Viruses and immune system evasion Flashcards

Question

What is hepatitis A virus?

Answer 1

``` 27-28 nm icosahedral non-enveloped ssRNA (linear) vaccine available ``` 15-45 days incubation period acute onset affects children and young adults more commonly faecal oral transmission and low rate sexually Dx: IgM serology Mild infection 0.1% fulminant disease does not become chronic 0.2% mortality

Answer 2

``` 42nm nucleocapsid core enveloped (contains HepBsAg) can circulate as incomplete (surface Ag only to trick host immune system) ss/ds DNA (circular/plasmid) ``` 20-150 days incubation period insidious or acute onset affects children or young adults (more common) percutenous, perinatal or sexual transmission Dx: IgM serology and PCR Often asymptomatic Can become chronic (especially when infected in early childhood) 0.5-2% cancer risk

Answer 3

HepB virus itself lacks oncogenes Long latency between HBV and hepatocellular carcinoma development viral DNA integrates into genome, which can itself disrupt host oncogenes Also, chronic inflammation can increase turnover/regeneration via stimulation of proliferative genes

Answer 4

30-60nm enveloped ssRNA (linear) positive sense RNA (can act as mRNA for viral protein synthesis) 15-150 days incubation period insidious onset affects all ages, more common in adults percutaneous (+perinatal+sexual) transmission Dx: IgG serology (no reliable IgM test) + Blood PCR 0.1% fulminant disease 75% develop chronic infection cancer risk (of HCC) 0.2% mortality

Answer 5

``` highest: IVDU then: - sexual/STD history - prison - transfusions - Haemodialysis (long term) ```

Answer 6

35-37nm hybrid particle (HDV core, HBsAg) ssRNA (linear, -ve sense) Can only be infected via co-infection with HepB ``` 15-150 days incubation period insidious or acute onset any age affected percutaneous, perinatal and sexual transmission can be severe disease 5-20% fulminant disease chronic infection possible 2-20% mortality HBV vaccine (prophylaxis) Dx: HDV Ab monitor HDV RNA levels by PCR ```

Answer 7

32-34nm non-enveloped icosahedral ssRNA (linear, +ve sense) ``` 15-60 days incubation period acute onset affects young adults faecal oral transmission generally mild but can be severe in pregnancy 1-2% fulminant disease 0.2% mortality Dx: IgM serology ```

Answer 8

HBV HCV HDV (remember only with HBV)

Answer 9

rhinovirus (common cold) influenza rotavirus, norovirus (diarrhoea) adenovirus (sore throat)

Answer 10

change viral proteins (immune system will not recognise new proteins) e.g. influenza strains different types of the same virus (e.g. rhinovirus and adenovirus) infect at time when immune defence is compromised e.g. varicella in perinatal period large dose of virus, immune system not equipped e.g. HSV in perinatal period

Answer 11

transplacental viral transmission Foetus unable to mount an adequate immune response primary infection will occur in mother (during pregnancy) same can happen with rubella virus

Answer 12

releases decoy particle (= HBsAg) | this diverts the immune response and the core virus (containing the virulence factors) are left alone

Answer 13

aim to establish latency after initial acute infection enter sites where the immune cells have restricted access e.g. dorsal root ganglia or lymphocytes here, they only make very few viral proteins e.g. herpesviridae family of viruses

Answer 14

``` CMV = cytomegalovirus down regulate MHC class I molecules, therefore impairs Ag presentation prevents detection by CD8+ CTLs ``` MHC class I - present on all nucleated host cells

Answer 15

= sites where they are most likely to establish latency infection lymphocytes macrophages (low level replication will occur here)

Answer 16

EBV = Epstein Barr virus Burkitt's lymphoma Nasopharyngeal carcinoma

Answer 17

HP = human papilloma virus cervical cancer

Answer 18

viruses replicating within cells will integrate with host genome elevated risk if this is in cells that do not normally divide that much integration may target host oncogenes and tumour suppressor genes promotes host cell proliferation

Answer 19

small pox - eradicated poliovirus - almost ``` in progress: mumps, measles, rubella, papilloma, hepatitis ```

Answer 20

Infants given 3-4 doses of HBV vaccine HBsAg seropositive rates fallen to <1% HepB Ig given to infants within 24 hr of birth if mother is at high risk of vertical transmission (if HBsAg or HBeAg positive)

Answer 21

HBsAg: surface Ag | thought to aid the entry of HBV into hepatocytes (via attachment to PM receptors)

Viruses and immune system evasion Flashcards

(46 cards)