VIROLOGIMorfologi, klasifikasi dan sifat umum

By

Sy. Miftahul El J.T

VirusPartikel infeksius yang terkecilDiameter: 18 300 nanometer [sebagian besar di bawah 200 nm] tidak dapat diamati dengan mikroskop cahayaTerdapat 25 famili, 1550 spesies beberapa penyebab penyakit pada manusiaPartikel virus berisi molekul asam nukleat DNA atau RNA, terbungkus oleh kapsid [protein]

Virus True parasites membutuhkan host untuk replikasiVirus parasit intrasellular obligat

Sifat Umum virus1. Definition and Properties of a Virus Viruses are filterable agents.Viruses are obligate intracellular parasites.Viruses cannot make energy or proteins independently of a host cell.Viral genomes may be RNA or DNA but not both.Viruses have a naked capsid or an envelope morphology.Viral components are assembled and do not replicate by "division."2. Consequences of Viral Properties Viruses are not living.Viruses must be infectious to endure in nature.Viruses must be able to use host cell processes to produce their components (viral messenger RNA, protein, and identical copies of the genome).Viruses must encode any required processes not provided by the cell.Viral components must self-assemble.

Sifat Umum virus3. Means of Classification and Naming of Viruses Structure: size, morphology, and nucleic acid (e.g., picornavirus [small RNA], togavirus)Biochemical characteristics: structure and mode of replication*Disease: encephalitis and hepatitis viruses, for exampleMeans of transmission: arbovirus spread by insects, for exampleHost cell (host range): animal (human, mouse, bird), plant, bacteriaTissue or organ (tropism): adenovirus and enterovirus, for example

Components of the basic virion.Downloaded from: StudentConsult (on 16 December 2009 04:15 PM) 2005 Elsevier

The DNA viruses and their morphology. The viral families are determined by the structure of the genome and the morphology of the virion.

Families of DNA Viruses and Some Important Members*The italicized virus is the important, or prototype, virus for the family. The size of type is indicative of the relative size of the virus.

Family MembersPOXVIRIDAE Smallpox virus, vaccinia virus, monkeypox, molluscum contagiosum HerpesviridaeHerpes simplex virus types 1 and 2, varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, human herpesviruses 6, 7, and 8 Adenoviridae Adenovirus Hepadnaviridae Hepatitis B virus Polyoma viridae JC virus, BK virus, SV40 Papilloma viridae Papilloma virus Parvoviridae Parvovirus B19, adeno-associated virus

Properties of Virions of Human DNA Viruses *Genome invariably a single molecule.Polymerase encoded by virus.Polymerase carried in the virion. Circular molecule is double-stranded for most of its length but contains a single-stranded region. [Verbar]Reverse transcriptase.ds, Double-stranded; ss, single-stranded.

Family Genome* VironMolecular Mass 106 Daltons Nature Shape Size (nm) DNA Polymerase Poxviridae 85-140 ds, linearBrick-shaped, enveloped300 x240x100 +Herpesviridae 100-150 ds, linearIcosahedral, enveloped Capsid, 100-110 Envelope, 120-200 +Adenoviridae 20-25ds, linear Icosahedral 70-90 +Hepadnaviridae 1.8ds, circular Spherical, enveloped 42+[Verbar]Polyoma and papilloma viridae 3-5ds, circular Icosahedral45-55-Parvoviridae 1.5-2.0 ss, linear Icosahedral 18-26 -

The RNA viruses, their genome structure, and their morphology. The viral families are determined by the structure of the genome and the morphology of the virion.

Families of RNA Viruses and Some Important Members*The italicized virus is the important or prototype virus for the family. The size of the type is indicative of the relative size of the virus.

FamilyMembers* Paramyxoviridae Parainfluenza virus, Sendai virus, measles virus, mumps virus, respiratory syncytial virus, metapneumovirus OrthomyxoviridaeInfluenza virus types A, B, and C CoronaviridaeCoronavirus, SARS (severe acute respiratory syndrome)Arenaviridae Lassa fever virus, Tacaribe virus complex (Junin and Machupo viruses), lymphocytic choriomeningitis virus Rhabdoviridae Rabies virus, vesicular stomatitis virus Filoviridae Ebola virus, Marburg virus Bunyaviridae California encephalitis virus, LaCrosse virus, sandfly fever virus, hemorrhagic fever virus, Hanta virus Retroviridae Human T-cell leukemia virus types I and II, human immunodeficiency virus, animal oncoviruses Reoviridae Rotavirus, Colorado tick fever virus Picornaviridae Rhinoviruses, poliovirus, echoviruses, coxsackievirus, hepatitis A virus TogaviridaeRubella virus; western, eastern, and Venezuelan equine encephalitis virus; Ross River virus; Sindbis virus; Semliki Forest virus Flaviviridae Yellow fever virus, dengue virus, St. Louis encephalitis virus, West Nile virus, hepatitis C virusNoroviridaeNorwalk virus, calicivirus Delta Delta agent

Properties of Virions of Human RNA Viruses*Some enveloped viruses are very pleomorphic (sometimes filamentous).No matrix protein. Genome has two identical single-stranded RNA molecules. Reverse transcriptase.ds, Double-stranded; seg, segmented; ss, single-stranded; +or -, polarity of single-stranded nucleic acid.

Family Genome* Virion Molecular Mass 106 Daltons Nature Shape* Size (nm) Polymerase in Virion EnvelopeParamyxoviridae 5-7 ss, - Spherical 150-300 ++Orthomyxoviridae 5-7ss, -, seg Spherical 80-120 ++Coronaviridae6-7 ss, + Spherical 80-130- + Arenaviridae3-5ss, -, seg Spherical 50-300 ++ Rhabdoviridae4-7ss, - Bullet-shaped 180 x75 ++Filoviridae4-7ss, - Filamentous800 x 80++Bunyaviridae 4-7ss, - Spherical 90-100 + + Retroviridae 2 (2-3) ss, + Spherical 80-110 + +Reoviridae 11-15 ds, seg Icosahedral60-80+-Picornaviridae2.5 ss, + Icosahedral 25-30 --Togaviridae 4-5 ss, + Icosahedral 60-70 -+Flaviviridae4-7 ss, + Spherical 40-50-+Noroviridae 2.6ss, + Icosahedral 35-40 --

Relative sizes of viruses and bacteria. (Courtesy the Upjohn Company, Kalamazoo, Mich.)

KapsidKapsid tersusun atas protein biasanya glikoprotein menentukan hubungan spesifik antara virus dengan inang/host/pejamu nyaMempunyai tempat pengikatan yang memungkinkan virus menempel pd tempat reseptor yg khas pada sel inangKapsid melindungi asam nukleat dan memfasilitasi pengikatan dan penetrasi virus pada sel inangBertanggung jawab terhadap bentuk virion

The structures of a naked capsid virus (top left) and enveloped viruses with an icosahedral (left) nucleocapsid or a helical (right) ribonucleocapsid. The helical ribonucleocapsid is formed by viral proteins associated with an RNA genome.

Viral Structure: Naked Capsid Component : ProteinProperties : Is environmentally stable to the following:TemperatureAcidProteasesDetergentsDryingIs released from cell by lysisConsequences : Can be spread easily (on fomites, from hand to hand, by dust, by small droplets)Can dry out and retain infectivityCan survive the adverse conditions of the gutCan be resistant to detergents and poor sewage treatmentAntibody may be sufficient for immunoprotection

Capsid assembly of the icosahedral capsid of a picornavirus. Individual proteins associate into subunits, which associate into protomers, capsomeres, and an empty procapsid. Inclusion of the (+) RNA genome triggers its conversion to the final capsid form.

Printed from: Medical Microbiology 5E (on 10 December 2010) 2010 Elsevier

Cryoelectron microscopy and computer-generated three-dimensional image reconstructions of several icosahedral capsids. These images show the symmetry of capsids and the individual capsomeres. During assembly, the genome may fill the capsid through the holes in the herpesvirus and papovavirus capsomeres. 1, Equine herpesvirus nucleocapsid; 2, simian rotavirus; 3, reovirus type 1 (Lang) virion; 4, intermediate subviral particle (reovirus); 5, core (inner capsid) particle (reovirus); 6, human papillomavirus type 19; 7, mouse polyomavirus; 8, cauliflower mosaic virus. Bar = 50 nm. (Courtesy Dr. Tim Baker, Purdue University, West Lafayette, IN.)

Virus Structure: Envelope Components : MembraneLipidsProteinsGlycoproteinsProperties : Is environmentally labile-is disrupted by the following:AcidDetergentsDryingHeatModifies cell membrane during replicationIs released by budding and cell lysisConsequences : Must stay wetCannot survive the gastrointestinal tractSpreads in large droplets, secretions, organ transplants, and blood transfusionsDoes not need to kill the cell to spreadMay need antibody and cell-mediated immune response for protection and controlElicits hypersensitivity and inflammation to cause immunopathogenesis

Steps in Viral Replication Recognition of the target cellAttachmentPenetrationUncoatingMacromolecular synthesisEarly messenger RNA (mRNA) and nonstructural protein synthesis: genes for enzymes and nucleic acid-binding proteinsReplication of genomeLate mRNA and structural protein synthesisPost-translational modification of proteinAssembly of virusBudding of enveloped virusesRelease of virus

TERIMA KASIHTERIMA KASIHTERIMA KASIHTERIMA KASIH

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