biology

Simian immunodeficiency virus

Simian immunodeficiency virus is a biology 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 Simian immunodeficiency virus rather than just read about it. In short: Simian immunodeficiency virus (SIV) is a species of retrovirus that cause persistent infections in at least 45 species of non-human primates. Based on analysis of strains found in four species of monkeys from Bioko Island, which was isolated from the mainland by rising sea levels about 11,000 years ago, it has been concluded that SIV has been present in monkeys and apes for at least 32,000 years, and probably much l…

Key takeaways

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

Reference excerpt

Simian immunodeficiency virus (SIV) is a species of retrovirus that cause persistent infections in at least 45 species of non-human primates. Based on analysis of strains found in four species of monkeys from Bioko Island, which was isolated from the mainland by rising sea levels about 11,000 years ago, it has been concluded that SIV has been present in monkeys and apes for at least 32,000 years, and probably much longer. Virus strains from three of these primate species, SIVsmm in sooty mangabeys, SIVgor in gorillas and SIVcpz in chimpanzees, are believed to have crossed the species barrier into humans, resulting in HIV-2 and HIV-1 respectively, the two HIV viruses. The most likely route of transmission of HIV-1 to humans involves contact with the blood of chimps and gorillas that are often hunted for bushmeat in Africa. Four subtypes of HIV-1 (M, N, O, and P) likely arose through four separate transmissions of SIV to humans, and the resulting HIV-1 group M strain most commonly infects people worldwide. Therefore, it is theorized that SIV may have previously crossed the species barrier into human hosts multiple times throughout history, but it was not until recently, after the advent of modern transportation and global commuterism, that it finally took hold, spreading beyond localized decimations of a few individuals or single small tribal populations. Unlike HIV-1 and HIV-2 infections in humans, SIV infections in their natural simian non-human hosts appear in many cases to be non-pathogenic due to evolutionary adaptation of the hosts to the virus. Extensive studies in sooty mangabeys have established that SIVsmm infection does not cause any disease in these primates, despite high levels of circulating virus. Regulation of the activity of the CCR5 coreceptor is one of the natural strategies to avoid disease in some natural host species of SIV. Research on SIVcpz in chimpanzees suggests that infected chimpanzees experience an AIDS-like illness similar to HIV-1 infected humans. The later stages of SIVcpz infection in chimpanzees develop into an illness with characteristics that strongly resemble end-stage AIDS in humans.

Taxonomy The simian (monkey-hosted) immunodeficiency viruses are a species of retrovirus in the Primate group of genus Lentivirus along with the human viruses HIV-1 and HIV-2 that cause AIDS, and a few other viruses that infect other primates. Related viruses in other groups in the genus infect other mammals like sheep and goats, horses, cattle, cats, and a few others. The genus is one of six genera in subfamily Orthoretrovirinae, which together with subfamily Spumaretrovirinae form the family Retroviridae of all RNA retroviruses (RNA viruses which use a DNA intermediate). The ICTVdB code of SIV is 61.0.6.5.003. Although HIV-1 and HIV-2 cladistically fall into SIV, ICTV considers them distinct species from ordinary, non-human-infecting SIV.

Strains

While human immunodeficiency virus has a limited number of subtypes, SIV is now known to infect a few dozen species of non-human primates, and distinct strains are often associated with each species, or with a set of closely related species. The thus far categorized ~40 strains are divided into five distinct groups and one subgroup:

i) HIV-1, SIVcpz (chimpanzee), SIVgor (gorilla), SIVrcm (red-capped mangabey), SIVagi (agile mangabey), SIVmnd 2 (mandrill), SIVdrl (drill monkey) ii) HIV-2, SIVsmm (sooty mangabey), SIVmac (rhesus macaque), SIVmne (pig-tailed macaque), SIVstm (stump-tailed macaque) iii) SIVagm[generic] (African green monkeys): SIVsab, SIVver, SIVgri (grivet monkey), SIVtan (tantalus monkey) iv) SIVmnd 1 (mandrill), SIVlho (L'hoest's monkey), SIVsun (sun-tailed monkey), SIVprg (Preuss's guenon), SIVwrc (western red colobus), SIVolc (olive colobus), SIVkrc (Kibale red colobus), SIVtrc (Tshuapa red colobus) v) SIVsyk (Sykes' monkey), SIVdeb (De Brazza's monkey), SIVden (Dent's mona monkey), SIVwol (Wolf's mona monkey), SIVgsn/SIVmon/SIVmus 1/SIVmus 2 clade, SIVtal (northern talapoin), SIVasc (red-tailed guenon), SIVbkm (black mangabey), SIVreg[formerly SIVery] (red-eared guenon), SIVblu (blue monkey) vi) SIVcol (colobus guereza), SIVkcol 1 (black-and-white colobus), SIVkcol 2, SIVblc (formerly SIVbcm) (black colobus), In addition to the subgroups defined for extent SIVs, two endogenous SIVs are found in prosimian lemurs. These paleo-SIVs form a basal branch relative to extant SIVs.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Simian immunodeficiency virus

Start with the simplest possible case. Write down what Simian immunodeficiency virus 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 Simian immunodeficiency 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 Simian immunodeficiency 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 Simian immunodeficiency virus

In research: Simian immunodeficiency virus 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 Simian immunodeficiency 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: Simian immunodeficiency virus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Animal viral diseases, Lentiviruses, Primate diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Simian immunodeficiency 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.

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How to study Simian immunodeficiency virus in 20 minutes

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

Frequently asked questions

What is Simian immunodeficiency virus in simple terms?

Why does Simian immunodeficiency virus 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 Simian immunodeficiency 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 Simian immunodeficiency virus.