Fetal infection with bovine leukemia virus in sheep.

Several sheep fetuses were thymectomized, and their tails were removed at 58 to 65 days of gestation for tissue culture. Bovine leukemia virus (BLV) antigens were detected in serial culture of tissues from fetuses whose dams and sires were both BLV positive. However, no BLV antigens were detected in serial cultures of tissues from fetuses whose dams were negative but whose sire was positive. Precolostral serums from 3 of 16 neonatal lambs, whose sire and dams were both BLV positive, were BLV antibody positive. Thus, BLV may be vertically transmitted from a positive dam to her lamb via the placenta and/or germinal cells but not from sire to lamb.

B-lymphocytes and T-lymphocytes in three types of bovine lymphosarcoma.

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.

Concanavalin A and the production of bovine leukemia virus antigen in short-term lymphocyte cultures.

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.

Pathology of lymphosarcoma in sheep induced with bovine leukemia virus.

Sixty-nine sheep were infected with bovine leukemia virus from bovine lymphosarcoma materials. Twenty-four developed lymphosarcoma and died from 13 to 66 (average, 29) months later. Circulating lymphocytes were increased to leukemia levels (70,000 to 403,000/cu mm blood) in only eight sheep within 2 to 3 months of death. Various lymph nodes and visceral organs including heart, abomasum, uterus, kidneys, and urinary tract were commonly affected as in cattle with the adult form of lymphosarcoma. In one sheep the skin was involved. The liver was involved in only one case. This was in contrast to more frequent involvement reported in literature for naturally occurring lymphosarcoma. The neoplasms in experimental sheep are regarded as a mixture of reticulum or histiocytic cells and lymphoid cells with transitional forms supported by a usually sparse and diffuse fibroplasia and a web of silver-staining reticulin fibers.

Lack of infectivity of bovine leukemia (C-type) virus to rats.

Sprague-Dawley rats were given ip injections of bovine culture and sheep cultures of bovine leukemia virus (BLV) and Gross passage-A leukemia virus [MuLV(G)]. Sera were tested to BLV antigens. BLV did not induce tumors in Sprague-Dawley rats, but the rats were susceptible to MuLV(G) at low doses.

An ether-sensitive antigen associated with bovine leukemia virus infection.

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.

Inhibition of bovine leukemia virus release.

Sera from 3 cows with the adult form of lymphosarcoma inhibited release of leukemia virus from a cell line of fetal lamb spleen infected with bovine leukemia virus (BLV). Sera from 5 to 7 cattle experimentally infected with BLV also suppressed virus release. The inhibition of virus release was reversible. Sera from cattle with the calf form and the thymic form of lymphosarcoma and normal bovine control sera did not repress virus release.

Survey for antibodies to leukemia (C-type) virus in cattle.

Serums from 4,394 dairy cattle in 100 herds and from 2,794 beef cattle in 50 herds were tested for antibody to the bovine (C-type) leukemia virus (BLV), using the agar gel immunodiffusion test. Reactors were found in 66% of the dairy herds (10.2% of the cattle) and in 14% of the beef herds (1.2% of the cattle). The prevalence of reactors was examined with respect to age, herd size, and sex. Few of the reactors were less than 2 years old. There was a high percentage of reactors in small dairy herds (less than 50 cattle). In 22 dairy herds (1,354 cows and 96 bulls), the rate of infection in cows was compared with that in bulls. In those herds, 13.5% of the cows and 10.4% of the bulls were reactors.