Extracellular Immunity 2 Flashcards
What are the two mosquito-born pathogens? (2)
Mosquito-borne viruses:
– Arthopod-borne viruses
– Arboviruses
– Mosquitoes, ticks, midges
Mosquito- borne parasites
– Malaria
– Plasmodium
Describe what happens when a mosquito bites (3)
Mosquitoes deposit saliva and virus
Saliva is biologically active and inflammatory
Little direct transfer to blood
Immune response to bite and pathogen
Describe the transmission cycle (4)
Arboviruses must replicate to high levels in the blood
‘Not just syringes’ - virus has to infect the mosquito as well the human
Day biting mosquitoes
Dense urban environments
What are the problems with arboviruses and their diseases (6)
Outbreaks hard to predict
Difficult to stockpile
Diagnosis?
No licensed antivirals
Prognostic indicators?
Very few effective vaccines
Arboviruses and their replication (10)
Injected into the skin
Receptor-mediated endocytosis (virus binds to receptor on surface)
Virus material enters cell by acidic pH mechanism
Changes shape and membrane of virus and fuses and becomes part of the end-some membrane releasing virus into the cytoplasm and taking over the cell:
Genome looks like a cellular
mRNA
Uses cellular machinery to
replicate
Translated into polyprotein
Structural proteins
Non-structural proteins (replication and immune
evasion)
Each arbovirus family has
distinct way of replication
Where do arboviruses replicate and where do they not (1)
Replicate in the cytoplasm, NOT nucleus
What is dengue? (3)
Spread by infected Aedes species mosquito
Four related viruses – each has a serotype
RNA genome – replicates in cytoplasm complications occur when infected 2nd time with different serotype
What are the symptoms of dengue? (5)
Fever with any of the
following:
- often confused with other
arbovirus infections
- Severe dengue – sudden
onset haemorrhagic fever
- Severe bleeding
- Organ shut down
What happens when you get dengue infection the second time? (3)
- Severe dengue – sudden
onset haemorrhagic fever - Severe bleeding
- Organ shut down
What is Zika? (5)
Clinically similar to dengue
Infects developing CNS; diagnosis?
Eye problems
Guillain-Barré complications (adults)
Spread by Aedes
What is Microcephaly? (2)
Shrunken head
Calcium deposit and fluid
Give an example of re-emerging vector-borne disease (1)
Chikungunya
What happens during biting? (5)
Innate immune response to the bite / saliva
Innate immune response to pathogen
Activation of antigen presentation
Monocytes and dendritic cells can become infected with viruses which helps to spread the virus around the body
Describe innate Immunity to pathogens (3)
Initial response to microbes to limit spread
Activates / informs adaptive responses
Different pathogens have different “shapes”
What is the strategy of the host against the pathogen (6)
Microbes are heterogeneous and mutate
Recognised by Pathogen Associated Molecular Patterns - PAMP
- produced only by the microbe – specific
- usually essential for microbe survival or pathogenicity – microbes mutate
- shared by entire class of pathogen e.g. RNA genome – evolutionary conserved
RNA genome recognised by pattern recognition receptors
What part of the virus do PRRs
recognize? (4)
Have to be
– unique i.e. different to us
– common to many viruses
– essential for life cycle
Structural components?
- Varied/mutate
Their genome?
* ssRNA, DNA, dsRNA
* Tri-phosphate 5’ cap (5’ppp)
How they replicate?
* Intermediate RNA species e.g. dsRNA
What effect do type 1 interferons have (2)
Have potent anti-viral effects - stop the cell from being susceptible to infection
Most viruses have strategies to counteract IFN system
What is the problem with dengue? (8)
4 types of Dengue virus
Reinfection with different type bad
Blood vessels haemorrhage
IgG responses are responsible
Virus-IgG complex is eaten by
phagocytes
Phagocytes become infected
More virus
More inflammation
Describe malaria (4)
Plasmodium parasites via Anopheles mosquitoes
Fever (mild) after 10-15 days
Progresses to anaemia, cerebral
Anti-malarials (preventative) or therapeutic (artemisinin-based)
Describe the immune response to malaria (4)
Adaptive immune responses; Th1, CD8 and IgG
Malaria has evolved to switch its immunodominant peptides (variant surface antigens)
Immune system playing catch-up
Repeated exposure - immunity
