Construction and In Vitro Characterization of Attenuated Feline Immunodeficiency Virus Long Terminal Repeat Mutant Viruses

Abstract

AP-1-and ATF-binding sites are cis-acting transcriptional elements within the U3 domain of the feline immunodeficiency virus (FIV) long terminal repeat (LTR) that serve as targets for cellular activation pathways and may regulate virus replication. We report that FIV LTR mutant proviruses encoding U3 deletions of the ATF-binding sequence exhibited restricted virus expression and replication in both feline lymphocytes and macrophages. In contrast, deletion of the AP-1 site had negligible effects on virus expression and replication. FIV LTR mutant proviruses encoding deletions of both the AP-1 and ATF sites or a 72-bp deletion encompassing the AP-1 site, duplicated C/EBP sites, and ATF sites were severely restricted for virus expression. These results demonstrate that deletion of either the ATF-binding site or multiple cis-acting transcriptional elements attenuates FIV. These attenuated FIV mutants provide opportunities to characterize the role of cis-acting elements in virus replication in vivo and to test LTR mutants as attenuated virus vaccines.

Preferential Feline Immunodeficiency Virus (FIV) Infection of CD4+CD25+T-Regulatory Cells Correlates both with Surface Expression of CXCR4 and Activation of FIV Long Terminal Repeat Binding Cellular Transcriptional Factors

“…HIV and FIV LTRs encompass binding sites for several cellular transcription factors, including activating protein 1 (AP-1), activating transcription factor (AP-4), ATF CAAT enhancer binding protein (CEBP), NF-B, and SP-1 (5,11,36). Although the role of NF-B in HIV mRNA transcription is well established (11,36), the role of a putative NF-B binding site in FIV LTR transactivation remains unclear.…”

“…These cells have a partial activation phenotype, are anergic, and demonstrate immunosuppressive function in the presence of interleukin-2 (IL-2) (51). While little is known of the factors regulating anergy in Treg cells, the activation-proliferative state of lymphocytes is largely controlled by a group of cellular transcription factors that regulate IL-2 gene expression, such as NF-B and AP-1 (1), which also regulate transcription of HIV and FIV genes (5,11).…”

“…Kawaguchi et al (25) demonstrated by sitespecific mutations that the CEBP site in the FIV LTR is necessary for efficient viral replication in both feline fibroblasts and a T-lymphoblastoid cell line. A number of studies demonstrated that mutations or deletions of both ATF and AP-1 sites resulted in severely reduced basal promoter activity from the FIV LTR and impaired ability of viruses to replicate both in feline lymphocytes and in macrophages (5,21,23).…”

“…HIV and FIV depend on both cellular and viral factors for efficient transcription of their genomes, and the activity of their promoters within the long terminal repeat (LTR) regions are highly dependent on the level of host cell activation (5,45). HIV and FIV LTRs encompass binding sites for several cellular transcription factors, including activating protein 1 (AP-1), activating transcription factor (AP-4), ATF CAAT enhancer binding protein (CEBP), NF-B, and SP-1 (5,11,36).…”

Pantropic retroviruses as a transduction tool for sea urchin embryos

“…2B1) based on previous studies (36,37). The viral enhancer/promoter in the U3 region is composed of tandem 72-bp repeats as well as CAAT and TATA boxes (36,50); we generated LvOtx CRM3-incorporating SIN viral constructs that eliminated the 72-bp repeats and either retained or eliminated the CAAT and TATA elements from the viral promoter (Fig. 2B1).…”