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Biomedical subjects

J F Ferrer

Publications and source records attributed to J F Ferrer.

At least 73 records · Page 4Linked to original sources
PubMed1977

Inhibition of the reverse transcriptase of bovine leukemia virus by antibody in sera from leukemic cattle and immunological characterization of the enzyme.

Sera from some leukemic cattle contain an antibody that inhibits the reverse transcriptase activity of the bovine leukemia virus. The antibody is not directed against the synthetic template or the major internal and envelope viral antigens. The antibody failed to inhibit the DNA polymerases of the murine leukemia virus, simian sarcoma-associated virus, avian myeloblastosis virus, or Escherichia coli. Conversely, the bovine leukemia virus enzyme was not inhibited by antibody against the reverse transcriptases of other C-type viruses. These findings agree with previous results showing that the major internal bovine leukemia virus protein lacks the known interspecies- and intraspecies-specific antigenic determinants indentified in the homologous proteins of other oncornaviruses.

Animals↗
PubMed1977

A reverse transcriptase assay for detection of the bovine leukemia virus.

An RNA-dependent DNA polymerase or reverse transcriptase has been demonstrated in highly purified bovine leukemia virus (BLV) particles. The viral enzyme responded very effectively to the exogenous template primer polyneucleotide (poly) (rA)-oligonucleotide (oligo) (dT). Unlike the reverse transcriptases of most mammalian C type RNA viruses, and of the ubliquitous foamy-like bovine syncytial virus, the BLV enzyme prefers magnesium rather than manganese for optimal activity. The identification of several other conditions required for optimal activity of the viral reverse transcriptase led to the development of a rapid, sensitive, semiquantitative assay, which is comparable in sensitivity to the syncytia-infectivity assay for the detection of BLV in supernatant fluids of monolayer cell cultures. However, the reverse transcriptase assay is not sufficiently reproducible for obtaining routine detection of BLV in short-term cultures of bovine peripheral blood lymphocytes. Therefore, this assay does not seem to provide an accurate method for the diagnosis of BL virus infection in cattle.

Cells, Cultured↗
PubMed1976

Bovine leukemia virus genes in the DNA of leukemic cattle.

Reverse transcripts of the rna genome of the bovine leukemia virus (BLV) as well as 125I-labeled BLV RNA hybridize to the DNA of tissues from leukemic cattle with the adult form of the disease but not to bovine thymic lymphoma or normal bovine tissues.

Animals↗
PubMed1976

Detection, quantitation, and characterization of the major internal virion antigen of the bovine leukemia virus by radioimmunoassay.

The major internal polypeptide of the bovine leukemia virus (BLV) was purified to homogeneity with the use of gel filtration and affinity chromatography. Like previous results, the protein had a molecular weight of 25,000 daltons as determined by electrophoresis in polyacrylamide gels with sodium dodecyl sulfate. More than 90% of the 125I-labeled protein was precipitated by bovine sera that reacted in immunofluorescence tests with acetone-fixed BLV-infected cells. In contrast, minimal precipitation (less than 5%) was observed with sera from 36 cattle in leukemia-free herds; these sera, negative by immunofluorescence, included six samples that had high titers of antibodies to the foamy-like bovine syncytia virus (BSV). Antisera prepared against several other oncornaviruses or the Mason-Pfizer monkey virus (M-PMV) did not bind the BLV p25 protein. Conversely, the labeled p30 polypeptides of several oncornaviruses tested did not react with bovine sera that had high titers of antibodies to BLV p25. Competitive radioimmunoassay(s) (RIA) also failed to detect cross-reactions between BLV p25 protein and the internal polypeptides of other mammalian and avian oncornaviruses, M-PMV, or foamy-like BSV. The RIA for BLV p25 antigen was also highly sensitive and specific for the detection and quantitation of the antigen in virus preparations and cell homogenates.

Animals↗
PubMed1976

Induction of syncytia by the bovine C-type leukemia virus.

Bovine buffy coat cells infected with the bovine leukemia virus (BLV) induce syncytia formation in human diploid embryonic lung cells as well as in monolayer cell cultures of bovine, simian, ovine, bat, and caprine origin, but not in mouse fibroblast cells, normall rat kidney cells, or RSV-transformed rat cells. Syncytia were not observed in diploid embryonic lung cells inoculated with bovine buffy coat cells free of BLV. The syncytia-induction effect is associated with the synthesis of complete BLV by the buffy coat cells and is independent of whether these cells are viable, disrupted, normal, or malignant. Cell-free preparations of BLV and density gradient-purified virus also induce syncytia when added directly to diploid embryonic lung cells and to bovine, bat, and caprine monolayer cell cultures. Ether treatment, ultraviolet light irradiation, heating, freezing, and thawing destroy the syncytia-inducing activity of BLV. This activity is also neutralized when the virus is incubated with sera containing antibodies to BLV, but not when incubated with sera free of these antibodies or reference serum for the foamy-like bovine syncytial virus. Several other lines of evidence rule out the possibility that this virus or other bovine viruses are responsible for the syncytia-inducing phenomenon described here. BLV antigen was consistently detected by the immunofluorescent test in the syncytia-positive monolayer indicator cultures. However, syncytia formation was not necessarily associated with BLV production by the indicator cells. The ability to induce syncytia in monolayer cultures of nontransformed cells distinguishes BLV from all the known C-type luekemia viruses.

Antibodies, Viral↗
PubMed1976

Development of an in vitro infectivity assay for the C-type bovine leukemia virus.

The ability of the bovine C-type leukemia virus to induce syncytia formation in monolayer cell cultures has been used to develop a specific and simple infectivity assay for the virus. Using bovine embryonic spleen cells or human diploid embryonic lung cells as indicator cells, the results of the assay can be evaluated in 4 to 6 or 6 to 8 days, respectively. Pretreatment of the indicator cells with DEAE-dextran greatly increases the sensitivity of the assay. The assay is quantitative and can be applied as a direct method for the identification of bovine C-type leukemia virus-infected animals; it also provides a simple, and sensitive procedure for the detection and titration of virus-neutralizing antibodies.

Antibodies, Viral↗
PubMed1976

Isolation and characterization of an antigen of the bovine C-type virus.

By means of gel filtration and isoelectric focusing, an antigen of the bovine C-type leukemia virus was isolated in a highly purified form from extracts of infected cells. The antigen has a molecular weight of approximately 25,000 daltons and an isoelectric point of 6.4 to 6.6. In immunodiffusion experiments, the antigen forms a line of identity with an antigen extracted from highly purified bovine C-type leukemia virus by treatment with ether or Triton X-100. As determined by immunodiffusion analyses, the bovine C-type leukemia virus antigen does not have antigenic determinants in common with the murine or feline leukemia viruses, the foamy-like bovine syncytia virus, or the Mason Pfizer monkey virus.

Antigens, Viral↗
PubMed1976

In vitro transmission and propagation of the bovine leukemia virus in monolayer cell cultures.

This study demonstrates that the bovine leukemia virus (BLV) can infect in vitro cells of human, simian, bovine, canine, caprine, ovine, and bat origin. Cultures of these cells, cocultivated with BLV-infected cells or inoculated with cell-free BLV preparations, continuoously showed the presence of cells with the internal BLV antigen as well as BLV-induced syncytia. Virus replication was abundant and increased with passage in bat lung cells and was moderate but constant in fetal canine thymus cells. The amounts of virus released by the simian DBS-FRhL-1 and caprine S-743 cultures were low to moderate during the first 4 to 8 weeks and decreased thereafter. In the infected fetal lamb spleen cell cultures, virus production was low and declined further with passage. Bovine embryonic spleen and human diploid embryonic lung WI-38 cell cultures produced very small amounts of virus only during the first two passages after inoculation despite the fact that they remained infected, as determined by the continuous presence of cell BLV antigen and syncytia. Morphologically and antigenically, the virus particles released by the monolayer cell cultures were indistinguishable from those found in short-term and long-term cultures of BLV-infected bovine lymphoid cells. Repeated electron microscopic examinations and serological tests showed that all the BLV-infected cultures, including those from which the infecting inocula were obtained, were free of the foamy-like bovine syncytial virus, parainfluenza 3 virus, infectious bovine rhinotracheitis virus, bovine viral diarrhea virus, and the maedi-like bovine R-29 virus.

Animals↗
PubMed1975

Further studies on the antigenic properties and distribution of the putative bovine leukemia virus.

The C-type viruses found in long-term cultures. New Bolton Center (NBC) cell lines, of peripheral lymphocytes from leukemic cattle and in short-term cultures of bovine buffy coat(BC) cells share an immunofluorescent(IF)antigen detected in the cytoplasm of infected cells as well as an antigen demonstrable in gel diffusion experiments. Therefore the viruses from these cultures most likely represent different isolates of the putative bovine leukemia virus (BLV). The BLV precipitin antigen is analogous to the group specific (gs) antigens of the leukemia viruses of other species in that it is soluble, ether resistant, and apparently located within the virion. These observations, together with results showing that the specificity of the BLV precipitin antigen differs from that of the gs antigen of other mammalian leukemia viruses, indicate that the former antigen represents the intraspecies (gs-1) determinant of BLV. Antibodies to the precipitin viral antigen were found in 82% of cattle with leukemia and in 40% of clinically normal adult cattle in multiple-case herds. These groups of animals also had fluorescent antibodies to the virus, but with significantly higher frequencies (100% and 76%, respectively). On the other hand, in leukemia-free herds, precipitating antibodies were not found and the incidence of fluorescent antibodies was only 3%.

Animals↗
PubMed1975

Cytogenetic, cytological, and virological characteristics of a bovine fibrosarcoma.

The features of a bovine tumor with typical histopathological characteristics of a malignant fibrosarcoma are described. Direct karyotype preparations from the tumor tissue showed two populations of cells with bizarre karyotypes. An in vitro cell culture, designated BS-2, derived from the tumor had a normal diploid karyotype. This culture formed syncytia and produced a virus morphologically indistinguishable from the ubiquitous bovine syncytial virus. BS-2 cells reacted strongly in immunofluorescent tests with both bovine syncytial virus reference serum and serum from the tumorous cow. The virus was also demonstrated by immunofluorescence and mixed culture techniques in the buffy coat cells of the same cow.

Animals↗
PubMed1975

Seroepidemiological evidence for horizontal transmission of bovine C-type virus.

Thirty colostrum-deprived calves from leukemia-free herds were foster nursed for 10 weeks on cows infected with bovine C-type virus (BLV) from multiple-case herds or on cows from leukemia-free herds. After weaning, the calves were raised in continuous contact with BLV-infected animals of approximately the same ages. Sera collected at 6 to 18 and 43 to 48 months of age were examined for the presence of antibodies to BLV by the immunofluorescent antibody test. At 6 to 18 months of age, only 1 of the 30 calves from leukemia-free herds had a detectable antibody response to BLV. By 43 to 48 months of age the number of antibody-positive animals had risen to 17. The foster dam's herd of origin did not significantly affect the rate of BLV infection. These results indicate that BLV can be horizontally transmitted from infected to noninfected animals.

Animals↗
PubMed1975

Serological diagnosis of infection with the putative bovine leukemia virus.

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.

Animals↗