(BQ) Part 1 book "Medical microbiology and infection at a glance" presentation of content: Influenza viruses, parainfluenza and other respiratory viruses, filamentous fungi, yeast infections, intestinal protozoa, gut helminths, tissue helminths, systemic infection,. and other contents. | 29 Virus structure, classification and antiviral therapy Virus proteins Possible structural components Envelope from host cell Nucleoprotein Capsid forming virus structure Nucleic acid ds DNA +ss RNA –ss RNA +ss RNA Parvovirus Picornaviridae Paramyxoviridae Retroviridae (HIV) Calicivirus Herpesvirus ss DNA Orthomyxoviridae Pox virus DNA RNA Togavirus & flavivirus Arenavirus Coronavirus Adenovirus +ss RNA Hepadnavirus +ss RNA Viral proteins New virus Viral classification Viral classification is based on the nucleotides in the virus, its mode of replication, the structure and symmetry of the structural proteins (capsids) and the presence or absence of an envelope. Genetic material and replication DNA viruses • Double-stranded DNA viruses include poxviruses, herpesviruses, adenoviruses, papovaviruses and polyomaviruses. • Single-stranded DNA viruses include parvoviruses. Rhabdoviridae –ss RNA +ss RNA New virus Host membrane Viral proteins Enveloped virus –ss RNA New virus Viral proteins DNA viruses usually replicate in the nucleus of host cells by producing a polymerase that reproduces viral DNA. Viral DNA is not usually incorporated into host chromosomal DNA. RNA viruses RNA viruses possess a single strand of RNA and adopt different reproductive strategies: • RNA sense (positive) may serve directly as mRNA and be translated into structural protein and an RNA-dependent RNA polymerase. Medical Microbiology and Infection at a Glance, Fourth Edition. Stephen H. Gillespie, Kathleen B. Bamford. © 2012 John Wiley & Sons, Ltd. 64 Published 2012 by John Wiley & Sons, Ltd. • RNA antisense (negative) contains an RNA-dependent RNA polymerase that transcribes the viral genome into mRNA. Alternatively, the transcribed RNA can act as a template for further viral (antisense) RNA. • Retroviruses have single-stranded sense RNA that cannot act as mRNA. This is transcribed into DNA by reverse transcriptase and incorporated into host DNA. The .
