Comparison of serological and virological findings from subgroup J avian leukosis virus-infected neoplastic and non-neoplastic flocks in Israel

A Genetically Engineered Commercial Chicken Line Is Resistant to Highly Pathogenic Avian Leukosis Virus Subgroup J

Viral diseases remain a major concern for animal health and global food production in modern agriculture. In chickens, avian leukosis virus subgroup J (ALV-J) represents an important pathogen that causes severe economic loss. Until now, no vaccine or antiviral drugs are available against ALV-J and strategies to combat this pathogen in commercial flocks are desperately needed. CRISPR/Cas9 targeted genome editing recently facilitated the generation of genetically modified chickens with a mutation of the chicken ALV-J receptor Na+/H+ exchanger type 1 (chNHE1). In this study, we provide evidence that this mutation protects a commercial chicken line (NHE1ΔW38) against the virulent ALV-J prototype strain HPRS-103. We demonstrate that replication of HPRS-103 is severely impaired in NHE1ΔW38 birds and that ALV-J-specific antigen is not detected in cloacal swabs at later time points. Consistently, infected NHE1ΔW38 chickens gained more weight compared to their non-transgenic counterparts (NHE1W38). Histopathology revealed that NHE1W38 chickens developed ALV-J typical pathology in various organs, while no pathological lesions were detected in NHE1ΔW38 chickens. Taken together, our data revealed that this mutation can render a commercial chicken line resistant to highly pathogenic ALV-J infection, which could aid in fighting this pathogen and improve animal health in the field.

Biotic concerns in generating molecular diagnosis matrixes for 4 avian viruses with emphasis on Marek's disease virus

The great advance in the field of diagnosis of avian viruses is reflecting the highly sophisticated molecular assays of the human and general virology in providing highly sensitive and fast methods of diagnosis. The present review will discuss the biotic factors and the complexities that became evident with the evolution of the novel molecular diagnostic assays with emphasis on 4 avian viruses, chicken anemia, infectious laryngotracheitis, turkey meningoencephalitis, but mainly on Marek's disease virus. To create a biologically meaningful diagnosis, attention should be dedicated to various biotic factors and not only of the diagnostic assay. Included among the important factors are, (a) the sample examined and the sampling strategy, (b) the outcomes of the pathogen amplification ex vivo, (c) the sampling time and its reflection on the disease diagnosis, (d) the impact of simultaneous multiple virus-infections regarding the ability to demonstrate all pathogens and inter- and intra-interactions between the pathogens. A concerted consideration of the relevant factors and the use of advanced molecular diagnostic assay would yield biologically significant diagnosis in real-time that would beneficiate the poultry industry.

The Importance of Being Non-Defective: A Mini Review Dedicated to the Memory of Jan Svoboda

Jan Svoboda triggered investigations on non-defective avian sarcoma viruses. These viruses were a critical factor in the genetic understanding of retroviruses. They provided the single and unique access to the field and facilitated the discovery of the first oncogene src and of the cellular origin of retroviral oncogenes. They continue to be of importance as singularly effective expression vectors that have provided insights into the molecular functions of numerous oncogenes. Combined with the contributions to the validation of the provirus hypothesis, Jan Svoboda’s investigations of non-defective avian sarcoma viruses have shaped a large and important part of retrovirology.

Characterization of subgroup J avian Leukosis virus isolated from Chinese indigenous chickens

Background

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.

Methods

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.

Results

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.

Discussion

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.

Vertical transmission of avian leukosis virus subgroup J (ALV-J) from hens infected through artificial insemination with ALV-J infected semen

Background

Avian leukosis virus (ALV) is one of the main causes of tumour development within the poultry industry in China. The subgroup J avian leukosis viruses (ALV-J), which induce erythroblastosis and myelocytomatosis, have the greatest pathogenicity and transmission ability within this class of viruses. ALV can be transmitted both horizontally and vertically; however, the effects of ALV infection in chickens—especially roosters—during the propagation, on future generations is not clear. Knowing the role of the cock in the transmission of ALV from generation to generation might contribute to the eradication programs for ALV.

Results

The results showed that two hens inseminated with ALV-J-positive semen developed temporary antibody responses to ALV-J at 4–5 weeks post insemination. The p27 antigen was detected in cloacal swabs of six hens, and in 3 of 26 egg albumens at 1–6 weeks after insemination. Moreover, no viremia was detected at 6 weeks after insemination even when virus isolation had been conducted six times at weekly intervals for each of the 12 females. However, ALV-J was isolated from 1 of their 34 progeny chicks at 1 week of age, and its gp85 had 98.4%–99.2% sequence identity with the gp85 of ALV-J isolated from semen samples of the six cocks.

Conclusions

Our findings indicated that females that were late horizontally infected with ALV-J by artificial insemination might transmit the virus to progeny through eggs, which amounts to vertical transmission.

Seroprevalence of avian hepatitis E virus and avian leucosis virus subgroup J in chicken flocks with hepatitis syndrome, China

Background

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.

Results

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.

Conclusions

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0892-4) contains supplementary material, which is available to authorized users.

Complete genome sequence of an american avian leukosis virus subgroup j isolate that causes hemangiomas and myeloid leukosis

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.

Diagnosis and sequence analysis of avian leukosis virus subgroup J isolated from Chinese Partridge Shank chickens

The diagnosis of avian leukosis virus subgroup J (ALV-J) infection in Chinese Partridge Shank chickens was confirmed by necropsy, histopathological examinations, antibody tests, viral isolation, immunofluorescence assays, and sequence analysis. Myelocytoma, myeloma, and fibrosarcoma were simultaneously found in Partridge Shank flock with ALV-J infection. Sequence analysis of the env genes of ALV-J demonstrated that both gp85 and gp37 were highly homologous among the three strains from local chickens of those among ALV-J strains isolated from white meat-type chickens. The phylogenetic trees indicated that the three strains isolated in this study were closely related to reference strains isolated in so-called Chinese yellow chickens and some strains isolated from white meat-type chickens, both from the USA and China. The observed ALV-J infection was the first report on Partridge Shank chickens, and myelocytoma, myeloma, and fibrosarcoma were found at the same time in this batch of local chickens.

The MET gene is a common integration target in avian leukosis virus subgroup J-induced chicken hemangiomas

Avian leukosis virus subgroup J (ALV-J) is a simple retrovirus that can cause hemangiomas and myeloid tumors in chickens and is currently a major economic problem in Asia. Here we characterize ALV-J strain PDRC-59831, a newly studied U.S. isolate of ALV-J. Five-day-old chicken embryos were infected with this virus, and the chickens developed myeloid leukosis and hemangiomas within 2 months after hatching. To investigate the mechanism of pathogenesis, we employed high-throughput sequencing to analyze proviral integration sites in these tumors. We found expanded clones with integrations in the MET gene in two of the five hemangiomas studied. This integration locus was not seen in previous work characterizing ALV-J-induced myeloid leukosis. MET is a known proto-oncogene that acts through a diverse set of signaling pathways and is involved in many neoplasms. We show that tumors harboring MET integrations exhibit strong overexpression of MET mRNA.

IMPORTANCE

These data suggest that ALV-J induces oncogenesis by insertional mutagenesis, and integrations in the MET oncogene can drive the overexpression of MET and contribute to the development of hemangiomas.

Molecular characteristics of the complete genome of a J-subgroup avian leukosis virus strain isolated from Eurasian teal in China

The J-subgroup avian leukosis virus (ALV-J) strain WB11098J was isolated from a wild Eurasian teal, and its proviral genomic sequences were determined. The complete proviral sequence of WB11098J was 7868 nt long. WB11098J was 95.3.9 % identical to the prototype strain HPRS-103, 94.2 % identical to the American strain ADOL-7501, 94.5-94.7 % identical to Chinese broiler isolates, 94.8-97.5 % identical to layer chicken isolates, and 94.4-95.0 % identical to Chinese local chicken isolates at the nucleotide level. Phylogenetic analysis showed that the WB11098J isolate shared the greatest homology with the layer strain SD09DP03 and was included in the same cluster. Interestingly, two 19-bp insertions in the U3 regions of the 5'LTR and 5'UTR that were most likely derived from other retroviruses were found in the WB11098J isolate. These insertions separately introduced one E2BP-binding site in the U3 region of the 5'LTR and a RNA polymerase II transcription factor IIB and core promoter motif of ten elements in the 5'UTR. A 5-bp deletion was identified in the U3 region of the 5'LTR. No nucleotides were deleted in the rTM or DR-1 regions in the 3'UTR. A 1-bp deletion was detected in the E element and introduced a specific and distinct binding site for c-Ets-1. Our study is the first to report the molecular characteristics of the complete genome of an ALV-J that was isolated from a wild bird and will provide necessary information for further understanding of the evolution of ALV-J.

Detection and molecular characterization of J subgroup avian leukosis virus in wild ducks in China

To assess the status of avian leukosis virus subgroup J (ALV-J) in wild ducks in China, we examined samples from 528 wild ducks, representing 17 species, which were collected in China over the past 3 years. Virus isolation and PCR showed that 7 ALV-J strains were isolated from wild ducks. The env genes and the 3′UTRs from these isolates were cloned and sequenced. The env genes of all 7 wild duck isolates were significantly different from those in the prototype strain HPRS-103, American strains, broiler ALV-J isolates and Chinese local chicken isolates, but showed close homology with those found in some layer chicken ALV-J isolates and belonged to the same group. The 3′UTRs of 7 ALV-J wild ducks isolates showed close homology with the prototype strain HPRS-103 and no obvious deletion was found in the 3′UTR except for a 1 bp deletion in the E element that introduced a binding site for c-Ets-1. Our study demonstrated the presence of ALV-J in wild ducks and investigated the molecular characterization of ALV-J in wild ducks isolates.

Different quasispecies with great mutations hide in the same subgroup J field strain of avian leukosis virus

Blood samples were collected from a local strain of chickens associated with serious tumor cases in Shandong Province. The samples were inoculated into chicken embryo fibroblast and DF-1 cells for virus isolation and identification, respectively. The inoculated cells were screened for three common chicken tumor viruses. Nine strains of avian leukosis virus subgroup J (ALV-J) were identified, and were designated LY1201-LY1209. The env gene from the LY1201 strain was amplified and cloned. All nine resultant env clones (clones 01-09) were sequenced, and the gp85 and gp37 amino acid regions were subjected to homology analysis. Clones 01 and 03 had 10 amino acid deletions in the gp85 region compared to the other seven clones, suggesting that at least two quasispecies with obvious mutations coexist in the same field strain. Among these nine clones, three had identical gp85 and gp37 sequences, and were recognized as the dominant LY1201 quasispecies. The amino acid sequence homology of gp37 and gp85 among the nine clones was 98.5%-100.0% and 96.6%-100.0% respectively, suggesting that the gp85 region of the env gene can better display the quasispecies diversity of ALV-J than gp37.

Simultaneous endemic infections with subgroup J avian leukosis virus and reticuloendotheliosis virus in commercial and local breeds of chickens

Epidemiological studies of subgroup J avian leukosis virus (ALV-J) and reticuloendotheliosis virus (REV) infections were conducted during 1999 to 2009 on 29 chicken flocks of various commercial and local breeds located in six provinces in China. Samples were typically from chickens with myelocytomas or proventricular lesions. ALV-J was isolated from 25 flocks including seven out of seven flocks containing "yellow chickens" or other local breeds and several flocks of layer chickens. REV was isolated from 19 flocks. Co-infection of ALV-J and REV was confirmed in 11/38 birds of 8/15 flocks with myelocytomatosis and in 11/24 birds of 3/5 flocks with proventricular lesions. Both ALV-J and REV were vertically transmitted in four breeder flocks of local chicken breeds. One experiment in specific pathogen free chickens indicated that co-infection at hatch strongly depressed antibody responses to ALV-J but not to REV. The results suggest that infections with both ALV-J and REV have become endemic in local breeds, including breeder flocks where both viruses appear to be perpetuated by vertical transmission. In addition, both viruses were present in at least some commercial broiler, layer and breeder flocks. Eradication programmes are needed but will be difficult, especially in local breeds. This unprecedented concurrence of simultaneous endemic infections with ALV-J and REV may have serious economic consequences and needs to be better understood.

Epidemiological and pathological studies of subgroup J avian leukosis virus infections in Chinese local “yellow” chickens

Epidemiological, pathological and molecular studies indicate that subgroup J avian leukosis virus (ALV-J) infections are widely spread in "yellow chickens" of local breeds in China. ALV-J induced tumour mortality and the serological conversion rates to ALV-J were very high in some breeder flocks. Typical myelocytomatosis was demonstrated not only in livers, spleens, kidneys, and sternums, as in white meat-type chickens, but also in thymuses and the bursa of Fabricius. Especially, severe myeloid cell infiltration was found throughout the whole enlarged thymuses of some birds. ALV-J was isolated at high positive rates from both liver tumour samples and embryos collected from breeder flocks with tumours. At the same time, reticuloendotheliosis virus was also co-isolated with ALV-J in some tumour samples and embryos. Sequence analysis of env genes demonstrated that the gp85 and gp37 among six ALV-J isolates from "yellow chickens" of Chinese local breeds varied as highly as among ALV-J strains isolated from white meat-type chickens worldwide. But strain GD0512 isolated in 2005 from a "yellow chicken" farm in southern China had high identity of 95.1% for gp85 or 99.5% for gp37 to strain HN0001 isolated in 2000 from a white meat-type breeder farm in northern China, a much higher identity than to other yellow chicken and white chicken strains. This is the first report of the isolation and identification of ALV-J from yellow chickens of Chinese local breeds and also the first report of vertical co-infection of ALV-J and reticuloendotheliosis virus. The significance of co-infection of ALV-J and reticuloendotheliosis virus in pathogenesis is discussed.

Reduced serologic response to Newcastle disease virus in broiler chickens exposed to a Chinese field strain of subgroup J avian leukosis virus

In this study, a Chinese field strain of subgroup J avian leukosis virus (ALV-J), NX0101, was studied for its immunosuppressive effects in both commercial broilers and SPF white Leghorn chickens infected at 1 day of age. Our data demonstrated that NX0101 induced much more significant body and immune organ weight loss in the infected commercial broiler chickens in an earlier age than that in the SPF white Leghorn chickens. At the same time antibody responses to vaccinations of Newcastle disease virus (NDV) and infectious bursa disease virus (IBDV) in the NX0101-infected chickens were also evaluated and compared between the commercial broiler chickens and the SPF white Leghorn chickens. Compared with the control group of chickens, the hemagglutination inhibition (HI) antibody response to NDV vaccines was significantly reduced in the NX0101-infected commercial broiler chickens from as early as 20 days after vaccination. However, no significant difference in HI antibody response was seen when HI titers reached their peaks in the NX0101-inoculated and control SPF white Leghorn chickens, except it declined significantly faster in infected birds. Neither of these two types of chickens showed significant decrease of antibody response to IBDV vaccination. Herein, we conclude that this NX0101 strain of ALV-J could selectively suppress humoral immune reactions to NDV, especially in broilers. But challenge experiments were not conducted and, therefore, it cannot be known if decreased antibody levels correlated with decreased protection against NDV in this case.

Nested polymerase chain reaction for detection of the avian leukosis virus causing so-called fowl glioma

The complete nucleotide sequence of the avian leukosis virus causing so-called fowl glioma has been previously determined. Primers were designed for detection of the fowl glioma-causal virus (FGV) based on the 3' untranslated region of the viral genome. The provirus and viral RNA of FGV were specifically detected in various organs and tissues, including feather pulp, from experimentally infected birds using nested polymerase chain reaction (PCR) and reverse transcription nested PCR. The prevalence of FGV was evaluated in 131 Japanese fowls of a zoological garden in Japan based on the detection of the FGV genome in feather pulp using PCR and the detection of viral antigen in faeces by enzyme-linked immunosorbent assay. FGV proviral DNA was detected in feather pulp of 52 birds (39.7%) by nested PCR. Later, nine dead birds from among the 52 were histologically diagnosed as having fowl glioma and found to have the proviral DNA in the affected brain. These results demonstrated that the PCR-based detection of FGV in feather pulp is useful for epidemiological studies on fowl glioma.