viral pathogenesis L16

Question 1

route of horizontal transmission

Answer 1

direct contact like secretions and blood
respiratory
contaminated inanimate objects
faeceal/oral
insect vector
zoonoses

Question 2

route of vertical transmissions

Answer 2

mother to foetus - transplacental

Question 3

how can transmission occur

Answer 3

occurs with or without disease symptoms
during asymptomatic shedding of virus
during incubation period before symptoms

this results in primary infection and reactivation of some viruses can result in secondary diseases

Question 4

what influences that host-organism relationship

Answer 4

hosts primary physical barriers
hosts immunologic ability to control and eliminate the invading organisms
organisms ability to evade destruction
pathogen virulence factors
ability to spread in body

Question 5

cycle of infection

Answer 5

entry
primary site of replication
spread in host
secondary site of replication
shedding
transmission

Question 6

what is acute viral infection

Answer 6

rapid onset and short duration
virus replicates quickly and causes symptoms fast
usually cleared by immune system

Question 7

what is chronic viral infection

Answer 7

a long term infection where the virus remains in body and continues to replication, causing ongoing or recurrent symptoms
immune system does not fully clear virus

Question 8

what is a latent viral infection

Answer 8

virus remains in body in a dormant / inactive state after initial infection
no symptoms during latency but can be reactivate later and replication only resumes occasionally

Question 9

abortive infection

Answer 9

this occurs when virus enters cell but cannot complete its replication cycle due to host restriction factors that block viral replication

no new virus is produced and infection fails

Question 10

host cell protein translation switch off

Answer 10

this is where the virus shuts down the host protein synthesis in order to prioritise viral protein production and disable the immune response

cell cannot function properly

Question 11

apoptosis due to viral infection

Answer 11

either as a host defence role - infected cell triggers self-destruction to limit virus spread

or as viral evasion to block apoptosis to survive longer

Question 12

transformation of cells due to virus

Answer 12

some virus cause cells to divide uncontrollably leading to immortalisation or tumour formation

Question 13

virus effecting PRRs

Answer 13

some viruses hide or block PRR signalling to evade detection

Question 14

interferons

Answer 14

these are small molecules that are produced in response to viral infection that play a major role in inhibiting viral infection in cells

Question 15

IFN - ALPHA

Answer 15

produced by all cells, inducted by viral infection - mainly dendritic cells or virus infected ones
detected by PRRs and alerts nearby cells
type 1 interferon

antiviral defence, immune modulation (increase NK activity, increase MHC1 expression and T cells activation) or apoptosis

Question 16

IFN - BETA

Answer 16

type 1 interferon produced mainly by fibroblasts, epithelia cells and non-immune cells
released early in immune response
antiviral effect, immune system activation (increase MHC 1 and NK) and signalling to bind to IFNAR to activate interferon stimulated genes (ISGs)

Question 17

IFN-y

Answer 17

TYPE 2 interferon produced by T cells, important in adaptive immune response

immune activation to increase MHC 1 2, activate macrophages and CTL, antiviral and anti tumour effects and regulation immune response

Question 18

IFN-lambda

Answer 18

type 3 interferon produced by epithelial cells, fibroblasts and myeloid cells

antiviral response especially at mucosal surfaces
immune modulation, NK and macrophage activation, enhance dendritic cells and induce T cell differentiation and local immune response

Question 19

viral immune evasion techniques - secreted modulators

Answer 19

viruses will produce proteins hat mimic host cytokines or chemokine or bind to their receptors to either block or interfere with immune signalling

Question 20

viral immune evasion techniques - modulators on infected cell surface

Answer 20

virus produce proteins that interfere with immune cell signalling by mimicking or blocking host receptors or molecules
produced decoy receptors that bind to immune molecules and prevent them from activating immune system

Question 21

viral immune evasion techniques - stealth/latency

Answer 21

virus remain dormant or express minimal proteins to avoid detection

Question 22

viral immune evasion techniques - antigenic hypervariability

Answer 22

rapid mutation of antigens on viruses help to escape immune recognitions

Question 23

viral immune evasion techniques - block adaptive immune response

Answer 23

viruses can block T cell activation or antibody production or target immune cells and kill them selves to prevent a strong adaptive response

Question 24

viral immune evasion techniques - inhibit complement system

Answer 24

virus can interfere with complement system by producing proteins that bind to complement proteins to inhibit proteins

Question 25

viral immune evasion techniques - interfere with PRRs

Answer 25

block or inhibit PRRs that normally detect viral RNA or DNA

Question 26

viral immune evasion techniques - block interferon and/or inflammatory cytokines

Answer 26

produce interferon binding proteins to block action or interfere with host ability to produce cytokines to reduce immune response activation