Maedi-Visna Virus and Caprine Arthritis Encephalitis Virus Genomes Encode a Vpr-Like but No Tat Protein

Abstract

A small open reading frame (ORF) in maedi-visna virus (MVV) and caprine arthritis encephalitis virus (CAEV) was initially named "tat" by analogy with a similarly placed ORF in the primate lentiviruses. The encoded " Tat Lentiviruses comprise a genus of complex, nononcogenic retroviruses that infect diverse mammalian hosts, including primates (human immunodeficiency virus [HIV] and simian immunodeficiency virus), carnivores (feline immunodeficiency virus), and ungulates (equine infectious anemia virus, bovine immunodeficiency virus, and the small-ruminant lentiviruses [SRLV]). In addition to the three essential retroviral genes, gag, pol, and env, lentiviruses carry a variable number of regulatory and accessory genes, most of which are situated between the end of pol and the beginning of env. The most complex of these viruses, HIV type 1 (HIV-1), encodes three regulatory genes, tat, rev, and vif, and three accessory genes, vpu, vpr, and nef. The three conserved open reading frames found between pol and env in the SRLVs maedi-visna virus (MVV) and caprine arthritis-encephalitis virus (CAEV) have classically been assigned to the regulatory genes tat, rev, and vif.Some MVV-infected sheep progress to a stage of chronic debilitating disease affecting mainly the lungs (progressive interstitial pneumonia) and the central nervous system (progressive demyelinating encephalomyelitis) many years after infection (24,25). Goats infected by the related CAEV can develop leukoencephalomyelitis (young kids) or chronic arthritis and mastitis (adult animals) (5, 6). In vivo, MVV and CAEV chiefly replicate in cells of the monocyte/macrophage lineage, and

Heat-shock protein 70 exerts opposing effects on Vpr-dependent and Vpr-independent HIV-1 replication in macrophages

“…Given that macrophage is the main (and sometimes the only) target cell for lentiviruses, 54 the fact that both primate and nonprimate lentiviruses encode a Vpr-like protein 55 indicates a critical role that this protein plays in lentiviral infection of macrophages. Therefore, the activity of Hsp70 to bind and neutralize Vpr is likely an important innate antilentiviral mechanism.…”

Equine Infectious Anemia Virus (EIAV): what has HIV?s country cousin got to tell us?

“…Interestingly, recent studies on the initially named Tat protein of Small Ruminant Lentiviruses (SRLV), infecting goats and sheep, showed that this protein has a minimal effect on the transcriptional level from the LTR [181]. In fact, the gene initially designed as the tat gene may encode a Vpr-like protein, suggesting that SRLV differ from the other lentiviruses in their control of expression from the viral LTR [180].…”

Duplicated Sequence Motif in the Long Terminal Repeat of Maedi-Visna Virus Extends Cell Tropism and Is Associated with Neurovirulence

“…The U3 region contains the promoter and enhancer regions of the virus, and unlike human immunodeficiency virus (HIV), no transactivation response element has been identified in the R region. The Tat protein of MVV has in most studies been shown to activate transcription 2-to 8-fold (compared to 100-fold activation by HIV type 1 [HIV-1] Tat) and has been suggested to be analogous to the Vpr protein in HIV-1 (6,16,56). The LTR has been associated with tissue tropism in a number of retroviruses (11,14,32,35,38,39,49,55).…”