Intro to Viruses Flashcards
Which antibodies arise during a viral infection?
IgM arises acutely
IgG arises during recovery
what sort of virus is HIV?
retro RNA virus
what is the ‘envelope’ of a virus derived from?
derived from the ‘budding’ process
What ways can viruses spread between cells?
- Intracellular (cell - cell) via intracellular bridges
- Extracellular - released from infected cell and spreads to other cells locally and distally (lymphatic cells)
- neural = peripheral nerves to CNS
- Nuclear - viral genome incorporated in host genome and passed on to succeeding cell generations
what do you use to visualize viruses?
electron microscopy
how do viruses replicate?
- attaches to host cell recpetor
- virus internalized into cell via endocytosis
- viruses ‘uncoat’ to allow nucleic acid to enter the cytplasm and nucleus
- one way or another, the protein is made for the virus using host cell mechanisms (virion assembly)
- the protein is exocytosed and matures outside of the host cell into a new virus
what are the properties of enveloped viruses?
they ARE sensitive to drying, heat, detergents, acid etc.
therefore they must stay wet during transmission, they transmit in large droplets and secretions, cannot survive the GI tract, and they do not need to kill cells in order to spread
what sort of virus is Polio?
RNA
what sort of virus is the Varicella Zoster virus?
(chickenpox)
DNA Herpes virus
what is the role of the envolope?
antigens on the envelope stimulate host immune response
confers a distinctive serological characteristic - can be diagnosed
proteins on envelope can bind to receptor sites on the host cells and some viruses have enzymes on the envelope which helps the virus spread between cells
what sort of virus is the herpes simplex virus?
DNA virus -
what is an example of a non-specific vs. antigen specific immune response
non-specific = fever, high WCC, interferon production
specific = T-cell and B-cell activation , antibody production
what are the components of a virus?
Envelope (only on some viruses)
capsid (proteinaceous coat)
Nucleic Acid (DNA or RNA)
what differnet effects can a virus have on cells?
- Cytopathic = death of cells
- Transformation effect= cell becomes malignant or pre-malignant
- Latent effect = virus remains and may subsequently reactivate
what is ‘cell tropism’?
a viruses affinity for a specific body tissue
ex) influenza has a tropism for the respiratory tract) and herpes simplex virus has a tropism for the skin
Tropism is determined by cell receptors for the virus, ability of the cell to suppor virus replication , physical and enzymatic barriers
how do we use Microscopy to detect viruses?
- Electron Microscope = visualize the virus
- fluorescent microscope = detect virus using commercially produced antibodies
- Light Microscope = detects virus-induced masses within cytoplasm of cells
what is the role of the ‘capsid’
remember capsid = coat
protein shell composed of capsomers surrounding the genome - forms a protective shield
comes in different shapes
It introduces viral genome into host cells by protein interaction with host cell receptors
contains antigens which stimulate the host immune systema and give it different serological characteristics
what sort of virus is the influenza virus?
RNA virus
what are the properties of a non-enveloped virus?
capsid is resistant to drying, heat, detergents, acids, proteases
therefore, it can survive in teh GI tract, retain infectvity upon drying, survive on environmental surfaces, spread easily via fomites etc.
What makes viruses unique?
contain only one type of Nuc. Acid. DNA or RNA
totally dependent on host cell for replication
very small
