약품미생물학 생명산업과학대학 생물환경학과 김정호

 Virus : organism at the edge of life Latin, poison 1728 "agent that causes infectious disease" 1892 Dmitri Ivanovsky Non-bacterial pathogen, Tobacco Mosaic Disease (TMD) 1898 Martinus Beijerinck Causative agent for TMD – Virus the agent multiplied only in cells that were dividing contagium vivum fluidum : viruses are liquid in nature 1935 Wendell Stanley Virus : particulate Isolation of TMV : nucleoprotein 1935 Friedrich Loeffler, Paul Frosch first animal virus : agent of foot-and-mouth disease Virus

 Virus Non-cellular microorganism Obligate parasite a small infectious agent that replicates only inside the living cells of other organisms Host : animals, plants, microorganisms bacteriophage (phage) Virion : stable infective viral particle fully capable of infecting other cells Virus

 Virus particle (virion) Core : Genetic material, DNA or RNA Enzymes for replication Capsid : protein coat Protomers - Capsomers : self-assembly Helical (Spiral) Icosahedral Complex Envelope : lipids, enzymes Non-enveloped (naked virus) : Nucleocapsid Enveloped virus : from host - nuclear or cell membrane attachment Influenza virus H : Hemaglutinin N : Neuraminidase Virus

 Classification based on phenotypic characteristics morphology, nucleic acid type, mode of replication, host organisms, type of disease  ICTV (The International Committee on Taxonomy of Viruses) International Union of Microbiological Societies Based on : types of nucleic acid, strandedness (ss, ds), positive(sense) or negative(antisense) strand RNA, envelope viral morphology and symmetry of capsid, mode of replication Phylum : Virus Order : -virales Family : viridae Subfamily : -virinae Genus : -virus Species : [Disease] virus * names of orders and families are italicized Viral Taxonomy

 Seven orders + α Caudovirales : tailed dsDNA (group I) bacteriophages Herpesvirales : large eukaryotic dsDNA viruses. Ligamenvirales : linear, dsDNA (group I) archaean viruses. Mononegavirales : nonsegmented (-) strand ssRNA (Group V) plant and animal viruses Nidovirales : (+) strand ssRNA (Group IV) viruses with vertebrate hosts. Picornavirales : small (+) strand ssRNA viruses that infect a variety of plant, insect and animal hosts Tymovirales : monopartite (+) ssRNA viruses that infect plants Virus families not assigned to an order Viral Taxonomy – ICTV system

 Seven groups nucleic acid (DNA/RNA), strandedness (ss/ds), replication Groups are designated by Roman numerals (I ~ VII) I : dsDNA viruses : Adenoviruses, Herpes viruses, Poxviruses II : ssDNA viruses : Parvoviruses III : dsRNA viruses : Reoviruses IV : (+) ssRNA viruses : Picornaviruses, Togaviruses V : (−) ssRNA viruses : Orthomyxoviruses, Rhabdoviruses VI : (+) ssRNA-RT viruses - replicate thru a DNA intermediate, (reverse transcription involved) : Retroviruses VII : dsDNA-RT viruses - replicate thru an ss RNA intermediate, (reverse transcription involved) : Hepadnaviruses  Other classifications : the disease caused by the virus morphology Viral Taxonomy - Baltimore classification

 Only inside the living cells 1. 부착, 흡착 (Attachment, Adsorption) 2. 침투 ∙ 탈피 (Penetration & Uncoating) 3. 생합성 (Biosynthesis) 4. 조립 ∙ 포장 (Assembly & Packaging, Maturation, 성숙 ) 5. 방출 (Release) Viral Replication

1. 부착, 흡착 (Attachment, Adsorption) host specificity : virus - adsorption site ( 흡착부위 ) host cell - receptor site ( 수용체 ) 2. 침투 ∙ 탈피 (Penetration & Uncoating) Injection : phage, viral genome only ( 주입, injection) Fusion : viral envelope + cell membrane Endocytosis : capsid + 핵산 ( 세포 내에서 Uncoating) most animal viruses Viral Replication

동물바이러스의 세포내흡입과정

3. 생합성 (Biosynthesis) : genome, protein Enzyme synthesis : enzymes for genome replication, … Genome replication : Proteins synthesis : protomers (capsomers) Viral genome replication (Homework). ds DNA. ss DNA. ds RNA. (+) ss RNA with mRNA function. (-) ss RNA. (+) ss RNA with no mRNA function : reverse transcription. Partially ds DNA : reverse transcription

Replication of ds DNA virus : Group I  DNA replication Semiconservative DNA polymerase Protein synthesis Transcription Translation  Nuclear replicating Hijack the host’s replication machinery Adenoviridae, … Cytoplasmic replicating Encode for their own enzymes Poxviridae, …

Replication of (+) ss DNA virus : Group II  DNA replication in nucleus of host ds DNA intermediate (+) ss DNA replication using (-) ss DNA as the template Protein synthesis transcription of int. ds DNA translation Circoviridae, Parvoviridae

Replication of ds RNA virus : Group III  Segmented ds RNA genome Double Capsid  Protein synthesis In viroplasm Viral RdRP transcribe (-) RNA strand RdRP (RNA-dependent RNA polymerase) Monocistronic (+) mRNA → cytoplasm Translation → viral proteins RNA replication Viral RdRP transcribe (+) mRNA : (-) mRNA Basepairing of (+) & (-) RNA → ds RNA In viroplasm Reoviridae, Birnaviridae

Replication of (+) ss RNA virus : Group IV  (+) ss RNA genome  Protein synthesis (+) ss RNA : act as mRNA Polycistronic mRNA Translation to viral proteins (+) ss RNA replication RNA-dependent RNA polymerase Replication of (-) ss RNA from (+) ds RNA replicative complex Relpication of (+) ss RNA from (-) (+) ss RNA as mRNA or viral genome Coronaviridae, Flaviviridae, Picornaviridae, Togaviridae

Replication of (-) ss RNA virus : Group V  (-) ss RNA genome  Protein synthesis Transcription of (+) ss RNA from (-) strand viral RdRP Translation to viral proteins (+) ss RNA act as mRNA (-) ss RNA replication Replication of (+) ssRNA from (-) ss RNA viral RdRP ds RNA replicative complex Relpication of (-) ss RNA from (+) strand Orthomyxoviridae, Paramyxoviridae, Bunyaviridae, Rhabdoviridae

Replication of (+) ss RNA-RT virus : Group VI  Retroviruses Retro : backwards (+) ss RNA : no mRNA function  Reverse transcription Viral Reverse transcriptase : RNA-dependent DNA polymerase DNA intermediate from ss RNA ds DNA (replicative form) DNA-dependent DNA polymerase ds DNA into host genome viral integrase integrated DNA : provirus From the integrated DNA DNA-dependent RNA polymerase production of viral proteins transcription of viral genome

 Hepadnaviridae (Hepatitis B virus) Partially ds DNA : gapped genome partially ds, partially ss circular DNA Replication thru (+) ss RNA intermediate 1. Entry of viral DNA into nucleus Conversion of "gapped" DNA into cccDNA by host repair synthesis 2. Transcription into mRNA(s) & subgenomic (pregenome) RNA host RNA polymerase, cccDNA as template 3. Translation of mRNA in cytoplasm : viral proteins 4. Assembly of provirions : viral proteins + pregenome (+) ss RNA 5. Reverse transcription of pregenome RNA to RNA/DNA complex inside virions by viral reverse transcriptase (RT) 6. Conversion of RNA/DNA complex to circular, gapped dsDNA viral reverse transcriptase 7. Virion maturation Partially ds DNA-RT virus : Group VII

4. 조립 ∙ 포장 (Assembly & Packaging) 자가조립 (self-assembly) capsid encapsidation 성숙 (maturation) 5. 방출 (Release) Non-enveloped vs Envelovped 방출량 (burst size) 용균반점 (plaque) * 세포병변효과 (cytopathic effect, CPE) 바이러스에 감염된 숙주세포에 나타나는 형태와 구조의 변화

 Virus 병원성 (virulent) : 용균성 생활환 (Lytic cycle) 잠재성 (temperate): 용균성 & 용원성 생활환 (Lysogenic cycle)  용균성 생활환 (lytic cycle) 감염 (infection) 용원성 생활환 (lysogeny) virus 의 유전물질이 숙주세포 염색체의 일부로 존재 provirus(prophage) 면역 (immunity) 유도 (induction) : provirus 가 숙주세포의 염색체에서 떨어져 나옴 ⇒ 용균성 생활환 형질변환 (Phage conversion) provirus 의 유전자에 의해 숙주세포의 형질이 바뀌는 현상 Corynebacterium diphtheriae : 디프테리아 독소 Clostridium botulinum : botox Horizontal Gene Transfer (HGT) Lytic & Lysogenic cycle

인플루엔자 바이러스가 세포막 출아에 의해 방출되는 과정

 Viroid single stranded RNA circle : not encoding for proteins No capsid, No envelope Infectious agent : plant diseases  Virusoid single stranded RNA circle : encoding for proteins Need helper virus for infection Human hepatitis D virus (helper virus : hepatitis B virus)  Prion Proteinaceous infectious particle Creutsfeldt-Jacob disease (CJD) Bovine spongiorm encephalopathy (BSE, 광우병 )