A novel recombinant avian leukosis virus isolated from gamecocks induced pathogenicity in Three-Yellow chickens: a potential infection source of avian leukosis virus to the commercial chickens

Abstract

One natural recombinant avian leukosis virus (ALV) strain GX14DJ3–18 was isolated from a native gamecock by DF-1 cell culture and identified with Polymerase Chain Reaction (PCR), immunofluorescence assay and the viral genome's nucleotide sequencing. This strain was revealed as a novel recombinant virus with nucleotide sequence similarities of 95.4% Long Terminal Repeated (LTR), 95.8% 5′, UTR, 97.9% gag, and 92.9% 3′untranslated regions (UTR) in ALV-J. Also we found sequence similarities of 99.3% pol and 99.0% gp37 in ALV-E, and 89.9% gp85 in ALV-A. The simulated congenital infection with GX14DJ3–18 in Three-Yellow chickens exhibited a significant negative effect on the development of immune organs (P < 0.05). Also, lower antibody responses were found to vaccinations with the commercial vaccines of Newcastle disease virus and with subtypes H5 and H9 of avian influenza virus (P < 0.05). The incidence of tumor or tumor-like lesions in the challenged birds was 14.28% (5/35), while none were observed in the un-challenged control group (0/35). These results suggested that GX14DJ3–18 is a novel recombinant ALV that can induce pathogenicity in the commercial Three-Yellow chickens. We speculated that cross-provincial sales of gamecocks in which ALVs have not been eradicated thoroughly might be a potential route for the transmission of ALVs to commercial chickens.

Whole‐genome analysis of an emerging recombinant avian leukosis virus in yellow chickens, south China

“…Furthermore, the analysis showed that pol and gag genes were highly conservative, and the homology of different strains was all higher than 95.0%. The env gene of GXRJ01 shares 96.8% identity with NX0101 (ALV‐J) but around 58% identities with strains in other subgroups, while the LTR of GXRJ01 shares the highest identity with EV‐1 (94.7%, ALV‐E), demonstrating that it is a natural recombinant virus, which has the same recombination pattern as the previous strains (Barbosa et al., 2008; Wang et al., 2017, 2019), that is, the LTR region is replaced by counterparts of other subgroups.…”

“…But beyond that, the genomic variability of ALV is also shown as gene recombination, which refers to the integration of gene fragments from different ALVs in the process of reverse transcription during mixed infection, thus forming natural recombinant strains (Cai et al., 2013; Lin et al., 2017; Wu et al., 2010; Zhao, Rao, Liao, & Cao, 2018). Most of the recombination events occurred in A, B, E and newly identified K subgroups, while the main form was the replacement of long‐terminal‐repeat (LTR) region (Barbosa, Zavala, & Cheng, 2008; Wang, Yang, Lin, Li, & Wei, 2017; Wang et al., 2019). Several analyses revealed that ALV‐J is also easy to be recombined, while most of the recombinant events appeared in the env gene with no report mentioning that the coding region ( gag‐pol‐env ) of ALV‐J is recombined with the LTR of other subgroups (Liang et al., 2019; Lin et al., 2017; Wu et al., 2010).…”

“…Currently, China's ALV Eradication Program has achieved great success in commercial broiler and layer chickens, but some ALV field strains still circulate in several small‐scale native chicken breeds, such as yellow chickens (Wang et al., 2017, 2019). More seriously, it has been found that there are mixed infections of ALV from different subgroups in these flocks (Li et al., 2016; Su et al., 2017), so it is likely to be a hotbed for ALV mutation and recombination, which deserves our long‐term attention and monitoring.…”

Full-length cDNA sequence analysis of 85 avian leukosis virus subgroup J strains isolated from chickens in China during the years 1988–2018: coexistence of 2 extremely different clusters that are highly dependent upon either the host genetic background or the geographic location

“…After 3 blind passages in DF-1 cells, the viruses were respectively confirmed by indirect immunofluorescence assay using subgroup specific monoclonal antibody JE-9 ( Wang et al., 2019 ). The culture supernatants of the third passage of each sample were harvested for the detection of ALV group-specific antigen p27 with the enzyme-linked immunosorbent assay kit (IDEXX, Westbrook, ME).…”

“…Avian leukosis virus belongs to the genus Alpharetroviru s and the family Retroviridae ( Wang et al., 2019 ). The proviral DNA arrangement of the genome of ALV was 5′LTR-leader- gag - pol - env -3′LTR and the full-length of the genome sequences of ALV was 7,200 bp-7,800 bp ( Wang et al., 2018a ).…”