Lymphocystivirus

Key takeaways

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

Reference excerpt

Lymphocystivirus is a genus of viruses, in the family Iridoviridae. Fish serve as natural hosts. There are four species in this genus. Diseases associated with this genus include: tumor-like growths on the skin.

Hosts Lymphocystivirus is one of seven genera of viruses within the viral family Iridoviridae, and one of three genera within this family which infect teleost fishes, along with Megalocytivirus and Ranavirus. Lymphocystiviruses infect more than 140 freshwater and marine species, spanning at least 42 host families worldwide, causing the chronic, self-limiting clinical disease, lymphocystis. While lymphocystis does not cause mass mortality events like megalocytiviruses and ranaviruses, fish with lymphocystis exhibit grossly visible papilloma-like skin lesions which substantially reduce their commercial value. No vaccines are currently available for lymphocystis viruses.

Taxonomy The genus contains the following species, listed by scientific name and followed by the exemplar virus of the species:

Lymphocystivirus micropogonias1, Lymphocystis disease virus-White croaker (LCDV-WC Lymphocystivirus paralichthys1, Lymphocystis disease virus-China (LCDV-C) Lymphocystivirus platichthys1, Lymphocystis disease virus 1 (LCDV-1) Lymphocystivirus sparus1, Lymphocystis disease virus-Sparus aurata (LCDV-Sa)

LCDV genome Lymphocystiviruses are Group I viruses with a dsDNA genome. The LCDV-1 genome is approximately 102.7 kilobase pairs (kbp) in length, with 195 potential open reading frames (ORF), and codes for two DNA-dependent RNA polymerase subunits, a DNA methyltransferase, a DNA polymerase, a guanosine triphosphate phosphohydrolase (GTPase), a helicase, protein kinases, a ribonucleoside diphosphate reductase, and zinc-finger proteins, among others. The LCDV-2 genome is similar to that of LCDV-1 but is slightly smaller, approximately 98 kilobase pairs (kbp) in length.

Structure Viruses in the genus Lymphocystivirus are enveloped, with icosahedral and polyhedral geometries, and T=189-217 symmetry. The diameter is around 120-350 nm. Genomes are linear, around 100kb in length.

Life cycle Lymphocystiviruses attach to the host cell and enter by receptor-mediated endocytosis similar to other iridoviruses. Viral particles are uncoated and move to the nucleus of the cell, where DNA replication begins via a virally encoded DNA polymerase. Viral DNA then moves to the cytoplasm for the second stage of DNA replication, which results in the formation of DNA concatemers. The concatameric viral DNA is subsequently packaged via a headful mechanism into virions. The lymphocystis viral genome is circularly permuted with terminally redundant DNA. DNA-templated transcription is the method of transcription. Fish serve as the natural host.

Pathogenesis Lymphocystis disease is a chronic disease that rarely causes mortality. Infection causes transformation and hypertrophy (approximately 1000x) of cells in the dermis, forming grossly visible lymphocystis nodules, as well as transformation and hypertrophy in cells of the connective tissues of various internal organs. Fibroblasts and osteoblasts are specifically targeted by the virus. Lymphocystis viruses are not easily grown in cell culture, placing limitations on in vitro molecular pathogenesis experiments.

Diagnostic pathology As lymphocystis viruses are not easily grown in cell culture, diagnosis is based on clinical signs, gross pathology, histopathology, serology, and/or polymerase chain reaction (PCR)-based molecular assays.

Gross pathology The pathology of lymphocystis consists of papilloma-like skin lesions composed of greatly hypertrophied infected host cells embedded in extracellular matrix, sometimes called lymphocystis tumor cells, which are grossly evident as white spots on the skin and fins of infected fish. These lesions proliferate as epithelial tumors in some cases.

Histopathology In a recent comparison of lymphocystis histopathology of four unrelated marine species, lesions consistently associated with lymphocystis included hypertrophied cells displaying irregular nuclei, basophilic cytoplasmic inclusion bodies that stained positively via Feulgen and Mann's reaction and Periodic acid-Shiff (PAS)-positive hyaline capsules. Hyaline capsules arise from the extracellular matrix that is produced by the infected cells, and are composed of sulphated and carboxylated glycoproteins (acid mucopolysaccharides). In contrast, the inclusion body shape, distribution of viral particles within the cytoplasm and overall appearance of lymphocystis nodules varied by species. The species examined in this study included the white-spotted puffer (Arothron hispidus), the Japanese sea bass (Lateolabrax japonicus), olive flounder (Paralichthys olivaceus) and the "sting fish" or Schlegel's black rockfish (Sebastes schegeli)

Serology Several serologic assays have been developed to identify LCDV infections, including flow cytometry, immunoblot, and immunofluorescence. However, PCR-based molecular assays are more practical for most applications.

Electron microscopy Transmission electron microscopy (TEM) of infected cells reveals cytoplasmic virus particles typically measuring from 198-227 nm in diameter (in some cases as large as 380 nm) and electron-dense substances in the perinuclear space.

Molecular pathology Published PCR primers and protocol are available to amplify a portion of the LCDV-1 MCP. When the PCR diagnostic assay is combined with slot blot, diagnostic sensitivity is increased, facilitating the diagnosis of asymptomatic LCDV-1 infections.

References

External links ICTV Online (10th) Report: Iridoviridae

Worked examples

Example 1 — a first encounter with Lymphocystivirus

Start with the simplest possible case. Write down what Lymphocystivirus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Lymphocystivirus 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 Lymphocystivirus 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 Lymphocystivirus

In research: Lymphocystivirus appears in biology 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 Lymphocystivirus 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: Lymphocystivirus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fish viral diseases, Iridoviridae, Virus genera, so understanding it makes those chapters shorter.
In everyday life: Look for Lymphocystivirus 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.

How to study Lymphocystivirus in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lymphocystivirus 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 Lymphocystivirus out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lymphocystivirus in simple terms?

Lymphocystivirus is a genus of viruses, in the family Iridoviridae. Fish serve as natural hosts.

Why does Lymphocystivirus matter?

Because it connects several biology 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 Lymphocystivirus?

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 Lymphocystivirus.