Virus Families Flashcards
Steps in virus life cycle (6)
- Attachment 2. Entry 3. Uncoating 4. Synthesis of protein and nucleic acid 5. Assembly 6. Release
Important structures in a virus
Virion (entire virus particle); envelope; capsid; nucleocapsid; capsomere genome (nucleic acid)
Virion structures for Rabies
Nucleoprotein, ribonucleocapsid (RNP) phosphoprotein, polymerase, genomic RNA)
Virion structure for HIV
***Nucelocapsid, reverse transcriptase, GP41 (transmembrane glycoprotein), GP120 (docking glycoprotein)
Virion structure for HSV1
***Nucleocapsid, DNA, tegument, envelope proteins, lipid envelope
Enveloped viruses characterisitics
Envelope derived from host cell membranes, membrane composition can be variable depending on which membranes are used (plasma vs golgi), contains virally encoded proteins that are usually glycoproteins, also can contain host cell proteins, envelope glycoproteins form spike on surface
Virion structure
Capsid (coat) protein is the basic unit of structure
Functions of capsid proteins
- Protect viral nucelic acid from environmental stresses 2. Interact specifically with the viral nucleic acid for packaging
- Interact with host receptors for entry to cell
- Allow for release of nucleic acid upon entry into new cell
- Assist in processes of viral and/or host gene regulation
Protein coats
- Icosahedral (spherical, amount of nucleicacid that can be packaged is limited by the size of the particle (closed)
- Helical: Rod shaped, varying widths and specific architectures; no theoretical limit to the amount of nucleic acid that can be packaged “open” ex. influenza, rabies
Viral genome functions
- Genome replication 2. Genome assembly and packaging 3. Regulation of replication cycle 4. Modulation of host defenses. Not in the genome: genes that encode for protein synthesis machinery, energy metabolism, membrane biosynthesis
Enveloped Viruses
Outer enevelope with phospholipids, proteins, glycoproteins, released by budding-some less virulent to cell, sensitive to heat, acids, drying, less likely associated with GI tract disease
Non-enveloped (naked) virus
Outer covering is capsid protein, often cell lysis (some more virulent to cell), resistant to heat, acids, drying, survive the GI tract, some replicate in intestines
Examples of enveloped viruses
Herpes viruses, orthomyxoviruses (influenza), paramyxoviruses (measles, mumps, respiratory synctial virus)
Examples of non-enveloped (naked virus)
Norovirus, rotavirus, adenovirus, paillomavirus, parvovirus
Hepatitius A virus
Picornavirus, +ssRNA
Hep B virus
Orthohepadnavirus, dsDNA
Hep C virus
Hepacivirus, +ssRNA
Hep D virus
Deltavirus, -ssRNA, herpes virus, enterovirus
5 herpes viruses to know
- Herpes simplex virus type 1, Herpes simplex virus type 2, 3. Varicella-zoster virus (VZV), 4. Cytomegalovirus (CMV), 5. Epstein-barr virus (EBV)
HSV-1/HSV-2 (Herpes virus)
Primary infection: Gingivostomatitis (mouth) or genital herpes), Infection via direct contact, reactivation: “cold sore” or genital herpes, multiple other disease processes (encephalitis, hepatitis, etc.)
VZV (Herpes virus)
Primary infection: Chicken pox; reactivtion: Shingles (zoster); varicella much more contagious (1-2 days prior to rash onset until crusted); zoster only by contact, varicella complications: bacterial superinfection; also pneumonitis; hepatitis, encephalitis (ataxia or gneralized), prevention: vaccine
CMV (Herpes virus)
Often asymptomatic, can be “infectious mono”, significant disease processes: congenital infections, disease in immune compromised
EBV (Herpes virus)
Infectious mononucleosis, complications varied-hepatitis, other, sequelae in the immunocompromised host
Influenza A virus
Orthomyxovirus, genome negative sense, single stranded RNA in segments (rotavirus another important GI pathogen with a segmented genome) subtypes named based on envelope hemagglutinin and neuraminidase, important cause of upper respiratory disease and pneumonia
Structure of influenza virus
On the outside: Hemagglutinin (HA), Neuraminidase (NA), M2, M1; On the inside: polymerase proteins
