Experimental Infection of Attwater's/Greater Prairie Chicken Hybrids with the Reticuloendotheliosis Virus

Immunoprotection induced by CpG-ODN/Poly(I:C) combined with recombinant gp90 protein in chickens against reticuloendotheliosis virus infection

The present study is focused on investigating the immunoprotective effects of CpG-ODN/Poly(I:C) combined with the viral glycoprotein gp90 protein against reticuloendotheliosis virus (REV) infection in chickens. REV's gp90 gene was amplified from the REV-infected cells and expressed in Escherichia coli (E.coli). The expressed products, upon purification, were inoculated into 7-day-old chickens with PBS, CpG-ODN or Poly(I:C) adjuvant; Two booster inoculations were then conducted, and then each chicken was challenged. The presence of REV-antibodies in serum was determined weekly after the first vaccination. The viremia and immunosuppressive effects of REV infection were also monitored after the challenge. The neutralizing effects of the antisera were tested in vitro. The results showed that the recombinant gene containing REV gp90 gene was expressed into the recombinant protein with a size of 51 Kilo Dalton (KD), which could be recognized by a monoclonal antibody (MAb) against the gp90 protein. The viremia and immunosuppressive effects of avian influenza virus (AIV) vaccine caused by REV challenge in CpG-ODN group and in Poly(I:C) group were dramatically decreased. REV antibody with low titers was induced in gp90 group and the inoculated chickens were partly protected. Compared with those in gp90 group, the titers and the positive ratios of REV antibody in CpG+gp90 group were significantly increased, whereas the viremia and immunosuppressive effects of AIV vaccine caused by REV infection were significantly decreased. In the Poly(I:C) +gp90 group, the viremia and immunosuppressive effects caused by REV infection were also dramatically decreased, although REV antibody responses were softly increased. The diluted antisera from the vaccinated chickens in both groups could completely inhibit the replication of REV in chick fibroblast cells (CEF). Hence, it can be concluded that CpG-ODN or the Poly(I:C) adjuvant can enhance the antiviral effects of the REV subunit vaccine against REV infection, which may result from different mechanisms.

A DNA vaccine expressing ENV and GAG offers partial protection against reticuloendotheliosis virus in the prairie chicken (Tympanicus cupido)

Recurring infection of reticuloendotheliosis virus (REV), an avian oncogenic gammaretrovirus, has been a major obstacle in attempts to breed and release the endangered Attwater's prairie chicken (Tympanicus cupido attwateri). The aim of this study was to develop a DNA vaccine that protects the birds against REV infection. A plasmid was constructed expressing fusion proteins of REV envelope (env) and VP22 of Gallid herpesvirus 2 or REV gag and VP22. Birds vaccinated with these recombinant plasmids developed neutralizing antibodies; showed delayed replication of virus; and had significantly less infection of lymphocytes, specifically CD4+ lymphocytes. Although the vaccine did not prevent infection, it offered partial protection. Birds in field conditions and breeding facilities could potentially benefit from increased immunity when vaccinated.

New pathogenetic characters of reticuloendotheliosis virus isolated from Chinese partridge in specific-pathogen-free chickens

Avian reticuloendotheliosis virus (REV) infection can induce a runting syndrome, immunosuppression, acute reticulum cell neoplasia and lymphomas in a variety of domestic and wild birds. To evaluate the pathogenicity and oncogenicity of REV-JX0927 that isolated from Chinese partridge, experimental inoculated day-old specific-pathogen-free (SPF) White Leghorn chickens were examined at regular intervals. The examination procedures included hematology, serology and histopathology; also including immunohistochemistry and apoptosis assay. Body weight, relative immune organs weight and apoptosis assay results revealed that the immunosuppression of infected birds is associated with apoptosis of lymphocytes in lymphoid tissues, especially in thymus induced by REV-JX0927. Hematology and apoptosis assay results showed that the 7th week of post-infection is a critical time point for lymphocytes to be transformed into tumor cells. Histopathology evidences demonstrated that REV-JX0927 induced reticuloendotheliosis at early stage (1 week), and lymphosarcomas at middle stage (after 7 weeks). In addition, squamous-cell carcinoma, adenocarcinoma and aneurysm were found in infected birds. Arteritis was associated with concentration of serum protein and fat. REV antigen expression was observed in infected birds through the experimental period. REV has high tropism for proventriculus, kidney, liver, lymphoid tissues, pancreas, lymphosarcoma cells and blood vessels. Data from this study showed that several new pathogenitic characters caused by REV-JX0927 were observed. It indicated that REV-JX0927 is a multipotential oncogenic retrovirus.

A duplex real-time polymerase chain reaction assay for the simultaneous detection of long terminal repeat regions and envelope protein gene sequences of Reticuloendotheliosis virus in avian blood samples

The Reticuloendotheliosis virus (REV) group of retroviruses infects a wide range of avian species, including chickens, turkeys, ducks, geese, quail, and prairie chickens. The objective of the present study was to develop a highly sensitive and specific diagnostic test for the detection of REV in whole blood samples. In order to increase the diagnostic sensitivity, a duplex real-time polymerase chain reaction (PCR) that detects both the envelope protein gene ( env) and the long terminal repeat (LTR) region of REV was designed. This assay demonstrated greater analytical and diagnostic sensitivity than the gel-based PCR assay when using DNA extracted from whole blood by both phenol-chloroform and magnetic bead methods. In general, threshold cycle values in the duplex real-time PCR assay were lower from DNA extracted using the magnetic bead system compared to DNA extracted by the phenol-chloroform method. Data presented herein show the successful development of a rapid and accurate test procedure, with high-throughput capability, for the diagnosis of REV infection using avian blood samples.

Detection of reticuloendotheliosis virus as a contaminant of fowl pox vaccines

This study was designed to detect reticuloendotheliosis virus (REV) as a contaminant in fowl pox vaccines. A total of 30 fowl pox vaccine samples were examined for the presence of REV using both in vitro and in vivo methods. In in vitro testing, the fowl pox vaccine samples were inoculated into chicken embryo fibroblast cultures prepared from specific-pathogen-free embryonated chicken eggs, and the cultures were examined using PCR to detect REV. In in vivo testing, each fowl pox vaccine sample was inoculated into 5-d-old specific-pathogen-free chicks, which were kept under observation for up to 12 wk postinoculation; serum samples were collected at 15, 30, and 45 d postinoculation for the detection of REV-specific antibodies using ELISA. Tissue samples were collected at 8 and 12 wk postinoculation for histopathological examination. Of the tested vaccines, only one imported vaccine sample tested positive for REV using PCR. Serum samples collected from chicks infected with the PCR-positive vaccine batch also tested positive for REV-specific antibodies using ELISA. Histopathological examination of the liver, spleen, and bursa of Fabricius demonstrated the presence of tumor cells in these organs, confirming the results obtained using PCR and ELISA, and indicating that the sample was contaminated with REV. These data clearly indicate that the screening of all commercial poultry vaccines for viruses is an important factor in assuring the biosafety of animal vaccines.

An avian, oncogenic retrovirus replicates in vivo in more than 50% of CD4+ and CD8+ T lymphocytes from an endangered grouse

Reoccurring infection of reticuloendotheliosis virus (REV), an avian oncogenic retrovirus, has been a major obstacle in attempts to breed and release an endangered grouse, the Attwater's prairie chicken (Tympanicus cupido attwateri). REV infection of these birds in breeding facilities was found to result in significant decreases in the CD4(+) and increases in the CD8(+) lymphocyte populations, although experimental infection of birds resulted in only increases in the CD8(+) lymphocytes. Because our indirect immunofluorescent assay readily detected infection of both CD4(+) and CD8(+) lymphocytes, a triple labeling flow cytometric procedure was developed to quantify the individual lymphocytes infected in vivo with REV. Lymphocytes were gated with a biotinylated pan-leukocyte marker bound to streptavidin R-PE-Cy5. Chicken CD4 or CD8 specific mouse MAb directly labeled with R-PE identified the phenotype and with permeabilizing of cells, infection was indirectly labeled with rabbit IgG specific for the REV gag polypeptide and FITC conjugated goat anti-rabbit antibody. More than 50% of the total lymphocytes and of the total CD4(+) or CD8(+) lymphocytes supported in vivo viral expression in all infected birds examined. Remarkably, this level of infection was detected in the absence of visible clinical signs of illness.