Pathogenesis Flashcards
Def. pathogenesis, disease, virulence
Pathogenesis: entire process by which viruses cause disease
Disease: harmful pathologic consequence of infection
Virulence: relative capacity of pathogen to cause disease
Outcomes of infection
Productive: new infectious virus produced
Abortive: enters host but no infectious virus produced
Latent: no infectious virus detectable but can be reactivated
Def. susceptible, permissive, cell tropism
Susceptible: cells in which virus can enter, unclear if subsequent steps of viral replication can proceed
Permissive: steps in which all steps of viral replication can proceed
Cell tropism: spectrum of cells/cell lines that can be infected by virus
Requirements for starting infection
Sufficient viral particles must be transmitted.
Cells at site of infection must be accessible, susceptible and permissive.
Antiviral responses must be absent or insufficient.
Portals of entry
Conjunctiva, alimentary tract, respiratory tract, urogenital tract, capillaries etc
Protection of respiratory tract
Mucus, ciliary movement and macrophages protect respiratory tract against infection.
Infection of respiratory tract, NA?
Infected part determines disease.
Antiviral defenses.
Neuraminidase facilitates mucus penetration by destroying sialic acid.
How does NA promote virus infection?
Promotes viral release from infected cells.
Allows virus to penetrate mucus.
Def. local/disseminated/systemic infection
Local: spread limited to site of entry
Disseminated: spread beyond site of entry
Systemic: spread to several organs
Viral release in polarized cell - consequence?
Site of release can determine whether virus spreads locally or is disseminated.
Apical: local
Basolateral: disseminated
(determinant of release: GP sorting)
Neuronal vs hematogenous spread
Viruses can use blood/lymph (Measles, Mumps) or neurons (Herpes, Rabies) for dissemination.
Neurotropic, - invasive, -virulent
Neurotropic: can infect neuronal cells
Neuroinvasive: can enter CNS
Neurovirulent: can cause disease of nervous tissue
Invasion of organs detemrined by…
..properties of the endothelium (continuous/fenestrated/sinusoid with macrophages)
Viral trojan horses
Cells can ferry the virus from sites of entry to target organs:
Eg HIV > transported by DCs to lymphoid tissues
Methods to analyze pathogenesis
Monitor patients.
Experimental infection of animals.
Histopathology.
