We have determined the complete nucleotide sequence of a replication-competent clone of bovine foamy virus (BFV) and have quantitated the amount of splice pol mRNA processed early in infection. The 544-amino-acid Gag protein precursor has little sequence similarity with its primate foamy virus homologs, but the putative nucleocapsid (NC) protein, like the primate NCs, contains the three glycine-arginine-rich regions that are postulated to bind genomic RNA during virion assembly. The BFV gag and polopen reading frames overlap, with pro and polin the same translational frame. As with the human foamy virus (HFV) and feline foamy virus, we have detected a spliced pol mRNA by PCR. Quantitatively, this mRNA approximates the level of full-length genomic RNA early in infection. The integrase (IN) domain of reverse transcriptase does not contain the canonical HH-CC zinc finger motif present in all characterized retroviral INs, but it does contain a nearby histidine residue that could conceivably participate as a member of the zinc finger. The env gene encodes a protein that is over 40% identical in sequence to the HFV Env. By comparison, the Gag precursor of BFV is predicted to be only 28% identical to the HFV protein.
Lymphosarcoma in cattle can be divided into enzootic lymphosarcoma and sporadic lymphosarcoma.1 Enzootic bovine lymphosarcoma is caused by bovine leukemia virus (BLV), a retrovirus that is horizontally spread in cattle by infected lymphocytes.2 , 7 Sporadic lymphosarcoma has an unknown etiology, but there is no evidence that BLV is involved in this form of the disease. The sporadic form usually affects young cattle, and most cases can be further classified as juvenile, thymic, or skin forms.1 Multicentric lymphosarcoma not associated with BLV infection has been reported only rarely in mature dairy cattle. 3,5,6 A 3-year-old Holstein bull owned by a commercial breeding company was presented to Cornell University because of anorexia of 5 days duration and abnormally dark-colored manure for 3 days. Prior to hospital admission, the bull had been treated once with orally administered electrolytes a mixed in water and 3 g phenylbutazolidine.b Nonsteroidal anti-inflammatory drugs had not been administered to the bull prior to the clinical signs. On hospital examination, the abnormalities noted were depression, pale mucous membranes, cardiac arrhythmia, and melena. The packed cell volume was 15%, and the plasma protein concentration was 4.0 g/dl. The combination of clinical and laboratory finding were suggestive of hemorrhage into the upper intestinal tract. A macrocytosis (mean corpuscular volume = 63 fl), basophilic stippling, and Howell-Jolly bodies were present in the hemogram and were suggestive of a regenerative anemia most likely associated with the intestinal blood loss. The cardiac arrhythmia was further investigated by electrocardiographic examination. Ventricular premature contractions (VPCs) with an identical pattern were noted, suggesting that the VPCs were originating from the same site in the myocardium. The findings in this bull were thought to be most consistent with a diagnosis of multicentric enzootic lymphosarcoma caused by BTV infection. Examination of the medical records of the Received for publication February 4, 1994. bull revealed that he had been seronegative on 4 occasions for BLV antibody with the agar gel immunodiffusion (AGID) assay. The most recent assay had been performed just 4 weeks prior to hospital admission. Support for the diagnosis of lymphosarcoma and/or BLV infection could not be gathered from the leukogram; a lymphopenia (1,800 cells/µl) was noted. A peritoneal tap&as performed because it was considered the least invasive procedure that might supply information supportive of the diagnosis oflymphosarcoma. A large amount of light' red peritoneal fluid was easily obtained from the peritoneal cavity with an 18-gauge 3.8-cm needle inserted into the abdominal cavity at the lower right flank. The fluid contained <2.5 g of protein/liter and 54,400 white blood cells/µl. Lymphoblasts were numerous on cytologic examination of the fluid (Fig. 1). A diagnosis of lymphoma was made, and the bull was euthanized. Lymphosarcoma involving the sternal lymph nodes, tracheobronchial lymph nod...
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