Viral Dz Overview Flashcards
What are the parts of a virus?
Nucleic Acid Core
Capsid
+/- Envelope
What is the Nucleic Acid Core?
DNA, RNA, or dsRNA
What is a capsid?
an arrangement of protein subunits that surround the nucleic acid core
What is the envelope?
a lipoprotein coating that is usually gained from the host cell;
surrounds the capsid
Infectivity vs Virulence
The ability of different viruses and their strains to…
Infectivity –> infect a host
Virulence –> produce Dz
List the 4 steps needed for a virus to infect a host
- Adsorption
- Uncoating
- Replication
- Viral Assembly
What happens during adsorption?
the virus binds and enters the host cell;
the virus has adapted to be able to bind to a receptor present on the surface of the host cell
What happens during uncoating?
Now inside the host cell, the virus capsid breaks down, releasing nucleic acid into the host cell’s cytoplasm.
What happens during replication?
the virus inhibits the host cell’s ability to make its own DNA/RNA/proteins;
now the virus can use that same equipment to reproduce its viral genome
What happens during viral assembly?
after the viral proteins and nucleic info has been made inside the host cell, a new virion is formed; many virions can be made within a host cell, which can result in 3 different outcomes for the host cell.
What are the 3 consequences for a host cell infected by a virus?
- Little to no damage if the virus leaves via exocytosis (results in enveloped viruses)
- Lysis (results in non-enveloped viruses)
- Malignant transformation into a tumor (if virus damages host DNA during viral replication process)
Define acquired immunity
the ability of the body to recognize previous invaders when they attempt to re-invade and and to respond even more quickly with more assertiveness and efficacy
Name and describe the 2 types of acquired immune responses
- Humoral- targets extracellular invaders; uses antibodies
2. Cell Mediated- targets intracellular invaders; uses cytotoxic cells
How is acquired immunity related to vaccination?
Vaccines introduce an antigen (ie a killed or modified live virus) into the body to stimulate the humoral immune response. Lymphocytes begin to make antibodies against the antigen, which creates a template for if the actual virus enters the body.
What is the “memory response”?
The response that occurs at exposures after the first initial exposure.
What does the memory response indicate?
the immune system’s ability to remember the first exposure and respond accordingly
Why does the memory response occur?
Because memory T-lymphocytes have been made that last longer and retain their ability to recognize the specific antigen and immediately initiate a response to the antigen
How do vaccines work?
The patient is exposed to the selected antigen via injection/instillation –>
the body takes appx 1 wk to produce detectable antibody levels in the blood –>
after peek response occurs, antibodies decrease and disappear –>
the patient is exposed a second time to that same antigen –>
the body responds faster and with longer lasting antibody responses
What is the point of booster shots?
they get the body to respond faster then before with a longer lasting antibody response
Is there a maximum antibody response that can be reached?
Yes
How do neonates get maternal antibodies?
- in the womb
- via colostrum
Why are maternal antibodies a problem with vaccines?
They can bind to the vaccine antigens before the body is able to recognize the antigen is even there. This means antibodies won’t be made to target that antigen.
How long do maternal antibodies hang around? What does this mean for puppy/kitten vaccination schedules?
They decreased naturally as time goes on, but how quickly they decrease really varies by individual. By vaccinating them every 3-4 weeks until appx. 16 weeks of age, we are most likely able to get an effective first and second exposure.
Why do we still recommend that puppies/kittens don’t have access to unvax’ed animals/areas where the virus may exist until after their vaccine series is completed?
There will likely still be a window of time where maternal antibody levels are high enough to block vaccine antigens but not high enough to protect against exposure to the virus.
