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Virology > Week 10 > Flashcards

Week 10 Flashcards

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1
Q

Sporadic

A

occasional cases

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2
Q

Endemic

A

Present in a community at all times but in relatively low frequency

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3
Q

Epidemic

A

Sudden severe outbreak in a region or group

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4
Q

Pandemic

A

Widespread epidemic affecting whole region, continent, world

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5
Q

Stages of transmission

A
  1. agent only in humans - no further transmission to humans
  2. Primary infection –> from animals
  3. limited outbreak –> few animals or few cycles humans
  4. long outbreak –> animals or many cycles humans
  5. exclusive human agent –> only from humans
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6
Q

Endemic diseases

A

Seasonality, ongoing activity
Reports in excess –> epidemic
Age incidence determined by immunity duration

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7
Q

Pandemic

A

Novelty, susceptibility (20-40 yrs old over represented), transmissibility

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8
Q

Epidemiologic modelling

A

Considers causal processes involved in infection & transmission, recognises interdependence of observations –> scenario analysis and prediction

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9
Q

SIR paradigm

A

Susceptible (number of people)–> infectious –> recovered

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10
Q

Host susceptibility

A

Age, immune status, underlying risk conditions, pregnancy, ethnicity - confounded by socioeconomic determinants

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11
Q

Virus determines natural history

A

Latency - can’t be quarantined, alter behaviour
Infectiousness - asymptomatic, duration, mode of transmission
Induction of immune response - temporary (strain specific) or permanent (strain transcending)

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12
Q

Population determinants of spread

A 
Birth rate
Household size & crowding - influenza in a house, people 4x more likely to catch influenza
Social and employment networks
Population density and connectedness
Population mobility
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13
Q

Environmental risk determinants

A

Seasonality
Sanitation
Proximity to vector and reservoir animal populations
Natural disasters

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14
Q

Syndromic surveillance

A 
Not constrained by individual disease diagnosis
Year on year comparison
Identification of unseasonal activity
Threshold detection algorithms
Need astute clinician detection
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15
Q

Non-pharmaceutical measures

A

Environmental & personal hygiene
Case and contact quarantine
PPE
Social distancing - school closure, banning of mass gatherings

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16
Q

Pharmaceutical measures

A

Vaccines and antivirals

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17
Q

Ebola

A

Incubation period: 2-21 days

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18
Q

Containment

A

Only feasible when low transmissibility, high visibility

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19
Q

Cancer initiation

A

Appears to be genetic alteration

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20
Q

3 classes of cancer-causing agents

A
  1. chemical carcinogens - ethidium bromide
  2. UV and ionising radiation - sun exposure, nuclear bombing
  3. viruses - induction of cancer does not benefit viruses
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21
Q

Tumour

A

Growth produced by abnormal cell proliferation, most benign - remain localised
Some malignant - invasive = cancer
Metastatic - spread by lymph or blood

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22
Q

Carcinoma

A

Tumour of epithelial origin

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23
Q

Sarcoma

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A

Tumour of fibroblast

24
Q

Lymphoma

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A

Solid- leukocyte

25
Leukemia
Circulating cells
26
Carcinogenesis
Multistage process by which cancer develops
27
Cancers are clonal
Arise from single cell | Transformed
28
Transformation
Introduction of inheritable changes in a cell --> change in growth phenotype and immortalization of cell line ~ first step of cancer in humans
29
Transformed cells differ from normal cells
1. lack contact inhibition of growth 2. lack of dependence on exogenous growth factors 3. Lack of anchorage dependence of some cell types
30
Cell cycle
G1 - synthesis of proteins required for DNA synthesis, regulated by extracellular stimuli (mitogen, adhesion) S: replication of DNA G2: synthesis of proteins for daughter cells M: cell division
31
GO regulator
Growth factors, oncogenes, cyclins and CDKs
32
STOP regulators
Tumour suppressor genes, CDK inhibitors
33
Oncogenes
Genes encoding proteins that give GO signal = proto-oncogenes = cellular oncogens = c-onc
34
V-onc
Virus version of oncogene
35
Tumour suppressor gene
Cellular genes encoding proteins that negatively regulate cell cycle e.g. p53 and Rb
36
4 classes of oncogenes
1. growth factors 2. growth factor receptors 3. intracellular signal transducers 4. transcription factors
37
____% of human cancers associated with 1 of 5 viruses
20%
38
RNA viruses
Human T cell leukemia virus | Hep C
39
DNA viruses
Papilloma, Epstein Barr, Hep B
40
Retroviruses (RNA tumour) vs DNA tumour virus
RNA: - not lytic, integration essential - If v-onc involved is not unique --> c-onc counterpart - Transformation involves stimulating c-onc DNA: - Can be lytic, integration not essential - V-onc unique viral product, no c-onc - Transformation involves inactivation of inhibitors
41
Endogenous retrovirus
Integrated provirus Transmitted in germline to every cell In response to certain stimuli --> virus produced
42
Exogenous retrovirus
Typical infectious virus
43
Defective virus
Needs helper virus to produce progeny (coinfection with virus that has missing part) Carries oncogene instead of gag, pol, env
44
Replication competent
e.g. Rous sarcoma virus Hasn't swapped gene for retroviral genes, but in addition - gag, pol, env + SRC
45
Mechanisms of tumour production by exogenous retroviruses
1. transducing 2. cis-activating 3. trans-activating
46
Transducing
Acute transforming e.g. Rous sarcoma in chickens Introduce v-onc under LTR transcriptional control into host genome Doesn't need helper virus Never isolated from humans Tumours can be polyclonal - infecting different cells and introducing its v-onc
47
Cis-acting
Non-acute transforming retorviruses No v-onc, but LTR drives expression of c-onc (insertional mutagenesis) 1. Longer message that includes cellular oncogene (constantly read off) 2. Provirus incorporated more distantly but acts to unwind DNA (enhancer) at proto-oncogene --> normal transcript read off Not seen in humans E.g. Koala retrovirus
48
Trans-activating retrovirus
HTLV-1 exogenous containing gene regulation protein Asociated with adult T cell leukemia-lymphoma Prevalent in Japan, Caribbean, central Africa , (Indigenous Australians - no link to cancer) Can be transmitted across placenta, sexually transmitted, needles Persists for life Target CD4 receptor Tax - acts on LTR, upregulate gag, pol rev and acts on c-onc genes, acts on IL2 (T cell growth factor) and its receptor --> T cell proliferation
49
Overexpression of Tax
--> expression on MHC I --> killed by CD8 | Levels downregulated by HBZ protein
50
Tumour induction by DNA viruses
Most undergo lytic growth Require host enzymes to replicate DNA Escape cell cycle: encode early proteins that stimulate cells to enter S phase Tumours: early genes mostly, show integration
51
Rb protein
Controls transition from G1 -->S, hypophosphorylated form associated with E2F family of transcription factors, sequestering them --> break in cell cycle
52
p53
Transcription factor --> arrest growth of cell and initiate response to DNA damage 50% cancers have mutations of p53 Hep C binds p53 --> p53 can't bind DNA --> replication Papilloma protein --> degrades p53 --> replication
53
Papillomavirus
Epithelial layers Benign skin tumours - can spontaneously clear, HPV genome kept as episome HPV 16 & 18 --> cervical carcinoma, most common women cancer in developing world E6 and E7 interacts with p53 and pRb In malignant cells: HPV randomly integrated Loss of E2 during integration --> not able to repress transcription of E6 and E7
54
Hep B virus genome
Most integrated genomes retain X and its promoter X encodes transactivating gene which may deregulate nearby c-onc Indirect role: destruction and regeneration of cells lead to accumulation of chromosomal mutations
55
Epstein-Barr virus
Herpes - most strongly associated with cancer Burkitt's lymphoma Nasopharyngeal cancer B cell lymphomas in immune suppressed Hodgkins (EBV detected in 40% of patients)
56
Burkitt's lymphoma
Transforms B cells --> clonal expansion Malaria furhter expand B cells and decrease T cells Enhances chances of genetic accidents --> chromosomal translocation of c-myc Chromosome break: c-myc becomes under control of heavy chain enhancer region --> produces c-myc instead of Ig heavy chain c-myc encodes transcription factor --> GO signal

Virology (9 decks)

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