[概述及分类]
病毒是病原微生物中最小的一种，其结构简单只含有一种核酸（核糖核酸RNA，或脱氧核糖核酸DNA），外壳是蛋白质，不具细胞结构。大多数病毒缺乏酶系统，不能单独进行新陈代谢，必须依赖宿主的酶系统才能生存繁殖。抗病毒药物必须具有高度选择性地作用于细胞内病毒的代谢过程，并对宿主细胞无明显损害。
对病毒性疾病的治疗至今仍缺乏专属性强的药物,临床上常用的药物主要有如下几类:抑制病毒复制的抗病毒药;增强机体免疫功能的免疫调节剂;针对临床症状的止咳——镇痛——解热和消炎等治疗药;防止继发感染的抗感染药;预防病毒感染的疫苗及阻断病毒传播的消毒药等。
抗病毒药在某种意义上说只是病毒抑制剂(virustatic agents),不能直接杀灭病毒和破坏病毒体,否则也会损伤宿主细胞。抗病毒药的作用在于抑制病毒的繁殖,使宿主免疫系统抵御病毒侵袭,修复被破坏的组织,或者缓和病情使之不出现临床症状。至今,某些病毒性疾病如脊髓灰质炎和狂犬病还没有抗病毒治疗药,只能靠疫苗预防,一旦错过防疫期,后果十分严重。
按适应症的不同，国内抗病毒药物可分为以下几类：
抗HIV药物，包括依非韦伦等8个产品；
抗疱疹病毒(单纯疱疹,带状疱疹)药物，包括5个洛韦类产品及膦甲酸钠和阿糖腺苷；
抗乙（丙）肝药物，包括拉米夫定和α干扰素；
抗流感药物，包括奥塞米韦、复方金刚烷胺和金刚乙胺；
广谱抗病毒药，包括利巴韦林、吗啉双胍、溶菌酶和聚肌胞等。
[作用机制]
（1）与病毒竞争细胞表面的受体，阻止病毒的吸附，如肝素或带阴电荷的多糖。
（2）阻碍病毒穿入脱壳，如金刚烷胺能抑制流感病毒的脱壳而预防流感。
（3）阻碍病毒生物合成，如疱疹净抑制胸腺嘧啶核苷合成酶，影响DNA的合成；阿糖腺苷，阿糖胞苷干扰DNA聚合酶，阻碍DNA的合成；吗啉双胍对病毒增殖周期各个阶段几乎均有抑制作用（主要是阻抑RNA聚合酶的活性及蛋白质的合成）。此外，某些药物可被由病毒基因编码的酶（如胸苷激酶）磷酸化，该磷酸化合物为病毒DNA聚合酶的底物，二者结合后就可发挥抑制酶的作用，因而可阻止病毒DNA的合成，如阿昔洛韦。
（4）增强宿主抗病能力的物质，如干扰素能激活宿主细胞的某些酶，降解病毒的RNA，抑制蛋白的合成，翻译和装配。(源自: http://www.xgmed.cn/project/1-01-04.html)
奥司他韦（Oseltamivir）(商品名Tamiflu，中国大陆称达菲，港译特敏福，台湾译为克流感):是一种作用于神经氨酸酶的特异性抑制剂(Neuraminidase Inhibitor)，其抑制神经氨酸酶的作用，可以抑制成熟的流感病毒脱离宿主细胞，从而抑制流感病毒在人体内的传播以起到治疗流行性感冒的作用。
作用机理:
奥司他韦作用的靶点是分布于流感病毒表面的神经氨酸酶(Neuraminidase)。神经氨酸酶在病毒的生活周期中扮演了重要的角色，流感病毒在宿主细胞内复制表达和组装之后，会以出芽的形式突出宿主细胞，但与宿主细胞以凝血酶-唾液酸相连接，神经氨酸酶以唾液酸为作用底物，可催化唾液酸水解，解除成熟病毒颗粒与宿主细胞之间的联系，使之可以自由移动侵袭其他健康的宿主细胞。抑制神经氨酸酶的活性可以阻止病毒颗粒的释放，切断病毒的扩散链，因而神经氨酸酶可以成为治疗流行性感冒的一个药物靶点。
Structure of the influenza virion. The hemagglutinin (HA) and neuraminidase (NA) proteins are shown on the surface of the particle. The viral RNAs that make up the genome are shown as red coils inside the particle and bound to Ribonuclear Proteins (RNPs).
(源自: http://zh.wikipedia.org/wiki/%E5%A5%A5%E5%8F%B8%E4%BB%96%E9%9F%A6)
Viruses are tiny structures that are too small to be seen with a regular microscope. The powerful electron microscope invented in the 1940s revealed that a virus is nothing more than a core of genetic material (RNA or DNA), wrapped in a protective protein coat. These tiny agents of disease are not considered living things, because they can not reproduce on their own. They must invade the cells of other living things and take over the cells' machinery to make more copies of themselves. Once inside their hosts' cells, viruses reproduce wildly, spread through the body and cause illness. Some illnesses caused by viruses come and go -- common colds, flu, measles, mumps, and chicken pox, for example. Others, such as cytomegalovirus and Epstein-Barr virus, linger in the body for life.
Developing antiviral medicines has been difficult, because most drugs that kill viruses also damage the host's cells, where the viruses hide. However, since the 1980s, when the virus that causes AIDS began to receive attention, medical researchers have focused on the problem of treating viral infections, and encouraging progress has been made. Rather than killing the viruses, antiviral drugs block steps in the process through which viruses reproduce. Some may also stimulate the immune system so that the body can fight the viruses itself.
From: http://www.faqs.org/health/topics/78/Antiviral-drugs.html
10 steps of the virus replicative cycle : (1) adsorption, (2) penetration, (3) uncoating, (4) early transcription, (5) early translation, (6) replication of the viral genome, (7) late transcription, (8) late translation, (9) assembly, and (10) release of new virus particles.
Key terms:
Virus(病毒):A tiny, disease-causing structure that can reproduce only in living cells and causes a variety of infectious diseases.
Cytomegalovirus(巨细胞病毒):A type of virus that attacks and enlarges certain cells in the body. The virus also causes a disease in infants.
Epstein-Barr virus(埃-巴二氏病毒;EB病毒):A virus that causes infectious mononucleosis and is involved in some types of cancer.
Herpes simplex(单纯疱疹):A virus that causes sores on the lips (cold sores) or on the genitals (genital herpes).
Shingles(带状疱疹):An disease caused by an infection with the Herpes zoster virus, the same virus that causes chickenpox. Symptoms of shingles include pain and blisters along one nerve, usually on the face, chest, stomach, or back.
神经氨酸酶又称唾液酸酶:是分布于流感病毒被膜上的一种糖蛋白，它具有抗原性，可以催化唾液酸水解，协助成熟流感病毒脱离宿主细胞感染新的细胞，在流感病毒的生活周期中扮演了重要的角色。在甲型流感病毒中，神经氨酸酶的抗原性会发生变异，这成为划分甲型流感病毒亚型的依据，在目前已知的甲型流感病毒中共有9种不同的神经氨酸酶抗原型。(源自: wikipedia.神经氨酸酶)
音乐： yanni(雅尼) - with an orchid(和兰花一起)
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