Viral Pathogenesis Flashcards Preview

Microbiology > Viral Pathogenesis > Flashcards

Flashcards in Viral Pathogenesis Deck (52)
Loading flashcards...

modes of transmission

direct contact, injection, transplantation, fecal oral (+/- envelope important)


how often are we exposed to pathogen

constantly; they are everywhere though they vary based on living conditions


reasons viruses continue to persist in population

health, nutrition, genetic makeup, age, immune status


what is an outbreak

introduction of a virus into a new location which originates from a common source


how is the identification of the source of an outbreak so important

to stop the outbreak


what is an epidemic

introduction of a new strain of virus to an immunological naive population which occurs over a LARGER geographical area


what is a pandemic

worldwide epidemic


are a majority of viral disease symptomatic

no but those that target essential tissues/organs --> serious disease


symptoms and severity of viral diseases depend on what

• Patient’s ability to prevent/resolve infection
• Virulence and target tissue
• Ability to repair damage


what are some mechanisms of viral pathogenesis

• Circumvent protective barriers
• Evade immune control
• Kill cells or trigger destructive immune and inflammatory response (control infection)
• Possibly transform cells


what are some inherent barriers for host defenses

– Skin
– Mucous
– Ciliated epithelium
– Low pH


what are some induced barriers for host defenses

– Fever
– Low pH
– Humoral and cellular components


what are some non specific host defenses

– Interferon
– Complement
– Other cytokines


what are some specific host defenses

– Antibody production
– Specific immune system


when does transcription of interferons occur?

transcription only occurs after exposure to an inducer – viral infection, dsRNA – RNA viruses best


what do viruses do to our immune responses

it suppresses them


what can immune response to viral infection cause

tissue injury


example of immune response to viral infection causing tissue injury: what can circulating immune complexes lead to?

deposits ---> arthritis

aka CMV


in dengue, what is the mechanism in which tissue injury happens?

hemorhagic shock syndrome: fixation of complement by circulating immune complexes 􏰁--> release of products via complement cascade 􏰁--> sudden increase in vascular permeability, shock, death


basic steps of viral disease

• Acquisition
• Initiation of infection at the primary site
• Incubation period (amplification, spread to secondary site maybe)
• Replication in target tissues
• Immune responses (limit AND contribute)
• Transmission
• Resolution or persistent infection


can viruses cause more than one disease



what is it called for viruses to lose their virulence



result of viruses encoding their virulence factors

– Promoting replication, transmission
– Access and binding to target tissue
– Escape of immune system


outcomes of viral infection

1) Abortive - Failed “attempts”: no virus multiplication
2) Lytic - Cell death
3) Persisting - Infection without cell death, selection of ideal target cell subsets (Chronic – nonlytic, productive)
4) Latent-recurrent infection - Presence of virus without virus production but with potential for reactivation


difference between replication of virus during acute infection and during chronic infection via continuous productive infection

both of them after virus infects host cell --> entry and uncoating --> gene expression --> assembly and release (they have antigens for B and T cell recognition)

but in chronic a variant strand of the virus (one that was not killed) will begin the process all over again and produce variant antigens for B and T cell recognition


how is latency established

-modulation of viral gene expressions
-viral subversion of cellular apoptotic pathway
-avoidance of clearance by the immune system
-selection of cell subsets ideal for long-term maintenance of the viral genome


when does persistence occur in viral infections

when the cell is not killed - could be chronic, latent, recurrent, immortalizing, transforming


what are determinants on if a virus will be lytic or persistent

-access to target tissue
-ability to cross barriers, establish viremia, and spread


viruses apply a lot of avoidance strategies to persist. what are some of these strategies?

• viruses can alter / interfere with the processing of viral peptides by professional APCs
• can downregulate co-stimulatory and/or MHC molecules (required for T cell signaling, expansion)
• inhibit the differentiation of AP conventional dendritic cells, infect effector T and B cells directly

all of these are just ways in which the infected host's innate or adoptive immune system is suppressed


what does the susceptibility of host cell to virus depend on?

presence of receptor for virus attachment