Role of env gene and LTR sequence in the pathogenesis of subgroup K avian leukosis virus

Abstract

Avian leukosis virus (ALV) is a retrovirus that induces tumours in infected birds; ALV is divided into different subgroups according to the env gene and cellular tropism. In general, ALV subgroup J (ALV-J) is considered to be the most pathogenic and prevalent subgroup while subgroup K (ALV-K), a newly identified subgroup, only causes mild symptoms. To illuminate the roles of the env viral gene and LTR sequence in pathogenic differences between ALV-J and ALV-K, rescued ALV-J strain rSDAU1005, rescued ALV-K strain rJS11C1, and recombinant strains rENV(J)-LTR(K) and rENV(K)-LTR(J) were characterized and investigated in this study. Among rescued viruses, rSDAU1005 had the highest replication efficiency while rJS11C1 replicated the slowest (replication efficiency rankings were rSDAU1005 >rENV(K)-LTR(J)>rENV(J)-LTR(K)>rJS11 C1). The luciferase reporter gene assay results showed that the promoter activity of ALV-K LTR was lower than that of the ALV-J LTR promoter, which may have accounted for the slower replication efficiency of ALV-K. Pathogenicity of the four rescued viruses was determined via inoculating the yolk sacs of specific-pathogen-free chickens. The results demonstrated that all four viruses were pathogenic; rSDAU1005 caused the most severe growth retardation and immunosuppression. rENV(J)-LTR(K) was more pathogenic when compared to rENV(K)-LTR(J), indicating that env and the LTR sequence play important roles in pathogenicity between ALV-K and ALV-J. Additionally, env seemed to especially play a role in ALV-K pathogenesis. This study provided scientific data and insight to improve detection methods and judgement criteria in ALV clearance and surveillance.

Detection and genetic diversity of subgroup K avian leukosis virus in local chicken breeds in Jiangxi from 2021 to 2023

“…ALV-K infects chickens without clinical or only subclinical signs and has been considered non-pathogenic or low pathogenicity ( Li Y. et al, 2022 ). At the same time, long-term targeted testing and genetic evolutionary analyses of isolates in the field are lacking.…”

Establishment and application of a gold nanoparticle-based immunochromatographic test strip for the detection of avian leukosis virus P27 antigen in egg white samples

“…[26][27][28] The ALV gene fragments are sequentially 5′R-USgag-pol-env-U3-R3′. 29 As Fig. 1(a) shows, the gag gene encoded P19, P2A, P2B, P10, P27, P12 and P15.…”

Isolation, Identification, Sequence Analysis, and Pathogenicity of a CIAV Strain from Aegypius monachus

“…In order to evaluate the immunosuppressive efects of SDTY2021-TJ on response to NDV and AIV-H9 vaccination, chickens belonging to all groups were administered subcutaneous injections of inactivated NDV (Qilu Animal Health Co., Jinan, China) and AIV-H9 (Qilu Animal Health Co., Jinan, China) at 1day-old. Te hemagglutination inhibition (HI) assay was employed to measure NDV and H9-AIV titers in serums collected at 1, 2, and 3 weeks [22].…”