Abstract. A virus isolated in cell culture from the spleen of a cat with feline infectious peritonitis was identified by physicochemical, morphological and antigenic criteria as a coronavirus. The feline infectious peritonitis virus was compared in virro with canine coronavirus, a reported enteric pathogen of dogs. The feline isolate was characterized, by chloroform sensitivity and resistance to 5-iododeoxyuridine, respectively, as containing essential lipid and an RNA genome. Other traits of the isolate included resistance to acidic conditions, heat lability, and resistance to trypsin. Electron microscopy showed viral particles with a structure consistent with that of the prototype of the coronavirus group, infectious bronchitis virus.Indirect immunofluorescence with canine coronavirus monospecific antiserum showed the viral isolate to be antigenically related to canine coronavirus.Specific-pathogen-free cats inoculated by various routes with cell-culture-propagated virus had both clinical symptoms and lesions consistent with feline infectious peritonitis.
An ether-sensitive antigen (es-Ag) associated with bovine leukemia virus infection was detected by immunodiffusion tests. This antigen was sensitive to ether, sodium periodate, and trypsin treatment. Based on column chromatography, es-Ag was a larger molecule than that of ether-resistant antigen (gs-Ag). With infection, precipitating antibody against es-Ag developed earlier than the precipitating antibody against the gs-Ag.
Lymphoid cells of peripheral blood, lymph nodes, and thymus from clinically normal cattle, cattle infected with bovine leukemia virus (BLV), and cattle with lymphosarcoma were characterized for T- and B-cell surface markers. B-cells were detected by the erythrocyte-antibody-complement (EAC) rosette test and the surface immunoglobulin (sig) immunofluorescence assay. Peripheral blood from BLV-infected cattle had a higher than normal percentage of B-cells by both EAC rosette and sig immunofluorescence assays. Lymphoid cells from tumorous lymph nodes of cattle with the adult type of lymphosarcoma had a higher than normal percentage of sig-bearing cells, but in the same cell preparation the EAC rosette-positive cells were fewer than sig-positive cells. T-cells were detected by the erythrocyte rosette test. The percentage of T-cells by this test in lymph nodes of adult type lymphosarcoma was lower than that in normal cattle. A distinctly lower than normal percentage of lymphocytes could be characterized as either B- or T-cells in lymph nodes thymus, and peripheral blood from the calf type and thymic type of lymphosarcoma.
The influence of the mitogen concanavalin A (Con A) on the production of bovine leukemia virus (BLV) antigen in short-term lymphocyte cultures was determined by means of a single radial immunodiffusion test. Con A did not affect viral antigen production in peripheral blood lymphocytes from 60% of both experimentally and naturally infected cattle. Antigen production was stimulated by Con A in lymphocytes from 28% of the cattle, but it was inhibited in lymphocytes from 12%. Similar results were also obtained with lymphocytes from both blood and lymph nodes from 10 cattle with lymphosarcoma and from 10 clinically normal cattle with histologically normal lymph nodes. In sheep and goats, Con A had no effect on lymphocytes from 50%, stimulated BLV production in 43%, and inhibited BLV production in 7%. These results indicated that lymphocytes should be cultured with and without Con A to identify every BLV-infected animal.
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