Viral Replication在线视频

Welcome back. Let's continue.
感谢回来。我们继续。

How do viruses replicate?
病毒如何复制呢？

Did you answer correctly?
你能回答正确吗？

The major steps in viral replication
病毒复制的主要步骤

are the same for all viruses.
基本都是一样的

A single round
病毒的

of the viral replication cycle
一个复制周期

can be separated into several steps.
可以分为几个步骤

These are Attachment (adsorption)
分别是：吸附

Penetration
穿入

Uncoating
脱壳

Biosynthesis of viral components
病毒成分的生物合成

Assembly of new viral particles
新的病毒颗粒的装配

Release
以及释放

The first step in viral infection
病毒感染的第一步

is attachment,
是吸附

interaction of a virion with
即病毒体和

a specific receptor site
细胞表面的

on the surface of a cell.
特异性受体结合

The virus must recognize an
病毒必须识别

appropriate target cell,
适当的靶细胞

attach to the cell,
并吸附到细胞上

and then penetrate the plasma membrane
然后穿入细胞膜

and be taken up by the cell.
被细胞摄取

This table shows you some examples
这个表展示了

of viruses and their receptor on cells
病毒及其在宿主免疫细胞上的受体

of the immune system.
的一些例子

HIV binds to the CD4 molecules
HIV能结合到宿主免疫细胞

on immune cells;
上的CD4分子

Rhinovirus, rhino means nose,
鼻病毒，“rhino”是鼻子的意思

the receptor is ICAM-1
它的受体为ICAM-1

(intercellular adhesion molecules -1);
（细胞间黏附分子-1）

Epstein-Barr virus, the receptor
EB病毒，受体是

is CD21 on B cells.
B细胞上的CD21分子

Then is penetration.
接下来是穿入

After binding, the virus particle
在结合后，病毒颗粒

is taken up inside the cell.
被细胞摄取

This step is referred to as penetration
这个步骤就是穿入

or engulfment.
或者叫内吞

Interactions between multiple viral
多种病毒吸附蛋白(VAPs)

attachment proteins (VAPs)
和细胞受体

and cellular receptors initiate
之间的相互作用

the internalization
启动了病毒

of the virusinto the cell.
进入细胞的内化

The mechanisms of penetration depends
穿入的机制取决于

on the virion structure and cell type,
病毒颗粒的结构和细胞类型

which could include direct penetration,
包括直接穿入

fusion and endocytosis.
融合和胞吞

The naked viruses bind to the receptors
裸露病毒与宿主细胞上的

on the host cells,and then directly
受体结合，然后直接

penetrate the genome into the host cells.
穿入基因组进入宿主细胞

The enveloped viruses
包膜病毒

bind to the receptors,
与受体结合

and then fuse their membranes
然后病毒的包膜

with cellular membranes
与细胞膜融合

to deliver the nucleocapsid
将核衣壳或基因组

or genome directly into the cytoplasm.
直接传递到细胞质中

Also the viruses can enter the cell by
病毒也可以通过

receptor-medicated endocytosis.
受体介导的胞吞作用进入细胞

After binding to the receptor,
与受体结合后

the host cell can carry out
宿主细胞可以发挥

the endocytosis,
胞吞作用

and form an endosome.
形成一个内体

Then the viruses invade
然后，病毒就会侵入到

inside the host cells.
宿主细胞的内部

Next step is uncoating.
下一步是脱壳

Uncoating occurs at the same time
脱壳在穿入的同时

with or shortly after penetration.
或之后不久发生

Uncoating is the physical separation
脱壳是病毒核酸

of the viral nucleic acid
与病毒颗粒外部结构成分

from the outer structural components
的物理分离

of the virion such that it can function.
这样病毒就能在宿主细胞内发挥作用

Step 4,
第四步

biosynthesis of the viral components.
病毒成分的生物合成

Once inside the cell,
一旦进入细胞

the genome must direct the synthesis
基因组就一定会指导

of viral mRNA and protein and
病毒mRNA和蛋白质的合成

generate identical copies of itself.
并产生相同的自身副本

As what we have learned
就像我们在

in the last section,
上一节课学到的

there are 6 types of viruses.
一共有6种病毒

They are
它们是

dsDNA virus
dsDNA病毒

ssDNA virus
ssDNA病毒

dsRNA virus
dsRNA病毒

+ssRNA virus
+ssRNA病毒

-ssRNA virus
-ssRNA病毒

and retrovirus
和逆转录病毒

All the viral replication
所有的病毒复制过程

obey the central dogma.
都服从中心法则

DNA to RNA to protein.
从DNA到RNA到蛋白质

The genetic information is transferred
遗传信息

from parent to offspring via
通过DNA复制

DNA duplication,
从亲代传递到子代

within the cell,
在细胞内

genetic information is transferred
遗传信息从DNA

from DNA to mRNA (transcription)
传递到mRNA（转录）

and then to protein (translation).
然后传递到蛋白质（翻译）

Please note,
请注意

reverse transcription could happen.
可能会发生逆转录

Reverse transcription is the transfer
逆转录是指

of information from RNA to make new DNA,
从RNA传递信息来产生新的DNA

this occurs in the case
这会发生在

of retroviruses, such as HIV.
逆转录病毒的复制中，如艾滋病病毒

Most dsDNA viruses use host machinery
大多数dsDNA病毒利用

in the nucleus to make mRNA,
宿主细胞核里的组织来生产mRNA

which is translated
并被宿主细胞的核糖体

by host cell ribosomes into proteins.
翻译成蛋白质

Replication of viral DNA occurs
病毒DNA的复制

by semi-conservative means.
是通过半保留的方式进行的

The ssDNA is converted into dsDNA
ssDNA转化为dsDNA

and replicates like dsDNA.
并像dsDNA一样复制

Positive-sense RNA resembles a mRNA
正链RNA类似于一种

to make proteins.
制造蛋白质的mRNA

One of the proteins is RNA polymerase,
其中一种蛋白质是RNA聚合酶

that makes a negative RNA template
在它的作用下得到一个负链RNA的模板

and then more positive RNA
然后得到更多正链RNA的子代基因组

genome progeny and mRNAs.
和mRNA

Negative-sense RNA virion
负链RNA病毒

carries RNA polymerase.
携带RNA聚合酶

The viral RNA is transcribed into mRNAs
病毒RNA

and a full-length positive RNA template
被RNA聚合酶转录成

by the RNA polymerase.
mRNA和未被剪接的正链RNA模板

dsRNA acts like negative-sense RNA.
dsRNA类似于负链RNA

Retroviruses have positive-sense RNA
逆转录病毒有正链RNA

that is converted to complementary
它们被病毒粒子里的逆转录酶

DNA (cDNA) by reverse transcriptase
转化为

carried in the virion.
互补DNA（cDNA）

The cDNA integrates
这些cDNA整合到

into the host chromosome,
宿主的染色体中

and the host makes mRNAs, proteins,
然后宿主会产生mRNA，蛋白质，

and full-length RNA genome copies.
和未被剪接的RNA基因组副本

Newly synthesized viral genomes
新合成的病毒基因组

and capsid polypeptides assemble
和衣壳多肽

together to form progeny viruses.
装配形成子代病毒

Enveloped viruses released
包膜病毒通过

by a budding process.
出芽释放

Virus-specific envelope glycoproteins
具有病毒特异性的包膜糖蛋白

are inserted into cellular membranes;
会插入到细胞膜内

viral nucleocapsids then bud
接着病毒核壳体在这些

through the membrane
特定的修饰点上出芽

at these modified sites and,
然后通过这种方式

in so doing, acquire an envelope.
获得了包膜

There are no special mechanisms for the
裸病毒的释放

release of non-enveloped viruses;
没有特殊的机制

The infected cells eventually lyse
感染的细胞最终会溶解

and release the virus particles
并且通过细胞溶解

by cell lysis.
释放病毒体

The number of infectious viruses
病毒感染的数量

can also be evaluated
可以通过计算

with a count of the plaques produced
样本的十倍稀释液里

by tenfold dilutions
空斑的数量（空斑形成单位）

of sample (plaque-forming units).
进而计算病毒感染的数量

The summary of the viral replication.
以下是对病毒增殖的总结

Step 1,
第一步

Virus attaches to a cell.
病毒吸附到细胞上

VAPs bind to the receptors.
病毒吸附蛋白和受体结合

Step 2-3,
第二步和第三步

Virus penetrates cell membrane
病毒穿入细胞膜

and injects nucleic acid (DNA or RNA)
并且把核酸（DNA或RNA）

into the cell.
注入到细胞里

Step 4,
第四步

Viral nucleic acid replicates
病毒利用宿主细胞

using host cellular machinery.
进行复制

Step 5-6,
第五步和第六步

New viral nucleic acids are packaged
新合成的病毒核酸

into viral particles
装配成病毒颗粒

and released from the cell.
然后从细胞中释放

The host cell maybe destroyed
在这个过程中

in the process.
宿主细胞有可能会被破坏

This is a short video about
这是一个关于

flu virus replication.
流感病毒复制的小视频

Please watch the video
请观看这个视频

and find out each step of replication.
然后找出病毒复制的每一步

Can you figure out all steps?
你可以找出所有步骤吗？

Attachment, key and lock, right?
吸附，像钥匙和锁一样，对吗？

Penetration, endocytosis.
穿入，胞吞

Uncoating.
脱壳

Biosynthesis in the nucleus
细胞核和细胞质里的

and in the cytoplasm.
生物合成

Maturation and release by budding.
成熟和出芽释放

In this video,
在这个视频里

we can see that just one virus,
我们可以发现一个病毒

there will be millions
就可以产生

of progeny viruses.
数以百万计的子代病毒

But please note,
但是请注意

not all infections lead
不是所有的感染都会

to new progeny virus.
产生数以万计的子代病毒

One situation is abortive infection.
譬如顿挫感染

That means to fail to produce
不能产生

infectious progeny,
感染性的子代病毒

either because the cell may be
可能因为宿主细胞

non-permissive and unable to support
不支持所有

the expression of all viral genes
病毒基因的表达

or because the infecting virus
或者因为感染的病毒

may be defective,
是有缺陷的

lacking some functional viral gene.
缺乏某些功能性的病毒基因

Another one is defective virus.
另一种是缺陷病毒

A defective virus is a virus that need
缺陷病毒是一种

the help of another virus for
需要其他病毒的帮助来

the formation of infectious particles.
形成感染性颗粒的一种病毒

The most typical example is HDV.
最典型的例子就是丁型肝炎病毒（HDV）

HDV can not replicate in the host cell
如果没有乙肝病毒（HBV）的帮助

without the help of HBV.
HDV就不能在宿主细胞里复制

HDV is a defective virus.
所以说HDV是一种缺陷病毒

And interference.
还有干扰现象

The interference is the effect that
干扰现象指

infection of either cell cultures
当两种病毒

or whole animals with two viruses
感染同一个细胞时

often leads to an inhibition
一种病毒抑制另一种病毒

of multiplication
增殖的

of one of the viruses.
一种效应

Now break time.
现在我们休息一下吧

See you soon.
我们下节课再见