Viral Classification, Structure, and Replication - Chapter 44 PDF

Viral Classification, Structure, and Replication Chapter 44  Viruses First described as “filterable agents” (1) very small : Obligate intracellular parasites (2) rep ____________...

Viral Classification, Structure, and Replication Chapter 44  Viruses First described as “filterable agents” (1) very small : Obligate intracellular parasites (2) rep ____________ : cannot. cell who host – depend on biochemical machinery of host for replication – reproduction occurs by assembly of the individual components rather than by binary fission ~ viruses assemblethen release naked viws" Nucleic acid, protein, and in some cases membrane virus - (__________) envelope macromolecules 3 Physical structure and genetics of viruses have been optimized by mutation and selection to infect humans and other hosts  Classification Names may describe: – viral characteristics Smal picornavirus – disease they are associated with poxviruses Loading… – tissue or geographic local where they were first identified Norwalk virus USD = A  A Classification Viruses can be grouped by characteristics such as: Transmission of Dengue – _________ Virus disease- hepatitis – target tissue enteric – means of transmission respiratory – _________ Vector- arboviruses  Classification The most consistent and current means of classification is by physiological and biochemical characteristics such as: – size – morphology Loading… presence or absence of envelope – __________________ type of genome- DNA viruses associated with human disease are divided into 7 families RNA viruses may be divided into at least 13 families – means of replication  Classification – Families of DNA Viruses - Family Members* Poxviridae Smallpox virus, vaccinia virus, monkeypox, canarypox, molluscum contagiosum Herpesviridae Herpes 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 Papillomaviridae Papilloma virus Polyomaviridae JCvirus, BKvirus, SV40 Parvoviridae Parvovirus B19, adeno-associated virus Classification – Families of RNA Viruses - Family Members* Paramyxoviridae Parainfluenza virus, Sendai virus, measles virus, mumps virus, respiratory syncytial virus, metapneumovirus Orthomyxoviridae Influenza virus types A, B, and C Coronaviridae Coronavirus, 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, La Crosse 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 Togaviridae Rubella 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 Cvirus Zik Caliciviridae Norwalk virus, calicivirus a Picornaviridae Rhinoviruses, poliovirus, echoviruses, coxsackievirus, hepatitis A virus Delta Delta agent  Virion Structure Units for measurement of virion size are nanometers (nm) – clinically important viruses range from 18 nm (parvoviruses) to 300 nm (poxviruses) – larger virions can hold a larger genome that can encode more proteins, and they are generally more complex Virion Structure  Virion Structure ParvoviruS : issue if kid has Sickle Cell b this virus attacks Smallpox s RBC precursor virus CD C  CD C Virion Structure Virion (virus particle) – nucleic acid genome – 3 ____________ capsid – protein coat nucleocopsik- – envelope – membrane lipid bilayer surrounding nuchocapsid – Loading… certain essential or accessory enzymes to facilitate initial replication within the cell encapsulate : enzs. in to use capsid in host all HIV- RNA-RNActe E in chrom. all  Virion Structure Viral genome – ____________ DNA- single stranded double stranded linear circular – _____________ RNA - positive sense (+) – like mRNA immediately negative sense (-) complement to mRNA double stranded (+/-) segmented · different segments that could create recombinant viruses Virion Structure Baltimore Classification copy copythe copy Overall : + strand is mRNA , genomic info can be immediatelytranslated + RNA = mRNA translation replicate RDRP [NA] template RDRP +RNA + RNA = MRNA Virion Structure  Virion Structure The surface structures of the capsid and envelope mediate the interaction of the virus with the target cell through a viral attachment protein (______) VAP- – removal or disruption of the outer packaging inactivates the virus – antibodies generated against the components of these structures _______________ prevent viral infection COVID-19 surface spike proteins ex.: vax , recognizes Virion Structure Representative Virion Structure CCR5 1S  Virion Structure reverse transcriptase  Virion Structure Capsid- ______________ – rigid structure able to withstand harsh environmental conditions – generally resistant to drying, acid, and detergents = including acid and bile of the enteric tract – many transmitted by the fecal-oral route and can endure transmission even in sewage ______________ Envelope – membranous structure can be maintained only in aqueous solutions – readily disrupted by drying, acidic conditions, detergents, and solvents – must remain wet and are generally transmitted in fluids _________________, respiratory droplet, blood, and tissue to remain infectious (not alive)  Virion Structure Capsid viruses – the viral capsid is assembled from individual proteins associated into progressively larger units _________ subunits- - protomers capsomeres procapsid/_________ ~ caspid = empty shell – all of the components of the capsid have chemical features that allow them to fit together and to __________ assemble into a larger unit Virion Structure -  Virion Structure Simple Icosadeltahedro Icosahedron n - Virion Structure  Virion Structure Symmetric – ________________ helical- appear as rods – icosahedral Nonsymmetric – complex forms associated with certain bacterial viruses (phages)  Virion Structure Tobacco Mosaic Herpes Bacteriophag Virus Virus e -mmmummie Helica Icosadeltahedral Nonsymmetric Dl  Virion Structure Enveloped viruses HemagglutiniM – envelope composed of lipids, n > proteins, and glycoproteins Hemagglutinin membrane structurally similar to how he is Nuraminidase cellular membranes derived from allular membranes – ___________________________ cellular proteins rarely found in viral envelope – most are round or pleomorphic exceptions: – poxviruses – rhabdoviruses