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Soluble forms of the subgroup A avian leukosis virus [ALV(A)] receptor Tva significantly inhibit ALV(A) infection in vitro and in vivo.

ABSTRACT: The interactions between the subgroup A avian leukosis virus [ALV(A)] envelope glycoproteins and soluble forms of the ALV(A) receptor Tva were analyzed both in vitro and in vivo by quantitating the ability of the soluble Tva proteins to inhibit ALV(A) entry into susceptible cells. Two soluble Tva proteins were tested: the 83-amino-acid Tva extracellular region fused to two epitope tags (sTva) or fused to the constant region of the mouse immunoglobulin G heavy chain (sTva-mIgG). Replication-competent ALV-based retroviral vectors with subgroup B or C env were used to deliver and express the two soluble tv-a (stva) genes in avian cells. In vitro, chicken embryo fibroblasts or DF-1 cells expressing sTva or sTva-mIgG proteins were much more resistant to infection by ALV(A) ( approximately 200-fold) than were control cells infected by only the vector. The antiviral effect was specific for ALV(A), which is consistent with a receptor interference mechanism. The antiviral effect of sTva-mIgG was positively correlated with the amount of sTva-mIgG protein. In vivo, the stva genes were delivered and expressed in line 0 chicken embryos by the ALV(B)-based vector RCASBP(B). Viremic chickens expressed relatively high levels of stva and stva-mIgG RNA in a broad range of tissues. High levels of sTva-mIgG protein were detected in the sera of chickens infected with RCASBP(B)stva-mIgG. Viremic chickens infected with RCASBP(B) alone, RCASBP(B)stva, or RCASBP(B)stva-mIgG were challenged separately with ALV(A) and ALV(C). Both sTva and sTva-mIgG significantly inhibited infection by ALV(A) (95 and 100% respectively) but had no measurable effect on ALV(C) infection. The results of this study indicate that a soluble receptor can effectively block infection of at least some retroviruses and demonstrates the utility of the ALV experimental system in characterizing the mechanism(s) of viral entry.

SUBMITTER: Holmen SL

PROVIDER: S-EPMC113056 | biostudies-literature | 1999 Dec

REPOSITORIES: biostudies-literature

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Soluble forms of the subgroup A avian leukosis virus [ALV(A)] receptor Tva significantly inhibit ALV(A) infection in vitro and in vivo.

Holmen S L SL Salter D W DW Payne W S WS Dodgson J B JB Hughes S H SH Federspiel M J MJ

Journal of virology 19991201 12

The interactions between the subgroup A avian leukosis virus [ALV(A)] envelope glycoproteins and soluble forms of the ALV(A) receptor Tva were analyzed both in vitro and in vivo by quantitating the ability of the soluble Tva proteins to inhibit ALV(A) entry into susceptible cells. Two soluble Tva proteins were tested: the 83-amino-acid Tva extracellular region fused to two epitope tags (sTva) or fused to the constant region of the mouse immunoglobulin G heavy chain (sTva-mIgG). Replication-compe ...[more]

PMID: 10559319

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Project description:The receptor of the subgroup A avian leukosis virus (ALV-A) in chicken is Tva, which is the homologous protein of human CD320 (huCD320), contains a low-density lipoprotein (LDL-A) module and is involved in the uptake of transcobalamin bound vitamin B12/cobalamin (Cbl). To map the functional determinants of Tva responsible for ALV-A receptor activity, a series of chimeric receptors were created by swapping the LDL-A module fragments between huCD320 and Tva. These chimeric receptors were then used for virus entry and binding assays to map the minimal ALV-A functional domain of Tva. The results showed that Tva residues 49 to 71 constituted the minimal functional domain that directly interacted with the ALV-A gp85 protein to mediate ALV-A entry. Single-residue substitution analysis revealed that L55 and W69, which were spatially adjacent on the surface of the Tva structure, were key residues that mediate ALV-A entry. Structural alignment results indicated that L55 and W69 substitutions did not affect the Tva protein structure but abolished the interaction force between Tva and gp85. Furthermore, substituting the corresponding residues of huCD320 with L55 and W69 of Tva converted huCD320 into a functional receptor of ALV-A. Importantly, soluble huCD320 harboring Tva L55 and W69 blocked ALV-A entry. Finally, we constructed a Tva gene-edited cell line with L55R and W69L substitutions that could fully resist ALV-A entry, while Cbl uptake was not affected. Collectively, our findings suggested that amino acids L55 and W69 of Tva were key for mediating virus entry. IMPORTANCE Retroviruses bind to cellular receptors through their envelope proteins, which is a crucial step in infection. While most retroviruses require two receptors for entry, ALV-A requires only one. Various Tva alleles conferring resistance to ALV-A, including Tvar1 (C40W substitution), Tvar2 (frame-shifting four-nucleotide insertion), Tvar3, Tvar4, Tvar5, and Tvar6 (deletion in the first intron), are known. However, the detailed entry mechanism of ALV-A in chickens remains to be explored. We demonstrated that Tva residues L55 and W69 were key for ALV-A entry and were important for correct interaction with ALV-A gp85. Soluble Tva and huCD320 harboring the Tva residues L55 and W69 effectively blocked ALV-A infection. Additionally, we constructed gene-edited cell lines targeting these two amino acids, which completely restricted ALV-A entry without affecting Cbl uptake. These findings contribute to a better understanding of the infection mechanism of ALV-A and provided novel insights into the prevention and control of ALV-A.

Project description:Purpose: The goals of this study are to investigate the differentially expressed genes between ALV-J infected (WRR+) and uninfected (WRR-)chickens spleens by Illumina deep sequencing. Methods: 140-day-old female chickens of White Recessive Rock (WRR) were confirmed as J subgroup avian leukosis virus (ALV-J) infection. Total RNA from three ALV-J-infected spleens (designated: WRR1+, WRR2+, WRR3+) and three uninfected normal spleen samples (designated: WRR1-, WRR2-, WRR3-) was isolated by TRIzol following the manufacturer’s instruction (Invitrogen, CA, USA). RNA samples of three individuals within each group were pooled with equal amounts, and then were subjected to Illumina deep sequencing by Illumina Genome Analyzer IIx. Results: Through raw data processed, 49,979,648 and 43,704,401 clean reads with an average length of 101 bp, which represented total residues of 4,859,084,087 and 4,238,826,168 bp, were obtained for WRR- and WRR+ libraries, respectively. Subsequently, the clean reads in the two libraries were assembled. Altogether, 121,493 contigs were assembled with an average length of 927 bp (ranged from 300 bp to 23,402 bp), leading to generation of 82,829 unigenes. The length of unigenes varied from 351 bp to 28,928 bp, with an average length of 1,155 bp. Based on the FPKM value of each gene, 252 DEGs were identified by DEGseq package using Benjamini-q-value of 0.05 as a cut-off. In ALV-J infected spleens, 90 genes showed up-regulated and 162 showed down-regulated expression when compared to uninfected samples. Conclusions: Our study represents the first time to elucidate the ALV-J infected chickens’spleens at the transcription level by RNA-seq technology. A total of 252 genes were found to be differentially expressed in ALV-J infected spleens when compared to uninfected chickens. These genes can be considered as candidates for further study ALV-J invasion. Spleen mRNA profiles of 140-day-old ALV-J infected (WRR+) and uninfected (WRR-) female chickens of White Recessive Rock were generated by deep sequencing, using Illumina Genome Analyzer IIx.

Dataset Information

Soluble forms of the subgroup A avian leukosis virus [ALV(A)] receptor Tva significantly inhibit ALV(A) infection in vitro and in vivo.

Publications

Soluble forms of the subgroup A avian leukosis virus [ALV(A)] receptor Tva significantly inhibit ALV(A) infection in vitro and in vivo.

Similar Datasets

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