Polio virus

• Nervous system: Polio is a virus that infects the nervous system of humans (only)

• Paralysis: It can cause temporary or permanent paralysis or death

• Vaccine :There is a vaccine for polio

• Eradicate :The World Health Organization plans to eradicate polio in the next decade

• Continue: Polio outbreaks continue to occur in areas in which many are not vaccinated

• Since vaccine has become widespread in the United States, cases of polio are rare.

• However, polio remains a problem in many parts of the world.

•  

肠道病毒

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肠道病毒

• Poliovirus infects human cells by binding to an immunoglobulin-like receptor, CD155, (also known as the poliovirus receptor (PVR) on the cell surface

• Poliovirus is a positive stranded RNA virus. Thus the genome enclosed within the viral particle can be used as messenger RNA and immediately translated by the host cell.

• Poliovirus uses two key mechanisms to evade the immune system. First, it is capable of surviving the highly acidic conditions of the gastrointestinal tract, allowing the virus to infect the host and spread throughout the body via the lymphatic system.

• Second, because it can replicate very quickly, the virus overwhelms the host organs before an immune response can be mounted.[5]

Immune system avoidance

学习要求掌握1 、脊髓灰质炎病毒的致病性2 、特异性预防（剂型）

自学柯萨奇病毒

3 、熟悉脊髓灰质炎病毒抵抗力、感染类型

自学埃可病毒

polio virus

RNA 核衣壳蛋白VP1-4

VP1- 3: 与易感细胞受体结合VP4：与病毒核衣壳装配有关

基因组蛋白RNA启动病毒 复制

² ¡¶ ¾½ á¹ ¹

3-D image of poliovirus

VP1VP2VP3

5-fold Axis

3-fold Axis

2-fold Axis

• For decades, no one knew what poliovirus looked like, since viruses cannot be seen under a microscope. In 1985, a team led by James Hogle of Harvard Medical School obtained high-resolution, 3D images of poliovirus, and today, the newly formed Children's Hospital Boston -- Harvard Medical School structural biology unit is heir to the Enders tradition.

• Led by Stephen Harrison, this group is using a variety of sophisticated tools like X-ray crystallography and molecular electron microscopy to obtain detailed, dynamic, 3D views -- accurate down to the atom -- of how viruses move, transfer information and reconfigure themselves to attack their victims. These images are shedding light on many of today's viral scourges, such as HIV, dengue and rotavirus, and providing new leads for treatment and vaccine development.

Polio virus

• An ancient Egyptian stele, portraying a prince with a withered leg - probably polio.© WHO/GPEI

Researchers Glimpse Polio Virus as it Enters Host Cell Contact:

The image on the left shows a naked polio virus. The polio virus on the right is studded with 60 twig-like structures, the receptors.

See for a moment

Small thin stem on a tree

3-D structures

• The polio virus lives in the throat and intestinal tract of infected persons.

• The virus enters the body through the mouth, usually from hands contaminated with the stool of an infected person. Objects, such as eating utensils, can also spread the virus.

• Food and water are not thought to play a major role in the spread of polio.

•  

WHO

• Polio cases have decreased by 99.8% since 1988, from an estimated 350 000 cases to 483 in 2001*. The reduction is the result of the global effort to eradicate the disease.

Areas with high-intensity transmission

• Together, these countries accounted for more than 85% of the new polio caseload in 2001. They are characterized by having areas with large populations and low routine immunization coverage, sub-optimal sanitation and relatively wide geographical distribution of the wild poliovirus. These countries are:

• India • Pakistan/Afghanistan • Nigeria/Niger

病毒抵抗力• 在污水和粪便中可活数月• 食品中可保存数周• 不易被胃酸或胆汁灭活• 对氧化剂敏感• 56

。C30min 被灭活

致病性• 传染源：病人或无症状携带者• 传染方式：粪 - 口途径• 致病机理

二、致病性

病毒 咽部、肠壁淋巴组织

入血流 第 1次病毒血症

入全身淋巴组织

再次入血流

病毒入脊髓前角运动神经细胞：（脊髓型） 延髓和脑干：延髓型 大脑运动皮质区：脑炎型

第 2次病毒血症

感染类型• 人群中绝大多数为隐性感染或轻型感染• 显性感染• 引起麻痹者仅为显性感染的 0.1%-1%

• 顿挫感染

免疫性

• SIgA ：清除肠道内病毒，阻止病毒入血

• IgM,IgG: 阻断血流中病毒向中枢神经系统扩散

• 感染后获得对同型病毒较牢固的免疫力

Symptoms

• Not everyone will experience all the symptoms, which vary according to the type of polio one has. In mild polio the symptoms are:

• Headache • Nausea/vomiting • General discomfort or slight fever for up to

three days.

• In non-paralytic polio, the symptoms are similar to mild polio with the addition of:

• Moderate fever

• Stiff neck and back

• Fatigue

• Muscle pain

Individuals with paralytic polio will experience:

• Tremors • Muscle weakness • Fever • Stiffness • Constipation • Muscle pain and spasms • Difficulty swallowing

预防• 口服脊髓灰质炎减毒活疫苗糖丸 (1957

年发明） Oral vaccination with live vaccine

• Vaccination programs have

• eradicated it from the

• Western world and promise

• to eliminate it globally Dr Alber Sabin

疫苗使用的效果

Scientists have built the virus that causes polio from scratch in the lab, using nothing more than genetic sequence information from public databases and readily available technology.

The fact proves that even if all the polio virus in the world were destroyed, it would be easily possible to resurrect the crippling disease, says Aniko Paul at the State University of New York at Stony Brook, one of the researchers conducting the study.

新进展 Date: Thu, 11 Jul 2002

Bring back into use

轮状病毒

形态• 核心为 dsRNA ，外有双层衣壳，内外两

层呈放射状排列

轮状病毒• 分组：

A、 B、 C 组：可引起人、动物腹泻， 最常见 A 组 ( 有称为小儿轮状病毒） D-G 组：仅引起动物腹泻

• A 组抵抗力： 耐乙醚、弱酸 室温中传染性可保持 7 个月 -20

。C 长期保

存

A 组轮状病毒• 所致疾病：

婴幼儿尤其秋冬季急性胃肠炎• 传播途径：粪 - 口途径

• 机理：病毒在十二指肠粘膜细胞中增殖

影响肠道对水、盐的正常吸收 腹泻（粪便绿或白色），常伴发热，严重者可出现脱水或酸中毒

B 组轮状病毒• 引起成人腹泻• 我国 1982 年首先发现

特异性预防• 尚无疫苗接种

思考题• 为什么预防脊髓灰质炎的预防针选用口

服制剂？