Barriers to Infection Flashcards
What is the definition of viral tropism?
What is it dependent on?
Viral tropism is the ability of different viruses to infect different cellular types ultimately to produce a successful infection
- accessibility - virus cannot get to host tissue - e.g Dengue needs arthropod to inject into bloodstream
- susceptibility - receptors available for entry
- permissivity - host cell helps virus complete life cycle by producing proteins
Virus such as HSV are pantropic, and will infect any tissue and cause disseminated infection. Although forms latent state in neurones
What is difference between innate and intrinsic immune defences?
Innate are physical barriers/ mucus membranes/ complement/ antigen-presenting cells
Intrinsic are processes which do not require extra transcription/ translation/ activation - e.g interferons, apoptosis, microRNAs
What are limits to PCR testing, with regards to timing of viraemia?
Viruses primarily live in cells
May be a primary viraemia in initial infection, which then goes away, as viruses cleared from blood.
Lag period as viruses replicate
Then a significant secondary viraemia as viruses are released from cells
If PCR testing performed at specific times when virus is inside cells, it may falsely conclude that there is no infection present.
Also detectable low level viremias may have uncertain clinical significance, particualrly if reactivated viruses
What is the definition of these terms
Neurotropic
Neuroinvasive
Neurovirulent
Neurotropic - can infect neurons
Neuroinvasive - can enter CNS
Nurovirulent - can cause disease in CNS
HIV in semen
Why may the WGS of HIV in the blood and semen differ significantly?
Clonal amplification - one to several virus strains reproduce rapidly in T-cells, in short time frame. So appears to be the dominant homogenous strain, but has just multiplied more
Compartmentalisation - virus reproduces slowly over a long period, that is enough to allow a population genetically distinct from the virus in the blood to be selected
