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1.
We report on an accurate, rapid and inexpensive test for the identification of animals infected with the Bovine C-type virus (BLV). The test involves the detection of serum antibodies to BLV using the immunofluorescent (IF) technique on acetone-fixed, infected cells. The specificity of the test was demonstrated by the fact that virus was found by electron microscopy in 90% of cattle showing positive reactions. In contrast, virus was not found despite extensive examination in antibody negative animals. Thus, the presence of IF antibody is an accurate indicator of current rather than past BLV infection. In order for the IF test to be specific it is of critical importance that the target cells used are infected only with BLV. BLV antibodies can also be detected by the immunoprecipitation (Ouchterlony) technique. However, a significant proportion of BLV infected animals showing positive reactions in the IF test failed to show precipitin antibodies to the virus. Likewise, BLV infection was demonstrated by both the IF test and electron microscopy in many animals with persistently normal levels of blood lymphocytes. Thus, neither the precipitin test nor the blood lymphocyte count (Bendixen's key) can be used to rule out BLV infection.  相似文献   

2.
A trial was performed with heifers at the age of six to seven months. The animals were experimentally infected with the lymphocytes of a virus-productive donor. Infection was produced in all the nine cases, as demonstrated by means of the positive syncytial test. As indicated by the results of the trial, the antibodies to the enzootic bovine leucosis virus (BLV) were produced soon after experimental infection. A high sensitivity of the serum-neutralization test and the ELISA method was demonstrated in this connection: by these methods, the antibodies were identified already two to three weeks after experimental infection whereas by the immunodiffusion test they could be detected only after five weeks. Twenty-four animals were exposed to natural contact infection. Within 270 days of the trial, the disease after contact was recorded only in one heifer out of the four that were in close contact with the experimentally infected animals. In this case, as compared with experimental infection, the antibodies were produced much later--after 85 to 93 days. Leucosis was recorded in none of the remaining animals. The reasons why such a favourable result was obtained were the thorough disinfection of the stables after blood collections and the strict observance of the aseptic conditions. The results of experimental infection in three cows were identical with those obtained in young cattle. In the experimentally infected dairy cows, antibodies in milk were determined by the ELISA method. As found, in milk the antibodies to BLV appear two to three weeks later than they do in serum. The ELISA method of BLV antibody detection can be used for the identification of infected animals in herds where enzootic bovine leucosis occurs.  相似文献   

3.
BLV detection by the syncytial test was performed in 27 heifers experimentally and naturally infected by the enzootic bovine leukosis virus (BLV). The presence of BLV was demonstrated in 94.7% of the animals. The bovine foetal spleen cells (FBS) were found to be suitable for the syncytial test. Positive animals not reacting to infection by the production of anti-BLV antibodies were identified during the syncytial-test investigation. The importance of this finding for the programme of controlling enzootic bovine leukosis on farms is discussed. As suggested by the results, temporary occurrence of anti-BLV antibodies followed by their disappearance can be observed together with a negative result of the syncytial test in some circumstances. The discussion deals with the problems of the determination of anti-BLV antibodies in milk, and/or milk secretion, by the ELISA method.  相似文献   

4.
The ultra-thin section method, the method of negative staining, and immunoelectron microscopy were used for detecting BLV and for determining its morphological characteristics in the FLS continual cell line used as a virus antigen producer for the ELISA test. Particles of C type, about 110 nm in size, having a structure corresponding to BLV, were detected in the FLS cells on the ultra-thin sections. The viruses were located extracellularly, in cytoplasmic vacuoles, and in different stages of maturation by budding from cell plasma membrane. BLV presence was also demonstrated by immunoelectron microscopy.  相似文献   

5.
Haematological parameters and reactivity of lymphocyte antigens to monoclonal antibodies were studied over a 10-month period in sheep experimentally infected with bovine leukaemia virus (BLV). BLV-inoculated animals seroconverted within 1 month and showed a significant lymphocytosis 2-6 weeks after infection. Control animals inoculated with BLV-free lymphocytes showed a stronger and more immediate neutrophil response than those inoculated with BLV-positive lymphocytes. One month after infection, BLV-inoculated sheep showed a relative increase of cells bearing antigens T4, T6, T8 and T19, and 10 months into the trial, MHC II lymphocytes increased, T6 remained elevated, but T4 helper cells were significantly decreased in number. Lymphoma tissue showed the presence of T8 cells, and lymph nodes from seroconverted sheep had areas of concentrated T4 staining cells. These results demonstrate responses in cellular immune mechanisms to infection with BLV.  相似文献   

6.
Different cell cultures were studied for their susceptibility to bovine leucosis virus infection. Syncytial assay was used for this study. The FLS/BLV+ cell line served as virus source. Cell lines BHK-21 and ZP-1/58 were found to be susceptible to syncytium formation. Large cells with one to three large nuclei, and loose nuclei reaching the size of syncytium were observed to occur in the BHK-21 and ZP-1/58 cell lines, apart from the syncytial formations. The virus specificity of the syncytia arising in these two cell lines was confirmed by the immunofluorescence assay. In the case of the immunoperoxidase assay, a positive result was obtained only in the BHK-21 cell line. The occurrence of syncytia and large nuclei was observed even in the cases when the BHK-21 cells were infected with the lymphocytes of leucotic cows.  相似文献   

7.
Lymphocytes from sheep experimentally infected with bovine leukosis virus (BLV) and from non-infected normal sheep were examined for the presence of surface Ig by an immunofluorescence test. Surface Ig-bearing lymphocytes in blood from BLV-infected sheep increased when lymphocyte counts of blood were elevated in comparison with normal animals. The mitogen stimulation of cultured lymphocytes from BLV-infected sheep and from non-infected normal sheep was determined by measuring 3H-thymidine incorporation. Peripheral blood lymphocytes (PBL) from BLV-infected leukemic sheep with elevated PBL counts responded poorly to phytohemagglutinin M and concanavalin A but responded well to lipopolysaccharide compared with lymphocytes from uninfected animals. In BLV-infected preleukemic sheep with low PBL counts, stimulation indices of mitogen responses of lymphocytes with phytohemagglutinin M, concanavalin A, and pokeweed mitogen were low compared with those of lymphocytes from uninfected animals. The results indicated that B cells were affected by BLV infection in sheep as suggested by the increased number of surface Ig-bearing lymphocytes and that significant alteration of mitogen stimulation of lymphocytes occured in sheep with BLV infection.  相似文献   

8.
Expression of L‐selectin was determined by single‐ and two‐colour immunofluorescence on granulocytes, peripheral blood mononuclear cells (PBMC) and blasts of bovine origin by means of a monoclonal antibody IVA94 which recognizes bovine L‐selectin (CD62L). Cells were separated from peripheral blood of healthy cattle and colleagues infected with bovine leukaemia virus (BLV). BLV‐infected animals comprised lymphocytotic and non‐lymphocytotic cows. L‐selectin was expressed on 90–98 % of granulocytes in all tested animals. The percentage of PBMC expressing L‐selectin was lower in cattle with persistent lymphocytosis than in non‐lymphocytotic or BLV‐free cattle, and inversely correlated with lymphocyte counts. The ratio of B lymphocytes stained for L‐selectin was significantly decreased from 60.2 ± 1.9 % in BLV‐free cattle to 43.8 ± 3.6 and 22.5 ± 5.7 % in non‐lymphocytotic and lymphocytotic cattle, respectively. B‐lymphocytes stained for L‐selectin exhibited about 50 % reduction in L‐selectin expression in BLV‐infected cattle compared with BLV‐free cattle, as judged by the mean fluorescence intensity (MFI). The percentage of L‐selectin‐positive PBMC not bearing surface immunoglobulin M (predominantly T lymphocytes) was comparable in BLV‐free and BLV‐infected cattle. However, L‐selectin expression on T lymphocytes was reduced (about 50 %) in BLV‐infected cattle, as judged by the MFI. We suppose that BLV infection results in a decreased L‐selectin expression on lymphocytes, and accordingly, it may contribute to deregulation of the host immune system.  相似文献   

9.
The migration of fluorescein isothiocyanate labelled lymphocytes through the tracheobronchial mucosa has been studied in cattle. Following intratracheal inoculation of labelled non-infected autologous lymphocytes and bovine leukosis virus (BLV) infected heterologous (presumed allogeneic) lymphocytes, the labelled lymphocytes appeared in the blood circulation between 4 and 7 days post inoculation. Following intravenous inoculation of labelled autologous lymphocytes, the cells could be detected in the circulation for 10 days post inoculation whereas BLV infected and non-infected heterologous lymphocytes could be detected for only 2 days. The migration of BLV-infected heterologous lymphocytes through the tracheobronchial mucosa caused a delay in the appearance of labelled lymphocytes in the circulation and a corresponding delay in the appearance of BLV antibodies. Comparison was made of the effect of two different routes of inoculation, subcutaneous and intratracheal on the incubation period as indicated by the detection of antibody. Subcutaneous inoculation of 1 X 10(4), 5 X 10(3), 1 X 10(3) of lymphocytes from a BLV infected cow caused seroconversion whereas 5 X 10(2) cells did not. Intratracheal inoculation of 5 X 10(3) cells caused sero-conversion. One animal did not develop BLV antibody until 30 weeks after inoculation although BLV could be isolated from the blood at 24 and 26 weeks post inoculation.  相似文献   

10.
An indirect immunofluorescence (IF) test was developed to detect bovine leukemia virus (BLV) antigen expression in infected sheep lymphocytes, using monoclonal antibodies anti BLV-major envelope glycoprotein gp51. Peripheral blood lymphocytes were cultivated for 48 h in presence of phytohemagglutinin (PHA) (50 μg/ml), and then fixed with acetone. The cells were assayed for the IF test. All experimentally infected sheep were positive with this test.  相似文献   

11.
When six cattle persistently infected with bovine virus diarrhoea virus (BVDV) were inoculated with lymphocytes infected with bovine leukosis virus (BLV), a depressed antibody response to BLV was observed by ELISA which was due to a decrease in IgG1 synthesis. The ELISA was more sensitive and more reliable than the agar gel immunodiffusion (AGID) test in detecting BLV infection in cattle persistently infected with BVDV. Decreased antibody responses were manifested in the AGID test by negative, inconclusive or weakly positive reactions: only two of the six cattle developed antibodies that generated positive AGID reactions.  相似文献   

12.
Since bovine immunodeficiency virus (BIV), known as bovine lentivirus, has been detected in dairy and beef cattle in various countries around the world, a prevalence study of antibodies to BIV and bovine leukemia virus (BLV) was conducted in draught animals in five provinces in Cambodia, where protozoan parasite infections were suspected in some animals. To clarify the status of draught animals including Haryana, Brahman, mixed-breed, local breed cattle and muscle water buffaloes, a total of 544 cattle and 42 buffaloes were tested, and 26.3 and 16.7%, respectively, were found positive for anti-BIV p26 antibodies determined by Western blotting. There were 5.3% positive for anti-BLV antibodies detected by immunodiffusion test among the cattle, but no reactors among buffaloes and no dual infection for both BIV and BLV was determined in this study. Peripheral blood mononuclear cells from BIV-seropositive cattle were found to have BIV-provirus DNA, as detected by polymerase chain reaction and subsequent Southern blot hybridization. This is the first evidence for the presence of BIV and BLV infections in draught animals in tropical countries such as Cambodia. This wide distribution of BIV suggests its association with problems in animal health as reported worldwide, and that a primary BIV infection can predispose death of affected animals by other aggressive pathogens or stresses.  相似文献   

13.
To determine the phenotype of target cells for bovine leukemia virus (BLV) infection in sheep, we analyzed blood lymphocytes from BLV-infected clinically healthy and leukemic sheep by use of monoclonal antibodies. In clinically healthy and leukemic sheep that were BLV-infected, the blood concentration of T lymphocytes was within normal values, but the number of B lymphocytes was increased in several cases. In addition, the number of blood lymphocytes expressing the BLV antigen correlated well with that of B lymphocytes. Double immunofluorescence staining demonstrated that lymphocytes expressing BLV antigens bore B-cell but not T-cell surface markers. Moreover, neoplastic cells in the lymph nodes of leukemic sheep were stained immunohistochemically with an anti-B monoclonal antibody but not with any of anti-T monoclonal antibody tested, indicating that tumor cells are of B-lymphocyte origin. Collectively, these results show that BLV antigen-positive cells obtained from BLV-infected sheep that have no clinical signs and BLV-induced lymphosarcoma cells belong to the B-lymphocyte lineage.  相似文献   

14.
Six cattle persistently infected with bovine virus diarrhoea virus (BVDV) and seronegative, and two control, virus negative seropositive cattle were inoculated with lymphocytes infected with bovine leukosis virus (BLV). The two controls produced a normal immune response to BLV, developing antibodies at four and five weeks after inoculation. Two of the six cattle persistently infected with BVDV developed a strong antibody response by six weeks after inoculation with BLV. Four developed a depressed response to BLV, characterised in three by a 'hooking' reaction in the immunodiffusion test which persisted in successive bleedings but was interspersed occasionally by a weak positive reaction. In one of these animals, a series of 'hooking' reactions was followed by a number of negative results. The fourth animal remained serologically negative until 16 weeks after inoculation when a 'hooking' reaction was observed followed by a series of negative results. BLV was isolated from all the cattle persistently infected with BVDV at 42 or 58 weeks after inoculation regardless of whether the serum samples gave negative, 'hooking', weak positive or positive reactions in the immunodiffusion test. BLV was consistently isolated from the nasal secretions of a steer which was BVDV negative but seropositive. The possibility of decreased immune responsiveness to BLV in animals persistently infected with BVDV should be considered when formulating regulations governing the testing of animals for freedom from BLV.  相似文献   

15.
Expression of bovine leukemia virus (BLV) antigens in vivo has not been shown. After BLV infection, however, production of antibodies directed towards BLV proteins (e.g. gp51) can be easily demonstrated. Thus, production of BLV proteins has to take place somewhere in infected cattle. Tissues and organs of experimentally infected cattle were fixed in acetone and embedded in paraffin. Monoclonal antibodies directed to gp51 were used to demonstrate BLV expression immunohistologically by the peroxidase-antiperoxidase (PAP) method. The same samples were also used to demonstrate a tumor associated antigen (TAA) employing a monoclonal antibody. Our results indicate that very few cells, found in the intestinal mucosa, produce gp51 in vivo. The expression of TAA, however, increases significantly shortly after infection with BLV and remains high throughout life.  相似文献   

16.
Six calves sensitised by implanting skin from a calf were later inoculated with lymphocytes from the same calf after the calf had been infected with bovine leukosis virus (BLV). Two out of 6 calves challenged did not develop BLV antibodies and BLV was not isolated from these animals, whereas all of the 5 control calves became infected with BLV.  相似文献   

17.
In order to elucidate whether infection by Bovine Leukemia Virus (BLV) might induce an immunodeficient state, we inoculated sixteen calves with BLV. The calves were followed up for two years and were tested for humoral and cellular responses using various parameters, namely the appearance of antibodies to the BLV antigens, the changes in the numbers of lymphocytes involved, and the ratio between the two main populations of lymphocytes. Antibodies to the BLV antigens were of both the IgG and the IgM classes of immunoglobulins. The levels of antibodies of the IgM class were higher than those of IgG. There was a temporary decrease of reactive antibodies to the BLV antigens, to below detectable levels, during the 14-24 weeks post infection. A significant decrease in the level of plasma IgM was found in all BLV infected calves exhibiting lymphocytosis, while the level of IgG in the plasma of all experimental calves did not diverge significantly from the initial values, throughout the experiment. BLV infection was followed by lymphocytosis of B-cells in most infected calves, which persisted for the whole course of the experiment, while a decrease in the population of T-cells in peripheral blood was observed for a period of several months in all infected calves.  相似文献   

18.
A double polymerase chain reaction (PCR) assay has been devised for the direct detection of bovine leukemia virus (BLV). The assay was directly performed on blood leukocytes, avoiding the DNA-purification procedures. The PCR products were identified by gel-electrophoresis and the specificity of the test was confirmed by hybridization with a biotinylated oligonucleotide probe. When testing the sensitivity of PCR, less than eight genome copies of the provirus were detected in the background of two million negative lymphocytes. In a BLV infected herd 22 animals of various age groups were examined by the indirect (serological) diagnostic tests of agar-gel immunodiffusion and indirect ELISA as well as by the direct detection method of PCR. The tests were repeated at monthly intervals on five occasions. When examining the specimens from cows and heifers, a close agreement was found between the results of the various methods. The newborn calves, which were the offspring of BLV infected mothers, were consequently negative in PCR throughout the experimental period. However, in the indirect tests the calves were positive during the first samplings and became negative only around four months of age. Since the indirect tests can not discriminate infection from colostral immunity, PCR proved to be a useful complementary assay for the safe diagnosis of BLV infection in young calves.  相似文献   

19.
The BLV-induced leukemia--lymphosarcoma complex in sheep   总被引：3，自引：0，他引：3  
Sheep are highly susceptible to BLV infection and can be infected via several different means (routes). In all inoculated animals, specific anti-BLV antibodies can be demonstrated 1 to 3 months post-inoculation (p.i.). Between 10 and 13 months p.i., a moderate but persistent lymphocytosis (PL) may be detected in about 50% of the infected animals. This hematological disorder may be, but is not necessarily, associated with the development of a lymphosarcoma and can (might) be interpreted as a true lymphoid leukemia. According to findings revealed by immunolabelling and mitogen stimulation of peripheral blood lymphocytes, BLV-induced PL appears to be a B-cell disorder. Induced lymphosarcoma appears in about 40% of infected sheep during the 6 years p.i. It too is of B-lymphocyte lineage. In vitro studies demonstrate that BLV antigen is expressed exclusively in B-lymphocytes. Yet, BLV expression is greatly stimulated in whole lymphocyte culture by the addition of T-cell mitogen. This same phenomenon occurs when the supernatant of stimulated T-lymphocyte cultures is added to isolated BLV-infected B-lymphocytes. This observation supports the hypothesis that, as is the case with other retroviruses such as HIV, BLV is able to use the regular activation machinery of the immune system for its own replication and transmission. It seems, therefore, that the leukemia-lymphoma complex in sheep may serve as an accurate experimental model for the study of the biological properties of retroviruses.  相似文献   

20.
The bovine lymphoblastoid BL 20 cell line derived from a case of sporadic bovine leukosis when inoculated into sheep did not induce an antibody response directed against bovine leukosis virus (BLV) structural proteins. Sheep were inoculated twice with the BL 20 cell line and then challenged with BLV infected lymphocytes. Three out of four sheep challenged four weeks after BL 20 inoculation did not develop BLV antibodies. Of the 12 sheep challenged later, three sheep did not develop BLV antibodies. BLV was isolated from all the seropositive animals and from none of the seronegative animals.  相似文献   

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