The human T-lymphotropic Virus, abbreviated as HTLV, is one kind of human retroviruses and famous for the disease it may cause known as a type of cancer called adult T-cell lymphoma and a demyelinating disease.
Studies show that HTLV belongs to a bigger family of primate T-lymphotropic viruses, also called as PTLVs, and their name derives from finding that they have an ability to infect the old world monkeys and cause a symptom of immunologic deficiency in human being. Until now, there are four members in this virus group have been found, including human T-lymphotropic virus type I(HTLV-1), human T-lymphotropic virus type II (HTLV-2), human T-lymphotropic virus type III(HTLV-3) and human T-lymphotropic virus type IV (HTLV-4). Evidences also show that all those four subtypes originate from inter-species transmission of HTLVs and thus they share a very high similarity in their genetic substance, RNA. Nowadays, there is a promising to produce vaccine against the HTLV-1 and HTLV-2 but not suitable for HTLV-3 or HTLV-4 since later two have been found or researched only in a few cases. Figure 1 shows that surface structure of Human T lymphotropic Virus:
Fig. 1 Surface Structure of Human T-lymphotropic Virus
Human T lymphotropic Virus Type I, HTLV-1
Human T lymphotropic Virus Type I, abbreviated as HTLV-1, whose genome composed of two copies of a single-stranded RNA and formed a diploid virus. When HTLV-1 infects hosts, it would transcript into their RNA genetic substance double-strand DNA by using substance from the host and then the later will integrate into the host cell genome, at which point the virus is referred to as a provirus. After retro-transcript DNA integrates into the host genome by viral integrase, this virus starts to replicate and reproduce. However, studies indicate that HTLV-1 infects and spreads only through the process of dividing cells. To quantify the amount of provirus, therefore, could reflect the number of the HTLV-1-infected cells. Such as a customized service for developing an ELISA kit can be used as a high throughput method to quantify the amount of the cells and virus produce in a living cells and this would be very useful for the preclinical research of a vaccine.
Fig. 2 Genome Structure of Human T-lymphotropic Virus Type I, Type II
Human T lymphotropic Virus Type II, HTLV-2
Human T-lymphotropic Virus 2, abbreviated as HTLV-2, shares a similarity up to 70% to its brother of HTLV-1 in genomic structure. This subtype has been native to the Native Americans, Indian groups in South America as well as in Asian countries, more commonly in Korea and Japan. It can be transmitted into the next generation through body fluid contacted from ones’ parent and this virus gets into the cells through the glucose transporter signal pathway. It’s an interesting fact that HTLV-II seems not to cause any dominant symptoms in patients, but some evidence show that this virus subtype involved into several cases of diseases, one is called as myelopathy/tropical spastic paraparesis-like neurological disease. Fig.2 shows HTLV-1 and HTLV-2 have tax and rex genes with exons on either side of the env gene.