Viral Genetics and Classification在线视频

Can viruses change their antigenicity
病毒能改变其抗原性吗

and, if so,
and, if so,

how can they change?
它们是怎么改变的呢？

Firstly, we need to clarify
首先，我们先弄清楚

some associated terms.
一些相关术语

Genotype
基因型

refers to the genetic
是指一个生物个体

constitution of an organism.
的基因组合

Phenotype
表型

refers to the appearance of an organism,
是指生物个体

which are produced by the genotype
受基因型与环境共同影响

in cooperation with the environment.
而产生的外观特征

Mutation
突变

is a inheritable change in the genotype.
是指基因型中发生的一种可遗传的改变

Wild-type virus denotes
野生型病毒

the original
和普通突变体是相对的

virus from which mutants are derived
是指在原始病毒中

and with which the mutants are compared.
自然产生的突变体

Mechanisms of variation
病毒的变异机制

of viruses include mutation,
包括基因突变

gene recombination and reassortment,
基因重组和重配

and interaction
和病毒基因产物的

of viral gene productions.
相互作用

1 Mutation
1.基因突变

The conditional-lethal mutant
条件致死性突变株

is because of mutation.
是由突变产生的

Mutants are lethal
这种突变株会在

under one set of conditions
某些条件下死亡

(non-permissive conditions)
（非容许性条件）

but that yield normal
但是可以在

infectious progeny
另外一些条件下

under other conditions
产生有传染性的子代病毒

(permissive conditions).
（容许性条件）

For example,
例如

temperature-sensitive mutant.
温度敏感性突变株

This mutant can grow at low temperatures
这种突变株可以在低温下增殖

but not at high temperatures.
但不可以在高温下增殖

Oral poliomyelitis vaccine
口服脊椎灰质炎疫苗

is a temperature-sensitive mutant.
就是一种温度敏感性突变株

So when the children take the vaccine,
所以当小朋友接种这种疫苗时

make sure it should not be taken
一定要确保在口服的过程中

with hot water.
不要使用热水送服

Because the hot temperature
因为水的高温

may inactive the vaccine
可能会使疫苗失去活性

Another one is host-range mutant.
另一种突变株是宿主范围突变株

This mutant differs from the wild type
这种突变株与野生型毒株

in the targets that can be infected.
在对宿主细胞的感染范围上有所不同

2 Gene recombination
2.基因重组

and gene reassortment
与基因重配

The classic recombination
经典的基因重组机制

mechanism is that
指的是

the nucleic acid strands break,
核酸链断裂

and part of the genome of one parent
然后其中一个亲本的一部分基因组

is joined to part of the genome
连接到另一个亲本

of the second parent.
的一部分基因组上

Gene reassortment
基因重配

If a virus has a segmented genome
如果病毒中含有一个分节段的基因组

and if two variants
并且有两种这样的病毒

of that virus infect a single cell,
感染了同一个细胞

progeny virions can result
那么在产生的子代病毒中

with some segments from one parent,
有可能一些基因片段来自一种亲本

some from the other.
另一些片段来自另一种亲本病毒

Look at this diagram,
看看这张图

the pink virus and the green virus
粉色的病毒和绿色的病毒

infect the host cell at the same time.
同时感染宿主细胞

So the progeny viruses
所以在子代的病毒中

could carry the pink gene
能够同时携带粉色的基因

and the green gene.
与绿色的基因

That is the gene reassortment.
这就是基因重配

Typical example of gene reassortment
流感病毒

is flu virus.
是基因重配里一个典型例子

When human flu virus
当人类流感病毒

and non-human flu virus,
和非人类流感病毒

for example avian flu virus,
例如禽流感病毒

infect one respiratory epithelial cell,
感染了同一个呼吸道上皮细胞

the reassortant virus,
重配后产生的病毒

may contain
可能包含

some segments from human virus,
一些来自人类病毒的基因片段

and some segments from avian virus.
和一些来自禽类病毒的基因片段

And the reassorted virus
并且重配后的病毒

may have the ability to cause severe disease
可能会引发严重的疾病

and can be transmitted
还可能会在

from person to person.
人与人之间传播

That could be a big disaster.
那将会是一场大灾难

3 Interaction of viral gene productions.
3.病毒基因产物的相互作用

Complementation refers to the
互补作用是指

interaction of viral gene products
在感染了两种病毒的细胞内

in cells infected with two viruses,
病毒基因产物产生的相互作用

one or both of which may be defective.
其中可能某一种或者两种都有缺陷

It results in the replication
它会导致这一种或两种病毒

of one or both under conditions
在通常不会发生

in which replication
复制的条件下

would not normally occur.
发生复制

The example is HDV and HBV.
例如HDV和HBV

With the help of HBV,
在HBV的帮助下

the HDV can invade
HDV可以侵入肝细胞

and replicate in liver cells.
并在肝细胞中复制

Phenotypic mixing.
表型混合

If two different viruses infect a cell,
如果两株不同的病毒感染了同一个细胞

progeny viruses may contain
子代病毒可能包含

coat components
来源于两种亲本病毒的

derived from both parents
衣壳成分

and so they will have coat properties
并且会具有两种亲本的

of both parents.
衣壳特性

Phenotypic mixing, no changes in genome
表型混合时，基因组没有改变

but sensitivity to antibody
但是对抗体中和的敏感性

neutralization is altered.
改变了

If the genome is encased
如果基因组被包围在

in a completely different protein coat,
一个完全不同的蛋白质外壳里

this extreme example
这是表型混合

of phenotypic mixing
的一种极端例子

may be called “transcapsidation”.
可称为“核壳转移”

This progeny virus
这样的子代病毒

is also known as pseudotype.
也被称为假型

Two publications associated
两份关于假型

with pseudotypes.
的论文

People used pseudotypes
人们使用假型

as a tool to make vaccines.
作为制作疫苗的工具

The first paper showed
第一篇论文展示了

the“Pseudotyped inluenza A viruse
假型甲型流感病毒

as a vaccine for the induction
可作为一种诱导

of heterotypic immunity”.
异源亚型免疫的疫苗

Similarly for the second paper,
第二篇论文也是类似的

“...pseudotype virus-like particles
“...假型病毒样微粒

to generate antibodies.”
用于产生抗体”

Virus can change their antigenicity
病毒可以通过突变

by mutation,
基因重组与重配

gene recombination and reassortment,
互补作用

and complementation
以及表型混合

and phenotypic mixing.
改变其抗原性

How to classify the viruses?
如何对病毒进行分类？

Family of viruses
病毒分科

Family is based on morphology,
病毒分科是基于

genome structure and strategies of replication
基因组结构和复制方式类分的

suffix “–viridae” ,
后缀是“–viridae”

and should be in italic.
并且是用斜体字写的

Genus
属

Genus is based on physicochemical
属是基于物理化学

or serological differences
或者血清学上的差异类分的

suffix “-virus”
后缀是“-virus”

An example:
例如：

orthomyxoviridae, influenza virus
正黏病毒科，流感病毒属

orthomyxoviridae, is the family name;
正黏病毒科，是科名

influenza virus, is the genus name
流感病毒属，是属名

Based on biological properties,
根据生物特性

the viruses can be classified
病毒可以被分类为

as DNA viruses,
DNA病毒

RNA viruses, and retroviruses.
RNA病毒和逆转录病毒

There are enveloped DNA viruses
有包膜DNA病毒

and naked capsid DNA viruses.
和裸露DNA病毒

Enveloped DNA viruses include
包膜DNA病毒包括

poxvirus, herpesvirus, and hepadnavirus.
痘病毒，疱疹病毒和嗜肝DNA病毒

And naked capsid DNA viruses are
而裸露DNA病毒则包括

polyoma, papilloma,
多瘤病毒、乳头瘤病毒

adeno and parvo viruses.
腺病毒和细小病毒

Parvovirus is a ssDNA virus.
细小病毒是一种ssDNA病毒

The RNA viruses include
RNA病毒包括

+RNA, -RNA, dsRNA,
+RNA病毒，-RNA病毒，RNA病毒

and retro RNA viruses.
和逆转录RNA病毒

Most of them are enveloped.
其中大多数都是包膜病毒

Just picornavirus
只有细小病毒

and calicivirus are naked RNA viruses,
和萼状病毒是裸露RNA病毒

and reovirus has double capsids,
而呼肠孤病毒有两层衣壳

but no envelope.
但是没有包膜

The viruses can be classified
病毒可以根据传播方式

by the mode of transmission.
进行分类

They are viruses transmitted through
分为通过呼吸道

respiratory route,
传播的病毒

viruses transmitted through
通过粪口传播的病毒

fecal-oral route, and others.
和其他病毒

Others include hepatitis virus,
这里的其他病毒包括肝炎病毒

herpes virus,
疱疹病毒

hemorrhagic fever virus,
出血热病毒

arbovirus, and HIV.
虫媒病毒，和人类免疫缺陷病毒

In this course,
在这节课上

we will learn about the viruses
我们将根据这些分类

based on this classification.
了解病毒

Here are viruses
这些是我们将在本课程中

we will cover in this course,
涵盖的病毒

Medical Virology.
医学病毒学

Subviruses:
亚病毒

Viroids are essentially
类病毒的本质

circular RNA molecules
是与几种植物疾病

that have been associated
有关的

with several plant diseases
环状RNA分子

They do not encode proteins
它们不编码蛋白质

or possess a capsid.
也没有衣壳

Prions are infectious protein particles.
朊病毒是具有传染性的蛋白质颗粒

This pathogen
这种病原体

does not contain any genome,
不包含任何基因组

just the misfolded proteins.
只是错误折叠的蛋白质

But it can induce
但它可以诱发

a very serious disease,
一种非常严重的疾病

mad cow disease.
疯牛病

We will have one section on it.
我们会有一个章节来细说它

So far, we have learned the structures,
到目前为止，我们已经了解到病毒的结构

replications, genetics
复制，遗传

and classification of the virus.
和病毒的分类

The keys words are
重点包括

Virus
病毒

Basic structure
基本结构

Self-replication
自我复制

Temperature – sensitive mutant
温度敏感性突变株

Abortive infection;
顿挫感染

defective virus
缺陷病毒

Complementation;
互补作用

interference
干扰现象

Gene recombination and reassortment
基因重组和重配

Pseudotype
假型病毒

Now a quiz for you.
现在我们来看个题目

A 13-month-old boy presents
在冬天，一名13个月大的男孩

with a 4-day history
有四天的

of fever and watery
发烧和

non-bloody diarrhea in winter.
稀水样无血腹泻病史

On physical examination,
在进行体格检查时

he appears dehydrated.
他表现出脱水症状

Which of the following describes
下列哪一项描述是

the genome of the most likely organism?
最有可能的病原体的基因组？

A.Segmented -ssRNA
A.分段的-ssRNA

B.Non-segmented +ssRNA
B.非分段的+ssRNA

C.Segmented dsRNA
C.分段的dsRNA

D.dsDNA
D.dsRNA

E.ssDNA

E.ssDNA

To answer this quiz,
为了回答这个问题

firstly,
首先

you need make a preliminary diagnosis,
你需要做出一个初步的诊断

and then to recall
然后回忆一下

the knowledge about the genome type.
关于基因组类型的知识

You may not answer correctly now.
现在你或许不能正确回答

But do not worry about that.
但是不用担心

When we learn about each virus
当了解完每种病毒的时候

we will get to know all of them.
我们就会掌握上述的知识