Name: how viruses swap genes and spread
Uploaded: 2019-03-11T09:21:24.000Z
Duration: 57 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

from-molecules-to-organisms-structures-and-processes

From Molecules To Organisms: Structures And Processes

HS-LS1-8

Viral Recombination

- Certaines cellules peuvent être infectéespar deux souches de virus différentes en même temps,entraînant un mélange des séquences génétiquesen un processus appelé "recombinaison virale". 
Plus spécifiquement,après être entré dans le cytoplasme de la cellule,le virus se défait et commence à répliquer son génome. 
Des régions similaires du génome de chaque viruspeuvent se combiner et échanger des morceaux,reconnectant les brins. 
Autrement, les virus peuvent échanger des segments,dans un processus appelé "réassortiment",au cours duquel les nouveaux virus créés dans la cellulepeuvent présenter un mélange des souches,par exemple une moitié de ses segments venant de la souche 1et l'autre moitié de la souche 2. 
Ces virus nouvellement formésont évolué à partir des deux virus originaux,formant des populations qui peuvent continuer de changerau fil du temps.

He, Ping, Guojun Wang, Yanning Mo, Qingxiong Yu, Xiong Xiao, Wenjuan Yang, Weifeng Zhao, et al. « Nouveaux virus grippaux triplement réassortis chez les porcs, Guangxi, Chine ». Microbes émergents et infections 7 (16 mai 2018). <a href="https://doi.org/10.1038/s41426-018-0088-z » target="__blank">https://doi.org/10.1038/s41426-018-0088-z</a>.

recombinaison virale

Les cellules sont parfois infectées par plus d’un virus à la fois. Lorsque deux virus se désassemblent afin d’exposer leurs génomes pour la réplication dans la même cellule, des régions similaires de leurs génomes peuvent s’associer et échanger des séquences au cours d’un processus nommé recombinaison. Alternativement, les virus avec des génomes segmentés peuvent échanger des segments au cours d’un processus appelé réassortiment.
 
 <h4>La recombinaison virale peut créer de nouvelles maladies</h4>
 
 Certaines maladies peuvent infecter plusieurs espèces. Par exemple, les porcs peuvent être infectés par certains virus humains et aviaires, en plus des virus qui infectent habituellement les porcs. Parce que les virus peuvent se recombiner lorsqu’ils co-infectent la même cellule, les porcs peuvent agir comme des “ vaisseaux de mélange ” qui recombinent les virus d’autres espèces pour créer de nouveaux virus pouvant parfois infecter les humains. Ce phénomène inquiétant représente une voie par laquelle le matériel infectieux d’autres espèces peut entrer dans la population humaine. Les maladies qui passent des animaux aux humains sont connues sous le nom de zoonoses. Les humains peuvent être très sensibles à de tels virus parce que nous n’avons pas d’antécédents d’exposition qui auraient généré l’immunité.
 
 La grippe A est un excellent exemple de la théorie du “ vaisseau de mélange ” de la maladie virale. La recherche a démontré que des virus de la grippe A porcins, aviaires et humains ont été réassortis à l’intérieur des hôtes porcins. Ces événements ont donné lieu à des virus “ à double réassort ” qui contenaient des gènes provenant de virus humains et aviaires et de virus “ à triple réassort ” qui contenaient des gènes provenant de virus humains, aviaires et porcins. Aux Pays-Bas, un virus réassorti composé de gènes de grippe humaine et aviaire a été transmis du porc à l’homme.

Recombinaison virale

Les cellules sont parfois infectées par plus d’un virus à la fois. Lorsque deux virus se désassemblent pour exposer leurs génomes à la réplication dans la même cellule, ...

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how viruses swap genes and spread

Viral gene swapping can happen when more than one virus infects the same cell. After the viruses break open and expose their genomes for replication, matching regions can pair up and exchange sequences. This process is called recombination. Viruses with segmented genomes can also swap whole segments, which is called reassortment.

These changes can help create new diseases. Some diseases can infect more than one species. Pigs can be infected by some human and bird viruses, along with the viruses that usually infect pigs. When different viruses co-infect the same pig cell, the pig can act as a mixing vessel and help produce new viruses that may infect humans.

This matters because diseases that move from animals to humans are called zoonoses. Humans can be highly susceptible to these viruses because we may not have previous exposure. Without that exposure, we would not have developed immunity. Influenza A is a clear example of the mixing vessel theory. Research has shown that pig, bird, and human influenza A viruses have reassorted inside pig hosts.

Some of those events produced double reassortant viruses with genes from human and bird viruses. Others produced triple-reassortant viruses with genes from human, bird, and pig viruses. In the Netherlands, a reassortant virus made from human and bird flu genes was passed from pigs to humans.

How Viruses Swap Genes and Spread

what are viruses?

How Viruses Infect Cells and Multiply

Viruses infect cells and make new copies by using a host cell’s own machinery. A virus is a tiny infectious particle with an RNA or DNA genome inside a protective protein coat. It cannot reproduce on its own, so it must enter a cell to make more viruses. After infection, the virus sheds its protein coat and uses the host cell to transcribe and translate its genetic material. The cell then assembles many new viral particles. In many cases, these new viruses rupture the host cell and kill it.

viral structure

How Virus Shapes Help Infection

Viruses have specific structures that help them infect host cells and trigger immune responses. Each virus has a core that contains either a DNA-based or RNA-based genome. That core is surrounded by a protective protein coat called the capsid. The capsid is made of smaller subunits called capsomeres. The capsid and the genome-containing core together are called the nucleocapsid. Viruses are often grouped by capsid design. Most viruses have either icosahedral or helical capsids, but some have...

lytic cycle of bacteriophages

How Phages Infect and Burst Bacteria

Bacteriophages, or phages, are viruses that infect bacteria. They have a distinctive head-tail shape. In the lytic cycle, a phage first attaches to the outside of a bacterial cell. Tail proteins bind to specific receptor proteins on the bacterium’s surface. After attachment, the phage tail injects its DNA genome into the bacterial cytoplasm. The phage then uses the bacterium’s cellular machinery to make proteins needed for replication and dispersal. When phage replication is complete, some of...

lysogenic cycle of bacteriophages

Prophage Integration in Bacteria

The lysogenic cycle shows how bacteriophages can infect bacteria without killing the host right away. In this cycle, the phage genome joins the bacterial genome. The integrated phage DNA is called a prophage, and the bacterium copies it each time it replicates. Some prophages can switch back into the lytic cycle. This change can happen after DNA damage or even without an obvious outside trigger. When the prophage is induced, the phage begins making new virus particles again. Prophages can...

retrovirus life cycles

How Retroviruses Replicate in Host Cells

Retroviruses replicate by copying their RNA genome into DNA inside a host cell. After entry, the viral enzyme reverse transcriptase makes a double-stranded DNA copy from the single-stranded RNA genome. The viral DNA is then carried into the nucleus and inserted into the host genome by integrase. Once integrated, the retroviral DNA is transcribed whenever the host genome is transcribed. This produces new viral RNA that can be copied and used again. The new RNA moves into the cytoplasm, where it...

viral recombination

Viral gene swapping can happen when more than one virus infects the same cell. After the viruses break open and expose their genomes for replication, matching regions can pair up and exchange sequences. This process is called recombination. Viruses with segmented genomes can also swap whole segments, which is called reassortment. These changes can help create new diseases. Some diseases can infect more than one species. Pigs can be infected by some human and bird viruses, along with the...

viral mutations

How Virus Mutations Drive Outbreaks

Virus mutations can change how quickly a virus evolves and spreads. A mutation is a change in the sequence of bases in DNA or RNA. Some mutations happen when the genome is copied. They are caused by errors made by polymerase enzymes, which replicate DNA or RNA. RNA viruses often change faster than DNA viruses because RNA polymerase does not proofread its work. That means RNA-based genomes, such as HIV, can gather mutations more quickly. Mutation and recombination give viruses the raw material...

key terms and concepts

Learn how viral recombination and reassortment happen when viruses infect the same cell, and how pigs can help new flu viruses spread to humans.

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HS-LS1-1

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HS-LS1-2

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HS-LS1-4

How Viruses Swap Genes and Spread

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