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Biomedical subjects

W C Davis

Publications and source records attributed to W C Davis.

At least 217 records · Page 12Linked to original sources
PubMed1987

Antigenic and structural variation of the p28 core polypeptide of goat and sheep retroviruses.

The p28 core polypeptides of four isolates of caprine arthritis-encephalitis virus (CAEV) from goats was compared with those of visna virus (VV) and progressive pneumonia virus (PPV) from sheep. Monoclonal antibodies recognized p28 epitopes common to all six retrovirus isolates, a p28 epitope on four CAEV isolates, but not VV and PPV isolates, a p28 epitope on four CAEV isolates and VV, but not PPV and a p28 epitope unique to the CAEV isolate used for immunizing the mouse spleen donor. Comparison of two-dimensional maps of tyrosine containing tryptic peptides of p28 demonstrated that three CAEV isolates had similar maps while a fourth CAEV isolate, VV and PPV had several different from the three closely related CAEV p28s and from each other.

Animals↗
PubMed1987

Peripheral blood leucocytes subpopulation dynamics during Trypanosoma congolense infection in Boran and N'Dama cattle: an analysis using monoclonal antibodies and flow cytometry.

A panel of monoclonal antibodies (MoAb) with specificities for bovine leucocyte subsets were used in conjunction with routine haematological procedures to analyse sequential changes in peripheral blood leucocyte populations during the course of tsetse fly-transmitted Trypanosoma congolense infection in trypanotolerant N'Dama and trypanosusceptible Boran cattle. Subsequent to the first parasitaemic wave, the N'Dama cattle maintained packed cell volumes (PCV) above 22 and lower levels of parasitaemia than Boran throughout the 160 days of the experiment. In contrast, the Borans developed severe anaemia and required curative drug therapy (i.e., PCV dropped to less than 15) by 55 days (range: 22-55 days) post infection. There were significant (P less than 0.05) decreases in total white blood cells and total lymphocytes from pre-infection levels to the first peak of parasitaemia (day 16 post-infection) in both groups. Flow cytometric analyses using MoABs revealed that this change was due to an absolute decrease in T cells expressing BoT2 and either BoT4 or BoT8, surface immunoglobulin M-positive (sIgM+) B cells, and null cells which did not express T cell, B cell or monocyte markers. During this period there was significant variation over time, but no overall increase or decrease, in the number of cells expressing class II major histocompatibility (MHC) molecules or monocyte markers, or in the number of circulating neutrophils or eosinophils. The BoT4/BoT8 ratios were significantly (P less than 0.01) increased in both groups of infected animals at the first peak of parasitaemia. After day 22 in the infected N'Damas and in the Borans which required drug therapy, there was a leucocytotic response characterized by an increase in the total number of B cells, T cells, and null cells. Prior to infection and throughout the course of the experiment N'Dama cattle had significantly (P less than 0.01) higher numbers of B cells and null cells than Boran.

Animals↗
PubMed1986

Immunization with an isolate-common surface protein protects cattle against anaplasmosis.

Hemoparasitic diseases are endemic in half the world's livestock production areas and are the greatest obstacle to improved meat, milk, and fiber production in the Third World. The most prevalent of these diseases, anaplasmosis, occurs throughout tropical and subtropical regions and is responsible for 50,000 to 100,000 cattle deaths annually in the United States alone. Despite its prevalence and the severity of the losses, an effective immunoprophylaxis for anaplasmosis has not been developed. A neutralization-sensitive epitope on a surface protein with a molecular weight of 105,000 (Am 105) of the causative rickettsia Anaplasma marginale was identified by monoclonal antibody inhibition of infectivity. This epitope was determined to be common to eight isolates with antigenic, morphologic, and protein structural differences. Cattle immunized with Am 105 purified by immunoaffinity chromatography were protected against challenge with virulent Anaplasma marginale. The identification of Am 105 as bearing isolate-common epitopes capable of inducing protection in immunized cattle provides the basis for the development of an effective subunit vaccine for bovine anaplasmosis.

Anaplasma↗
PubMed1986

Surface antigen expression by bovine alveolar macrophages: functional correlation and influence of interferons in vivo and in vitro.

Alveolar macrophages (AM) procured by bronchoalveolar lavage of healthy calves were tested for the expression of two antigens defined by monoclonal antibodies. One of these, H34A, detects a MHC type II (Ia)-antigen; the other, B18A, a heterodimer of unknown function. No single AM-activity could be ascribed solely to the subpopulations defined by the presence or absence of these two surface antigens. The expression of both antigens could be modulated by in vitro treatment of the AM with recombinant E. coli-derived bovine interferon-gamma (rBoIFN-gamma), but not by interferon-alpha 1 (rBoIFN-alpha 1). Enhanced Ia-expression was detectable within 3 h of exposure to rBoIFN-gamma and reached a maximum by 24-48 h. Expression of the Ia-antigen required continual presence of bioactive IFN. However, cells that reverted from the Ia+ to the Ia- state did not become refractory to reinduction, and induction was possible even after several days (at least 96 h) in culture, despite the in vitro maturation and modulation of the AM that occurred. Treatment of calves with rBoIFN-gamma also resulted in increased numbers of Ia(H34A)+ cells, but in a decline of B18A+ cells. In contrast to the in vitro findings, rBoIFN-alpha 1 appeared to have some modulatory effect in vivo. The latter effect may be indirect rather than direct as for rBoIFN-gamma. As previously shown for rBoIFN-alpha 1, in vitro treatment of the AM with rBoIFN-gamma "activated" the AM as judged by enhanced cytotoxicity, enhanced accessory cell activity in mitogen-driven lymphocyte-proliferation, enhanced IgG Fc- and C3b-receptor expression and content of some enzymes. The fact that the two IFNs have very similar effects on cell functions, but differ markedly in their Ia-inducing immunoregulatory activity, supports the notion that the Ia-antigen expression may be irrelevant as a surface marker for macrophage activation, and may rather be a marker for a certain functional stage of the macrophage. Moreover, the acquisition of this stage appears to be, at least in the AM, a reversible event.

Animals↗
PubMed1986

Correction of equine severe combined immunodeficiency by bone marrow transplantation.

A 32-day-old horse with severe combined immunodeficiency was transplanted with equine bone marrow cells in an attempt to establish immunologic responsiveness. A histocompatible, mixed-leukocyte-culture-nonreactive, sex-matched, full sibling was used as the donor. Recipient total lymphocyte count, T and B lymphocyte numbers, and response of peripheral blood mononuclear cells to phytolectin stimulation increased by 14 days following transplantation. Circulating lymphocytes exceeded 1000 cells/microliter blood by 40 days posttransplantation, and by 170 days following transplantation, T and B lymphocyte numbers had reached normal values. The foal demonstrated significant primary and secondary antibody responses when immunized with bacteriophage phi X 174 at 100 and 142 days posttransplantation. Concentrations of IgG and IgM remained within the normal range following cessation of i.v. plasma therapy 156 days after transplantation. More than 300 days following transplantation, the foal remains healthy and is growing normally. At no time during the posttransplant period was there detectable evidence of graft-versus-host disease.

Animals↗
PubMed1986

Development and maintenance of bovine cytotoxic lymphocytes with recombinant human interleukin-2.

Long-term bovine lymphocyte cultures were initiated by stimulation with alloantigens and maintained in continuous culture using medium containing recombinant human interleukin-2 (rh IL-2). The development of specific and lectin-dependent killing was monitored following primary alloantigen challenge. Cytolytic activity was barely detectable after 7 days of culture, but gradually increased with peak activity occurring after 21 days of culture. A panel of monoclonal antibodies (MoAb) was used to determine whether a shift in the antigen phenotype of the cell population occurred during culture. The primary cell type that grew in culture was of the T-cell lineage with minimal or no expression of class II antigens. The activities of adenosine deaminase (ADA), purine nucleotide phosphorylase (PNP), adenosine kinase (AK), deoxyadenosine kinase (dAK), deoxycytidine kinase (dCK), 5'-nucleotidase (5'-N), AMP deaminase, hypoxanthine-guanine phosphoribosyl transferase (HGPRT or HPRT), and adenine phosphoribosyl transferase (APRT) were measured by microassay in resting peripheral blood lymphocytes (PBL) and in cells from long-term cultures. Large increases in the activities of PNP and HPRT with a decrease in the activity of ADA were observed. The data show that long-term cultures of lymphocytes can be readily generated, and that sequential changes in antigenic phenotype and function can be monitored and correlated with quantitative changes in enzyme activity.

Animals↗
PubMed1985

Monoclonal antibodies that distinguish bovine T and B lymphocytes.

The specificities of three monoclonal antibodies (MAbs) were investigated using microcytotoxicity, fluorescence microscopy and laser flow cytometry (LFC) techniques. By microcytotoxicity, bovine thymocytes (n = 4) were estimated to be 85% B26A+, 4% TH21A+, and 1% H4+. Nylon wool enriched peripheral blood T lymphocytes (n = 3) were 90% B26A+, 10% TH21A+ and 10% H4+. Adherent B cell enriched fractions (n = 3) were 10% B26A+, 90% TH21A+ and 90% H4+. The two fluorochrome method was used to simultaneously identify lymphocytes that were sIg+ and MAb+. In these experiments, 92% of all sIg+ cells were H4+. An identical result was obtained for TH21A. 85% of all sIg- cells were B26A+. Using LFC, the mean percentages of sIg+, H4+ and TH21A+ PBL (n = 5) were not significantly different. B26A recognized a significantly greater population of cells, equivalent to the expected percentage of T lymphocytes. LFC also revealed two relatively discrete sizes of B26A+ PBL. The larger population overlapped the size range in which sIg+, H4+, TH21A+ PBL were found. The more numerous smaller B26A+ PBL were in a size range in which few sIg+, H4+ and TH21A+ PBL were found. In a study of MAb reactions with PBL of 185 cows, it was shown that in 92% of the animals H4 and TH21A were positively correlated (r = +.93), when H4 and TH21A were negatively correlated with B26A (r = -.94 and r = -.92, respectively). These correlation coefficients indicate a converse relationship between B26A and both H4 and TH21A. The remaining 8% of the animals were heterogeneous in their expression of the H4 and TH21A markers but not the B26A marker. These results provide strong evidence that: 1) B26A is a pan-T lymphocyte MAb in cattle, 2) a small but significant degree of heterogeneity exists in the expression of the epitopes recognized by H4 and TH21A. However, both MAbs recognize all B lymphocytes of most individuals, and 3) using a variety of immunological methods these three MAbs can now reliably be used to assay bovine T and B lymphocytes.

Animals↗
PubMed1985

Functional and phenotypic characteristics of bovine natural cytotoxic cells.

Bovine natural cytotoxic (NC) cell activity of peripheral blood leukocytes (PBL) was studied in a chromium release assay, using xenogeneic tumor cells (YAC-1, P815) and herpes virus-infected bovine fibroblasts. The activity pattern resembled that of murine natural killer cells, in that YAC-1 cells were readily lysed, whereas P815 cells were resistant. However, 10-16 h of incubation were usually required to give appreciable cell lysis. Low, but consistent NC-activity was expressed against virus-infected fibroblasts. Using various biophysical and biochemical cell-separation methods, it was found that the effector cell active against both the xenogeneic tumor cells and virus-infected fibroblast belonged to the mononuclear phagocyte system. The indications are that at least two subpopulations of the blood monocytes, differing perhaps in maturation or clonal derivation, express NC-activity.

Animals↗
PubMed1985

Traumatic rupture of splenosis.

We believe this report represents the first of traumatic hemorrhage from splenosis which necessitated operation. We discuss previous reports of complications as a result of splenosis. With the increased interest in autotransplantation of splenic remnants following splenectomy, we expect that this complication may be reported with increasing frequency.

Adult↗
PubMed1985

Presence of common antigens, including major surface protein epitopes, between the cattle (intraerythrocytic) and tick stages of Anaplasma marginale.

Epitopes of major surface proteins of the intraerythrocytic cattle stage of Anaplasma marginale were demonstrated in the midgut stage of the organism within the infective tick host Dermacentor andersoni. These proteins were common to all A. marginale isolates tested and at all stages of parasitemia. Sera from cattle immunized with the tick midgut stage of A. marginale immunoprecipitated multiple-erythrocyte-stage proteins, as demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The major proteins recognized (primarily greater than 14 and less than 200 kilodaltons [kDa]) included two major-erythrocyte-stage surface proteins of 36 and 105 kDa molecular size. To confirm the presence of common tick and erythrocyte A. marginale antigens with the immunized cattle sera, we purified the 36-kDa erythrocyte-stage protein by monoclonal immunoaffinity chromatography and developed an enzyme-linked immunosorbent assay based on the purified protein. All sera from cattle immunized with tick-stage A. marginale and cattle infected with various isolates of A. marginale developed antibodies to the 36-kDa protein. The potential immunoprophylactic, diagnostic, and epidemiologic value of the major epitopes common to both the invertebrate and mammalian stages of A. marginale, especially the 36-kDa protein, is discussed.

Anaplasma↗
PubMed1985

Cell surface thiols, but not intracellular glutathione, are essential for cytolysis by a cloned murine natural killer cell line.

Cell surface thiols are required for a line of cloned murine natural killer lymphocytes to bind to and lyse tumor target cells. These lymphocytes neither bound to nor killed YAC-1 or G1Tc cells when the effector lymphocyte cell surface thiols were covalently coupled with the non-penetrating reagent, monobromotrimethylammoniobimane (qBBr). A limited number of thiol-bearing proteins were identified by gel electrophoresis on the cell surface using the fluorescence of the group that remains associated with the sulfur molecule. These results indicate that either one or more of these reactive proteins or different cell surface thiol-bearing molecules present at low frequencies are crucial to lymphocyte binding and killing. In contrast, we found little evidence that intracellular thiols are required for natural killer cell activity. Killing was relatively unimpaired when over 90% of lymphocyte glutathione was depleted with DL buthionine-S,R-Sulfoximine (BSO). Blocking the intracellular or the extracellular thiols of tumor targets had no effect on their ability to be lysed. Based on these data, we suggest that infrequently expressed extracellular thiols are required either for the conformation or for the disulfide crosslinking of proteins that participate in lymphocyte-mediated cytolysis.

Animals↗
PubMed1985

Monoclonal antibodies raised against bluetongue virus detect viral antigen in infected tissues using an indirect immunoperoxidase method.

An indirect immunoperoxidase method was developed to determine the presence of viral antigen in bluetongue virus (BTV) infected tissues. Embryonating chicken eggs were infected with each of the 4 United States BTV serotypes (10, 11, 13, 17) and the chorioallantoic membranes were subsequently formalin fixed and embedded in paraffin. The infected membranes were examined for the expression of viral antigen. Monoclonal antibodies raised against BTV 17 (BT 21A and BT 98A) were used as the primary antisera in the immunoperoxidase procedure. Excellent specific staining was observed when each of the antisera was applied to membranes expressing antigens of homologous BTV serotype. BT 98A showed outstanding reactivity with membranes infected with heterologous BTV serotypes as well.

Animals↗
PubMed1984

Common and isolate-restricted antigens of Anaplasma marginale detected with monoclonal antibodies.

Anaplasma marginale-infected erythrocytes were examined for the presence of maturation, isolate-restricted, and isolate-common antigens by indirect immunofluorescence with monoclonal antibodies. A panel of 18 monoclonal antibodies was used; none of the antibodies reacted with Anaplasma ovis, Babesia bigemina, babesia bovis, Trypanosoma brucei, Trypanosoma congolense, or uninfected bovine erythrocytes. Antigens common to all six A. marginale isolates were detected by nine antibodies. Single isolates from Florida, Southern Idaho, Northern Texas, and Virginia and two isolates from Washington state had four patterns of reactivity with a second panel of nine antibodies. Antigenically distinct stages were not detected, as sequential smears taken daily during acute infection had the same pattern of reactivity. The results demonstrate antigenic heterogeneity among isolates of A. marginale and the presence of common antigens. This information allows grouping of different isolates and, more importantly, provides a method for the identification and isolation of common antigens for diagnostic tests.

Anaplasma↗
PubMed1984

Quantitation of bovine immunoglobulin G2 antibodies binding Staphylococcus aureus, using a murine monoclonal antibody.

A murine monoclonal antibody specific for bovine immunoglobulin (Ig) G2 was used to develop an enzyme-linked immunosorbent assay (ELISA) to measure serum antibodies against the bovine pathogen Staphylococcus aureus. Anion exchange chromatography was used to prepare IgG2 from serum taken from a mastitic cow infected with S aureus. Specific-IgG2 antibodies binding S aureus were purified with an affinity column, using a heat-killed, low protein A strain of S aureus (M-10). Purified antibodies did not contain IgG1 or IgM and were composed of greater than 95% heavy and light chains determined on the basis of polyacrylamide gel electrophoresis. Purified IgG2 anti-S aureus antibody was used as a reference in an ELISA that (i) could detect 5.0 ng of IgG2, (ii) was specific for IgG2 antibodies binding S aureus, (iii) was precise within and among different assays, (iv) yielded 112% recovery of the purified standard, and (v) when diluted in nonspecific IgG2, generated a curve that was parallel to the standard when a sample was serially diluted. A field study with cows having elevated California mastitis test scores showed evidence of infection with S aureus, as judged by a 59% increase (P less than 0.01) in IgG2 S aureus-specific antibodies and a 25% increase (P less than 0.05) in total IgG2 antibodies. There were no differences in IgG1 concentrations in plasma. Using indirect immunofluorescence, we also confirmed that bovine polymorphonuclear cells bound IgG2 preferentially over IgG1 or IgM. Measurement of antigen-specific IgG2 antibodies may therefore be useful as an index of specific antibody immunity to mastitis-causing organisms.

Animals↗
PubMed1983

The interactions of ethanol with the benzodiazepine-GABA receptor-ionophore complex.

Ethanol, barbiturates and benzodiazepines have similar pharmacological effects. All of these drugs facilitate the inhibitory transmission mediated by GABA. Drugs that facilitate GABAergic transmission are effective in alleviating ethanol withdrawal symptoms. Acute ethanol administration increases the number of low affinity GABA receptor sites, while, during ethanol withdrawal, the affinity of this site is decreased. This decreased affinity during withdrawal correlated with the audiogenic seizure activity. These results indicate that in vivo ethanol interacts with GABA receptors, and this interaction may be responsible for some of the effects of ethanol and for some symptoms of withdrawal. Ethanol, like pentobarbital, also enhances [3H]diazepam binding to the Lubrol-solubilized membrane fraction in vitro. This effect was dose-related and was blocked by picrotoxinin and other GABA antagonists. Enhancement of [3H]diazepam binding by various alcohols did not correlate with lipid:water partition coefficients. Ethanol also partially inhibited the binding of [3H]-alpha-dihydropicrotoxinin in the Lubrol-solubilized fraction. These results indicate that ethanol, like pentobarbital, may modulate the benzodiazepine binding component of the benzodiazepine-GABA receptor-ionophore complex via the picrotoxinin site. The possible interpretation of these results, in relation to the GABAergic transmission, is discussed.

Animals↗
PubMed1983

Analysis of serum and lymphocyte surface IgM of healthy and immunodeficient horses with monoclonal antibodies.

Nine monoclonal antibodies which reacted with equine immunoglobulin (Ig)M and not other equine Ig and serum proteins were prepared. Cells producing antibodies (C 1.9) which precipitated with IgM and bound to staphylococcal protein A were triple-cloned (C 1.9/3.2) and the antibodies further characterized. Monoclonal antibody C 1.9/3.2 reacted with an IgM determinant present on serum IgM from horses of several breeds. Studies with 125I-labeled IgM revealed the presence of this determinant on all IgM molecules. The monoclonal antibody enabled quantitation of IgM in presuckling foal and adult horse sera, using rocket electrophoresis. This procedure was used because presumably it gives a positive precipitation reaction over a wide range of antigen-antibody ratios. The C 1.9/3.2 monoclonal antibody recognized an exposed mu-chain determinant on live B lymphocytes, as determined by immunofluorescence. Also, IgM-containing cells could be identified in acetone-fixed frozen sections of lymphoid tissue. Sera from several other species carry the determinant identified by C 1.9/3.2, suggesting that the reagent may be useful for IgM studies in other species.

Agammaglobulinemia↗