REV is a group of avian viruses in the family Retroviridae, specifically gammaretroviruses in the same genus as mammalian C-type retroviruses. The viruses included in this group are REV strains such as REV-T (replication defective and tumorigenic); REV-A (REV-T helper, replication competent); spleen necrosis virus; chick syncytial virus; duck infectious anemia virus; and other isolates obtained from turkeys, chickens, ducks, pheasants, geese, and prairie chickens. Notably, REV infection of captive prairie chicken can result in a high incidence (up to 100% of infected birds in some outbreaks) of tumors and wasting syndrome, and this infection has had a severe impact on the APC recovery program (Collisson, pers. obs.). Once detected, infected birds were removed from breeding populations, significantly reducing the genetic pool and the number of birds that can be released or kept as breeders. REV infection has been associated with acute reticular cell neoplasia, wasting disease, and chronic cell neoplasia of lymphoid and nonlymphoid tissues (Drechsler et al., 2013).
Vaccination Protocol:
Four birds (two males, two females) were vaccinated four times with a combination of 500 μg of VP22/gag and 250 μg of VP22/env plasmids expressing the fusion proteins (Drechsler et al., 2013).
Vaccine Immune Response Type:
VO_0003057
Efficacy:
The DNA vaccine containing REV proteins env and gag protected against infection early after birds were repeatedly inoculated with large doses of vaccine (500 μg) as evidenced by the lack of proviral DNA in lymphocytes of the vaccinated birds at 4 wk postchallenge. In contrast, nested PCR 4 wk postinfection showed REV proviral DNA in several of the PBS and vector mock-vaccinated control birds. However, 8 wk postinfection, two out of three vaccinated birds tested positive for REV, and all birds were positive 12 wk postinfection, showing that the vaccine delayed, thus inhibited, the onset of viral replication (Drechsler et al., 2013).
gp90 protein-based vaccine derived from a Reticuloendotheliosis virus strain isolated from a contaminated IBD vaccine induces protection in chicks. (Ren et al., 2018)
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Chicken Response
Vaccination Protocol:
Twenty 150-day-old SPF chickens were obtained from SPAFAS and randomly divided into two groups. Each chicken of immune group was immunized with 600 μg gp90 protein and 300 μg CPG-ODN. The control group was immunized with an equal volume of PBS and immunized once every two weeks (150, 164, 178, 182 days age). Eggs were collected from the immunized hens and REV-specific antibody was measured in the egg yolk. (Ren et al., 2018)
Immune Response:
Starting from the second week post-immunization, the REV antibody titer of the immunized hens increased rapidly, especially from weeks 6 to 8 post-immunization. The positive rate of antibody reached 100% and the antibody titer peaked at week 9 post-immunization. Three eggs were collected from each hen to determine if the egg yolks contained REV-specific antibody were consistent with the serum antibody test results. Hens in the control group were always antibody negative. (Ren et al., 2018)
Challenge Protocol:
Ten hatched 1-day-old chicks from the two experimental cohorts, which were REV maternal antibody positive or negative, were challenged intraperitoneally with 102.7 TCID50 of the REV-LN1201 strain. (Ren et al., 2018)
Efficacy:
At the sixth week after challenge, compared to five chicks in the control group, only one chick in the immunized group was viremic. One of the chicks in the control group died without any specific symptom during the sixth week. The presence of maternal antibodies in the chicks significantly affected the health and survival of chicks after REV infection, as supported by chicks in the control group always having a lower bodyweight than chicks in the immunized group. (Ren et al., 2018)
