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J F Ferrer

Publications and source records attributed to J F Ferrer.

At least 37 records · Page 2Linked to original sources
PubMed1986

Transmission of bovine leukosis virus by blood inoculation.

The experimental transmission of bovine leukosis virus (BLV)-infected whole blood was studied in 2 groups of Holstein calves. The 1st group of 4 BLV-seronegative calves was given 10 microliters of whole blood by either the IM, IV, subcutaneous, or intradermal routes. All 4 calves seroconverted to BLV within 8 weeks after they were inoculated. The 2nd group, also comprising 4 calves, was given the equivalent of 1 microliter of whole blood by the described routes. These calves seroconverted to BLV by 14 weeks after they were inoculated. The results indicated that small volumes of whole blood administered by 4 different routes were effective in the spread of BLV.

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PubMed1986

Enhanced expression of the c-myc gene in bovine leukemia virus-induced bovine tumors.

We have detected elevated levels of c-myc gene expression in neoplastic cells from all seven bovine leukemia virus (BLV)-induced bovine tumors examined, but not in BLV-infected, nonneoplastic lymphoid cells. No rearrangement or amplification of the c-myc gene could be demonstrated in any of the BLV-induced tumors. Furthermore, BLV proviral DNA was found to have no preferred site of integration in these tumors. The possible mechanisms of enhanced expression of the c-myc gene in BLV-induced tumors have been discussed.

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PubMed1985

Methylation and expression of bovine leukemia proviral DNA.

In vivo, the BLV proviral DNA usually resides in a transcriptionally inert state, and is hypermethylated. Upon short-term in vitro cultivation of the neoplastic or non-neoplastic lymphoid cells, the viral genome becomes transcriptionally active but without detectable change in its methylation state. Proviral DNA was found to be methylated in one but not in the other long-term BLV producer cell line examined. These data indicate that hypermethylation of proviral DNA may not be responsible for the covert nature of BLV infection in vivo.

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PubMed1985

Phytohemagglutinin activation of the transcription of the bovine leukemia virus genome requires de novo protein synthesis.

Addition of supramitogenic doses of phytohemagglutinin (PHA) to short-term cultures of neoplastic or nonneoplastic lymphocytes infected with bovine leukemia virus increased the synthesis of the major core virion antigen (p25) by 5- to 10-fold. Such stimulation was not due to the mitogenic effect of PHA or to a generalized increase in cellular RNA or protein synthesis but rather to enhanced transcription of the viral genome by a PHA-induced protein.

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PubMed1985

Characterization of the blood lymphocyte population in cattle infected with the bovine leukemia virus.

Blood leukocytes of cattle characterized in terms of bovine leukemia virus (BLV) infection and persistent lymphocytosis (PL) were examined for the presence of lymphocyte subpopulation markers and viral antigens. The percentages of cells with surface and intracytoplasmic immunoglobulin M (IgM) and erythrocyte-antibody-rosetting cells agreed closely in all infected cattle. This correlation and the results of double labeling experiments indicate that virtually all the surface IgM-positive B-lymphocytes in the blood of these animals carry Fc receptors. In PL cattle, the percentages of surface IgM-positive cells were more than twice those of normal cells and accounted for all the increase in peripheral blood lymphocytes. B-cells accounted for most of the increase in peripheral blood lymphocytes seen in cattle with PL. In contrast, most BLV-infected, nonlymphocytotic cattle had normal percentages of B-cells. Thus, the expansion of the B-cell population in blood, while being a conspicuous characteristic of PL, is not necessarily a consequence of BLV infection per se. Comparisons of the percentages of IgM-positive and erythrocyte-antibody complement-rosetting cells, together with the results of double labeling experiments, indicate that about one-half the B-cells in the blood of cattle with PL lacked C-3 receptors. The proportion of these cells (most likely immature B-lymphocytes) was smaller in the blood of BLV-infected nonlymphocytotic cattle. Direct comparison showed that, in BLV-infected cattle with or without PL, and in BLV-free cattle, virtually all erythrocyte-rosetting blood cells had peanut agglutinin receptors. With only one exception, the numbers of erythrocyte-positive cells in the blood of BLV-infected cattle with or without PL were within normal values. The "null" blood cell population, estimated as the difference between the IgM-positive and erythrocyte-positive populations, was essentially unaffected in BLV-infected cattle without PL, but it was absent in PL cattle. The large majority of the B-lymphocytes present in the blood of cattle with PL were infected with BLV. The proportion of infected B-lymphocytes in the blood of BLV-positive nonlymphocytotic cattle was much lower. Even in cattle with low or moderate levels of BLV-infected blood lymphocytes, the percentages of these cells were remarkably constant during the 12-month period of the study. The data indicate that most of the BLV-infected B-lymphocytes of cattle with PL lack C-3 receptors.

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PubMed1985

An amplified immunoperoxidase assay to detect bovine leukemia virus expression: development and comparison with other assays.

An amplified immunoperoxidase (AIP) assay using an avidin:biotin complex was developed to detect bovine leukemia virus (BLV) antigen expression in lymphocytes which had been cultured 24 h and fixed with acetone. Nonspecific reactions were eliminated by absorbing the test serum with 100% horse or cow serum. DNA synthesis inhibition did not decrease the number of AIP-positive cells, and there were no apparent preferential losses of major lymphocyte subpopulations during culture. Both viable and nonviable BLV-expressing cells were detected. Thus, the number of AIP-positive cells seems to be a good estimate of the minimum number of infected lymphocytes present in the uncultured blood cells. In direct comparisons, twice as many BLV-expressing cells were detected with the AIP assay as with an indirect immunofluorescence test. The AIP assay is as sensitive as the syncytia infectivity assay and only slightly less sensitive than an immunoperoxidase infectivity assay for detecting BLV-infected lymphocytes in the blood of infected cattle that were in early stages of infection and/or had low titers of antiviral antibodies. The AIP assay is the most sensitive, rapid, and reproducible procedure available for the identification of individual cells infected with BLV. This assay may be of great value in studies on the biology of BLV infection.

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PubMed1984

Molecular cloning of covalently closed circular DNA of bovine leukemia virus.

The two species of covalently closed circular DNA molecules of bovine leukemia virus were cloned in the lambda phage vector lambda gtWES X lambda B. Of the nine independent recombinant lambda-bovine leukemia virus clones that were analyzed, three were derived from the small and six were derived from the large circular molecules carrying, respectively, one and two copies of the long terminal repeat sequences. Comprehensive restriction endonuclease mapping of the unintegrated bovine leukemia virus and the cloned DNA molecules showed that eight of the nine clones carried viral information without any detectable deletions or insertions of more than ca. 50 base pairs. One of the nine clones, which carries a retroviral insert with one copy of the long terminal repeat, had a deletion of ca. 150 base pairs.

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PubMed1984

Transcriptional control of the bovine leukemia virus genome: role and characterization of a non-immunoglobulin plasma protein from bovine leukemia virus-infected cattle.

Using cloned bovine leukemia virus (BLV) DNA as a probe in the dot blot hybridization technique, we demonstrated that the expression of the BLV genome in infected lymphocytes is blocked in vivo at the transcriptional level. This blocking effect is due to a non-immunoglobulin protein present in the plasma but not in the serum of BLV-infected cattle. The plasma BLV-blocking protein also blocks the expression of the BLV genome in fibroblast cells of bovine and nonbovine origin infected with BLV in vitro. The plasma BLV-blocking factor has no inhibitory effect on the expression of Rauscher murine leukemia virus and feline leukemia virus in monolayer culture. The plasma BLV-blocking factor is not an interferon molecule. As determined by gel filtration chromatography, the plasma BLV-blocking factor has an apparent molecular weight of ca. 150,000.

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PubMed1983

Detection, purification, and characterization of two species of covalently closed circular proviral DNA molecules of bovine leukemia virus.

Cocultivation of uninfected and bovine leukemia virus-producing bat cells yielded, in addition to the unintegrated linear DNA duplex, DNA molecules that migrated as 4.4- and 4.8-kilobase-pair DNA fragments in gel electrophoresis. These DNA molecules were purified by acid-phenol extraction and cleaved with restriction endonucleases EcoRI, and HindIII, which have one recognition site each on the bovine leukemia virus proviral DNA. Such cleavage generated DNA molecules of approximately 10.0 and 9.4 kilobase pairs, thus indicating the existence of two species of covalently closed circular molecules of bovine leukemia virus proviral DNA.

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PubMed1982

Eradication of bovine leukemia virus infection from a high-prevalence herd, using radioimmunoassay for identification of infected animals.

Radioimmunoassay (RIA), using the virion glycoprotein antigen, was applied in an attempt to eradicate bovine leukemia virus (BLV) infection from a herd in which virtually all the adult cattle are infected. Considering that most calves born to BLV-infected cows are negative for BLV at birth and remain negative for the first several months of life, the eradication program was based on the identification and isolation of the BLV-free calves born to infected cows. Twenty-five calves raised on colostrum and milk from their infected dams were classified as BLV-free on the basis of negative results in the RIA at 6 to 8 and 9 to 11 months of age. These animals were maintained in either complete (10 calves) or partial (15 calves) isolation from infected cattle and were examined at regular intervals for BLV and BLV antibodies. With the exception of 1 calf in the group raised in partial isolation, the animals have remained free of BLV up to the time of the last evaluation, when they were 32 to 35 months old. At these ages, more than 90% of the nonisolated cattle in the herd are BLV-positive. The data also show that this eradication trial would have failed if, in the initial procedure used to classify the calves as BLV-free, the agar gel immunodiffusion test instead of the RIA had been used. Inasmuch as the 25 calves in this study were fed colostrum and milk from their dams, the fact that only 1 of the calves became infected during the 26 to 29 months of observation provides further evidence that milk-borne transmission of BLV is infrequent and perhaps inconsequential.

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PubMed1982

Expression of bovine leukemia virus genome is blocked by a nonimmunoglobulin protein in plasma from infected cattle.

Plasma of cattle infected with bovine leukemia virus contains a soluble factor that blocks the expression of the viral genome in cultured lymphocytes. The blocking factor is not present in plasma of bovine leukemia virus-free cattle or of cattle infected with common bovine viruses. Blocking of bovine leukemia virus expression by the plasma factor is reversible, and seems to be mediated by a nonimmunoglobulin protein molecule.

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PubMed1982

Haemagglutination by bovine leukaemia virus.

Bovine leukaemia virus (BLV) was found to agglutinate mouse erythrocytes. Under optimal conditions, including the use of neuraminidase-treated erythrocytes, 200 microgram/ml of BLV purified from the supernatant fluid of BLV-infected bat cells had haemagglutinating titres of about 512 units. BLV haemagglutination was drastically affected by pH and temperature; maximum agglutination occurred at pH 6 and 4 degrees C. That the BLV haemagglutinin is a glycoprotein was suggested by the fact that trypsin, potassium periodate or neuraminidase, but not lipid solvents or phospholipase C, significantly reduced the haemagglutinating (HA) activity of purified BLV. Furthermore, purified BLV glycoprotein of mol. wt. 51 000 (gp51) had HA activity. The receptors for BLV on mouse erythrocytes were inactivated by proteolytic enzymes but not by sodium deoxycholate or potassium periodate. Neuraminidase treatment of erythrocytes increase their agglutinability fourfold. Haemagglutination is a relatively sensitive test for detecting BLV glycoprotein because 0.4 microgram/ml of glycoprotein can be detected by this method. The pH and temperature sensitivity of the BLV HA reaction and specificity for mouse erythrocytes distinguish BLV from that of equine infectious anaemia virus and murine leukaemia virus, the other C type retroviruses known to have HA activity.

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PubMed1981

Milk of dairy cows frequently contains a leukemogenic virus.

Milk or viable milk cells collected from 24 dairy cattle naturally infected with bovine leukemia virus were inoculated into lambs, which were subsequently examined for the development of infection. With this bioassay, infectious virus was demonstrated in the milk of 17 of the cows. Bovine leukemia virus is leukemogenic in at least two mammalian species, is widespread in commercial dairy herds, and can infect a wide range of hosts in vivo and cells, including human cells, in vitro.

Animals↗
PubMed1981

Comparison of various serological and direct methods for the diagnosis of BLV infection in cattle.

The sensitivities of several serological and direct methods for the detection of bovine leukemia virus (BLV) infection in cattle have been critically compared. Among the serological methods, the radioimmunoassay (RIA) using the BLV glycoprotein (gp) was found to be more sensitive than the RIA using the internal virion antigen (p25) and the immunodiffusion test using the virion gp antigen. The differences in sensitivity between these tests were particularly evident with sera of cattle in early stages of infection. The sensitivities of the syncytia induction assay and the competitive RIA for the direct demonstration of BLV infection in cattle are comparable. Following natural infection, antibodies to the gp antigen in most cattle were detected by the RIA several months before infectious BLV became detectable by the SIA in the blood lymphocytes. It is concluded that the most accurate, sensitive, and rapid method for the detection of BLV infection in cattle is the RIA using the virion gp antigen. The data presented confirm that BLV infection as well as the antibody responses of naturally infected cattle to the BLV p25 and gp antigens are persistent.

Animals↗
PubMed1981

Evidence that the spontaneous blastogenesis of lymphocytes from bovine leukemia virus-infected cattle is viral antigen specific.

Cattle lymphocytes cultured for 3 days were found to spontaneously incorporate thymidine (3STI). Under optimal conditions of culture, the median magnitude of 3STI activity in lymphocytes from bovine leukemia virus (BLV)-infected cattle was higher than that of BLV-free cattle, but the ranges of the values overlapped. However, the 3STI activity of most BLV-infected cattle was specifically inhibited by serum containing BLV antibodies, whereas the 3STI activity of BLV-free cattle was not. The 3STI inhibitor copurified with immunoglobulin, and its activity could be absorbed with BLV. Rabbit anti-BLV serum inhibited 3STI, but rabbit anti-BLV p25 did not. These results indicate that BLV infection induces or expands a BLV-specific lymphocyte population. Spontaneous blastogenesis may be indicative of an immune response which controls virus spread.

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PubMed1981

Induction of lymphosarcoma in sheep by bovine leukemia virus.

Newborn sheep inoculated with phytohemagglutinin (PHA)-treated short-term, cultures of lymphocytes from cattle infected with bovine leukemia virus (BLV) or with a BLV- infected long-term culture of bovine leukemic lymphocytes became persistently infected with BLV. Fifty percent or more of the sheep died with histologically confirmed lymphosarcomas. Cytogenetic studies of representative cases demonstrated that the tumors did not result from the progressive growth of neoplastic lymphocytes in the inoculum but rather from the neoplastic transformation of the recipients lymphoid cells. Neither BLV infection nor lymphosarcoma was observed in control uninoculated sheep or in sheep given injections of PHA-treated cultures of lymphocytes from BLV-free cows. The virus recovered from the tumorous sheep was indistinguishable from BLV morphologically, antigenically, and biologically, and its reverse transcriptase had the same cation preference and immunologic properties as the BLV enzyme. Persistent BLV infection and lymphosarcoma were also observed in a group of sheep inoculated neonatally with BLV-containing cell-free culture supernatants. These results extend previous observations on the high susceptibility of sheep to BLV infection and provide definitive evidence that BLV is a tumor-inducing virus.

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PubMed1981

Use of a feline cell line in the syncytia infectivity assay for the detection of bovine leukemia virus infection in cattle.

This report describes a modified syncytia infectivity assay (SIA) for the direct detection of bovine leukemia virus (BLV) in blood lymphocytes of cattle, using transformed feline (CC81) cells as the indicator system. The data show that the syncytia present in cultures of CC81 cells inoculated with BLV-infected cells are specific and arise through a mechanism similar to that responsible for the phenomenon of "late" polykaryocytosis described in other virus systems. The susceptibility of the CC81 cells to the syncytia-inducing effect of BLV-infected cells is comparable with that of early passages of bovine embryonic spleen cells, which were previously used as the indicator system in the SIA. Unlike the bovine embryonic spleen cells, CC81 cells retain their susceptibility to syncytia induction for long periods of cultivation. Furthermore, the syncytia induced in the CC81 cultures are larger and easier to identify. Thus, the CC81 cells can be used advantageously as the indicator system when the SIA is applied to the detection of BLV-infected lymphocytes. The results of the SIA for the detection of infective BLV agreed closely with those of the radioimmunoassay for the detection of BLV antibodies in randomly examined cattle. On the other hand, many cattle in early stages of infection were positive in the radioimmunoassay several months before they reacted in the SIA. The detection of BLV in blood lymphocytes provides a useful method for the diagnosis of BLV infection in cattle when serologic tests cannot be used, eg, calves that may have passively acquired maternal antibodies and cattle given BLV vaccines.

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