Jiří Plachý

src-specific immunity in inbred chickens bearing v-src DNA- and RSV-induced tumors

The growth pattern (progression/regression) of v-src DNA- and Rous sarcoma virus (RSV)-induced tumors was analogous on a panel of inbred chicken lines. The decisive role of the major histocompatibility complex [Mhc(B)] alleles in resistance to the progression of these tumors was formally proved in segregating backcross populations. The immune mechanism of tumor regression was demonstrated by both in vivo and in vitro assays. A protective effect of v-src-specific immunity against RSV challenge was shown in Rous sarcoma regressor line CB (B12/B12). Immune cells from regressors of v-src DNA-induced tumors can protect syngeneic hosts from the development of tumor after challenge with both v-src DNA and RSV. Suppression of RSV-induced tumor cell growth in vitro was also achieved by the use of cocultivation with spleen cells from chickens in which v-src DNA-induced tumors had regressed. This in vitro sarcoma-specific response was Mhc(B)-restricted. Chickens of the congenic Rous sarcoma progressor line CC (B4/B4) are sometimes able to regress v-src DNA-induced tumors, but immune cells can only slow the growth of v-src DNA-induced tumors in syngeneic hosts. This suggests that the primary reason for the susceptibility of CC chickens is a weak v-src-specific immune response. Furthermore, some of the v-src DNA-induced tumors were transplantable across the Mhc(B) barrier. The growth of tumor allografts was able to be facilitated when immunological tolerance to the B-F/L region antigens (class I and class II) had been established. This demonstrated that a high tumorigenicity of the transplantable tumor was not due to the lack of Mhc(B) antigens on tumor cells.

Metastasis of aggressive amoeboid sarcoma cells is dependent on Rho/ROCK/MLC signaling

BackgroundAlthough there is extensive evidence for the amoeboid invasiveness of cancer cells in vitro, much less is known about the role of amoeboid invasiveness in metastasis and the importance of Rho/ROCK/MLC signaling in this process.ResultsWe analyzed the dependence of amoeboid invasiveness of rat and chicken sarcoma cells and the metastatic activity of chicken cells on individual elements of the Rho/ROCK/MLC pathway. In both animal models, inhibition of Rho, ROCK or MLC resulted in greatly decreased cell invasiveness in vitro, while inhibition of extracellular proteases using a broad spectrum inhibitor did not have a significant effect. The inhibition of both Rho activity and MLC phosphorylation by dominant negative mutants led to a decreased capability of chicken sarcoma cells to metastasize. Moreover, the overexpression of RhoA in non-metastatic chicken cells resulted in the rescue of both invasiveness and metastatic capability. Rho and ROCK, unlike MLC, appeared to be directly involved in the maintenance of the amoeboid phenotype, as their inhibition resulted in the amoeboid-mesenchymal transition in analyzed cell lines.ConclusionTaken together, these results suggest that protease-independent invasion controlled by elements of the Rho/ROCK/MLC pathway can be frequently exploited by metastatic sarcoma cells.

The Chicken Z Chromosome Is Enriched for Genes with Preferential Expression in Ovarian Somatic Cells

Theory predicts that sexually antagonistic mutations will be over- or under-represented on the X and Z chromosomes, depending on their average dominance coefficients. However, as little is known about the dominance coefficients for new mutations, the effect of sexually antagonistic selection is difficult to predict. To elucidate the role of sexually antagonistic selection in the evolution of Z chromosome gene content in chicken, we analyzed publicly available microarray data from several somatic tissues as well as somatic and germ cells of the ovary. We found that the Z chromosome is enriched for genes showing preferential expression in ovarian somatic cells, but not for genes with preferential expression in primary oocytes or non-sex-specific somatic tissues. Our results suggest that sexual antagonism leads to a higher abundance of female-benefit alleles on the Z chromosome. No bias toward Z-linkage for oocyte-enriched genes can be explained by lower intensity of sexually antagonistic selection in ovarian germ cells compared to ovarian somatic cells. An alternative explanation would be that meiotic Z chromosome inactivation hinders accumulation of oocyte-expressed genes on the Z chromosome. Our results are consistent with findings in mammals and indicate that recessive rather than dominant sexually antagonistic mutations shape the gene content of the X and Z chromosomes.

DNA vaccination against v-src oncogene-induced tumours in congenic chickens

DNA vaccination is particularly efficient for induction of cytotoxic T-lymphocyte (CTL) response. In our experiments, we used MHC(B) congenic chicken lines CB and CC (regressors and progressors of v-src-induced tumours, respectively) and a mutated, non-oncogenic v-src gene construct as the DNA vaccine. A high degree of vaccine protection against oncogenic v-src challenge was achieved in the CB line chickens. CTL response was demonstrated in vitro and by adoptive transfer of immune cells to the syngeneic host and to the CC line chickens rendered tolerant to CB cells. In the CC line chickens we observed tumour growth retardation after a low-dose DNA vaccination administered to immature recipients while higher amounts of DNA vaccine in immunocompetent chickens exerted an enhancing effect.

Intronic Deletions That Disrupt mRNA Splicing of the tva Receptor Gene Result in Decreased Susceptibility to Infection by Avian Sarcoma and Leukosis Virus Subgroup A

ABSTRACT The group of closely related avian sarcoma and leukosis viruses (ASLVs) evolved from a common ancestor into multiple subgroups, A to J, with differential host range among galliform species and chicken lines. These subgroups differ in variable parts of their envelope glycoproteins, the major determinants of virus interaction with specific receptor molecules. Three genetic loci, tva, tvb, and tvc, code for single membrane-spanning receptors from diverse protein families that confer susceptibility to the ASLV subgroups. The host range expansion of the ancestral virus might have been driven by gradual evolution of resistance in host cells, and the resistance alleles in all three receptor loci have been identified. Here, we characterized two alleles of the tva receptor gene with similar intronic deletions comprising the deduced branch-point signal within the first intron and leading to inefficient splicing of tva mRNA. As a result, we observed decreased susceptibility to subgroup A ASLV in vitro and in vivo. These alleles were independently found in a close-bred line of domestic chicken and Indian red jungle fowl (Gallus gallus murghi), suggesting that their prevalence might be much wider in outbred chicken breeds. We identified defective splicing to be a mechanism of resistance to ASLV and conclude that such a type of mutation could play an important role in virus-host coevolution.

Genetic Diversity of NHE1, Receptor for Subgroup J Avian Leukosis Virus, in Domestic Chicken and Wild Anseriform Species

J subgroup avian leukosis virus (ALV-J) infects domestic chicken, jungle fowl, and turkey and enters the host cell through a receptor encoded by tvj locus and identified as Na+/H+ exchanger 1 (NHE1). The resistance to ALV-J in a great majority of examined galliform species was explained by deletions or substitutions of the critical tryptophan 38 in the first extracellular loop of NHE1, and genetic polymorphisms around this site predict the susceptibility or resistance of a given species or individual. In this study, we examined the NHE1 polymorphism in domestic chicken breeds and documented quantitative differences in their susceptibility to ALV-J in vitro. In a panel of chicken breeds assembled with the aim to cover the maximum variability encountered in domestic chickens, we found a completely uniform sequence of NHE1 extracellular loop 1 (ECL1) without any source of genetic variation for the selection of ALV-J-resistant poultry. In parallel, we studied the natural polymorphisms of NHE1 in wild ducks and geese because of recent reports on ALV-J positivity in feral Asian species. In anseriform species, we demonstrate a specific and highly conserved critical ECL1 sequence without any homologue of tryptophan 38 in accordance with the resistance of duck cells to prototype ALV-J. Last, we demonstrated that the new Asian strains of ALV-J have not evolved their envelope glycoprotein to the entry the duck cells. Our results contribute substantially to the current discussion of possible heterotransmission of ALV-J and its spill-over into the wild ducks and geese.

Expression of nonspecific esterase (NSE) by thyroid follicular epithelium as a marker for the target organ susceptibility to immune system attack.

Spontaneous autoimmune thyroiditis in obese strain (OS) chickens provides an excellent animal model for the study of Hashimotos autoimmune thyroiditis in humans. The data presented in this paper indicate that nonspecific esterases (NSE) may play a role in or serve as a marker for the target organ susceptibility. Experiments have shown that follicular epithelial cells and interfollicular macrophages in connective tissue stain positively for NSE as early as the first day after hatching, a time at which infiltrating lymphocytes are not yet observed. We also have observed NSE positivity of follicular cells in the vicinity of mononuclear cell infiltration in all OS chickens, as well as weaker positivity in 6-month-old, avian leukosis virus free, Brown Leghorn outbred chickens, which appears in each case to correlate with infiltration of lymphocytes. In F2 hybrids between OS and healthy CB inbred chickens, the intensity of NSE staining was more variable than in OS chickens. Using specific inhibitors eserine, Na-taurocholat and p-hydroxymercuribenzoic acid, we were able to inhibit in vitro the NSE positivity of thyroid gland follicular epithelium, indicating that this staining was not an artifact. Experiments are currently in progress to clarify the relationship between the presence of NSE in follicular epithelium and the predisposition to spontaneous autoimmune thyroiditis.

Identification of New World Quails Susceptible to Infection with Avian Leukosis Virus Subgroup J

ABSTRACT The J subgroup of avian leukosis virus (ALV-J) infects domestic chickens, jungle fowl, and turkeys. This virus enters the host cell through a receptor encoded by the tvj locus and identified as Na+/H+ exchanger 1. The resistance to avian leukosis virus subgroup J in a great majority of galliform species has been explained by deletions or substitutions of the critical tryptophan 38 in the first extracellular loop of Na+/H+ exchanger 1. Because there are concerns of transspecies virus transmission, we studied natural polymorphisms and susceptibility/resistance in wild galliforms and found the presence of tryptophan 38 in four species of New World quails. The embryo fibroblasts of New World quails are susceptible to infection with avian leukosis virus subgroup J, and the cloned Na+/H+ exchanger 1 confers susceptibility on the otherwise resistant host. New World quails are also susceptible to new avian leukosis virus subgroup J variants but resistant to subgroups A and B and weakly susceptible to subgroups C and D of avian sarcoma/leukosis virus due to obvious defects of the respective receptors. Our results suggest that the avian leukosis virus subgroup J could be transmitted to New World quails and establish a natural reservoir of circulating virus with a potential for further evolution. IMPORTANCE Since its spread in broiler chickens in China and Southeast Asia in 2000, ALV-J remains a major enzootic challenge for the poultry industry. Although the virus diversifies rapidly in the poultry, its spillover and circulation in wild bird species has been prevented by the resistance of most species to ALV-J. It is, nevertheless, important to understand the evolution of the virus and its potential host range in wild birds. Because resistance to avian retroviruses is due particularly to receptor incompatibility, we studied Na+/H+ exchanger 1, the receptor for ALV-J. In New World quails, we found a receptor compatible with virus entry, and we confirmed the susceptibilities of four New World quail species in vitro. We propose that a prospective molecular epidemiology study be conducted to identify species with the potential to become reservoirs for ALV-J.

DELETIONS IN THE DNA–BINDING DOMAIN OF THE TP53 GENE IN v-src–TRANSFORMED CHICKEN CELLS

SummaryWe have examined the chicken TP53 tumor suppressor gene in v-src-transformed chicken tumor cells by reverse transcriptase-polymerase chain reaction and deoxyribonucleic acid (DNA) sequencing. Initially, we have detected frequent deletions of variable length in both DNA-binding and oligomerization domains of the TP53 in late as well as early in vitro passages of the chicken tumor cell line PR9692. This tumor cell line shows an immortal phenotype and acquires a metastatic potential that is unique in our experimental model of v-src-induced tumors in congenic chickens. Deletions in TP53 were also detected in an early passage of parallel in vivo subculture of the original v-src-induced tumor. In this case, tumor cells underwent replicative senescence later in tissue culture. Our results suggest that extensive deletions are efficient mechanisms of TP53 inactivation, occurring as early events during the immortalization of v-src-transformed chicken cells. Tumor cells with altered TP53 might, however, still be susceptible to growth control mechanisms, leading to withdrawal from the mitotic cycle in the early stage of the tumor lifeline.

Simultaneous detection of chicken cytokines in plasma samples using the Bio-Plex assay

ABSTRACT A chicken multiplex cytokine assay (Bio‐Plex) to detect four different cytokines (IL‐2, IL‐12, IL‐10, and interferon gamma) simultaneously in plasma samples was designed. Most standard curves range between 1 to 5 pg/mL and 5,000 pg/mL, except for IFN&ggr; with the range of 50 to 25,000 pg/mL. Such a chicken multiplex assay proved to be fast and reliable, and comparable in sensitivity, accuracy, and reproducibility to conventional enzyme‐linked immunosorbent assays. Comparison of the multiplex assay with the ELISA technique using the same clones of detection and capture antibodies resulted in correlation coefficients for all cytokines ranging from 0.95 to 0.99. Lower limit of detection and limit of quantification values were obtained for all tested cytokines by the Bio‐Plex assay compared with ELISA. To reduce the risk of cross‐reaction with other proteins, the Bio‐Plex system was used, combining the principle of sandwich immunoassay with the Luminex bead‐based technology. The cytokine standard recoveries for each cytokine varied between 86 and 118% in dynamic concentration ranges. A chicken multiplex cytokine assay (Bio‐Plex) provided a more complete picture of differences between the Th1/Th2 cytokine profiles of the immunized via a new system of antigen delivery into chicken antigen‐presenting cells and control groups. This multiplexed fluorescent‐bead‐based detection assay can be used as a quantitative or comparative tool for the study of the chicken ex vivo cellular immune response.