Flashcards
Viral Pathogenesis
Flashcards do conjunto (52)
- 1What is viral pathogenesis?Process by which viruses cause disease
- 2What are the 5 questions to answer when considering viral pathogenesis?How the virus enters the host
What cells the virus targets
What the normal function of these cells is
How the virus interferes with cell function
Effect of loss of function on the host - 3Give 5 routes of virus entry into the hostRespiratory
Oral
Cutaneous localised infection
Percutaneous injection
Sexually transmitted - 4What are the consequences of viral infections in the respiratory tract?Inflammation
Loss of cilia
Mucociliary clearance impaired - 5How does coronavirus cause diarrhoea?Enterocytes in villi are damaged but the crypts remain intact
This causes secretion of fluid but no absorption = diarrhoea - 6Why is recovery from coronavirus rapid?Crypts remain intact therefore villi are able to rapidly regrow
- 7Give an example of a virus that causes cutaneous localised infectionsPapilloma virus
- 8Give 3 ways in which viral infection may enter the host through percutaneous infectionBites from infected animal (saliva)
Bites from insect vectors
Iatrogenic e.g. dirty needles - 9What is the technical term for viral entry into the blood via an insect vector?Viraemia
- 10How are some viruses able to survive in an insect vector?Replication cycle both in the vector and the definitive host
- 11What determines the cell type targeted by a virus?Specific receptor-ligand interactions define the host species and cell type a virus may infect
- 12How does HIV bind to human CD4 T lymphocytes?Envelope glycoprotein binds with high affinity to CD4
Conformational change allows low affinity interaction with chemokine receptors CCR5 or CXCR4
Further conformational change = virus envelope fusion with cell membrane - 13What does fusion with the cell membrane allow?Viral genome is able to enter the cell
- 14Why will HIV not infect cats?Receptor-ligand interaction is highly specific
Often several amino acid differences between the same molecule (CD4) in different species, altering the bonding
This restricts virus host range - 15How does FIV bind to cat CD4 T lymphocytes?FIV envelope glycoprotein binds with high affinity to CD134 present on cell surface
Conformational change allows low affinity interaction with chemokine receptor CXCR4
Futher conformational change allows membrane fusion - 16Why is human CD134 unable to replace feline CD134 in FIV infection?High affinity interaction
FIV can only bind to feline CD134 which has aspartic acid residues at positions 60 and 62 - 17Why is human CXCR4 able to replace feline CXCR4 in FIV infection?Low affinity interaction so less specific
- 18What is an advantage to viruses of non-specific ligand binding?Wide host range potential
- 19Give an example of a virus with non-specific ligand bindingInfluenza haemagglutinin
Binds sialic acid (ubiquitous)
Infection of cells dependent on host protease to cut hinge - single amino acid change in cleavage site alters host specificity and severity of disease - 20What are lytic infections?Acute virus infections that cause cell death by lysis, resulting in complete loss of function
Release of new virus particles - 21What are the 2 types of spread of newly released viral particles?Local spreading
Systemic spread in blood or lymph - 22What are latent viral infections?Virus infections are non-cytopathic i.e. persist within cell without causing cell death
New virus particles can be released without killing the cell - 23Why are latently infected animals problematic?Source of infection for others
- 24What is persistent infection?Failure of immune response to the virus e.g. recognising it as self
- 25What are the 2 ways in which the enzymes which replicate host DNA can also be made to replicate viral DNA?Episome
Integrated into host cell genome - 26Why can some viruses cause tumours?Enhanced cell growth
Viruses can manipulate cell replication to increase the number of cell divisions and therefore the number of infected cells - 27Give 3 substances released by epithelial cells in response to viral infectionInterferon
Pro-inflammatory cytokines such as interleukin-1, 6 and 8
Chemokines - 28Give 2 viral products that can stimulate an interferon responsePoly uracil
Double stranded RNA - 29Give the 4 steps of the interferon responseDetection of virus products stimulates interferon response factor to move to nucleus
Stimulates gene transcription to synthesise interferon
Released from cell
Binding to other cells causes synthesis of proteins with antiviral activity - 30Give 4 effects of interferonSynthesis of anti-viral proteins in cells
Increases MHC expression
Activates macrophages and dendritic cells
Recruits and activates NK cells - 31Give 4 functions of activated macrophages and dendritic cells in the response to viral infectionSecrete interferon
Produce cytokines
Present antigen to T cells
Activate NK cells - 32Give 3 endogenous pyrogensInterferon
Interleukin 1
TNF alpha - 33Give 2 binding sites of endogenous pyrogens that can cause feverOpioid receptors on nerve cells in the circumventricular organ (connected to the hypothalamus)
Interferon receptors on the endothelium of the central nervous system - 34Give 2 additional ways that endogenous pyrogens can cause feverActivation of COX-2 leading to increased prostaglandin E2
Altered firing rate of temperature sensitive neurone in the anterior hypothalamus - 35What is the first step in the innate immune response againt viruses?Interferon release in response to pathogen associated molecular patterns
Other pro-inflammatory cytokines also released later - 36Give an example of a drug that targets COX-2 in order to reduce feverParacetamol
- 37What is sickness behaviour?Motivational state responsible for reorganising perceptions and actions, in order to enable sick individuals to cope better with an infection
- 38Give 6 examples of sickness behavioursDecreased motor activity
Social withdrawal and reduced responsiveness
Reduced food and water intake
Increased slow-wave sleep
Altered cognition
Increased pain sensitivity - 39What mediates sickness behaviour?Effects of pro-inflammatory cytokines, especially interleukin-1, on the central nervous system
- 40How does FMD virus enter the host?Ingestion or inhalation
Establishes a primary oro-nasal infection - 41Which molecules are targeted by FMD virus?Attaches to integrins
Integrins bind to an RGD motif in the virus capsid protein which mimics the natural ligand on matrix proteins - 42Where are integrins found at high density?Basal epithelial cells in the oropharynx (expressed at sites with high shear forces e.g. lip and foot)
Become infected by small abrasions or the tonsil crypt - 43The RGD motif is common to all species, so what limits the host range of FMD virus?Does not replicate equally well in all species
- 44Give 3 normal functions of squamous epithelium and basal epithelial cellsProtect sensitive submucosa
Maintain adhesion of epithelium to basement membrane
Repair/regenerate damaged epithelium - 45How does FMD virus affect cell function?Shuts down host cell protein synthesis
Loss of host cell integrity eventually leads to lytic cell death and release of new virus particles - 46Where do released FMD virus particles spread?Spread locally to basal epithelial cells with high integrin expression
Also spread systemically in blood to other sites where integrins are expressed at a high density - 47What does the FMD virus cause in the epithelium and surrounding tissues?Inflammatory response
- 48What causes the early clinical signs of FMD virus such as lip smacking and drooling?Inflammation at site of developing infection increases prostaglandin synthesis
Sensitises local nociceptors causing local pain sensations - 49What causes fever and inappetance in FMD virus?Release of interferons and pro-inflammatory cytokines from infected cells and inflammatory leukocytes
- 50Which 2 areas of the foot have the highest integrin expression?Laminae
Coronary band - 51Why is healing of FMD lesions prolonged?Basal epithelium most affected
- 52If the death rate of FMD is low, why is it such a serious production disease?Problem is pain and production losses NOT death rate
Informações
- Descrição
- Animal Disease 1 (Agents of Disease) FlashCards sobre Viral Pathogenesis, criado por Florence Edwards em 04-12-2016.
- Criado por
- Florence Edwards
- Visualizações
- 1
- Avaliação