Amyloid A amyloidosis in non-infected and avian leukosis virus-C persistently infected inbred ducks

Allelic Diversity in the Serum Amyloid A2 Gene and Amyloid A Amyloidosis in a Breeding Colony of Zebra Finches (Taeniopygia guttata)

A high incidence of amyloid A (AA) amyloidosis was observed in the research breeding colony of zebra finches at our institution. Some birds with hepatic AA amyloidosis were asymptomatic for comorbid conditions frequently associated with the development of AA amyloidosis, whereas other birds with comorbid conditions failed to develop AA amyloidosis, suggesting a potential genetic component to the disease. Sequencing the SAA2 gene from 20 birds yielded 18 distinct sequences that coded for 5 isoforms of the protein. Most of the amino acid substitutions are unlikely to affect the protein's structure or function, but 2 changes-R52L and V84M-were predicted to be disruptive. In particular, R52 is highly conserved across vertebrates, with only arginine or lysine found at this position in reported sequences to date. The atypical R52L substitution occurred in 2 otherwise healthy birds with hepatic AA amyloidosis, supporting the idea that this change is pathogenic.

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

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.

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.

Identification of two novel multiple recombinant avian leukosis viruses in two different lines of layer chicken

Avian leukosis virus (ALV) is the most common oncogenetic retrovirus that emerges spontaneously as a result of recombination between exogenous viruses, exogenous viruses and endogenous viruses, and exogenous viruses and non-homologous cellular genes. In the present study, two natural recombinant avian leukosis viruses (rALVs) (LC110515-5 and LC110803-5) carrying a subgroup C gp85 gene, a subgroup E gp37 gene, and a subgroup J 3'UTR and 3'LTR were isolated from two different lines of layer flocks, Black-bone silky fowl (BSF) and commercial layer chicken, that suffered from myeloid leukosis. Although tumours were not observed in rALV-infected individual chickens, other non-neoplastic inflammatory lesions were evident. The two rALVs were cultured on DF-1 cells and identified by PCR, immunofluorescence assay and gene sequencing. The gp85 nucleotide sequence in the two isolates displayed a high identity (>95 %) with that of the gp85 gene in ALV-C, but the identity was less than 90 % with ALV-A/B/D/E and only 51 % with ALV-J. Phylogenetic analysis of the nucleotide and amino acid sequences confirmed that the two isolates were recombinant between ALV-C, ALV-E and ALV-J. Subgroup C ALV is rarely found in field cases. This report is the first to provide evidence that ALV-C has recombined with ALV-E and ALV-J in two different chicken lines. The source and characteristics of the two rALVs and ALV-C need to be further investigated.

Differences in pathogenicity among strains of the same or different avian leukosis virus subgroups

An efficient induction of wasting disease in chickens by avian leukosis virus (ALV), particularly ALV subgroup C, requires >102 infectious units virus inoculated in mid embryogenesis. The most conspicuous symptoms of the disease were induced by ALV subgroup C; however, significant differences in the occurrence of wasting disease were found among individual members of this subgroup. Almost comparable pathogenicity was exhibited by ALV subgroup D, whereas viruses of subgroups B and A proved to be moderately and almost non-pathogenic, respectively. Using antibodies to cellular antigens, tissue alterations were shown clearly in ALV-C-infected chickens. An essential feature was depletion of lymphocytes in the thymus, bursa and spleen. While the number of dendritic cells in the bursa was increased, their representation in the thymus and spleen was reduced. In the spleen, however, the reduction of dendritic cells concerned only an ellipsoid compartment, which in itself was also markedly reduced. An increased number of macrophages in the thymus and spleen corresponded with the observed general activation of the monocyte-macrophage system. In the spleen, CD4+ T cells were reduced while CD8+ T cells were increased. In agreement with this finding was a failure of chickens to respond to Brucella antigen and an inability of their splenocytes to respond to Concanavalin A, both of which pointed to the damage of immune reactivity. Variation in the pathogenicity among individual ALV strains provides ground for depicting gene sequences playing an important role in ALV acute pathogenicity.

Serum amyloid A in geese; cloning and expression of recombinant protein

We defined the nucleotide-sequence of the full-length goose serum amyloid A and compared it to SAA sequences of the duck. The aim of this work was to clone and express recombinant goose SAA and to produce antibody against this protein: Total RNA was isolated from goose liver and used to synthesise first strand cDNA. The coding region of the goose SAA cDNA was amplified by PCR using primers corresponding to the appropriate conservative regions of duck SAA mRNA. The product was subcloned into pET-15b expression vector to result in a His*Tag fusion protein expression. The protein was purified by affinity chromatography. Rabbits were then immunized against the recombinant purified goose SAA protein. The anti-SAA serum was tested by Western blotting. Full-length goose SAA mRNA sequence has been obtained and sequenced.