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Endogenous Avian Leukosis Virus in Combination with Serotype 2 Marek's Disease Virus Significantly Boosted the Incidence of Lymphoid Leukosis-Like Bursal Lymphomas in Susceptible Chickens.
ABSTRACT: In 2010, sporadic cases of avian leukosis virus (ALV)-like bursal lymphoma, also known as spontaneous lymphoid leukosis (LL)-like tumors, were identified in two commercial broiler breeder flocks in the absence of exogenous ALV infection. Two individual ALV subgroup E (ALV-E) field strains, designated AF227 and AF229, were isolated from two different breeder farms. The role of these ALV-E field isolates in development of and the potential joint impact in conjunction with a Marek's disease virus (MDV) vaccine (SB-1) were further characterized in chickens of an experimental line and commercial broiler breeders. The experimental line 0.TVB*S1, commonly known as the rapid feathering-susceptible (RFS) line, of chickens lacks all endogenous ALV and is fully susceptible to all subgroups of ALV, including ALV-E. Spontaneous LL-like tumors occurred following infection with AF227, AF229, and a reference ALV-E strain, RAV60, in RFS chickens. Vaccination with serotype 2 MDV, SB-1, in addition to AF227 or AF229 inoculation, significantly enhanced the spontaneous LL-like tumor incidence in the RFS chickens. The spontaneous LL-like tumor incidence jumped from 14% by AF227 alone to 42 to 43% by AF227 in combination with SB-1 in the RFS chickens under controlled conditions. RNA-sequencing analysis of the LL-like lymphomas and nonmalignant bursa tissues of the RFS line of birds identified hundreds of differentially expressed genes that are reportedly involved in key biological processes and pathways, including signaling and signal transduction pathways. The data from this study suggested that both ALV-E and MDV-2 play an important role in enhancement of the spontaneous LL-like tumors in susceptible chickens. The underlying mechanism may be complex and involved in many chicken genes and pathways, including signal transduction pathways and immune system processes, in addition to reported viral genes.IMPORTANCE Lymphoid leukosis (LL)-like lymphoma is a low-incidence yet costly and poorly understood disease of domestic chickens. The observed unique characteristics of LL-like lymphomas are that the incidence of the disease is chicken line dependent; pathologically, it appeared to mimic avian leukosis but is free of exogenous ALV infection; inoculation of the nonpathogenic ALV-E or MDV-2 (SB-1) boosts the incidence of the disease; and inoculation of both the nonpathogenic ALV-E and SB-1 escalates it to much higher levels. This study was designed to test the impact of two new ALV-E isolates, recently derived from commercial broiler breeder flocks, in combination with the nonpathogenic SB-1 on LL-like lymphoma incidences in both an experimental egg layer line of chickens and a commercial broiler breeder line of chickens under a controlled condition. Data from this study provided an additional piece of experimental evidence on the potency of nonpathogenic ALV-E, MDV-2, and ALV-E plus MDV-2 in boosting the incidence of LL-like lymphomas in susceptible chickens. This study also generated the first piece of genomic evidence that suggests host transcriptomic variation plays an important role in modulating LL-like lymphoma formation.
Project description:We report the complete genome sequence of avian leukosis virus subgroup J (ALV-J) isolate PDRC-59831, which causes myeloid leukosis and hemangiomas in chickens. This is an American ALV-J isolate, which was found in a 38-week-old broiler breeder chicken on a farm in Georgia in 2007.
Project description:To survey avian leukosis virus subgroup J (ALV-J) integration in myeloid leukosis (ML) of chicken, we developed an ALV-J insertional identification platform based on hybrid-capture target enrichment and next-generation sequencing (NGS). In addition, we used gene expression profiling and bioinformatics to associate integration sites to transcriptional activity and to genetic features of the tumor cell genome. We selected six cases of ALV-J positive and diagnosed as ML for integration sites identify from commercial broiler breeder flocks in Guangdong Province of China between November 2011 and March 2012. All tumors were diagnosed on the basis of characteristic gross and microscopic lesions. Furthermore, PCR tests on the genomic DNA of tissues and virus isolation assay only showed ALV-J-specific positive results in previously study. We randomly chose 4 independent liver samples from the six cases for gene expression profile analysis. And 3 ALV-negative tissue samples from specific-pathogen-free (SPF) chickens at the same age were use as negative controls. Thus a total of 7 samples were hybridized, three representing control.
Project description:A new subgroup of avian leukosis virus (ALV) that includes a unique env gene, designated J, was identified recently in England. Sequence analysis of prototype English isolate HPRS-103 revealed several other unique genetic characteristics of this strain and provided information that it arose by recombination between exogenous and endogenous virus sequences. In the past several years, ALV J type viruses (ALV-J) have been isolated from broiler breeder flocks in the United States. We were interested in determining the relationship between the U.S. and English isolates of ALV-J. Based on sequence data from two independently derived U.S. field isolates, we conclude that the U.S. and English isolates of ALV-J derive from a common ancestor and are not the result of independent recombination events.
Project description:Avian leukosis virus subgroup J (ALV-J) is an immunosuppressive virus that causes considerable economic losses to the chicken industry in China. However, there is currently no effective vaccine to prevent ALV-J infection. In order to reduce the losses caused by ALV-J, we constructed two effective ALV-J vaccines by inserting the ALV-J (strain JL093-1) env or gag+env genes into the US2 gene of the Marek's disease herpesviruses (MDV) by transfection of overlapping fosmid DNAs, creating two recombinant MDVs, rMDV/ALV-gag+env and rMDV/ALV-env. Analysis of cultured chicken embryo fibroblasts infected with the rMDVs revealed that Env and Gag were successfully expressed and that there was no difference in growth kinetics in cells infected with rMDVs compared with that of cells infected with the parent MDV. Chickens vaccinated with either rMDV revealed that positive serum antibodies were induced. Both rMDVs also effectively reduced the rate of positive viremia in chicken flocks challenged with ALV-J. The protective effect provided by rMDV/ALV-env inoculation was slightly stronger than that provided by rMDV/ALV-gag+env. This represents the first study where a potential rMDV vaccine, expressing ALV-J antigenic genes, has been shown to be effective in the prevention of ALV-J. Our study also opens new avenues for the control of MDV and ALV-J co-infection.
Project description:In spite of the purification of the laying hens and broilers of avian leukosis virus (ALV) has made remarkable achievements, the infection of ALV was still serious in Chinese indigenous chickens.In order to assess the epidemic state of avian leukosis virus in indigenous chickens in China, 10 novel strains of ALV subgroup J (ALV-J), named JS16JH01 to JS16JH10, were isolated and identified by virus isolation and immunofluorescence antibody assays from a Chinese local breed farm with a sporadic incidence of tumors. To understand their virological characteristics further, the proviral genome of ENV-LTR was sequenced and compared with the reference strains.The homology of the gp85 gene between the ten ALV-J strains and NX0101 was in the range from 89.7-94.8% at the nuclear acid level. In addition, their gp85 genes were quite varied, with identities of 92-98% with themselves at the nuclear acid level. There were several snp and indel sites in the amino acid sequence of gp85 genes after comparison with other reference strains of ALV. Interestingly, a novel insertion in the gp85 region was found in two strains, JS16JH01 and JS16JH07, compared with NX0101 and HPRS-103.At present, owing to the large-scale purification of ALV in China, laying hens and broiler chickens with ALV infection are rarely detected, but ALVs are still frequently detected in the local chickens, which suggests that more efforts should be applied to the purification of ALV from indigenous chickens.
Project description:Avian leukosis virus (ALV) is an oncogenic virus causing a variety of neoplasms in chickens. The group of avian leukosis virus in chickens contains six closely related subgroups, A to E and J. The prevalence of ALVs in hosts may have imposed strong selective pressure toward resistance to ALVs infection. The tvb gene encodes Tvb receptor and determines susceptibility or resistance to the subgroups B, D, and E ALV. In this study, we characterized a novel resistant allele of the tvb receptor gene, tvbr3, which carries a single-nucleotide substitution (c.298C>T) that constitutes a premature termination codon within the fourth exon and leads to the production of a truncated TvbR3 receptor protein. As a result, we observed decreased susceptibility to infection by ALV-B, ALV-D and ALV-E both in vitro and in vivo, and decreased the binding affinity of the TvbR3 receptor for the subgroups B, D, and E ALV envelope glycoproteins. Additionally, we found that the tvbr3 allele was prevalent in Chinese broiler lines. This study demonstrated that premature termination codon in the tvb receptor gene can confer genetic resistance to subgroups B, D, and E ALV in the host, and indicates that tvbr3 could potentially serve as a resistant target against ALV-B, ALV-D and ALV-E infection.
Project description:BACKGROUND:Avian leukosis (AL), which is caused by avian leukosis virus (ALV), has led to substantial economic losses in the poultry industry. The kit used to detect all ALV-positive chickens in breeder flocks is very important for efficiently controlling AL. However, a new emerging ALV subtype is currently a severe challenge in the poultry industry. RESULTS:In this paper, we compared different enzyme-linked immunosorbent assay (ELISA) kits for detecting p27 of ALV in the same batch of meconium samples. Different positive samples were further analyzed by PCR or virus isolation. The results showed that 36 positive samples among the 1812 chicken meconium samples could be detected by a sandwich ELISA (sELISA) kit, but only 17 positive samples could be identified by a commercial kit. To verify this result, cloacal swabs and viruses isolated from the positive chickens (2 days old) were used to detect the presence of p27. The results showed that the positive rate of p27 was 100% for the swabs and 40% for virus isolation. Surprisingly, PCR and sequence analysis revealed that the env gene of ALV in these positive samples belonged to the novel subgroup K (ALV-K). CONCLUSION:These data not only demonstrate the relatively high sensitivity of the sELISA kit but also highlight the challenge of controlling ALV-K.
Project description:Avian leukosis virus subgroup J (ALV-J) was first isolated from meat-type chickens in 1988. No field cases of ALV-J infection or tumors in layer chickens were observed worldwide until 2004. However, layer flocks in China have experienced outbreaks of this virus in recent years. The molecular epidemiology of ALV-J strains isolated from layer flocks was investigated. The env genes of 77.8% (21/27) of the ALV-J layer isolates with a high degree of genetic variation were significantly different from the env genes of the prototype strain of ALV-J (HPRS-103) and American and Chinese strains from meat-type chickens (designated ALV-J broiler isolates). A total of 205 nucleotides were deleted from the 3' untranslated region of 89.5% (17/19) of the ALV-J layer isolates. Approximately 94.7% (16/17) of the layer isolates contained a complete E element of 146 to 149 residues. The U3 sequences of 84.2% (16/19) of the ALV-J layer isolates displayed less than 92.5% sequence homology to those of the ALV-J broiler isolates, although the transcriptional regulatory elements that are typical of avian retroviruses were highly conserved. Several unique nucleotide substitutions in the env gene, the U3 region, and the E element of most of the ALV-J layer isolates were detected. These results suggested that the env gene, E element, and U3 region in the ALV-J layer isolates have evolved rapidly and were significantly different from those of the ALV-J broiler isolates. These findings will contribute to a better understanding of the pathogenic mechanism of layer tumor diseases induced by ALV-J.
Project description:From 2014 to 2015 in China, many broiler breeder and layer hen flocks exhibited a decrease in egg production and some chickens developed hepatitis syndrome including hepatomegaly, hepatic necrosis and hemorrhage. Avian hepatitis E virus (HEV) and avian leucosis virus subgroup J (ALV-J) both cause decreasing in egg production, hepatomegaly and hepatic hemorrhage in broiler breeder and layer hens. In the study, the seroprevalence of avian HEV and ALV-J in these flocks emerging the disease from Shandong and Shaanxi provinces were investigated.A total of 1995 serum samples were collected from 14 flocks with hepatitis syndrome in Shandong and Shaanxi provinces, China. Antibodies against avian HEV and ALV-J in these serum samples were detected using iELISAs. The seroprevalence of anti-avian HEV antibodies (35.09%) was significantly higher than that of anti-ALV-J antibodies (2.16%) (p?=?0.00). Moreover, the 43 serum samples positive for anti-ALV-J antibodies were all also positive for anti-avian HEV antibodies. In a comparison of both provinces, Shandong chickens exhibited a significantly higher seroprevalence of anti-avian HEV antibodies (42.16%) than Shaanxi chickens (26%) (p?=?0.00). In addition, the detection of avian HEV RNA and ALV-J cDNA in the liver samples from the flocks of two provinces also showed the same results of the seroprevalence.In the present study, the results showed that avian HEV infection is widely prevalent and ALV-J infection is endemic in the flocks with hepatitis syndrome from Shandong and Shaanxi provinces of China. These results suggested that avian HEV infection may be the major cause of increased egg drop and hepatitis syndrome observed during the last 2 years in China. These results should be useful to guide development of prevention and control measures to control the diseases within chicken flocks in China.
Project description: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.