Lecture 1: Virus Nomenclature and Structures PDF

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.