Development and application of polymerase chain reaction (PCR) tests for the detection of subgroup J avian leukosis virus

Subgroup J avian leukosis virus (ALV) is a recently identified avian retrovirus associated with myeloid leukosis in meat-type chickens. The env gene of the HPRS-103 strain of ALV, the prototype of this subgroup, differs considerably from that of other subgroups, but shows close homology to the env-like sequences of members of the EAV family of endogenous retroviruses. Polymerase chain reaction (PCR) tests using two sets of primers were developed for the specific detection of the members of this new subgroup along with another pair of primers for detecting other subgroup viruses. The specificity and sensitivity of this detection system was compared with the conventional detection methods in experimentally and naturally infected samples. The use of PCR was found to be rapid, specific and more sensitive than the conventional diagnostic tests for the detection of ALV. Moreover, the two subgroup J ALV-specific PCR tests were found to be capable of differentiating between 'prototype-like' viruses and more recent isolates which show extensive antigenic and sequence variations. The use of this test as a rapid and sensitive method of detection of viruses in epidemiological studies and eradication programs is discussed.

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.

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.

Tissue tropism of the HPRS-103 strain of J subgroup avian leukosis virus and of a derivative acutely transforming virus

The tissue tropism was studied for the HPRS-103 strain of avian leukosis virus, which belongs to a new envelope subgroup, designated J. Studies were conducted in blood monocyte and bone marrow cell cultures and in chickens from six lines that had been shown previously to differ in susceptibility to induction by this virus of myeloid leukosis and other tumors. Using an immunohistochemical technique to detect expression of viral group-specific antigen (Gag) in various tissues, we detected no major differences among the six lines of chickens at 3 and 7 weeks of age following infection as embryos. Thus, Gag expression did not correlate with differences in tumor susceptibility. Of the tissues examined, greatest Gag expression was observed in cells specific to the adrenal gland, heart, kidney, proventriculus and especially in smooth muscle cells and connective tissue. After infection of 1-day-old chicks, greater tissue expression was observed in line 21 chicks, which mostly developed a tolerant viremic infection, than in Brown Leghorn chicks, which developed virus-neutralizing antibodies. An acutely transforming virus, strain 966, derived from HPRS-103-induced myeloid leukosis, showed a tropism similar to HPRS-103. The HPRS-103 strain showed a lower propensity to replicate in the medullary region of the lymphoid follicles of the bursa of Fabricius than did the RAV-1 strain of subgroup A avian leukosis virus. This low bursal tropism may be a factor in why HPRS-103 does not induce lymphoid leukosis. The HPRS-103 and 966 virus replicated in blood monocyte cultures from chickens from the six lines, indicating a tropism for the myelomonocytic cell lineage. In comparison, as previously reported, RAV-1 did not replicate well in the monocyte cultures, whereas RAV-2, a subgroup B avian leukosis virus, did replicate. The tropism of HPRS-103 for monocytes may relate to its ability to cause myeloid leukosis. Monocyte and bone marrow cell cultures from the six lines ranked similarly in differences in susceptibility to transformation by 966 virus and showed evidence that their relative susceptibilities correlated with susceptibility of chickens from these lines to induction of myeloid leukosis by HPRS-103, suggesting common tissue-specific viral and host factors involved in oncogenesis by these two viruses.

Sequence of host-range determinants in the env gene of a full-length, infectious proviral clone of exogenous avian leukosis virus HPRS-103 confirms that it represents a new subgroup (designated J)

A genomic DNA library was constructed, in a bacteriophage lambda vector, from line 0 chick embryo fibroblasts (CEFs) infected with HPRS-103, an exogenous avian leukosis virus (ALV; envelope subgroup J) recently isolated from meat-type chickens. The library was screened at high stringency using a full length RAV-1 (subgroup A) proviral probe. From 10(6) plaques, two clones which hybridized strongly to the RAV-1 probe were isolated; one contained a full-length copy of the proviral genome of HPRS-103 and the other contained a copy lacking the 5'-long terminal repeat (LTR) and part of gag. The relative strength of hybridization of RAV-1 and HPRS-103 clones, to RAV-1 probes representing different parts of the proviral genome, indicated that the gag and pol genes of HPRS-103 share a high level of identity with those of RAV-1 but that the env gene and the LTRs are considerably less well conserved. Infectious virus was recovered from CEFs transfected with the full-length clone, as detected by ELISA. The recovered virus appeared to be identical to HPRS-103 by electron microscopy and by Southern blotting of proviral DNA. The recovered virus was shown to be of the same subgroup as HPRS-103 by serum neutralization and receptor interference assays. Sequence analysis of the env gene of HPRS-103 shows that it differs considerably from the env genes of other ALV subgroups, particularly in the host range determinants, consistent with the finding that HPRS-103 represents a new subgroup (designated J).

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.

Host range of Rous sarcoma virus pseudotype RSV(HPRS-103) in 12 avian species: support for a new avian retrovirus envelope subgroup, designated J

The host ranges of the Rous sarcoma virus (RSV) pseudotype RSV(HPRS-103) of a novel avian leukosis virus (ALV), strain HPRS-103, and representative RSV pseudotypes of subgroups A to F, have been determined in embryo fibroblasts from 12 avian species. Domestic fowl, red jungle fowl, Sonnerat's jungle fowl and turkey were susceptible to infection by RSV(HPRS-103); ring-necked pheasant, Japanese green pheasant, golden pheasant, Japanese quail, guinea-fowl, Peking duck, Muscovy duck and goose were resistant. The host range pattern of RSV(HPRS-103) differs from those of viruses of subgroups A to G and I, and provides support for placing the HPRS-103 strain of ALV in a new envelope subgroup, designated J.

Myeloid leukaemogenicity and transmission of the HPRS-103 strain of avian leukosis virus

The HPRS-103 strain of avian leukosis virus (ALV) was isolated recently from meat-type chickens and represents a new envelope subgroup. Its oncogenicity has been studied in three meat-type and five Leghorn strains of chickens. In the meat-type strains, the virus, following embryonal inoculation, induced an overall incidence of 27% myelocytic myeloid leukosis (myelocytomatosis) and 12% renal adenomas, with long median latent periods. Amongst the Leghorn lines, these tumors occurred with similar incidence in line 0, but with lower or zero incidences in the other lines. A variety of other tumours occurred with low incidence. Embryonal infection resulted in a permanently tolerant viraemic state with shedding of ALV group specific (gs)-antigen to egg albumen; contact infection resulted mainly in the development of non-shedder birds with serum virus-neutralising antibodies. Contact infection in a meat-type line was associated with the development of transient or permanent viraemia in some birds, and a low tumour incidence. A viraemic phase was not detected following contact infection in a Leghorn line and no tumours developed. The long latent period between embryo infection and tumour mortality, apparently differing from the consequences of infection with acutely transforming ALVs, and the inability of HPRS-103 ALV to transform cultured bone marrow cells, suggests that this virus may lack a viral oncogene and exert its oncogenic properties by some other mechanism such as promoter insertion activation of a cellular oncogene.

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.

A study of autologous blood collected after joint replacement surgery

Blood from the surgical drains of 11 patients undergoing joint replacement was collected in the Solcotrans Orthopaedic autologous transfusion device and analysed for microparticulate matter before and after micro-aggregate filtration and for its effect on the coagulation of paired venous blood samples. An average of 165 ml (range 0-260 ml) was collected into the Solcotrans during the first hour. Using a Coulter Counter Zm particle counter, particulate matter of diameter 10-20 microns was found in only 2 of 10 collections at an average concentration of 33 x 10(3)/l. All units contained acoagulable blood [kaolin partial thromboplastin time (KPTT) greater than 600 s] but when mixed with paired post-operative venous samples exhibited the ability to shorten the KPTT by an average of 4.3 s inspite of the marked dilutional effect of mixing. Retransfusion of blood collected in the Solcotrans Orthopaedic device appears to be a suitable method to supplement or substitute pre-deposit and reduce exposure to homologous blood. Given the low incidence and concentration of microparticles detected, retransfusion of shed blood by this method is unlikely to cause significant pulmonary vascular occlusion resulting directly from deposition of microparticles.

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.

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.

Eradication of exogenous avian leukosis virus from commercial layer breeder lines

On the basis of earlier studies, a programme for eradicating exogenous avian leukosis virus from commercial poultry stock was devised and applied to 11 layer breeder lines. After three years of testing, avian leukosis virus infection was eradicated completely from all but one, a slow-feathering line.