Element:HTLV-1

From The Gypsy Database

Description

Human T-Cell Leukemia Virus (HTLV-1) is a complex retrovirus responsible of inducing adult T-cell leukemia (ATL) in humans (Poiesz et al. 1980). HTLV-1 is associated with a neurologic degenerative disorder known as tropical spastic paraparesis (TSP) or more commonly, HTLV-1-associated myelopathy (HAM). Currently, there are 20 million people worldwide infected with HTLV-1 (Edwards et al. 2003), which is spread via semen (sex), needles, milk, and blood. Several evidences suggest that HTLV-1 may have arisen from interspecies transmission between STLV-1-infected monkeys and humans, followed by evolution in the human host (Masahiro et al. 1996). Phylogenetic analyses have revealed four HTLV-1 molecular subtypes:

  • Subtype A (Cosmopolitan), is the most widespread and it is found in many geographic areas (Japan, Transcontinental, North African, and West African)
  • Subtype B (Central African)
  • Subtype C or the Australo-Melanesia clade, it is present in Papua New Guinea and the Solomon Islands
  • Subtype D (Central African Pygmies), it was shown to be present in some individuals living in Cameroon, Central African Republic, and Gabon.

The genomic structure of HTLV-1 is 8.5 Kb in size including LTRs of 986 nt (pro-5´LTRs and pro-3´LTR of 405-581 nt, respectively). The internal region of this retrovirus displays a Primer Binding Site (PBS) complementary to a tRNAPro, Open Reading Frames (ORFs) for gag, pol, and env genes. HTLV-1 displays a region termed the pX region, which contains the accessory genes rex and tax (both essential for viral replication and cellular transformation in infected cells), as well as two ORFs that encode for the proteins Tof and Rof (see accessory genes), and the Polypurine Tract (PPT) common to all retroviruses (Malik, Even and Karpas 1988; Yoshida et al. 1995; Koralnik et al. 1992; Pique et al. 2000).

Structure

Htlv-1.png


Figure not to scale. If present, long terminal repeats (LTRs) have been highlighted in blue. Amino acid motifs noted with lines indicate the conserved residues in each protein domain, abbreviations below mean:

MA=matrix PR=protease DU or DUT=dUTPase TM=transmembrane TAV or IBMP=transactivator/viroplasmin or inclusion body matrix protein
CA=capsid RT=reverse transcriptase INT=Integrase CHR=chromodomain
NC=nucleocapsid RH=RNaseH SU=surface MOV=movement protein
PPT=polypurine tract PBS=primer binding site ATF=aphid transmission factor VAP=virion associated protein

Related literature

Genbank accession:AF033817
Clade:Oncovirinae C-type
Cluster or genus:Deltaretrovirus
Branch or class:Class 2
Family:Retroviridae
System:LTR retroelements
Host:
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