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Week 4- Immune system and viruses > viruses > Flashcards

viruses Flashcards

1
Q

what are viruses

A

-simple acellular infectious pathogens
- incapable of self replication and metabolic activity
-obligate intracellular parasites

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2
Q

describe the viral genome

A

-consists of DNA or RNA (can not be both)
- the DNA or RNA can be linear or circular
-RNA can be ‘+ve sense’ (can synthesise proteins) or ‘-ve sense’ ( needs to covert to +ve sense to allow synthesis of proteins

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3
Q

describe the viral components

A

genome: nucleic acid
capsid: protein coat
nucleocapsid: complete unit of nucleic acid and capsid
- may also contain essential or accessory enzymes to facilitate initial replication
can be naked or enveloped

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4
Q

define virion

A

fully assembled infectious extracellular particle
(intracellular viral structures are not always fully assembled)

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5
Q

describe the capsid structure

A

composed of caposomeres- several different polypeptides grouped together
distinctively symmetrical - helical or icosahedral

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6
Q

describe enveloped viruses

A
  • characterised by a phospholipid bilayer derived from the host cell
    plasma membrane, Golgi apparatus, ER, nuclear membrane
    -composed of lipids, viral proteins and glycoproteins
  • host cell membrane proteins replaced by virally encoded glycoproteins (spike proteins)
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7
Q

what are viral attachment proteins

A
  • viruses that express glycoproteins which facilitate host cell entry.
    -alongside capsid proteins in naked viruses or anchored in the phospholipid bilayer of developed viruses
  • different viruses express different glycoproteins which attend to specific host cell receptors.
  • these spike glycoproteins confer virus antigenicity
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8
Q

viral tropism

A
  • most viruses infect only specific types of cells and tissue in one host
  • viral tropism: ability of a given virus to productively infect a:
    -particular cell (cellular tropism)
    -tissue (tissue tropism)
    -host species (host tropism)
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9
Q

modes of transmission

A

-oral transmission (hepatitis A)
- droplet transmission (influenza)
- direct inoculation (yellow fever)
-sexual transmission (HIV)
-direct skin contact (herpes)

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10
Q

nucleocapsid composition pt2

A

-nucleocapsid can either be naked or enveloped
-both contain viral attachment protein
- viruses can be classified using: size, genetic material, capsid structure and symmetry, naked or enveloped.

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11
Q

what are bacteriophage

A

complex viral structure
viruses that infect bacteria

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12
Q

list respiratory illnesses and its cause

A

resp illnesses can arise from rhinovirus, influenza, coronavirus and parainfluenza
-common cold, bronchiolitis, croup, viral pneumonia

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13
Q

coronavirus

A

large family of viruses including SARS-CoV, MERS-CoV and SARS-CoV-2
-good example of zoonis: and infection which is passed from non human to human host
-this can expose humans to novel viruses

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14
Q

Influenza

A
  • Type A+B - human disease
    -Type B+C - limited genetic diversity
  • Type D - only infects cattle
  • ## sudden onset of fever, chills, headache, muscle pain, extreme fatigue, dry cough, sore throat, blocked nose.
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15
Q

Influenza A

A

-zoonotic infection (between species)
-broad host range
- viral sub-types distinguished according to surface proteins
>HA- Haemagglutinin (17 subtypes)
>NA- Neuraminidase (9 subtypes)

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16
Q

Human Herpesviruses

A

-cold sores, chicken pox and shingles
- all herpesviruses persist for the lifetime of the host
-establish a latent (non replicating) state
- may be reactivated under certain conditions

17
Q

Measles

A

-flu like illness, fever, cough, conjunctivitis
- rash, spots inside the mouth
-encephalitis

18
Q

Mumps

A

-swelling of face, ears, headaches and fever
-viral meningitis

19
Q

Rubella

A

-rash, aching joints, fever
-can cause congenital rubella syndrome
-80-90% of infections in early pregnancy cause miscarriage or stillbirths

20
Q

MMR vaccination coverage

A

anti- vaccination movements perpetuate misinformation about safety of vaccines
- highlights the importance of clear, evidence-based science communication

21
Q

HIV/AIDS

A
  • human immunodeficiency virus
  • single stranded +ve sense RNA retrovirus
    -spreads through the body fluids where the body immune cells are found (CD4+ cells)
    -acute infection: flu like illness
  • clinical latency: HIV inactivity or dormancy
    AIDS: CD4 count bellow 200 cells/mm^3
22
Q

Opportunistic Pathogens

A
  • epstein-barr: virus infection (hairy leukoplakia) raised white lesions of oral mucosa
  • fungal infection: oral candidates
    -HHV-8 Virus- Kaposi’s sarcoma Brown pigmented lesions
    -Fungal infection_ Pneumocytis pneumonia
    extensive infiltrate in both lungs
23
Q

Zika virus

A
  • outbreaks in pacific, region South+Central America, Caribbean, Africa
  • spread by infected mosquitos and sexual intercourse
    -commonly asymmetrical, symptoms: fever, rash, headache, joint pain, conjunctivitis and muscle pain
    -passed from pregnant women to foetus (congenital Zika syndrome- microcephaly) + associated with Guillian-Barre syndrome
24
Q

Ebola virus

A

zoonotic origin
- human and non human primates (monkeys, gorillas and chimps)
-5 known Ebola viruses species, 4 cause disease in humans
-fast symptoms onset including nausea, blood in faeces and bleeding from ears, eyes, nose and mouth
-transmitted by direct contact

25
Q

stages of viral replication

A
  1. attachment/absorption
  2. penetration
  3. uncoating
    4.replication/synthesis
  4. assembly
  5. release
26
Q

viral genetic replication

A
  • viruses can exhibit single stranded DNA and circular DNA genomes
    -these can be transcribed into mRNA by viral RNA polymerase
    -viral mRNA genomes have many types of replication
27
Q

DNA VS RNA viruses replication

A

DNA: replicates in the nucleus
RNA: replicates in the cell cytoplasm

28
Q

Cellular outcomes of viral infections

A
  • virus release and host cell destruction aka cell lysis (polio)
  • exit by budding (influenza)
  • exist in host cell cytoplasm and release by exocytosis (herpes)
    -incorporated into the genome (retroviruses and hep B)
    -oncogenic viruses, stimulate uncontrolled cell growth and can lead to cancer (HPV)
29
Q

retrovirus case, HIV

A
  • enveloped retrovirus virus
    -+ve sense ssRNA viral genome encodes 9 genes
    -HIV expresses 72 transmembrane glycoprotein antigens
    -also expresses a matrix and capsid protein
  • enzymes, reverse transcriptase, integrase and protease are found within the nucleocapsid.
30
Q

HIV infection stages

A
  1. HIV infects T lymphocytes and monocytes (macrophages) through the interaction of gp120 and the CD4 receptor
  2. After attachment. the nucleocapsid penetrates the cell membrane
  3. The ssRNA genome is replicated as dsDNA
  4. HIV integrase incorporates viral DNA into the host DNA
  5. Viral DNA is transcribed and translated by the host, and HIV proteases process mature HIV proteins
  6. Mature HIV virions are formed from the host plasma membrane.
31
Q

Virale genome variation

A

-viral genome can vary between replication cycles (in host) or between hosts as the virus passes through a host population
- the do this due to evolutionary pressure from host immune systems and antiviral drugs
- 3 molecular mechanism that can cause viral genome variation: mutation, recombination and gene switching/ reassortment

32
Q

Rna vs Dna viruses mutation (viral genome variation)

A

rna viruses mutate faster than DNA viruses
SS mutate faster than DS
smaller viral genomes mutate faster than larger viral genomes
- this generates both advantageous ada deleterious genomic changes

33
Q

viral mutations

A

-insertion, deletion and substitution occur frequently in viral genomes
- RNA dependent RNA polymerase has no proof reading or correction ability (compared to DNA polymerase)
- small mutations within antigenic genes allow viruses to evade host immune systems, called antigenic drift, drives the need for viral genome surveillance

34
Q

gene recombination and reassortment

A
  • if two stains of a virus infect a host recombination and/or reassortment can occur
    -both methods result in extensive genome variation called antigenic shift
35
Q

Gene recombination vs reassortment

A

recombination- exchange of entire genes between two strains
reassortment- exchange of entire segments of genome between strains

36
Q

Influenza

A

-exhibits both antigenic drift and antigenic shift
has 8 segments of -ve sense single stranded RNA
-susceptible to insertion, deletion and substitution mutations
-able to infect and co-infect multiple species
-leads to zoonotic spread of new strains

37
Q

antigenic shift and drift in influenza

A

antigenic shift of entire segments of influenza genome can occur during co-infection
-antigenic drift of the HA and NA glycoproteins causes the repeat outbreaks of seasonal flu

Week 4- Immune system and viruses (6 decks)

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