Frequent detection of reviraemia in ducks persistently infected with avian leukosis retroviruses.

Ducks intraembryonally infected with avian leukosis viruses of subgroup C (ALV-C) were followed for a long period (up to 6.8 years), and the viraemia and production of virus-neutralizing antibodies were measured. In three independent experiments comprising ducks inoculated with uncloned and/or molecularly cloned ALV-C, we found that after the elimination of primary post-hatching viraemia, reviraemia could be detected in 60-70% of infected animals.

Vaccination with a low-oncogenic strain of Rous sarcoma virus prevents visceral tumors in chickens.

The oncogenic potential of different strains of Rous sarcoma virus (RSV) varies significantly in two Mhc(B) congenic chicken lines CB and CC and in their F1 hybrids with the unrelated inbred line IA. The Bryan high-titer pseudotype of RSV of antigenic subgroups D and B (BH-D, and BH-B) was highly oncogenic, eliciting mostly fatal, progressively growing tumors. Visceral tumor formation and erythroblastosis were seen after challenge with BH-B in CB and CC chickens, but not in their F1 hybrids with IA.

Origin and evolution of the c-src-transducing avian sarcoma virus PR2257.

Avian sarcoma virus PR2257 transduced de novo the c-src gene and about 900 bp of 3' non-coding sequences belonging to the src locus. This virus contains only one mutation in the c-src coding sequence causing a reading frame shift after Pro-525. The molecular clone studied was derived from a cell line of transformed quail fibroblasts, C7.

New case of c-src gene transduction: the generation of virus PR2257.

PR2257 is a new replication-defective avian sarcoma virus which harbours in addition to the spliced version of the c-src gene also about 950 bp of no-coding cellular sequences located downstream from the c-src stop codon (Geryk et al., 1989). Comparison of the 950 bp region transduced by PR2257 with the chicken c-src cDNA (Dorai et al.

Pathogenicity of avian myelocytomatosis virus MC29 in two lines of chickens.

The pathogenicity of avian myelocytomatosis virus MC29 was studied in F1 hybrids of two Prague inbred lines of chickens-CC xIA (B4/B7 genotype) and CB x IA (B12/B7 genotype). A shorter latent period and a higher mortality was found in the CC x IA chickens. In most chickens of this group, subperiosteal accumulations of primitive cells on the ribs, sternum and pelvic bones were observed, which were never detected in the CB x IA chickens.

Tumor induction by the LTR, v-src, LTR DNA in four B (MHC) congenic lines of chickens.

We report that the cloned DNA harboring the long terminal repeat (LTR), v-src, LTR proviral structure is tumorigenic in chickens of the Prague congenic lines. The growth rate of these tumors is by far the highest in the recombinant CC.R1 line, the B haplotype of which is composed of the B-F/L4 and B-G12 subregions originating from different naturally occurring haplotypes.

The influence of bursocytes and thymocytes on graft versus host reaction and IgG level in chickens.

Graft versus host reaction was induced by the blood of chickens previously transferred by the bursa and thymus cells. These bursa and thymus cells were taken from bursectomized or thymectomized chicken. It was occurred that graft versus host reaction was influenced by transfer of bursa and thymus cell.

Graft versus host reaction induced by thymectomized and bursectomized chicken blood.

Graft versus host reaction in chicken embryos was induced by blood taken from thymectomized or bursectomized or nonoperated donors. The intensity of graft versus host reaction induced by the blood of thymectomized chickens was increased comparing to the reaction induced by blood from control donors. No such result was recorded when the blood donors had the bursa of Fabricius removed.

Ducks: a new experimental host system for studying persistent infection with avian leukaemia retroviruses.

Long-term persistence of the avian leukosis virus (ALV), the transformation-defective mutant of Prague strain Rous sarcoma virus subgroup C (td PR-C) was established in heterologous duck hosts after infection in mid-embryogenesis. Transient viraemia was observed for about 4 weeks after hatching and was lost in most of the infected ducks by about 6 months. Loss of viraemia was accompanied by the increasing synthesis of virus-neutralizing antibodies.

Transduction of the cellular src gene and 3' adjacent sequences in avian sarcoma virus PR2257.

When injected into chickens, a transformation-defective mutant of the Prague C strain of Rous sarcoma virus induced tumors at low incidence and after a long latency. One such tumor released a replication-defective virus designated PR2257. We molecularly cloned and sequenced the proviral DNA from quail fibroblasts transformed by PR2257.

B (MHC) antigen dependent modulation of GvH reactivity by neonatal thymectomy and alloimmunization.

Using Prague recombinant congenic lines of chickens, we found that neonatal thymectomy led either to a marked suppression (CC donors) or to a transient increase (CB donors) of GvH response against the B-F/L + B-G and B-F/L disparate congenic embryos. Similarly, preimmunization with the B (MHC) different blood led either to the suppression or increase of GvH reactivity of the CC and CB line donors depending on the antigenic difference (B-F/L + B-G, B-F/L, B-G) between the blood used for preimmunization, the immunized donor for GvH splenomegaly assay and the recipient embryos. In all cases, the suppression of GvH response of the CC line donors is accompanied with a marked increase in GvH reactivity against syngeneic and B-G 12 disparate embryos, suggesting an autoimmune state.

Prague inbred lines of chickens: a biological model for MHC research.

Evidence for further complexity of the genetic structure of chicken major histocompatibility complex (B) is reviewed, with a historical account showing mutual dependence of the development of an animal genetic model and the growth of scientific knowledge concerning the chicken MHC.

Genome structure of a new avian sarcoma virus PR2257 determined by restriction analysis.

The genome structure of a new avian src-containing acute transforming virus, designated PR2257, was studied by restriction analysis. PR2257 was isolated from a sarcoma grown in a 155-day-old chick inoculated intraembryonally with a transformation-defective mutant of daPR-C retaining no src sequences. The 4.

Haematological and pathomorphological studies on chickens inoculated with transformation-defective sarcoma virus.

A transformation-defective mutant of Rous sarcoma virus (td PR-RSV-C) inoculated into chicken embryos caused a number of pathological changes in chickens after hatching. Disturbances in haematopoiesis were manifested by anaemia of different degree and by the presence of immature blood elements in the peripheral blood. The haematological picture of erythroblastosis was confirmed histologically.

Humoral immune response in experimental allergic encephalomyelitis in inbred chicken lines.

Chickens of the inbred IA line develop clinical signs of experimental allergic encephalomyelitis (EAE) after immunization with myelin basic protein (MP) or spinal cord tissue (SCT). The disease is accompanied by convulsions and paralysis of wings and legs. EAE leads to a 100% mortality in IA line chickens.

Cyclophosphamide in allergic encephalomyelitis in chickens.

The studies concerned the effect of cyclophosphamide on immunological and biochemical indices of MBP-induced encephalomyelitis. Unlike isoprinosine, cyclophosphamide was observed to exert irregular effect. Contrary to the expected, the results obtained in some experimental systems show increased level of the parameters tested-IgG, antitrypsin and sialic acid.

Concomitant immunity leads to retardation or acceleration of the growth of Rous sarcomas in genetically resistant or susceptible inbred lines of chickens.

We report results on the age-dependent effect of the B (MHC) genotype on resistance to the growth of a second RSV tumour in chickens from highly inbred lines genetically resistant or susceptible to progressive growth of primary RSV-induced tumours. Furthermore, the second inoculation of RSV caused either accelerated or retarded growth of the primary tumours induced by the same virus. These two types of response to a second challenge with RSV were controlled by alleles of the chicken major histocompatibility (B) complex.

The effect of thymectomy on immunological tolerance to human serum albumin in chickens.

The effect of thymectomy performed on the day of hatching has been studied in chickens rendered tolerant by 100 mg of HSA injected also on the day of hatching. After challenge at the age of 6 and 9 weeks, no significant difference was observed between the group of tolerant chickens, in which the thymectomy was complete or incomplete, and the non-operated tolerant one. The delayed recovery from tolerance observed in mammals was not seen even in chickens in which thymus was removed completely and no thymic residue remained.

Isolation of two transforming viruses from sarcomas obtained in chickens inoculated intraembryonally with a transformation defective mutant of Prague strain Rous sarcoma virus.

Sarcomas appeared after long latency with a frequency of about 2% in Brown Leghorn and (CB X IC)F1 chickens after intraembryonic and neonatal inoculation of transformation-defective mutants of ASVs subgroup C. Only the freshly isolated td mutants, td daPR-C and td daPR-C morphf, exhibited the tumorigenic activity, whereas the standard td mutants induced no sarcomas. Two (862 and 2257) out of four tumours could be transplanted in young chickens and produced low titres of transforming virus.

Modulation of immunological reactivity in the course of allergic encephalomyelitis by isoprinosine.

It was observed that in the course of allergic encephalomyelitis (EAE) in chickens. Isoprinosine reduced the production of the specific IgA and IgM antibodies against encephalic antigen. Its influence on IgG production was slight.

Induction of tolerance in chickens by low doses of human serum albumin administered after hatching.

The possibility was tested whether tolerance can be induced in newly hatched chickens by a single injection of HSA on the day of hatching in doses one or several orders lower than the dose employed in previous experiments (100 mg of HSA). Doses of 10 and 1 mg of HSA induced a statistically significant suppression of anti-HSA antibody formation after challenge at the age of 2 and 4 weeks. Injection of 0.

Antibody-producing cells in chickens tolerant to human serum albumin.

Cells forming antibodies to HSA were determined by the haemolytic plaque technique in the spleens of chickens in which tolerance to HSA was induced on the day of hatching. After immunization with HSA 2 weeks after hatching, no anti-HSA PFC or their very low numbers were observed in chickens rendered tolerant by the dose of 100 mg HSA. In a considerable proportion of the chickens, in which tolerance was induced by 1 mg or 0.

Different importance of primary lymphoid organs for Rous sarcoma regression in inbred lines of chickens.

Resistance to progressive growth of tumours induced by Rous sarcoma virus is controlled mainly by genes linked to the B complex (the major histocompatibility complex) of the chicken. The effect of thymectomy and bursectomy on this resistance was studied in chickens from highly inbred lines and their F1 hybrids which differ by the genotype at the B complex and by the degree of genetically controlled resistance or susceptibility. The results show that thymectomy has considerable effect on growth of RSV-induced tumours in the CB line genetically resistant to progressive Rous sarcoma growth and little effect in (CB X IC)F1 (also genetically resistant) and (CC X IC)F1 (intermediate responders to RSV) hybrid chickens.

Morphological and biochemical studies on experimental allergic encephalomyelitis in inbred lines of chickens.

An attempt to establish the relation between morphological and biochemical indices determining the inflammatory state in brain after induction of allergic encephalomyelitis in chickens was taken up. Symptoms of encephalomyelitis were accompanied by the changes within T and B lymphocyte population and by distinct increase of activity of trypsin inhibitor and content of sialic acid in blood serum.

Immunological unresponsiveness to HSA in chickens.

HSA injected into chickens after hatching induces suppression of anti-HSA antibody formation. Unresponsive chickens react by producing the anti-HSA antibodies earlier and more intensively after BSA challenge than after challenge with HSA. This effect cannot be ascribed to T cells, because they were found to play no substantial role in the unresponsiveness to HSA.