Lecture 1: Virus Nomenclature and Structures PDF

Summary

This lecture covers the nomenclature and structures of viruses. Students will learn how viruses are categorized and the characteristics of their structures. The lecture also discusses the classification of viruses and the differences between DNA and RNA viruses.

Full Transcript

Lecture 1: Virus nomenclature and structures Yap Wei Boon, Ph.D Assoc. Professor [email protected] Learning outcomes In the end of the lecture, students are able to: – categorize viruses accordingly. – describe virus structures and functions. General Nomenclature of Viru...

Lecture 1: Virus nomenclature and structures Yap Wei Boon, Ph.D Assoc. Professor [email protected] Learning outcomes In the end of the lecture, students are able to: – categorize viruses accordingly. – describe virus structures and functions. General Nomenclature of Viruses – Virus classification was done on the basis of: i. Type of host (human immunodeficiency virus, human influenza virus, avian influenza virus). rashes ii. Type of disease (measles virus, small pox virus, influenza virus). & to categorize iii. Transmitted by a vector or not. (mosquito-borne disease) virus according iv. City, town or river where the disease was first reported (Ebola virus, Nipah to big group - virus, Hendra virus, Hantaan virus). Malaysia Australia tree in of host + type of disease Monkey pox : type Evolution of Virus Nomenclature – Based on virus particle characteristics: Why do we need to know the genome type (RNA/DNA) ? which test to - to identify i. Genome type: DNA or RNA. Conduct in ordergetto the correct treatment/ ii. Single or double stranded nucleic acid. for diagnosis. &iii. Segmented or non-segmented genome. need extra - - step for cultivation iv. Virion size. onecompea DNA long round because there v. Helical or icosahedral capsid. for identification light microscope) - -- are many pieces - Clook under of nucleic acid vi. Naked or enveloped virion. need - use C to identify which wrong drug : might trigger some part higher close > of drug - -f virus drug to use * Then it comes to the Era of International Committee on Taxonomy of viruses… Taxonomic suffix Eg. 1 Eg. 2 group E Order -virales Mononegavirales Nidovirales - imic Family -viridae Paramyxoviridae - Coronaviridae Subfamily -virinae Paramyxovirinae - Common to 3 group virus Genus -virus Morbilivirus Coronavirus (simple structure) Species - Measles virus (MeV) Severe acute respiratory X not all - syndrome virus (SARS- Italic S virus have CoV) only species name Capitalize - Members of a species may share characteristics in common but no one first letter characteristic is essential for membership of the species. Baltimore Classification of Viruses – On the basis of the type of genome (DNA or RNA, ss, ds, segmented, non- segmented) and the way in which the genome [plus-strand (+ve polarity) or negative strand (-ve polarity)] is transcribed and replicated. – 7 classes. The Baltimore Classification System Based on genetic contents and replication strategies of viruses. flu/HFMD skin infection & double 1. dsDNA viruses (poxvirus, adenovirus, herpes virus) - -- stranded redness on cheek - evereSept limiting , 2. ssDNA viruses (parvovirus) (self - single unhygenic food/ for anemia, stranded Water consumption immunocompromised (not common) 3. dsRNA viruses (rotavirus, reovirus) - - double stranded L (common children protein (faster, translate directly) > C+) sense - 5. (-) sense ssRNA viruses (influenza virus, rabies virus, measles virus, Nipah virus, - 1) Sense Ebola virus) protein 2) E 6. RNA reverse transcribing viruses (HIV, Human T-lymphotrophic virus, HTLV1, convert RNA-CDNA HTLV2). strong inflammatory (induce response > host - X detect) 7. dsDNA with RNA intermediate (HBV) (combine with host's DNA- host confuse > - Stay Ponyer/live together with attech to envelope spike protein no envelope , spike protein attack to capsid / capsid = spire protein VIRIONS not mad Protein & from Bost cell  Outside host cells, viruses survive as VIRIONS INFECTIOUS!!! (How long viruses survive outside hosts is virus-dependent!!!)  Virions carry: - genomes. - capsids. - lipid envelopes (only for certain viruses). - proteins. Virus GENOMES 3 minic – Especially RNA genome: may function as mRNA (with 5’methylated cap - real RNA of and 3’polyadenosine tail). help translation host - to to stop translating occur – Maybe contain repeat sequences at the ends (terminal repeats): as promoters, enhancers, origin of replication. - Methyl guanosine Virus PROTEINS found in virus's structure  Structural proteins: components of virions. - Functions: protect virus genome, virus attachment to host cells, fusion of virus envelope with host membrane, virus replication (replicase).  Non-structural proteins: Encoded by virus genes but only synthesized in infected cells (NOT VIRIONS components) Functions: enzymes (proteases), transcription factor, primers for genome replication, interference with host immune responses. Virus proteins: CAPSIDS – Major function: protect virus genomes – Other functions: reorganize and attach to host cells, release genome into host cells. – Capsid + genome : NUCLEOCAPSID – Helical or Icosahedral carry helical capsid only no envelope spikes >thin layer Envelope envelope - of > capsid - Capsid TEM micrograph of herpesvirus Virion MEMBRANES Spike protein > - help to penetrate host  Derived from host cell membranes.  Enveloped virions: ▪ Mostly animal viruses: influenza virus, herpesviruses. ▪ Carry integral membrane proteins (most glycosylated) known as glycoproteins. ▪ Functions: Attachment and fusion of virion membrane with cell membrane during infection.

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