Lec 11 Classification and nomenclature of viruses.pptx

Classification and Nomenclature of Viruses PREPARED BY : MR. ZAKARIA BIN ISMAIL (2021) Content 1.Virus genome replication 2.Classification and nomenclature of viruses 3.Herperviruses (and other dsDNA viruses) 4.Parvoviruses (and other ssDNA viruses) 5.Reoviruses (and other dsRNA viruses) 6.Pico...

Classification and Nomenclature of Viruses PREPARED BY : MR. ZAKARIA BIN ISMAIL (2021) Content 1.Virus genome replication 2.Classification and nomenclature of viruses 3.Herperviruses (and other dsDNA viruses) 4.Parvoviruses (and other ssDNA viruses) 5.Reoviruses (and other dsRNA viruses) 6.Piconarviruses (and other plus-strand RNA viruses) 7.Rhabdoviruses (and other minus-strand RNA viruses) 8.Retroviruses 9.Hepadnaviruses (and other reverse-transcribing DNA viruses) 1. Virus genome replication There are 6 basic stages in the life cycle of viruses; i. attachment ii. penetration(viral entry), iii. Uncoating iv. Replication& translation v. Assembly vi. lysis. 2. Classification & Nomenclature of viruses The classification of viruses based on; 1. Whether the nucleic acid is DNA or RNA. 2. Whether the nucleic acid is single stranded or double stranded. 3. Whether or not the genome is segmented. 4. The size of the virion 5. Whether the capsid has helical symmetry or icosahedral symmetry. 6. Whether the virion is naked or enveloped. 3. Herpesviruses and other dsDNA viruses (group I) 3. Herpesviruses (and other dsDNA Viruses) The name derive from Greek word herpein meaning creep/crawl. > 100 herpesviruses have been isolated from range of hosts ( mammals, birds, fish, reptiles, amphibians and mollusks) Only 8 of these viruses are human virus. Once they have infected a host, they often remain as persistence infections for the lifetime of the host. These infections are often latent infections, which can be reactivated from time to time especially if the host become immunocompromised. The 8 human herpesviruses 3.1 Other dsDNA viruses (group 1) Family Example Animal viruses Baculoviridae Autographa california nucleopolyhedrovirus Papillomaviridae Human papillomaviruses Polyomaviridae Simian virus Poxviridae Smallpox virus Bacterial viruses Myxoviridae Phage T4 4. Parvovirus and other ssDNA Viruses (group II) 4. Parvoviruses (and other ssDNA viruses) Parvovirus are amongst the smallest known viruses with virions in the range 18-26 nm in diameter. Derive their name from Latin parvus(= small) The family of Parvoviridae has been divided into 2 subfamilies: Parvovirinae(vertebrate viruses) and the Densovirinae (invertebrate viruses). Subfamily of Parvovirinae include the genus Dependovirus,the members of which are defective, normally replicating only when the cell co-infected with a helper virus. Other that do not require helper viruses are known as autonomous parvoviruses.  4.1 Other ssDNA viruses (group 2) Family Example Animal viruses Circoviridae Porcine circovirus Majority of these viruses have circular genomes. The only viruses known with ssDNA linear Plant viruses Germiniviridae Maize streak virus genomes are parvoviruses. Bacteria viruses Cystoviridae Phage φX174  5. Reoviruses and other dsRNA viruses (group III) Some of the genera in the family Reoviridae Genus Hosts Number of dsRNA segments Cypovirus Inserts 10 Orbivirus Mammals, birds, 10 invertebrates Orthoreovirus Mammals, birds 10 Phytoreovirus Plants, inserts 12 Rotavirus Mammals, birds 11  5.1 Other dsRNA viruses (group 3) Family Example The virion of the most dsRNA viruses have Animal viruses Birnaviridae Infection bursal icosahedral symmetry and most of them disease virus are naked; exception is the family Cystoviridae, the members of which are enveloped bacteriophages. Plant viruses Partitiviridae White clover cryptic virus 1 The challenge that dsRNA viruses must overcome is that dsRNA is a potent inducer of a number of cell defense mechanism. Fungal viruses Chrysoviridae Penicillium chrysogenum virus To overcome, These viruses always enclosed the genetic materials and never free in cytoplasm. Bacteria viruses Cystoviridae Pseudomonas phage φ6 6. Picornaviruses and other plus-strand RNA viruses (group IV) Introduction to picornaviruses Pico =(small) RNA viruses, icosahedral shape, 25-30 nm diameter size, 7-8kb. Family of Picornaviridae are found in mammals and birds. Most picornaviruses grow readily in cell culture, easy to purify and are stable making them popular viruses for laboratory studies. The picornaviruses are class IV viruses; their genome is a plus-strand RNA that functions as mRNA once release into a host cell. The first virus molecules to be synthesized in an infected cells are therefore proteins, in contrast to all other viruses, where transcription of virus genes must occur before virus protein synthesis can start. The most common diseases cause by picornaviruses those related to human are; common cold, polio, hepatitis A and foot and mouth disease.  Picornaviruses Genus Name derivation from Greek word Examples Hepatovirus Hepatos=liver Hepatitis A virus Enterovirus Enteron=intestine Poliovirus Coxsackieviruses Rhinovirus Rhinos=nose Common cold viruses Aphthovirus Aptha=visicles in the mouth Foot and mouth disease virus 6.1 Other Plus-Strand RNA viruses (group 4) Family Virus example (s) Animal Flaviviridae West nile virus Hepatitis C virus Coronaviridae SARS virus Togaviridae Rubella virus Plant virus Potyviridae Potato virus Y Flexiviridae Potato virus X Comoviridae Cowpea mosaic virus 7. Rhabdoviruses( and other minus-strand RNA viruses) (group V) Introduction to Rhabdoviruses Rhabdoviruses have minus-strand RNA genomes in the size range 11- 15kb. Derives from Greek word rhabdos=a rod. The virion of some rhabdoviruses, especially infecting plants are in the shape of rods with rounded ends, while those infecting animals, are bullet shaped. Rhabdoviruses are found in a wide range of hosts, including mammals, fish, plants and inserts. Some important rhabdoviruses are rabies virus and vesicular stomatitis virus.  Examples of rhabdoviruses Genus Name derivation hosts Example(s) Vesiculoviruses Vesicle=blister Mammals, fish Vesicular stomatitis virus Lyssaviruses Lyssa (Greek)=rage, fury, mammals Rabies virus canine madness Norvirhabdovirus A non-virion protein is encoded Fish Infectious hematopoietic necrosis virus Nucleorhabdovirus Replication cycle includes a Plants, inserts Potato yellow dwarf virus nuclear phase Vesicular stomatitis vs Rabies virus 7.1 Other minus-strand RNA viruses (Group 5) Family Virus Examples Orthomyxoviridae Influenza virus Paramyxoviridae Measles virus Respiratory syncytial virus Filoviridae Ebolavirus Bunyaviridae Hantaan virus 8. Retroviruses(Group VI) The retroviruses are RNA viruses that copy their genome into DNA during replication. The human immunodeficiency viruses (HIV-1 and HIV-2) are retroviruses. Many retroviruses can cause cancer in their hosts. retro(Latin)= backwards Hosts; mammals, birds and other vertebrate animals. Enveloped virus, 8-110 nm diameter and contains reverse transcriptase enzyme.  Examples of retroviruses Simple retroviruses Complex retroviruses Genus Virus examples Genus Virus examples Alpharetrovirus Rous sarcoma Deltaretrovirus Human T- virus lymphotropic viruses 1&2 Betaretrovirus Mouse mammary tumour virus Epsilonretrovirus Walleye dermal sarcoma virus Gammaretrovirus Murine Lentivirus Human leukaemia virus immunodeficiency virus 1 Feline leukaemia virus Spumavirus Chimpanzee foamy virus 9. Hepadnaviruses and other reverse- transcribing DNA viruses (group VII) Introduction to Hepadnaviruses Hepatitis- causing DNA viruses. They are known as hepatitis B viruses (HBVs) and are classified in the family Hepadnaviridae. Some infect mammals and some infect birds. Have very small genome (3kb) DNA genome replicated via an RNA intermediate (reverse transcription) and contrast with other DNA viruses that replicate their DNA directly to DNA. The discovery of the mode of replication led to the Baltimore class VII. Hepatitis B virus replication 9.1 Other reverse-transcribing DNA viruses (Group 7) There are some plant viruses with dsDNA genomes that replicate by reverse transcription. These viruses are classified in the family Caulimoviridae, which includes viruses with isometric virions, such as cauliflower mosaic virus, and viruses with rod-shaped virions, such as rice tungro bacilliform virus. Summarization  References John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, Virology: Principles and Applications John B. Carter and Venetia A. Saunders. 2007 John Wiley & Sons, Ltd ISBNs: 978-0-470-02386-0 (HB); 978-0-470-02387-7 (PB). Viral replication (n.d.) Lumen learning. Retrieved on 17 may 2020 from https://courses.lumenlearning.com/boundless-microbiology/chapter/viral-replication/ Jill Seladi Schulman (2019). What is a retroviruses? Healthline. Retrieved on 17 May 2020 from https://www.healthline.com/health/what-is-a-retrovirus Kristeen Cherney (2020). What is a rotavirus? Healthline. Retrieved on 17 May 2020 from https://www.healthline.com/health/rotavirus D.W Deshkar (2018). Rhabdovirus lecture. D.Y Pathil Medical College,Kolhapur. Slideshare. Retrieved on 1st June 2020 from https://www.slideshare.net/deshkar/rhabdovirus-lecture Herpes simplex virus (2020). World Health Organization. Retrieved on 1 st June 2020 from https://www.who.int/news-room/fact-sheets/detail/herpes-simplex-virus  If you can't fly, then RUN. If you can't run, then WALK. If you can't walk, then CRAWL. But whatever you do, YOU HAVE TO KEEP MOVING. Martin Luther King, Jr. – Civil Rights Activist and Pastor We can only see a SHORT distance ahead, but we can see PLENTY there that needs to be done. THANK YOU Alan Turing – British Computer Scientist