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Biomedical subjects

J F Ferrer

Publications and source records attributed to J F Ferrer.

At least 19 recordsLinked to original sources
PubMed1992

Induction and inhibition of bovine leukaemia virus expression in naturally infected cells.

Bovine leukaemia virus (BLV) resides in infected lymphocytes in a latent, repressed state but becomes expressed a few hours after the cells are cultured in vitro. We have identified several conditions and factors affecting the expression of BLV in short-term cultures of naturally infected lymphoid cells. The presence of foetal calf serum in the culture medium greatly stimulates virus expression. This stimulation is not due to cellular proliferation. Transcription of BLV RNA and synthesis of p25 in the cultures of peripheral blood lymphocytes are preceded by a lag period of several hours. Synthesis of BLV p25 in these cultures takes place almost immediately after viral RNA synthesis. Extending previous results, we demonstrate that the plasma and lymphatic fluid of cattle contain factors that suppress and stimulate BLV expression. As a result of systematic examination of several parameters, we have developed reproducible assays for the detection of these factors. It is very likely that their relative concentration in the host is an important determinant of susceptibility and resistance to the development of lymphosarcoma and persistent lymphocytosis in BLV-infected cattle.

Animals↗
PubMed1992

Amplification and analysis of specific DNA and RNA sequences of bovine leukemia virus from infected cows by polymerase chain reaction.

Bovine leukemia virus (BLV) is the etiologic agent of leukemia in cattle and is believed to cause decreases in milk productivity, fertility, and life span in infected cows. BLV is a type C retrovirus in the Oncovirinae subfamily. It is most closely related to human T-cell lymphoma/leukemia virus type I (HTLV-I) and type II (HTLV-II). Since the polymerase chain reaction (PCR) provides rapid and efficient amplification of DNA sequences, primers were designed to amplify regions of the polymerase (pol) and pX genes specific for BLV targets. These sets of primers consistently amplified as few as 10 copies of BLV DNA contained in a plasmid in the background of 1 microgram of either human or bovine chromosomal DNA. In addition, no amplification products were detected from cell lines infected with HTLV-I, HTLV-II, or human immunodeficiency virus type 1 or 2 by the BLV PCR systems. Samples of peripheral blood mononuclear cells from 18 cows, previously determined to be serologically positive or negative, were correctly identified in a blind study as containing proviral DNA by use of the BLV primers and probes. Cloning and sequencing of amplified products revealed finite sequence variations among a previously cloned BLV isolate, the wild-type virus, and the published genome. Reverse transcriptase-directed PCR with the primers for both BLV pol and BLV pX was performed on plasma from a BLV-infected cow and detected in vivo BLV RNA expression. In summary, we have developed a specific and sensitive assay using PCR for the detection and identification of BLV infections; this assay can now be applied to clinical and basic research questions in veterinary medicine.

Animals↗
PubMed1979

An infectivity assay for bovine leukemia virus using the immunoperoxidase technique.

This report describes the development of a 7-day infectivity assay for bovine leukemia virus (BLV) which is based on the induction of the major internal virion antigen (a protein with a molecular weight of 25,000) in susceptible indicator monolayer cell cultures. In this assay, the antigen is detected in the indicator cells by the immunoperoxidase antibody technique using a specific rabbit antiserum to a BLV protein with a molecular weight of 25,000. The immunoperoxidase infectivity assay is specific, quantitative, reproducible, and more sensitive than the previously described syncytia induction assay. The immunoperoxidase infectivity assay can be applied to the detection of BLV-infected cells and provides a reliable method for the direct diagnosis of BLV infection in cattle.

Animals↗
PubMed1978

An improved syncytia infectivity assay for the bovine leukemia virus.

Several factors that influence the sensitivity of the syncytia infectivity assay for the bovine leukemia virus (BLV) and BLV-infected lymphocytes have been examined. The use of early-passage indicator bovine embryonic spleen (BESP) cells and their pretreatment with diethylamino-ethyl-dextran (DEAE-D) was essential for optimal sensitivity. Polybrene was less effective than DEAE-D. The combination of DEAE-D and polybrene was more effective than DEAE-D alone when BLV-infected leukocytes were used as the inoculum, but not when the inoculum was a cell-free BLV preparation. Using BESP cell passages 4 to 11 as indicators, reproducible titers were obtained when aliquots of the same virus stock were assayed at different times after freezer storage. When assaying peripheral blood lymphocytes from infected cattle, optimal syncytia responses were observed consistently by inoculating 5 X 10(6) viable lymphocytes per 60-mm Falcon dish. Centrifugation of peripheral blood leukocytes from BLV-infected cattle in discontinuous bovine serum albumin gradients can be used to separate a subpopulation of infected lymphocytes. Use of this subpopulation as the inoculum, rather than unseparated buffy-coat leukocytes, greatly increases the sensitivity of the syncytia infectivity assay.

Animals↗
PubMed1978

A critical comparison of the virus neutralizaiton, radioimmunoprecipitation and immunodiffusion tests for the serological diagnosis of BLV infection.

Several serological tests are available for the detection of antibodies to BLV. Thus far, only the virus neutralization antibody (VNA) test, the immunofluorescence test, and the immunodiffusion test with the major internal virion protein have been critically evaluated as diagnostic methods for the identification of BLV-infected cattle. Of these tests, the VNA test is the most sensitive and specific. Therefore, in the present study the VNA test has been applied to evaluate the reliability of the radioimmunoassay for BLV p25 (RIAp25) and of the immunodiffusion test with BLV-associated glycoprotein antigen (IDgp). The results show a very close agreement between the RIAp25, and the VNA test. The IDgp test is less sensitive than the RIAp25, particularly for the detection of BLV antibodies in early stages of infection. The RIAp25 is more rapid than the VNA test and does not require tissue culture techniques. Thus, the RIAp25 seems to be the most practical and sensitive available method for the serolgical diagnosis of BLV infection in cattle.

Animals↗
PubMed1978

Natural mode of transmission of the bovine leukemia virus: role of bloodsucking insects.

The development of bovine leukemia virus (BLV) infection was studied in 14 noninfected young adult cattle exposed to 25 to 30 BLV-infected cows in an area of approximately 0.5 ha. Of 7 cattle (group 1) exposed beginning in July and August (midsummer) of 1976, 4 were infected by October, and all 7 by November (4 months' exposure). Of 7 cattle (group 2) exposed from February 1977 (midwinter), all remained negative for 3 months, and only 1 was positive after 6 months. By October 1977, however, 4 cattle in this group were infected, indicating that contact transmission of BLV is prevalent during the summer months. This, and the fact that BLV-infected lymphocytes were recovered from tabanids allowed to feed on a BLV-positive cow, supports the idea that bloodsucking insects play a major role in the spread of BLV.

Animals↗
PubMed1978

Detection of a precursor of bovine leukemia virus structural proteins in purified virions.

Gel filtration chromatography of disrupted bovine leukemia virus (BLV) resulted in the isolation of the 25,000 dalton major virion internal protein and two previously uncharacterized virion proteins of molecular weight 65,000 and 12,000 respectively. The 65,000 dalton protein does not bind to concanavalin A and its antigenicity is ether-resistant. Therefore, this polypeptide is different from the previously described glycoprotein associated with BLV. Radiommunoprecipitation and competitive radioimmunoassays indicated that the 65,000 molecular weight polypeptide shares antigenic determinants with the 25,000, 15,000, and 12,000 dalton BLV proteins, respectively. Thus, the 65,000 dalton polypeptide may represent the precursor of these three smaller virion proteins.

Chromatography, Gel↗
PubMed1978

An infectivity assay for the bovine leukemia virus based on the induction of the major internal virion antigen in susceptible cell cultures.

This report described the development of a 7-day infectivity assay for the bovine leukemia virus (BLV) which is based on the induction of the major internal virion antigen (p25) in susceptible indicator monolayer cell cultures. In this assay the antigen is detected in the indicator cells by the immunoperoxidase antibody technique using a monospecific anti-BLV serum. The immunoperoxidase infectivity assay (IPIA) is specific, quantitative, reproducible and more sensitive than the previously developed syncytia induction assay. The IPIA can be applied for the detection of BLV-infected cells and provides a reliable method for the direct diagnosis of BLV infection in cattle.

Antigens, Viral↗
PubMed1978

An evaluation of the role of milk in the natural transmission of BLV.

In order to evaluate the role of milk in the transmission of BLV, the presence of the virus and viral antibodies was investigated in cattle that were born to, and nursed on, infected dams and then raised in isolation or in contact with infected animals. Only 3 of the 17 isolated cattle became infected during 25-29 months of observation. During the same period of time, all 17 cattle raised in contact with BLV-positive animals developed BLV infection. From these results, it is apparent that milk-borne transmission of BLV, if it occurs, is much less frequent than contact transmission.

Animals↗
PubMed1978

Persistent lymphocytosis in cattle: its cause, nature and relation to lymphosarcoma.

Studies in well-characterized cattle populations strongly support the view that the bovine leukemia virus (BLV) is the causative agent of the adult (enzootic) form of bovine lymphosarcoma and persistent lymphocytosis (PL), and that host genetic factors play an important role in the development of these two conditions. On the other hand, the available information indicates that the genetic factors controlling the development of PL are frequently independent of those controlling the development of lymphosarcoma. There is no evidence that clinically normal cattle with PL harbor malignant cells or have any other clinical abnormality. In these animals lymphocytosis results from the expansion of two distinct subpopulations of non-neoplastic B lymphocytes, one of which is free of BLV. Long-term studies have shown that the large majority of cattle with PL do not develop lymphosarcoma even when kept to advanced age. These data indicate that PL is not a disease nor a preclinical stage of lymphosarcoma. Rather PL should be considered as a benign response to BLV infection which, although frequently associated with lymphosarcoma, is independant of it.

Animals↗
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↗