclear cells infected with FeLV C-33 was significantly lower than that of cells infected with 61E. This suggests that FeLV C-33 has myeloid lineage-specific pathogenicity for cats, and that FeLV C-33 infection is useful as an experimental model for investigating pathogenesis of MDS and AML.     

Blood smear from a cat: features to "dys"cover

A 4-year-old, spayed female, domestic shorthair cat was presented for lethargy, nonregenerative anemia, and inappetence. Results of a CBC included macrocytic, normochromic, nonregenerative anemia and a glucocorticoid-associated leukogram. On blood smear examination, neutrophils had abnormal features including hyposegmentation and a diffuse chromatin pattern with nuclear filament formation and nuclear blebbing. Microscopic examination of a roll preparation of bone marrow revealed hypolobulated megakaryocytes with asynchronous maturation of nuclei. The granulocytic to erythrocyte (G:E) ratio was 76. Segmented neutrophils had asynchronous maturation and dysplastic features. The entire erythroid lineage was markedly decreased for the degree of anemia and rare dysplastic features were noted in erythroid precursor cells. The interpretation of bone marrow findings was erythroid hypoplasia, megakaryocytic dysplasia, and granulocytic hyperplasia with dysplasia. Histopathologic examination of a bone marrow core sample also revealed myeloid hyperplasia and erythroid hypoplasia. The result of a direct immunofluorescence assay for FeLV performed on the bone marrow roll preparation was positive. A diagnosis of dysmyelopoiesis associated with FeLV infection was made. This case was unique in that the dysplastic changes occurred in cell lines that did not have associated cytopenias. The dysmyelopoiesis most closely resembled myelodysplastic syndrome with refractory cytopenia (MDS-RC); however, secondary dysmyelopoiesis could not be ruled out.     

Chronic eosinophilic leukemia in a cat: cytochemical and immunophenotypical features

A 3-year-old, male, domestic shorthaired cat was presented with a 3-day history of anorexia and depression. The cat was moderately dehydrated, had pale, slightly icteric, mucous membranes, oral ulcerations, and mild hepatosplenomegaly. A feline leukemia virus (FeLV) antigen test was positive. CBC results obtained at initial presentation included severe normocytic, normochromic, nonregenerative anemia, severe thrombocytopenia, and marked leukocytosis (>100,000/microL) with 77% eosinophils. After 15 days of treatment with prednisone and doxycycline, the cat had persistent severe nonregenerative anemia (HCT 3.4%), thrombocytopenia (28,000/microL), and extreme eosinophilia (total eosinophils, 123.1 x 10(3)/microL; segmented 103.0 x 10(3)/microL; immature 20.1 X 10(3)/microL). Cytologic examination of aspirates from bone marrow, liver, lymph nodes, and spleen revealed a predominance of mature and immature eosinophils, many with dysplastic changes. The M:E ratio was 96.4. On histopathologic examination, multiple organs were infiltrated by eosinophilic granulocytes. Neoplastic cells in blood and bone marrow stained positive for alkaline phosphatase and were negative for myeloperoxidase, chloroacetate esterase, and alpha-naphthyl acetate esterase. On flow cytometric analysis of peripheral blood, the neoplastic cells were positive for CD11b and CD14. These findings were consistent with chronic eosinophilic leukemia. To our knowledge, this is the first report of chronic eosinophilic leukemia in a cat associated with naturally acquired FeLV infection, in which flow cytometry was used to characterize the neoplastic cells.     

Chronic myelomonocytic leukemia in a cat

A 1-year-old spayed domestic short-haired cat was referred with anorexia and weight loss. Hematologic findings indicated nonregenerative anemia, severe neutropenia and monocytosis. The feline leukemia virus (FeLV) antigen test was positive reaction by enzyme-linked immunosorbent assay. Dysgranulopoiesis with slight increase in blast cells were observed in bone marrow smears. On the basis of blood and bone marrow findings, the cat was diagnosed as chronic myelomonocytic leukemia (CMMoL), which possibly corresponds to a kind of the subtypes in human myelodysplastic syndrome (MDS).     

Spinal lymphoma in cats: 21 cases (1976-1989).

Medical records of 21 cats with spinal lymphoma were reviewed. All cats were evaluated for neurologic deficits, although 85% of cats necropsied had multicentric disease. Eighty-one percent of cats had hind limb paresis. Results of FeLV tests were positive in 84.2% (16/19) of the cats, and 68.7% (11/16) of the cats had leukemic bone marrow. Spinal lymphoma was confirmed by necropsy in 13 cats, by examination of a biopsy specimen in 1 cat, and by examination of cells aspirated from an epidural lesion in 2 cats. In the remaining 5 cats, a presumptive diagnosis was made on the basis of neurologic examination findings, positive FeLV test results, and leukemic bone marrow. Nine cats were treated with chemotherapy alone. The complete remission rate was 50% in 6 cats given cyclophosphamide, vincristine, and prednisone. The median duration of complete remission was 14 weeks. Complete remissions were not observed in 3 cats given only corticosteroids. A single cat treated by laminectomy and postoperative chemotherapy had a prolonged remission (62 weeks). At necropsy, lymphoma of the CNS was limited to the vertebral canal in 10 of 13 cats; 2 cats had malignant tissue in the brain and vertebral canal, and in the remaining cat, the tumor extended into the brachial plexus. Most tumors extended over multiple vertebral bodies, and 4 cats had more than 1 level of spinal cord involvement. The lymphoma was high-grade lymphoblastic or immunoblastic type in all cats.     

Detection of feline leukaemia virus in blood and bone marrow of cats with varying suspicion of latent infection

The purpose of this study was to determine if polymerase chain reaction (PCR) could be used to detect FeLV proviral DNA in bone marrow samples of cats with varying suspicion of latent infection. Blood and bone marrow samples from 50 cats and bone marrow from one fetus were collected, including 16 cats with diseases suspected to be FeLV-associated. Serum enzyme-linked immunosorbent assay (ELISA), blood and bone marrow immunofluorescent antibody test (IFA), and blood and bone marrow PCR were performed on each cat, and IFA and PCR on bone marrow of the fetus. Forty-one cats were FeLV negative. Five cats and one fetus were persistently infected with FeLV. Four cats had discordant test results. No cats were positive on bone marrow PCR only. It appears persistent or latent FeLV infection is not always present in conditions classically associated with FeLV.     

Suspected myelodysplastic/myeloproliferative neoplasm in a feline leukemia virus‐negative cat

A 10‐year‐old castrated Domestic Short‐Haired cat was presented to a primary care veterinarian for a wellness examination and laboratory examination for monitoring of diabetes mellitus. The CBC revealed marked thrombocytosis, leukopenia and macrocytic, normochromic anemia. The cat tested negative for FeLV and feline immunodeficiency virus, but was positive for Mycoplasma haemominutum by PCR. Hematologic abnormalities were not responsive to therapy, so a repeat CBC and a bone marrow aspiration for cytology were performed. Additional blood smear findings included anisocytosis with megaloblastic erythroid precursors, large platelets, eosinophilic myelocytes and metamyelocytes, and rare unidentified blasts. The bone marrow smear was highly cellular, and the cytologic pattern was consistent with myelodysplastic syndrome with an erythroid predominance. At that time, 15% blasts were present. The cat was treated with a vitamin K₂ analog, doxycycline, and prednisolone, but without a clinical response. Within 3 months, euthanasia was elected due to declining quality of life, and a necropsy was performed. Postmortem bone marrow smears were highly cellular and dominated by monomorphic blasts of unknown line of origin (52%), persistent marked erythroid and megakaryocytic dysplasia, and ineffective erythropoiesis and granulopoiesis. Immunohistochemical, immunocytochemical, and cytochemical stains resulted in a diagnosis of acute myeloid leukemia of unclassified type. Additional histologic findings included mixed hepatitis with trematode infestation and lymphoplasmacytic interstitial nephritis with fibrosis. The marked thrombocytosis with myelodysplastic syndrome and the FeLV‐negative status of this cat were unusual. The difficulty in classifying the myelodysplasia and subsequent leukemia highlights a need for further reporting and characterization of these types of disease.     

Hematologic abnormalities preceding apparent recovery from feline leukemia virus infection

A 5-month-old domestic short-haired cat was referred to the Western College of Veterinary Medicine because of hemorrhage from the mouth. Neutropenia and bone marrow dyscrasia developed within 2 weeks, and results of a fluorescent antibody test for feline leukemia virus (FeLV) were positive. During the next 6 months, the feline oncornavirus cell membrane-associated antibody titer increased, the hematologic abnormalities regressed, and the cat became negative to the FeLV fluorescent antibody test (FeLV test). The results of 3 consecutive FeLV tests were negative, and the cat has been clinically normal for the past 18 months.     

Disseminated sarcocystosis in a cat with lymphosarcoma

Cysts of the protozoan Sarcocystis sp were found in skeletal and cardiac musculature in a 1.5-year-old cat with lymphosarcoma. The cat was FeLV-positive and had grossly visible neoplastic involvement of the spinal cord, mediastinum, bone marrow, and kidneys. Ultrastructural examination of the parasitic cyst wall suggested that the species in this case was different from that described in the only other reported case. It was hypothesized that immunosuppression from FeLV infection permitted an aberrant life cycle with encystment of Sarcocystis sp in this cat.     

Detection of feline immunodeficiency virus infection in bone marrow of cats.

Natural or experimental feline immunodeficiency virus (FIV) infection in cats is often associated with hematologic abnormalities which are similar to those observed in human immunodeficiency virus (HIV) infected patients. To determine if cells in bone marrow are infected with FIV and whether severity of hematopoietic disorder is correlated with the level of viral infection, bone marrow tissues from ten experimentally and two naturally FIV infected cats were examined by in situ hybridization for presence of FIV RNA. Seven of the 12 FIV infected cats were also naturally or experimentally coinfected with feline leukemia virus (FeLV). FIV RNA was detected mainly in megakaryocytes and unidentified mononuclear cells in the bone marrow of cats that were sick and had marrow hypercellularity and immaturity. These included all cats in the acute phase of FIV infection and two of seven long term FIV infected cats. One long term FIV infected cat with lymphosarcoma was also positive for FIV RNA in bone marrow cells. The other four long term FIV infected cats were relatively healthy, with normal bone marrow morphology, and were negative for FIV infected cells. Bone marrow from three non-infected and two cats infected with FeLV alone were also negative for FIV RNA by in situ hybridization. We concluded that megakaryocytes and mononuclear cells were targets of the viral infection and that the presence of FIV RNA in cells of the bone marrow correlated with marrow hypercellularity and immaturity, and severity of illness.     

Erythremic myelosis (AML6er) in a cat

A 4-year-old male European domestic cat was presented with dysorexia, weakness and depression. Normocytic normochromic non-regenerative anaemia, leucopaenia and thrombocytopenia were detected. Rubriblasts were detected both in the blood and in the bone marrow. Tests of blood chemistry revealed no alterations of renal and hepatic function and a positive reaction to FeLV antigen was detected in the cat's serum. Neoplastic cells did not show positive to cytochemical reactions against granulocytes, monocytes and lymphocytes. According to haematological and bone marrow cytological findings, a diagnosis of erythremic myelosis (AML6er) was made. Histopathology showed extramedullary haematopoiesis in the liver, spleen, kidney and lymph nodes and chronic nephropathy and degenerative signs in the liver.     

Immune-mediated erythroid and megakaryocytic aplasia in a cat

CASE DESCRIPTION: A 6-month-old domestic shorthair cat was evaluated because of acute lethargy. CLINICAL FINDINGS: Severe nonregenerative anemia and thrombocytopenia were identified. Cytologic examination of a bone marrow aspirate revealed selective erythroid and mega-karyocytic aplasia and a high number of apparently normal small lymphocytes. Infectious agents implicated in feline hematologic disorders were excluded on the basis of serologic tests or PCR amplification, including FeLV, Ehrlichia canis, Anaplasma phagocytophilum, Mycoplasma haemofelis, Candidatus Mycoplasma haemominutum, and Candidatus Myco-plasma turicensis. TREATMENT AND OUTCOME: A 10-day course of prednisolone administration did not improve the hematologic disorder. Administration of human polyclonal immunoglobulins preceded increased reticulocyte count by 3 days. A second bone marrow examination confirmed restoration of erythroblasts and megakaryocytes. After 1 relapse, the disease was successfully controlled with prednisolone for > 3 years. CLINICAL RELEVANCE: Immune-mediated bone marrow aplasia is rare in cats and usually affects only erythrocyte progenitors. Concomitant involvement of erythroid and megakaryocytic cell lines can be successfully treated via immunosuppressive therapy. Human immunoglobulins seem to be well tolerated in cats; however, proof of a beneficial effect requires further study.     

Ocular manifestations of a metastatic pulmonary adenocarcinoma in a cat

A primary pulmonary bronchogenic adenocarcinoma originating from an intramediastinal accessory lung was diagnosed in a 14.5-year-old cat. The cat had been admitted because of a cloudy right eye. Physical examination revealed a thin cat with severe iritis, aqueous flare, and a fibrin clot in the anterior chamber of the right eye. Right fundic examination revealed bullous retinal detachment superior to the optic disc. Euthanasia and necropsy were requested when FeLV test results were positive. Metastatic neoplastic cells similar to those of the primary tumor were detected in the choroid, ciliary body, and ciliary processes of the right eye. Ciliary and iridic stromal necrosis attributable to neoplastic embolization of uveal vessels had led to severe uveitis. Foci of metastasis were also in the heart, kidney, and cerebral meninges.     

Large granular lymphoma in an FIV-positive and FeLV-negative cat

The clinical course of a feline leukaemia virus (FeLV)-negative and feline immunodeficiency virus (FIV)-positive cat affected with a large granular lymphocyte lymphoma is presented. Cyto-logical examination showed neoplastic cells in the pleural effusion and in two abdominal masses. Bone marrow and peripheral blood were moderately involved and chemotherapy was used to control the tumour. Cytochemistry, immunohis-tochemistry and ultrastructural studies were applied to define the cellular lineage; cytochemistry suggested a T-cell lineage.     

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.     

Cyclic hematopoiesis associated with feline leukemia virus infection in two cats

Cyclic oscillations in the numbers of blood elements were detected in 2 cats with FeLV infection. Periodic neutropenia, followed by a return to normal neutrophil numbers, was detected in both cats. The mean cycle duration was 11.8 days, with a range of 8 to 14 days. Just before the return of normal neutrophil numbers, monocytosis developed. In 1 cat, cyclic variations in the number of reticulocytes and platelets also were detected. Bone marrow aspirates obtained during periods of neutropenia had a predominance of progranulocytes in the myeloid cell line. myeloid hyperplasia, with numerous segmented neutrophils, was seen in bone marrow aspirates obtained during periods of normal neutrophil numbers. Oral administration of prednisolone resulted in cessation of the cyclic oscillations of blood elements in 1 cat. Cyclic hematopoiesis appeared to be another non-neoplastic manifestation of FeLV infection.     

Acute monocytic leukaemia in a cat

A three-year-old cat with lymphadenopathy, non-regenerative anaemia and marked leucocytosis (171.3 x 10(9) white blood cells/l) was diagnosed with monocytic leukaemia and treated with a combination of anticancer drugs. A number of mature and immature monocyte-like cells were detected in the peripheral blood and bone marrow; they proved to be monocytic cells by cytochemical examination and an analysis of their cell surface phenotype, indicating that the cat suffered from acute myeloid leukaemia, subclassified as monocytic leukaemia (M5). Treatment with cytarabine, doxorubicin, vincristine and prednisolone greatly reduced the number of blast cells in the cat's peripheral blood and bone marrow. The cat was in partial remission for 67 days and survived for 95 days after it was first examined.     

Chronic Idiopathic Neutropenia in a Cat

Persistent neutropenia (0-0.6 X 10(9) neutrophils/l) was documented during a 10-month period in a 4-year-old spayed female domestic shorthair cat that was presented for anorexia and depression. Salient abnormalities detected on physical examination were fever (40.3 degrees C), dehydration, and gingivitis. The cat was neutropenic (0.5 X 10(9) neutrophils/l) and enzyme-linked immunosorbent assay (ELISA) test for feline leukemia virus was negative. A bone marrow aspirate showed decreased numbers of mature granulocytic cells. In vitro bone marrow cultures for colony-forming units-granulocyte/macrophage (CFU-GM) were performed comparing bone marrow from the patient with that of a normal cat. The patient had fewer CFU-GM than the control. The number of CFU-GM increased when bone marrow mononuclear cells were cultured in the presence of 10(-5) and 10(-6) mol/l of hydrocortisone, but the cat did not respond to oral prednisolone therapy. The pathogenesis of the neutropenia in this cat remains obscure, but resembles the chronic idiopathic neutropenia syndrome of man.     

Bone marrow necrosis and myelophthisis: manifestations of T‐cell lymphoma in a horse

Abstract: A 14‐year‐old spayed American Paint mare was evaluated for mild colic, anorexia, pyrexia, and pancytopenia. Physical examination revealed mild tachycardia, tachypnea, and pale mucous membranes. Serial laboratory analyses revealed progressive pancytopenia, hyperfibrinogenemia, and hyperglobulinemia. A few large atypical cells were observed in peripheral blood smears. Results of tests for equine infectious anemia and antipenicillin antibody were negative. Serum protein electrophoresis indicated a polyclonal gammopathy. Smears of bone marrow aspirates contained hypercellular particles, but cell lines could not be identified because the cells were karyolytic, with pale basophilic smudged nuclei and lack of cellular detail. A diagnosis of bone marrow necrosis was made. Treatment consisted of antimicrobials, nonsteroidal anti‐inflammatory drugs, and corticosteroids. The pyrexia resolved; however, the pancytopenia progressively worsened and petechiation and epistaxis developed. The horse was humanely euthanized. Postmortem examination revealed a diffuse round cell neoplasm infiltrating the kidneys, spleen, lymph nodes, lungs, and bone marrow. Immunophenotyping results (CD3+, CD79α−) indicated the neoplastic cells were of T‐cell lineage. Infiltration of lymphoma cells into the bone marrow appeared to have resulted in severe myelophthisis and bone marrow necrosis. Bone marrow necrosis has been associated previously with lymphoma in humans and dogs. To our knowledge, this is the first reported case of lymphoma resulting in bone marrow necrosis in a horse.     

Abnormal erythroid cell proliferation and myelofibrosis in a cat

A cat was presented with severe progressive anemia despite marked erythroblastosis. The cat was negative for feline leukemia virus antigen and feline immunodeficiency virus antibody. Bone marrow cytology revealed an excess of erythroid cells with a predominance of prorubricytes and basophilic rubricytes. No response to immunosuppressive therapy was obtained, and a tentative diagnosis of myelodysplastic syndrome was made. The cat showed a partial response to low-dose cytarabine (20 mg/m(2) subcutaneously q24) but died 51 days after the 1st admission. Histopathological examination revealed fibrosis in the bone marrow and marked infiltration of erythroid cells into other organs.