Permissive
Encyclopedia
When a cell or host is defined as permissive in virology
, it refers to the fact that the virus
is able to circumvent host defenses and is able to replicate. Usually this occurs when the virus has modulated one or several of the host cellular intrinsic defenses, and the host immune system
. The permissive state of a host has now been determined to be the primary factor in determining whether a virus will cause pathological symptoms in a host.
-lethal myxoma virus
. Many species of rabbit cells in culture (without the presence of any antiviral defenses that would normally be in a host) can be infected by the myxoma virus, causing infection and cell death. However, inoculation
of the myxoma virus in many species of rabbit shows that only one species of rabbit is affected, the rest being completely unharmed by the virus (lack of even viral shedding
). This has been determined to be a result of the myxoma virus's inability to suppress other species' interferon
expression, and hence resulting in the interferon in turn suppressing the myxoma virus.
This is a result of the positive susceptibility of many species of rabbit's cells, but negative permissibility of all but one of the rabbit species' cells.
Virology
Virology is the study of viruses and virus-like agents: their structure, classification and evolution, their ways to infect and exploit cells for virus reproduction, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy...
, it refers to the fact that the virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
is able to circumvent host defenses and is able to replicate. Usually this occurs when the virus has modulated one or several of the host cellular intrinsic defenses, and the host immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. The permissive state of a host has now been determined to be the primary factor in determining whether a virus will cause pathological symptoms in a host.
Susceptible versus Permissive
The significance between the difference of the two has now been elucidated with study of the rabbitRabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
-lethal myxoma virus
Myxoma virus
The Myxoma virus causes Myxomatosis in rabbits and was used as a pest control in Australia.- Structure :Virions are enveloped, have a surface membrane with lateral bodies. The envelope contains host-derived lipids and self-synthesized glycolipids. They are brick shaped and are about 250 nm in...
. Many species of rabbit cells in culture (without the presence of any antiviral defenses that would normally be in a host) can be infected by the myxoma virus, causing infection and cell death. However, inoculation
Inoculation
Inoculation is the placement of something that will grow or reproduce, and is most commonly used in respect of the introduction of a serum, vaccine, or antigenic substance into the body of a human or animal, especially to produce or boost immunity to a specific disease...
of the myxoma virus in many species of rabbit shows that only one species of rabbit is affected, the rest being completely unharmed by the virus (lack of even viral shedding
Viral shedding
Viral shedding refers to the successful reproduction, expulsion, and host-cell infection caused by virus progeny. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses may begin to leave the cell by several methods.The term is used...
). This has been determined to be a result of the myxoma virus's inability to suppress other species' interferon
Interferon
Interferons are proteins made and released by host cells in response to the presence of pathogens—such as viruses, bacteria, or parasites—or tumor cells. They allow communication between cells to trigger the protective defenses of the immune system that eradicate pathogens or tumors.IFNs belong to...
expression, and hence resulting in the interferon in turn suppressing the myxoma virus.
This is a result of the positive susceptibility of many species of rabbit's cells, but negative permissibility of all but one of the rabbit species' cells.