Viral Pathogenesis Flashcards
1
Q
What are the stages of viral pathogenesis and infection?
A
- Animal vs Cell
- Entry into the host - Absorption
- Primary replication - Penetration
- Spread through the host - Uncoating
- Cell and tissue tropism - transcription
- Host immune responses - Translation
- Secondary replication - Replication
- Cell injury - Assembly
- Persistence - Release
2
Q
What is the Cytopathic effect?
A
- Can be seen in cell culture as:
- Cytoskeletal disruption
- Inclusions
- Syncytia
- Necrosis
- Apoptosis
- Lysis
- CPE caused by virus infection is not an unintended consequence of virus infection on the host cell
- Normally part of the virus infection/replication process
3
Q
What is an Inclusion body?
A
- Viral replication complexes in the nucleus or in the cytoplasm
- Cells may stay intact, but form “inclusion bodies”
- Inclusions are assembled in the nucleus or cytoplasm for synthesis of viral nucleic acids and assembly of virions
4
Q
What is a Syncytium?
A
- Fusion of cells into a single multinucleated cell
5
Q
Why study infection of cells?
A
- Diagnostic tool
- Obtain a pure virus culture
- Understand basic biological process related to pathogenesis
- Develop and test antivirals and vaccines
- Replace the use of live animals
6
Q
How do viruses cause disease?
A
- Virus enters the host
- Primary replication of the virus
- Spread in the host
- Fate of the virus infection
- cleared
- persistent
- Acute
- Benign
- Transmission to another host
7
Q
What do viruses need for a successful infection?
A
- Enough virus to infect
- Susceptible and permissive cells
- Host defenses must be compromised or not effective
8
Q
How many virions are enough to cause infection?
A
- Varies a lot with the host and the virus
- Health of host - immune compromised
- Age of Host - young or old
- Behavior of host - outside a lot for vector-borne viruses
- Virulence of the virus
9
Q
How do viruses survive outside a host?
A
- Some don’t
- Some stay in body fluids or fecal-oral
- Some survive the environment
10
Q
How can a Virus enter the host?
A
- Something needs to compromise the barrier for the virus to infect
- Virus get through the skin or mucosal membranes:
- Skin - puncture
- Eye - conjunctiva infected
- blinking is a host defense
- Alimentary tract - abrasions
- Urogenital tract - abrasions
- Mucosal Membranes of the Respiratory tract
- does have host defenses such as mucus, cilia, macrophage
11
Q
Why is the skin a good barrier to viruses?
A
- low pH 5.5
- other microorganisms
- also desiccates the virus
12
Q
Which viruses enter through the skin?
A
- Poxviruses - mouse, cow, rabbit infect through breaks in the skin
- Papillomavirus - sexual contact
- Rhabdovirus - Animal bite
- Arboviruses - via the bite of an infected arthropod
13
Q
How do viruses enter through the respiratory tract?
A
- Barriers:
- Mucus, cilia
- Humoral and cellular immunity
- Viruses enter through droplets of saliva
- Environmental factors are important to stability of aerosolized virions
- Temperature
- humidity
14
Q
What viruses enter through the respiratory tract?
A
- Upper:
- Arenaviruses, coronaviruses, respiratory syncytial virus (RSV), coxsackievirus
- :Lower
- RSV, Influenza
- Entry to respiratory tract leading to systemic spread:
- Hantavirus, poxvirus, arenaviruses
15
Q
How is the GIT susceptible to infection?
A
- Small intestine is a selectively permeable barrier
- There is direct contact with the outside
- Contains polarized epithelial cells
-
Localized Infections:
- stay in the epithelial cells next to the intestinal lumen
- Coronavirus, rotaviruses
- stay in the epithelial cells next to the intestinal lumen
-
Systemic infections:
- spread within the host
- enterovirus, reovirus, adenovirus
- spread within the host