science

Primate T-lymphotropic virus

Primate T-lymphotropic virus is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Primate T-lymphotropic virus rather than just read about it. In short: The primate T-lymphotropic viruses (PTLVs) are a group of retroviruses that infect primates, using their lymphocytes to reproduce. 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).

Key takeaways

Primate T-lymphotropic virus belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Primate T-lymphotropic virus to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Primate T-lymphotropic virus from memory before moving on to harder problems.

Reference excerpt

The primate T-lymphotropic viruses (PTLVs) are a group of retroviruses that infect primates, using their lymphocytes to reproduce. 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). 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. On the other hand, newer PTLVs are simply placed into the group by similarity and their connection to human disease remains unclear. HTLVs have evolved from STLVs by interspecies transmission. Within each species of PTLV, the HTLV is more similar to its cognate STLV than to the other HTLVs. 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). The first known, and still most medically important PTLV is HTLV-1, discovered in 1980. HTLVs belong to the genus Deltaretrovirus. The only other recognized species in the genus is Bovine leukemia virus, an economically-important cattle pathogen. As its name suggests, this virus causes leukemia in cows.

General virology

HTLV-1 is the prototypical PTLV, from which comparisons are drawn for the newly-known types. A retrovirus, PTLV shares the common gag-pro-pol-env set of genes, yet shows great complexity in the unique 3' end. These new proteins provide a great source of new adaptive function:

Tax, the transactivator, is common to all 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. Rex is also common to all extant Deltaretrovirus. As it gets expressed, Rex binds mRNA to control the extent of splicing. HBZ is the first novel protein, only common among PLTV. It encodes a basic leucine zipper, and is known to be enhance HLTV-1 replication and oncogenicity. It is encoded in the opposite ("antisense") direction compared to all other ORFs. p12, p8, p30, p13 are the newest class of proteins only found in HTLV-1. HTLV-1 has three tandem imperfect 21-base repeats as the long terminal repeat, but other PTLVs only have two. 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). The virion is spherical to pleomorphic, about 80-100 nm in diameter. Unusually, the single-stranded RNA genome is present in two copies, forming a dimer specifically packed by parts of the gag protein.

Nomenclatural clarification The use of "HTLV-3" can cause some confusion, because the name HTLV-III was one of the names for HIV in early AIDS literature, but has since fallen out of use. The name HTLV-IV has also been used to describe HIV-2. 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.

PTLV-1

PTLV-1 is the medically most important species in the class. Discovered by Robert Gallo and colleagues in 1980, HTLV-1 has been implicated in several kinds of diseases, including tropical spastic paraparesis and as a virus cancer link for adult T-cell leukemia/lymphoma. Between 1 in 20 and 1 in 25 infected people are thought to develop cancer as a result of the virus. STLV-1 is oncogenic in Japanese macaques. HTLV-1 has seven reported subtypes (subtypes A through G). The great majority of infections are caused by the cosmopolitan subtype A. The HTLV-I/STLV-I history might suggest a simian migration from Asia to Africa not much earlier than 19,500–60,000 years ago.

HTLV-2

Discovered in 1982, HTLV-2 has not yet been conclusively linked to any disease. It generally causes no symptoms. 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.

HTLV-3 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. Multiple strains have been identified. A strain has been fully sequenced. PTLV-3 is about 40% different from PTLV-1 and -2. It occasionally cross-reacts with HTLV-2 tests. It is not yet known how much further transmission has occurred among humans, or whether the virus can cause disease.

HTLV-4 HTLV-4 was discovered at the same site as HTLV-3 in 2005. Even less is known about this virus, as no simian counterpart has ever been found. The International Committee on Taxonomy of Viruses does not recognize it as a species. The sequence is, however, available.

STLV-5 STLV-5 is a name used for a highly divergent PTLV-1 strain isolated from Macaca arctoides.

Transmission HTLV-1 and HTLV-2 can be transmitted sexually, by blood to blood contact (e.g. by blood transfusion or sharing needles when using drugs) and via breast feeding.

Epidemiology Two HTLVs are well established. HTLV-1 and HTLV-2 are both involved in actively spreading epidemics, affecting 15–20 million people worldwide. HTLV-1 is the more clinically significant of the two: at least 500,000 of the individuals infected with HTLV-1 eventually develop an often rapidly fatal leukemia, while others will develop a debilitative myelopathy, and yet others will experience uveitis, infectious dermatitis, or another inflammatory disorder. HTLV-2 is associated with milder neurologic disorders and chronic pulmonary infections. In the United States, HTLV-1/2 seroprevalence rates among volunteer blood donors average 0.016 percent. No specific illnesses have yet been associated with HTLV-3 and HTLV-4.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Primate T-lymphotropic virus

Start with the simplest possible case. Write down what Primate T-lymphotropic virus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Primate T-lymphotropic virus before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Primate T-lymphotropic virus ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Primate T-lymphotropic virus

In research: Primate T-lymphotropic virus appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Primate T-lymphotropic virus in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Primate T-lymphotropic virus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Deltaretroviruses, Unaccepted virus taxa, so understanding it makes those chapters shorter.
In everyday life: Look for Primate T-lymphotropic virus outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Primate T-lymphotropic virus” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Primate T-lymphotropic virus in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Primate T-lymphotropic virus means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Primate T-lymphotropic virus out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Primate T-lymphotropic virus in simple terms?

Why does Primate T-lymphotropic virus matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Primate T-lymphotropic virus?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Primate T-lymphotropic virus.