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Biomedical subjects

K Howes

Publications and source records attributed to K Howes.

28 records · Page 2Linked to original sources
PubMed1991

A recombinant fowlpox virus that expresses the VP2 antigen of infectious bursal disease virus induces protection against mortality caused by the virus.

The coding sequences of VP2 from a virulent strain, 52/70, of infectious bursal disease virus (IBDV) were excised from a cDNA clone and inserted into a fowlpox plasmid insertion vector. The resulting plasmid, pIBD 1, was used to construct a recombinant fowlpox virus, fpIBD 1, which expressed VP 2 as a beta-galactosidase fusion protein. Chickens vaccinated with fpIBD 1 at 1 and 14 days of age, were challenged at 28 days with either IBDV strain 52/70 or the highly virulent strain CS 89. These chickens were protected against mortality, but not against damage to the bursa of Fabricius. The protection achieved by the use of fpIBD 1 shows that VP 2 is a host protective antigen.

Amino Acid Sequence↗
PubMed1991

A novel subgroup of exogenous avian leukosis virus in chickens.

An avian leukosis virus with a wide host range belonging to a new subgroup for chickens was isolated from meat-type chicken lines. The virus, of which HPRS-103 strain is the prototype, was of low oncogenicity in chickens but appeared to behave like an exogenous leukosis virus. Neutralizing antibodies to the virus were found in three of five meat-type chicken lines, but not in seven layer lines. The virus and its Rous sarcoma virus pseudotype did not replicate in, or transform, mammalian cells.

Animals↗
PubMed1981

Use of an agar culture technique for establishing lymphoid cell lines from Marek's disease lymphomas.

Lymphoblastoid cell lines derived from Marek's disease (MD) lymphomas have been established with difficulty by a number of workers. We have compared with conventional liquid culture methods the efficiency of a new technique for establishing lymphoid cell lines in which lymphoma cells were cultured initially in agar medium. Cells from 39/79 lymphomas gave rise to loose lymphoid colonies in the seeded agar after 7 days' incubation at 41 degrees C. Two types of macrophage colony also developed. When lymphoid colonies in agar were transferred to liquid culture, 23/39 gave rise to permanent lymphoid cell lines, compared with 8/33 comparable cultures initiated in liquid medium. Twenty-nine new cell lines have been developed from Rhode Island Red, line 6 and line 7 chickens. All carry T-cell markers and the MD tumour-associated surface antigen (MATSA) and showed variable but low responsiveness to lectin mitogens. The new cell lines, when first established, consisted mainly of small, lymphocytoid cells, but, after varying times, these changed into typical lymphoblastoid lines and an increased expression of an embryonic antigen was associated with this change. The lymphocytoid line cells were more slowly growing and density-dependent than were the lymphoblastoid cells, and lymphocytoid lines grew better at 41 degrees C and lymphoblastoid lines better at 37 degrees C. MD virus could be rescued from some of the lines but others appeared to be true non-producers.

Agar↗
PubMedDate not supplied

Some chickens which are viraemic with subgroup J avian leukosis virus have antibody-forming cells but no circulating antibody.

New immunoperoxidase-based assays for splenic IgG -antibody-forming cells (AFC) and serum IgG-antibody were used to look for antibody to HPRS-103 in meat-type birds. Meat type birds are known to be less likely to produce neutralising antibody and to be less likely to clear virus from their serum than layer-type birds after infection at hatch. In this work all 12 of the brown leghorn layer-type birds and 5/12 of the line 21 meat-type birds had produced AFC and serum antibody and had cleared serum virus at 63, 82 and 110 days of age. None of the seven viraemic line 21 birds contained serum antibody but three produced AFC. The four viraemic line 21 birds which lacked AFC occurred later in the experiment and had a higher level of virus than the three viraemic line 21 birds which possessed AFC. This suggests that most line 21 birds do not control HPRS-103 and eventually become anergic.

Animals↗
PubMedDate not supplied

Experimental factors affecting mortality following inoculation of chickens with avian nephritis virus (G-4260).

Groups of approximately 20 one-day-old chickens were inoculated with G-4260, the reference strain of avian nephritis virus (ANV), or saline. Based on mortality rates from severe nephritis in comparable experiments, light Sussex chickens generally were more susceptible than Rhode Island red (RIR) chickens. Mortality was greater in those given broiler starter than those given other feeds, and was greater when light Sussex chickens were given broiler starter feed and cold-stressed at 15 +/- 1 C for 2 hr daily during the first week rather than brooded normally. Inoculation with G-4260 either orally or by intraperitoneal injection produced similar results in RIR chickens. Thirty-three inoculated chickens died of severe nephritis between 4 and 12 days postinoculation, and 24 (73%) of them had visceral urate deposits. Inoculated inbred white leghorn Line 15 chickens with maternal antibody to ANV were brooded normally and given broiler feed: they were susceptible to infection as evidenced by subsequent histological lesions in the kidneys and serology, but mortality was not a feature. There were no deaths from nephritis in inoculated non-inbred white leghorn chickens free of maternal antibody to ANV that were given broiler feed and brooded normally. These results have implications in standardizing experimental conditions for the study of mortality induced by G-4260 and similar viruses.

Animal Feed↗
PubMedDate not supplied

Recovery of acutely transforming viruses from myeloid leukosis induced by the HPRS-103 strain of avian leukosis virus.

Viruses rapidly able to transform cultured chicken bone marrow cells have been isolated from cases of myelocytic myeloid leukosis (MML) induced experimentally by the HPRS-103 strain of avian leukosis virus, and from field cases of MML. HPRS-103 virus itself did not acutely transform cultured bone-marrow cells. These findings suggest that during myeloid leukemogenesis by HPRS-103 virus, recombinant viruses are generated with transduced cellular oncogenes. The transformed cell appeared to be a macrophage precursor cell. Transformed cells in culture lost their proliferative capacity after a few weeks and then tended to resemble more differentiated macrophages. This change could be reversed temporarily by addition of a myelomonocytic growth factor, cMGF, to the culture medium. In oncogenicity tests, a selection of the virus strains induced MML, nephroblastomas, renal adenomas/adenocarcinomas, and other tumors in line 21 meat-type chickens but not in line 0 chickens. This difference may have been related to a propensity for the virus strains to induce persistent tolerant viremic infections in the line 21 chickens following infection at 1 day of age. The oncogenic pattern was not clearly related to the ability of the viruses to transform cultured bone-marrow cells. The generation of acutely transforming viruses during myeloid leukemogenesis may be relevant to the occurrence of MML in the field.

Animals↗
PubMedDate not supplied

Recombinant env-gp85 of HPRS-103 (subgroup J) avian leukosis virus: antigenic characteristics and usefulness as a diagnostic reagent.

We describe the construction of a recombinant baculovirus containing the cloned DNA encoding the gp85 envelope glycoprotein of HPRS-103 (subgroup J) avian leukosis virus fused to the carboxy-terminus of the affinity tag glutathione-S-transferase. The fusion protein was efficiently secreted into the supernatant medium of the infected insect cell culture and could be purified in a single step using immobilized glutathione. An enzyme-linked immunosorbent assay using the recombinant protein was found to be specific and sensitive for detection of HPRS-103 virus-specific antibodies in the sera of infected birds.

Animals↗