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1.
An experimental model of chronic infection with bovine leukemia virus (BLV) was established in young calves within a relatively short time. In the sera of all infected calves, precipitating antibodies were detected within 5 weeks after infection but upon disease progression pattern of cellular profiles varied. Three calves exhibited transient lymphocytosis 3-5 weeks after infection, two became persistent lymphocytotic (PL+) by that time and one stayed non-lymphocytotic (PL-) for 11 weeks and became PL+ after 4.5 months. Eventually all infected calves became PL+ by the end of the experiment, 6-12 months after infection. Increase of total counts of peripheral blood mononuclear cells (PBMC) related to polyclonal expansion of B-cells. The latter was assessed in all infected calves where the expansion of CD5-bearing cells (B+ CD5+) correlated with increase or decrease of total PBMC counts. Other cell populations such as CD4 and CD8 were also affected. Percentages decreased by 5 weeks after experimental infection to about half their original values though actual cell numbers stayed relatively stable. The experimental model we established compared well with field cases of naturally BLV-infected cattle and thus permitted the investigation of the disease at early stages of infection.  相似文献   

2.
Immunological control of bovine leukemia virus (BLV)-infection has been reported as dependent on the expression balance of types 1 and 2 cytokines. In this report, mRNA expression of interferon (IFN)-gamma and interleukin (IL)-2 (type 1 cytokines), and of IL-4 and IL-10 (type 2 cytokines) were evaluated in concanavalin A-stimulated peripheral blood mononuclear cells (PBMC) from BLV-infected sheep. Despite the same dose of BLV-infection, the extent of viral propagation was markedly different between eight individual sheep by 12 weeks post infection. The virus did not propagate well in three sheep, which showed augmented mRNA expression of IFN-gamma, a strong indicator of cell-mediated immunity, immediately after BLV-infection. Among the other five sheep having more than 2% of BLV-infected cells among PBMC at 12 weeks post infection, four sheep developed B-cell leukemia or lymphoma within 2 years after infection. These observations indicate IFN-gamma expression may play an important role in the protective mechanism against BLV propagation at the early phase of the infection.  相似文献   

3.
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4.
This study was designed to determine the relative infectivity of lymphocytes and secretions from BLV-infected cattle with and without persistent lymphocytosis (BLV+PL+ and BLV+PL-). Ninety-seven sheep of mixed sex and age were assembled into 21 experimental groups. The recipient sheep were inoculated intravenously with serial dilutions of whole blood, saliva or nasal secretions from BLV+PL+ and BLV+PL- donor cows. Between 200 to 20,000 cells from single and mixed BLV+PL+ or single and mixed BLV+PL- donor cattle were used for inoculation. A very small number of BLV-infected lymphocytes (200 cells) was sufficient to induce BLV infection in sheep inoculated with diluted whole blood from BLV+PL+ cattle. The inoculation of whole blood (containing up to 20,000 lymphocyte cells) from BLV+PL- cattle did not induce BLV infection in recipient sheep. Saliva and nasal secretions also failed to bring about BLV transmission.  相似文献   

5.
Direct immunofluorescence and fluorescence-activated cell sorter techniques were used for the detection of surface immunoglobulin positive (SIg+) cells in peripheral blood lymphocytes (PBL's) of bovine leukaemia virus (BLV) infected cattle with or without persistent lymphocytosis (PL+, PL-) and in BLV-free cattle. The percentage of SIg+ cells was more than twice as high in BLV+PL+ cattle than in BLV-free and BLV+PL- cattle. Bovine T cells, and T cell subsets were identified indirectly by the same techniques using three monoclonal antibodies (MAb's) specific for all T cells (IL-A43), T helper (BoT4) cells (IL-A12) and T cytotoxic (BoT8) cells (IL-A17). The major histocompatibility complex (MHC) determinants of both class II (BoT4) and class I (BoT8) as well as all T cells were significantly reduced in BLV+PL+ compared to BLV-free cattle. The actual decrease in the BoT8 cell subset or the dilution effect that would change effector:target cell ratio suggests that a resultant decrease in cytotoxic activity in BLV+PL+ cattle may play an important role in the progress of BLV infection in cattle.  相似文献   

6.
A DNA vaccination trial was performed on sheep to determine whether vaccination with bovine leukemia virus (BLV) transactivator Tax DNA is effective against BLV infection. Immunization was carried out with cationic liposomes containing the Tax-expressing plasmid DNA and subsequently all sheep were challenged with BLV. BLV titers in peripheral blood mononuclear cell (PBMC) determined by syncytium formation assay and BLV provirus load detected by genomic PCR analysis showed higher levels of virus titers in control sheep than those in Tax-vaccinated sheep. Higher levels of IFN-gamma mRNA expression have been demonstrated in vaccinated sheep after the challenge. These results suggested that Th1 type immune response induced by Tax DNA vaccine inhibited BLV propagation in vaccinated sheep at the early phase of infection.  相似文献   

7.
ABSTRACT: The immunoinhibitory receptor T cell immunoglobulin domain and mucin domain-3 (Tim-3) and its ligand, galectin-9 (Gal-9), are involved in the immune evasion mechanisms for several pathogens causing chronic infections. However, there is no report concerning the role of Tim-3 in diseases of domestic animals. In this study, cDNA encoding for bovine Tim-3 and Gal-9 were cloned and sequenced, and their expression and role in immune reactivation were analyzed in bovine leukemia virus (BLV)-infected cattle. Predicted amino acid sequences of Tim-3 and Gal-9 shared high homologies with human and mouse homologues. Functional domains, including tyrosine kinase phosphorylation motif in the intracellular domain of Tim-3 were highly conserved among cattle and other species. Quantitative real-time PCR analysis showed that bovine Tim-3 mRNA is mainly expressed in T cells such as CD4+ and CD8+ cells, while Gal-9 mRNA is mainly expressed in monocyte and T cells. Tim-3 mRNA expression in CD4+ and CD8+ cells was upregulated during disease progression of BLV infection. Interestingly, expression levels for Tim-3 and Gal-9 correlated positively with viral load in infected cattle. Furthermore, Tim-3 expression level closely correlated with up-regulation of IL-10 in infected cattle. The expression of IFN-γ and IL-2 mRNA was upregulated when PBMC from BLV-infected cattle were cultured with Cos-7 cells expressing Tim-3 to inhibit the Tim-3/Gal-9 pathway. Moreover, combined blockade of the Tim-3/Gal-9 and PD-1/PD-L1 pathways significantly promoted IFN-γ mRNA expression compared with blockade of the PD-1/PD-L1 pathway alone. These results suggest that Tim-3 is involved in the suppression of T cell function during BLV infection.  相似文献   

8.
To examine whether tumor necrosis factor alpha (TNF alpha) contributes to the pathogenesis of bovine leukemia virus (BLV) infection, the mRNA expression patterns of TNF alpha and its receptors, type 1 (TNF R1) and type 2 (TNF R2) were investigated. Sheep inoculated with BLV were divided into two groups; one was BLV-positive and the other BLV-negative based on the detection in peripheral blood mononuclear cells (PBMC). Expression of TNF R1 mRNA was down-regulated in PBMC from the BLV-positive compared to BLV-negative sheep. No difference was shown in the expression levels of TNF R2 mRNA between the two groups. Furthermore, proliferative responses of PBMC in the presence of TNF alpha were observed from the BLV-positive, but not BLV-negative sheep. Membrane-bound TNF alpha (mTNF alpha) is thought to be one of the ligands, inducing B-cell activation. Flow cytometric analysis demonstrated that the number of PBMC, that were positive for mTNF alpha expression, was increased in the BLV-positive sheep. Thus, the expression of TNF alpha and its receptors may be closely associated with lymphocytosis induced by BLV.  相似文献   

9.
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   

10.
Two calves each were inoculated with 1.5 x 10(8) or 5 x 10(9) lymphocytes collected from each one cow which had persistent lymphocytosis (PL) and antibodies to bovine leukemia virus (BLV). A sudden increase in the number of peripheral blood lymphocytes (PBL) was observed 14 and 23 days, respectively, after inoculation and the maximum number reached 29,000 and 52,000/microliters 72 and 57 days after inoculation. Although the degree of PL decreased gradually in these cattle, it continued until 14 and 44 months after inoculation when one animal was sacrificed and the other died of lymphosarcoma. The PL was passaged in cattle by inoculation of a large number of PBL obtained from cattle at the stage of PL (PLL). The degree of PL was severer in cattle inoculated with a larger number of PLL. PL was not caused by inoculation of PBL obtained from either BLV-infected non-PL cattle or cattle free of BLV. The PL was also caused by inoculation of PLL into BLV-infected non-PL cattle. On the other hand, it was not observed after inoculation of a large amount of cell-free virus obtained from short-term cultures of PLL. Antibodies to BLV developed earlier and to higher levels in cattle inoculated with PLL than in those inoculated with cell-free virus. These facts show that infection with BLV was established more effectively by PLL than by cell-free virus, the infection may occur by lymphocyte to lymphocyte interaction and the actual number of infected BLV may have an important role in development of PL.  相似文献   

11.
The effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on B lymphocytes from persistent lymphocytosis (PL) cattle and lymphoma cells induced by bovine leukemia virus (BLV) was studied in vitro. Flow cytometric analysis showed that high levels of receptors to GM-CSF were expressed on these cell types. Proliferation of these B cells was induced in response to bovine GM-CSF. In tumor cell lines, the rate of cell proliferation was correlated with expression of GM-CSF receptors. A monoclonal antibody to GM-CSF inhibited lymphocyte proliferation and blocked the GM-CSF binding of lymphocytes. Cells expressing GM-CSF receptor were Ig positive and both CD5 and CD11 positive (B-1a cell). These results suggest that an abnormal expression of GM-CSF receptors on B lymphocytes from PL and lymphoma cells induced by BLV plays important roles in the PL and proliferation of lymphoma.  相似文献   

12.
Peripheral blood lymphocytes (PBL) from normal and bovine leukemia virus (BLV)-infected cattle were prepared by density gradient technique and incubated with and without phytohaemagglutinin (PHA) and pokeweed mitogen (PWM). RNA synthesis was determined at different periods of incubation by 3H-uridine incorporation. PBL from BLV-infected cows with persistent lymphocytosis (PL) showed the highest spontaneous RNA synthesis. PBL from BLV-infected cows with normal lymphocyte counts synthesized more RNA than cells from normal animals. Decreased mitogen responses were observed in PBL from infected cows with PL in comparison to normal and BLV-infected cattle without PL. PHA and PWM did not show significant differences in their degree of stimulation of RNA synthesis.  相似文献   

13.
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   

14.
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   

15.
The acceptance of the fetal allograft by pregnant women and mice seems to be associated with a shift from a Th 1 dominated to a Th 2 dominated immune response to certain infectious agents. The goal of this study was to examine cytokine expression in peripheral blood mononuclear cells (PBMCs) from cattle immune to bovine viral diarrhea virus (BVDV) to determine whether pregnancy also has an influence on the type of immune response in this species. Forty-six heifers and cows between 14 months and 13 years of age were included in this study. Twenty-four were seropositive and 22 seronegative for BVDV. Eleven of the seropositive animals and 11 of the seronegative animals were in the eighth month of gestation, the remaining animals were virgin heifers. PBMC from these animals were analyzed for Interferon (IFN)-gamma and Interleukin (IL)-4 mRNA expression by real-time RT-PCR after stimulation with a non-cytopathic strain of BVDV. Additionally, an ELISA was performed to measure IFN-gamma in the supernatants of stimulated cell cultures. In BVDV seropositive animals, IFN-gamma mRNA levels were significantly higher than in BVDV seronegative animals and there was a significant positive correlation between the changes in IFN-gamma and IL-4 mRNA expression. There was, however, no significant difference in IFN-gamma and IL-4 mRNA levels between pregnant and non-pregnant animals. These results are inconsistent with BVDV inducing a Th1 or Th2 biased immune response. Furthermore, a shift in the cytokine pattern during bovine pregnancy was not evident.  相似文献   

16.
We investigated the distribution of B and T cells in the peripheral blood of haematologically inconspicuous (non-persistent lymphocytotic, PL-) cattle infected with the bovine leukaemia virus (BLV). Flow cytometric data were obtained from six PL- cattle and compared with six age-matched animals with persistent lymphocytosis (PL+) and five non-infected healthy controls (BLV-). In the PL- group, the percentage and number of surface immunoglobulin-positive (sIg+) B cells were significantly reduced. Whereas in BLV-cattle, about 40% of the peripheral blood lymphocytes (PBL) were sIg + and 24% were sIgM + B cells. In the PL- group, less than 20% of the PBL were sIg+ and sIgM+ B cells. Only 5% of the PBL co-expressed sIgM+ and CD5+ versus 16% in BLV-. This decrease was persistent over 3 years and predominantly affected: (i) B cells that did not express sIgM; (ii) sIgM + B cells co-expressing CD5 and CD11b; and (iii) equally both lambda- and K-type light chain B-cell subpopulations. In contrast, the number of all circulating lymphocytes, CD5- and CD11b- sIgM+ B cells and CD2+ T cells did not differ. In PL+ animals, about 75% of the PBL were sIgM+ CD5+ B cells. These cells were of polyclonal origin, as light chains of the lambda- and K-type were expressed in a ratio of 4:1 (57.7% of PBL lambda+, 14% kappa+) as in BLV- animals (33.6% of PBL lambda+, 8.7% kappa+). In PL+ cattle the absolute number of B-cells and, therefore, their relative percentage is significantly increased. For this reason, even in case of absolutely increased T-cell numbers, the relative percentage of T-cells could be lower than in normal controls. The cause for the observed B cell decrease in PL- cattle is unknown, but it can be assumed that cytotoxic T cells are involved in this B-cell lymphopenia.  相似文献   

17.
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18.
The effects of bovine leukemia virus (BLV) on the immune response have been extensively investigated; however, its effects on mammary gland immunity are only speculative. Although BLV has a tropism for B cells, it can affect both adaptive and innate immunities because these systems share many effector mechanisms. This scenario is the basis of this investigation of the effects of BLV on mammary gland immunity, which is largely dependent upon neutrophilic functions. Thus, the present study sought to examine neutrophilic functions and the lymphocyte profile in the milk of naturally BLV-infected cows. The viability of the milk neutrophils and the percentage of milk neutrophils that produced reactive oxygen species (ROS) or phagocytosed Staphylococcus aureus were similar between BLV-infected and BLV-uninfected dairy cows. Furthermore, the expression of CD62L and CD11b by the milk neutrophils and the percentage of milk neutrophils (CH138+ cells) that were obtained from the udder quarters of the BLV-infected cows were not altered. Conversely, the median fluorescence intensity (MFI) representing intracellular ROS production and the phagocytosis of S. aureus, the expression of CD44 by the milk neutrophils and the percentage of apoptotic B cells were lower in the milk cells from BLV-infected dairy cows, particularly those from animals with persistent lymphocytosis (PL). The lymphocyte subsets were not different among the groups, with the exception of the percentage of CD5−/CD11b− B cells, which was higher in the milk cells from BLV-infected cows, particularly those with PL. Thus, the present study provides novel insight into the implications of BLV infection for mammary gland immunity.  相似文献   

19.
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20.
In order to elucidate whether natural infection of BLV in cattle might induce humoral immunological responses, changes in IgG1, IgG2, and IgM concentrations in the sera of infected cattle were determined. Twelve BLV-infected cattle were used. Cattle of different breeds were classified serologically and haematologically into BLV + PL+, BLV + PL- and BLV-free groups. Ig concentrations in the sera of the three groups were quantitated using a commercial single radial immunodiffusion assay. The findings were compared to those of BLV-free cattle. The serum IgM concentrations were significantly lower in cattle with PL (P less than 0.001) than in BVL + PL- and BLV-free cattle. The IgM concentrations tended to be lower in BLV+ PL- than those of BVL-free cattle. There were no significant differences in IgG1 and IgG2 serum concentrations between the three experimental cattle groups. IgG1 was the predominant subtype in the sera of all cattle groups.  相似文献   

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