【正文】 ? 輔助結(jié)構(gòu) ?包膜（ Envelope）： 是脂質(zhì)液態(tài)雙層生物膜，是病毒出芽釋放時局部細(xì)胞膜包裹病毒衣殼即成胞膜，但包膜上含有病毒特異蛋白分子，如一些病毒的糖蛋白。 ? 核衣殼（ Nucleocapsid） = Capsid + nucleic acid. ? 結(jié)構(gòu)單位 (Structural units): 衣殼基本的蛋白結(jié)構(gòu)單位。 病毒的結(jié)構(gòu) ? 基本結(jié)構(gòu) ?核酸： DNA或者 RNA，線性或環(huán)狀，完整或分段。 ? 螺旋對稱 （ Helical）：衣殼殼粒螺旋狀排列包裹核酸，多數(shù)有包膜。 pitch (the distance covered by each plete turn of the helix) Icosahedra ? 20 equilateral triangles arranged into a sphere based on 235 rotational symmetry ? Bacteriophage 216。Virus Taxonomy39。soluble living germ39。s results on tobacco mosaic virus amp。 there can be many reasons for nonpermissiveness . no receptor. ? restringent or restrictive, cell is transiently permissive and a few virus are produced. Virus production stops but the genome remains in the cell, examples include Epstein Barr Virus and herpes simplex virus. This kind of infection may still have serious consequences cell transformation and cancer. History of Virology ? Viruses are probably as old as life on earth. Ancients were aware of viral diseases Perhaps the first written record of a virus infection consists of a heiroglyph from Memphis, drawn in approximately 1400BC, which depicts a temple priest called Siptah showing typical clinical signs of paralytic poliomyelitis ? Smallpox, endemic in China by 1000BC. Recognizing that survivors of smallpox outbreaks were protected from subsequent infection, the practice of variolation developed. Involved inhalation of dried crusts from smallpox lesions, or in later modifications, inoculation of the pus from a lesion into a scratch on the forearm. Practice survived until this century. On May 14, 1796, Edward Jenner used cowpoxinfected material obtained from the hand of Sarah Nemes, a milkmaid from Berkley in Gloucestershire to vaccinate 8 year old James Phipps. On July 1, 1796, Jenner challenged the boy by deliberately inoculating him with material from a real case of smallpox ! He did not bee infected! ? In 1892, Dmitri Iwanowski, a Russian botanist, showed that extracts from diseased tobacco plants could transmit disease to other plants after passage through ceramic filters fine enough to retain the smallest known bacteria. Generally recognised as the beginning of Virology ? In 1898, Martinus Beijerinick confirmed amp。 bovine spongiform encephalopathy (BSE) in cattle. –ve RNA ve RNA pol Proteins ve RNA +ve RNA RI Genomes 14 Ambisense Genomes ? Some ssRNA viruses are ambisense, since they are part ()sense amp。uninfected39。), they are packaged into virus capsids as passengers. Present in animals and plants. Associated with disease. 3. Prions ? Prions. “pree ons” believed to consist of a single type of protein with no nucleic acid ponent. The prion protein amp。 and little fleas have lesser fleas and so ad infinitum. ? Viruses consist of proteins, nucleic acids and sometimes lipids. However there are other infectious agents studied by virologists. ? Viroids small (200400nt), circular RNAs, possessing no capsid or envelope. Associated with certain plant diseases. They are infectious obligate intracellular parasites. ? Virusoids are satellite, viroidlike RNAs, larger than viroids (approximately 1000nt). Depend on the presence of virus replication for multiplication (hence 39。 or immortalized cell lines, which grow in culture indefinitely. Viruses can be grown in them. 16. Quantifying viruses. ? The plaque assay dilutions of the virus are used to infect a cultured cell monolayer, covered with agar to restrict virus diffusion virus. Results in localized cell killing amp。 culture of many viruses . 15. Cell Culture methods ? Whole an cultures, progressed to methods involving individual cells。C 10 min方可殺死 ?有包膜病毒比無包膜病毒對熱更敏感 ? pH ?多數(shù)在 pH 5~9范圍穩(wěn)定 ?腸道病毒耐酸（ pH 3~5） ? 射線 X線、 ?射線可將病毒核酸致死性斷裂，從而殺死病毒 化學(xué)因素 ? 脂溶劑：乙醚、氯仿、去氧膽酸鹽 ?有包膜病毒敏感 。C 30 min或 100186。C長期保存。它是病毒在細(xì)胞內(nèi)增殖的場所 頓挫感染 ? 原因 ?宿主細(xì)胞 不能提供 病毒復(fù)制所需的 酶、能量或成份 ?病毒雖被復(fù)制，但 不能裝配釋放 缺陷病毒 ? 因病毒 基因組不完整 或有點(diǎn)突變而不能進(jìn)行正常復(fù)制的病毒，當(dāng)與 輔助病毒 共同培養(yǎng)，如能為其提供缺乏的物質(zhì)，則缺陷病毒也能培殖 ?