14 Virology 3 Flashcards
What are some physiological factors in the host that impact viral susceptibility?
-Temperature
-Age
-Nutritional status
-Hormonal status
-Cell differentiation
-Development (maturation/pregnancy)
-Co-infections
-Microbiome
-Immunity to other pathogens
What are the main steps of a viral infection?
Entry
Replication
Spread (in host tissue)
Shedding
Clearance (complete or incomplete from host tissue)
What is primary viremia?
Primary viremia occurs when a virus replicates at the site of infection, replicates, and enters the bloodstream to infect other tissue sites.
What is secondary viremia?
Virus from primary viremia infects other tissues in the host, replicates there, and then puts more virus into the blood
What is the purpose of secondary viremia?
To maximize shedding
Neurons facilitate viral spread for which genera of viruses?
Rhabdoviridae, lyssavirus (Rabies lyssavirus)
Why would a virus affect the CNS if it cannot be shed from there?
-Behavioral modification to facilitate transmission (aggression in carnivores, horses not flicking flies off tail in WNV, etc)
- Immune evasion
Describe how rabies virus uses the CNS to facilitate replication and spread.
Rabies virus enters through a bite wound and is inoculated in the muscle –> replication in muscle –> binds to and infects a motor neuron via compatible receptor –> travels through motor neurons up to CNS –> once in close proximity, it infects the salivary glands –> shedding of virus from apical side of salivary gland cells
What are the 5 routes of invasion for viruses to invade the CNS?
- Sensory neurons of the peripheral neural ganglia
- Neuromuscular junctions from muscles into somatic motor neurons in the spinal cord
- Neurons in the nasal olfactory epithelium
- Infection of leukocytes that can cross the BBB
- Infection of endothelium
Describe how West Nile Virus is transmitted from a mosquito bite to the CNS.
Infection of monocytes/macrophages/dendritic cells in the skin –> travel to lymph node in immune cell –> viremia –> enters CNS in WBC crossing the BBB (unknown if WNV infects endothelial cells)
How does viral replication cause host cell damage?
-Decreased production of proteins
-Selective toxicity of viral protein
What does a cytocidal infection do to the host cell?
Cytopathic effects (cell damage), RNA/DNA synthesis, inhibition of protein, cell death
What are some viral families that cause cytocidal infections?
Alphaherpesviruses
Enteroviruses
Reoviruses
What do persistent productive viral infections do in the host cell?
No cytopathic effects, little metabolic disturbance, continued cell division, some loss of cell function but goal is not to kill cell
What are some viral families that cause persistent productive viral infections?
Pestiviruses
Arenaviruses
Rabies virus
Several retroviruses
