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. 2022 Nov;101(11):102116.
doi: 10.1016/j.psj.2022.102116. Epub 2022 Aug 5.

Isolation, identification, and pathogenicity of a ALV-K strain from Chinese indigenous chicken breed

Hao Chen  1 , Youjiang Diao  2 , Xiaolong Sun  3 , Yixin Wang  4
Affiliations

Isolation, identification, and pathogenicity of a ALV-K strain from Chinese indigenous chicken breed

Hao Chen et al. Poult Sci. 2022 Nov.

Abstract

Subgroup K avian leukosis virus (ALV-K) is a new subgroup of avian leukosis virus (ALV) first identified in Chinese indigenous chickens in recent years. In this study, an ALV-K strain was isolated from Luhua chicken in Shandong province, China, and designated SD20LH01. The full-length genomic sequence of SD20LH01 was 7491 bp, which had the highest homology with ALV-K reference strains GDFX0601, GDFX0602 and GDFX0603. The nucleotide homology of env gene of SD20LH01 with reference strains of subgroup A, B, C, D, E, and J was ranged from 57.1 to 93.2%, while 94.1 to 99.4% with other ALV-K reference strains. The nucleotide difference of SD20LH01 mainly clustered with gp85 gene and U3 sequence when compared with the reference strain of ALV-K. In order to investigate the pathogenicity of SD20LH01, SPF chicken embryos were infected by yolk sac inoculation, and 1-day-old chickens were infected by intraperitoneal inoculation of SD20LH01. The results showed that yolk sac inoculation of SD20LH01 could induce persistent viremia, growth retardation and reduce the immune response to NDV and AIV-H9 vaccines. However, intraperitoneal inoculation in 1-day-old chickens could only induce a low level of viremia. In addition, no tumors were found in infected chickens during the animal experiments. This study enriched the genomic sequence data of ALV-K isolated in Chinese indigenous chickens, and laid a foundation for further study on the pathogenesis and prevention of ALV-K.

Keywords: Chinese indigenous breed; full-length genomic sequence analysis; pathogenicity; subgroup K Avian leukosis virus; virus isolation and identification.

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Figures

Figure 1
Figure 1
Electrophoresis of env sequence of isolated strains. M: 5 000 DL Marker; 1, 2: Amplification of env gene of isolated strains.
Figure 2
Figure 2
IFA results of DF-1 cells infected with SD20LH01. A. DF-1 cells infected with SD20LH01; B. Uninfected DF-1 cells (400 ×).
Figure 3
Figure 3
The genomic structure of SD20LH01. The reference strains with high sequence similarity to this isolate are shown above the genome structure.
Figure 4
Figure 4
Phylogenetic tree based on gp85 gene of SD20LH01 and reference strains. The phylogenetic analysis was carried out by Neighbor-joining method by a bootstrap analysis of 1,000 replicates using MEGA 7.0 software program. SD20LH01 was labeled with red circles.
Figure 5
Figure 5
Phylogenetic tree based on LTR (A) and U3 sequence (B) of SD20LH01 and reference strains. The phylogenetic analysis was carried out by Neighbor-joining method by a bootstrap analysis of 1,000 replicates using MEGA 7.0 software program. SD20LH01 was labelled with red circles.
Figure 6
Figure 6
Comparison of viral replication dynamics of three viruses.
Figure 7
Figure 7
Influence of SD20LH01 infection on the body weights in SPF chickens. * indicates significant differences (P < 0.05), based on Duncan's multiple range test. The error bars represent the SEM.
Figure 8
Figure 8
The effect of SD20LH01 infection on the immune responses against NDV and AIV-H9 vaccines in SPF chickens. * indicates significant differences (P < 0.05), based on Duncan's multiple range test. The error bars represent the SEM.
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