![]() Even less is known about this virus, as no simian counterpart has ever been found As of 2011. HTLV-4 was discovered at the same site as HTLV-3 in 2005. It is not yet known how much further transmission has occurred among humans, or whether the virus can cause disease. It occasionally cross-reacts with HTLV-2 tests. PTLV-3 is about 40% different from PTLV-1 and -2. HTLV-3 was discovered in 2005 in rural Cameroon, and were, it is presumed, transmitted from monkeys to hunters of monkeys through bites and scratches. It might impact the platelet count, contribute to chronic lung infections, or lead to future cutaneous T-cell lymphoma (CTCL), among a host of other proposals. Main article: Human T-lymphotropic virus 2ĭiscovered in 1982, HTLV-2 has not yet been conclusively linked to any disease. A large Canadian study documented this confusion among healthcare workers, where >90% of HTLV tests ordered by physicians were actually intended to be HIV tests. The name HTLV-4 has also been used to describe HIV-2. The use of "HTLV-3" can cause some confusion, because the name HTLV-3 was one of the names for HIV in early AIDS literature, but has since fallen out of use. Unusually, the single-stranded RNA genome is present in two copies, forming a dimer speficially packed by parts of the gag protein. The virion is spherical to pleomorphic, about 80-100 nm in diameter. The lifecycle is common to retroviruses, starting at the envelope glycoprotein (Env) surface subunit (SU) binding to a cellular receptor (in this case GLUT1 and a host of other molecules), and ending with lysis of the cell (in this case, a lymphocyte). HTLV-1 has three tandem imperfect 21-base repeats as the long terminal repeat, but other PTLVs only have two. p12, p8, p30, p13 are the newest class of proteins only found in HTLV-1.It is encoded in the opposite ("antisense") direction compared to all other ORFs. It encodes a basic leucine zipper, and is known to be enhance HLTV-1 replication and oncogenity. HBZ is the first novel protein, only common among PLTV.As it gets expressed, Rex binds mRNA to control the extend of splicing. Rex is also common to all extant Deltaretrovirus.In a HTLV-1 infection, it is the first protein to be expressed, and in turn is responsible for the expression of the provirus at the LTR during the early phase. Tax, the transactivator, is common to all Deltaretrovirus.These new proteins provide a great source of new adaptive function: A retrovirus, PTLV shares the common gag-pro-pol-env set of genes, yet shows great complexity in the unique 3' end. HTLV-1 is the prototypical PTLV, from which comparisons are drawn for the newly-known types. Genomic organization of Deltaretrovirues gag-pro-pol part trimmed off. As its name suggests, this virus causes leukemia in cows. The only other recognized species in the genus is Bovine leukemia virus, an economically-important cattle pathogen. ![]() HTLVs belong to the genus Deltaretrovirus. ![]() The first known, and still most medically important PTLV is HTLV-1, discovered in 1980. There are currently three species of PTLVs recognized by the ICTV (P/H/STLV-1, -2, -3), plus two that are reported but unrecognized (HTLV-4, STLV-5). Within each species of PTLV, the HTLV is more similar to its cognate STLV than to the other HTLVs. HTLVs have evolved from STLVs by interspecies transmission. On the other hand, newer PTLVs are simply placed into the group by similarity and their connection to human disease remains unclear. PTLVs are named for their ability to cause adult T-cell leukemia/lymphoma, but in the case of HTLV-1 it can also cause a demyelinating disease called tropical spastic paraparesis. The ones that infect humans are known as human T-lymphotropic virus (HTLV), and the ones that infect Old World monkeys are called simian T-lymphotropic viruses (STLVs). The primate T-lymphotropic viruses ( PTLVs) are a group of retroviruses that infect primates, using their lymphocytes to reproduce. Simian T-lymphotropic virus 5 (unrecognized).Human T-lymphotropic virus 4 (unrecognized).Informal grouping of virus species Primate T-lymphotropic virusĪ micrograph showing both Human T-lymphotropic virus 1 and HIV ![]()
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