Retroviral transformation in vitro of chicken T cells expressing either alpha/beta or gamma/delta T cell receptors by reticuloendotheliosis virus strain T

Characterization of a novel chicken γδ TCR-specific marker

Chickens are a species with a high number of γδ T cells in various tissues. Despite their abundance, γδ T cells are poorly characterized in chickens, partially due to a lack of specific reagents to characterize these cells. Up until now, the TCR1 clone has been the only γδ T cell-specific monoclonal antibody (mAb) in chickens and additional reagents for γδ T cell subsets are needed. In order to address this issue, new mAb were generated in our laboratory by immunizing mice with in vitro cultured γδ T cells. In an initial flow cytometric screen a new mAb, clone "8D2", displayed an interesting staining pattern that mirrored γδ TCR up- and downregulation in the γδ T cell line D4 over time, prompting us to characterize this antibody further. We compared the expression of the unknown 8D2 epitope in combination with TCR1 staining across various primary cells. In splenocytes, peripheral blood lymphocytes and intestinal epithelial cells, 8D2 consistently labeled a subset of TCR1+ cells. To determine, whether specific γδ T cell receptors were recognized by 8D2, we sorted γδ T cells according to their 8D2 and TCR1 expression and analyzed their TCR V(D)J gene usage by TCR profiling. Strikingly, sorted 8D2+ cells preferentially expressed Vγ3 genes, whereas the TCR Vγ genes used by TCR1+ 8D2- cells were more variable. γδ TCR in 8D2+ cells were most frequently comprised of gamma chain VJ genes TRGV3-8 and TRGJ3, and delta chain VDJ genes TRDV1-2, TRDD2, TRDJ1. To confirm binding of 8D2 to specific γδ TCR, the preferentially utilized combination of TRG and TRD was expressed in HEK293 cells in combination with CD3, demonstrating surface binding of the 8D2 mAb to this Vγ3 γδ TCR-expressing cell line. Conversely, HEK293 cells expressing either Vγ1 or Vγ2 TCR did not react with 8D2. In conclusion, 8D2 is a novel tool for identifying specific Vγ3 bearing γδ T cells.

Sequence of a complete chicken BG haplotype shows dynamic expansion and contraction of two gene lineages with particular expression patterns

Many genes important in immunity are found as multigene families. The butyrophilin genes are members of the B7 family, playing diverse roles in co-regulation and perhaps in antigen presentation. In humans, a fixed number of butyrophilin genes are found in and around the major histocompatibility complex (MHC), and show striking association with particular autoimmune diseases. In chickens, BG genes encode homologues with somewhat different domain organisation. Only a few BG genes have been characterised, one involved in actin-myosin interaction in the intestinal brush border, and another implicated in resistance to viral diseases. We characterise all BG genes in B12 chickens, finding a multigene family organised as tandem repeats in the BG region outside the MHC, a single gene in the MHC (the BF-BL region), and another single gene on a different chromosome. There is a precise cell and tissue expression for each gene, but overall there are two kinds, those expressed by haemopoietic cells and those expressed in tissues (presumably non-haemopoietic cells), correlating with two different kinds of promoters and 5′ untranslated regions (5′UTR). However, the multigene family in the BG region contains many hybrid genes, suggesting recombination and/or deletion as major evolutionary forces. We identify BG genes in the chicken whole genome shotgun sequence, as well as by comparison to other haplotypes by fibre fluorescence in situ hybridisation, confirming dynamic expansion and contraction within the BG region. Thus, the BG genes in chickens are undergoing much more rapid evolution compared to their homologues in mammals, for reasons yet to be understood.

Many immune genes are multigene families, presumably in response to pathogen variation. Some multigene families undergo expansion and contraction, leading to copy number variation (CNV), presumably due to more intense selection. Recently, the butyrophilin family in humans and other mammals has come under scrutiny, due to genetic associations with autoimmune diseases as well as roles in immune co-regulation and antigen presentation. Butyrophilin genes exhibit allelic polymorphism, but gene number appears stable within a species. We found that the BG homologues in chickens are very different, with great changes between haplotypes. We characterised one haplotype in detail, showing that there are two single BG genes, one on chromosome 2 and the other in the major histocompatibility complex (BF-BL region) on chromosome 16, and a family of BG genes in a tandem array in the BG region nearby. These genes have specific expression in cells and tissues, but overall are expressed in either haemopoietic cells or tissues. The two singletons have relatively stable evolutionary histories, but the BG region undergoes dynamic expansion and contraction, with the production of hybrid genes. Thus, chicken BG genes appear to evolve much more quickly than their closest homologs in mammals, presumably due to increased pressure from pathogens.

The dominantly expressed class I molecule of the chicken MHC is explained by coevolution with the polymorphic peptide transporter (TAP) genes

In most mammals, the MHC class I molecules are polymorphic and determine the specificity of peptide presentation, whereas the transporter associated with antigen presentation (TAP) heterodimers are functionally monomorphic. In chickens, there are two classical class I genes but only one is expressed at a high level, which can result in strong MHC associations with resistance to particular infectious pathogens. However, the basis for having a single dominantly expressed class I molecule has been unclear. Here we report TAP1 and TAP2 sequences from 16 chicken lines, and show that both genes have high allelic polymorphism and moderate sequence diversity, with variation in positions expected for peptide binding. We analyze peptide translocation in two MHC haplotypes, showing that chicken TAPs specify translocation at three peptide positions, matching the peptide motif of the single dominantly expressed class I molecule. These results show that coevolution between class I and TAP genes can explain the presence of a single dominantly expressed class I molecule in common chicken MHC haplotypes. Moreover, such coevolution in the primordial MHC may have been responsible for the appearance of the antigen presentation pathways at the birth of the adaptive immune system.

The drug monosodium luminol (GVT) preserves thymic epithelial cell cytoarchitecture and allows thymocyte survival in mice infected with the T cell-tropic, cytopathic retrovirus ts1

A mutant of MoMuLV, called ts1, causes an AIDS-like syndrome in susceptible strains of mice. In mice infected at birth, thymic atrophy, CD4+ T cell loss, body wasting, and death occur by approximately 30-40 days postinfection (dpi). We have shown previously that the death of ts1-infected cells is not caused by viral replication per se, but by oxidative stress and apoptosis following their accumulation the ts1 viral envelope precursor protein, gPr80(env). In infected mice treated with the antioxidant monosodium alpha-luminol (GVT), T cell loss and thymic atrophy are delayed for many weeks, and body wasting and death do not occur until long after infected, untreated control mice have died. We show here that GVT treatment of ts1-infected mice maintains the thymic epithelial cell (TEC) cytoarchitecture and cytokeratin gradients required for thymocyte differentiation. It also suppresses thymocyte reactive oxygen species (ROS) levels, upregulates and stabilizes levels of the antioxidant-regulating transcription factor Nrf2, and prevents accumulation of gPr80(env) in thymocytes. We conclude that GVT treatment can make ts1 a non-cytopathic virus for thymocytes, although it cannot prevent thymocyte infection. Since oxidative stress also contributes to the loss of T cells in HIV-AIDS, the antioxidant effects of GVT may make it a useful therapeutic adjunct to HAART treatment.

A sensitive bioassay for chicken interleukin-18 based on the inducible release of preformed interferon-gamma

Conventional tests for measuring the biological activity of chicken interleukin (IL)-18 require primary chicken spleen cells. We now describe a sensitive bioassay that is based on interleukin-18-induced release of interferon (IFN)-gamma by a permanent chicken cell line. In B19-2D8 cells, cytoplasmically stored interferon-gamma is quickly secreted in response to interleukin-18 exposure.

Multiple mutations contribute to the oncogenicity of the retroviral oncoprotein v-Rel

The avian Rev-T retrovirus encodes the v-Rel oncoprotein, which is a member of the Rel/NF-kappaB transcription factor family. v-Rel induces a rapidly fatal lymphoma/leukemia in young birds, and v-Rel can transform and immortalize a variety of avian cell types in vitro. Although Rel/NF-kappaB transcription factors have been associated with oncogenesis in mammals, v-Rel is the only member of this family that is frankly oncogenic in animal model systems. The potent oncogenicity of v-Rel is the consequence of a number of mutations that have altered its activity and regulation: for example, certain mutations decrease its ability to be regulated by IkappaBalpha, change its DNA-binding site specificity, and endow it with new transactivation properties. The study of v-Rel will continue to increase our knowledge of how cellular Rel proteins contribute to oncogenesis by affecting cell growth, altering cell-cycle regulation, and blocking apoptosis. This review will discuss biological and molecular activities of v-Rel, with particular attention to how these activities relate to structure - function aspects of the Rel/NF-kappaB transcription factors.

Recombinant Marek's disease virus (MDV)-derived lymphoblastoid cell lines: regulation of a marker gene within the context of the MDV genome

Marek's disease is a herpesvirus (Marek's disease virus [MDV])-induced pathology of chickens characterized by paralysis and the rapid appearance of T-cell lymphomas. Lymphoblastoid cell lines (LBCLs) derived from MDV-induced tumors have served as models of MDV latency and transformation. We have recently reported the construction of mutant MDVs having a deletion (M. S. Parcells et al., J. Virol. 69:7888-7898, 1995) and an insertion (A. S. Anderson et al., J. Virol. 72:2548-2553, 1998) within the unique short region of the virus genome. These mutant MDVs retained oncogenicity, and LBCLs have been established from the mutant-induced tumors. We report the characterization of these cell lines with respect to (i) virus structure within and reactivated from the cell lines, (ii) surface antigen expression, (iii) kinetics of MDV and marker gene induction, (iv) localization and colocalization of induced MDV antigens and beta-galactosidase (beta-Gal), and (v) methylation status of the region of lacZ insertion in recombinant- and non-recombinant-derived cell lines. Our results indicate that (i) recombinant-derived cell lines contain no parental virus, (ii) the established cell lines are predominantly CD4(+) CD8(-), (iii) the percentage of Lac-expressing cells is low (1 to 3%) but increases dramatically upon 5'-iododeoxyuridine (IUdR) treatment, (iv) lacZ expression is induced with the same kinetics as several MDV lytic-phase genes (pp38, US1, gB, gI, and US10), and (v) the regulation of lacZ expression is not mediated by methylation. Furthermore, the MDV-encoded oncoprotein, Meq, could be detected in cells expressing beta-Gal and various lytic antigens but did not appear to be induced by IUdR treatment. Our results indicate that regulation of the lacZ marker gene can serve as sensitive measure of virus lytic-phase induction and the reactivation from latency.

Chicken guanylate-binding protein. Conservation of GTPase activity and induction by cytokines

To gain further insights into the cytokine network of birds, we used polymerase chain reaction technology to clone a cDNA that codes for a chicken homolog of the interferon-induced guanylate-binding proteins (GBPs). In its N-terminal moiety, the 64-kDa chicken GBP contains two sequence blocks of 100 and 19 amino acids, respectively, that are about 70% identical to mammalian GBPs. The first region includes two motifs of the canonical GTP-binding consensus element. The other parts of chicken GBP are poorly conserved, except for a CAAX motif at the extreme C terminus which might signal isoprenylation. Like mammalian GBPs, recombinant chicken GBP specifically bound to agarose-immobilized guanine nucleotides and hydrolyzed GTP to both GDP and GMP. Regulation by interferons was also conserved: chicken GBP RNA was barely detectable in uninduced chicken cells. Low GBP RNA levels were found in cells treated with type I interferon, whereas very high levels were observed in cells treated with supernatant of a chicken T cell line that secretes a gamma-interferon-like activity. Together with recent phylogenetic studies of interferon genes, these results suggest that in spite of low sequence conservation, the various components of the avian interferon system are functionally well conserved.

Dendritic cell progenitor is transformed by a conditional v-Rel estrogen receptor fusion protein v-RelER

A conditional v-Rel estrogen receptor fusion protein, v-RelER, causes estrogen-dependent but otherwise unaltered v-rel-specific transformation of chicken bone marrow cells. Here, we demonstrate that such v-relER-transformed cells exhibit B lymphoid determinants in line with earlier studies on v-rel-transformed cells. However, following inactivation of v-RelER oncoprotein activity by administration of an estrogen antagonist, cells differentiate into antigen-presenting dendritic cells as judged by several morphological and functional criteria. Additionally, under yet different culture conditions, v-relER cells differentiate into cells resembling polymorphonuclear neutrophils. Our studies therefore suggest that the conditional v-RelER, and probably also the authentic v-Rel, transform a common progenitor for neutrophils and dendritic cells.