Viral infections, oncoviruses & antiviral chemotherapy

Question 1

Dynamic viral infections

Answer 1

• Virus to cause disease
• Infect specific host cell
• Replicate efficiently with host
• Damage target tissue

Question 2

Viral pathogenesis

Answer 2

• ## The process of a virus producing disease

Question 3

3 Requirements for sucessful infection

Answer 3

• Enough virus
• Accessible Cells that permits the viral replication
• Local antiviral defense/immune system absent or overcome

Question 4

Asimptomatic infection

Answer 4

• Evidence of disease that can be observed by others - sign
• Apparent only to patient

Question 5

Acute infection

Answer 5

• Display short incubation periods upon virus entry
  into the host.
• Rapid onset of disease
• Brief period of sympthoms
• Quick resolution

Question 6

Acute viral infections

Answer 6

• Genetic factors
• Age
• Comorbidity (other diseases)
• Individual immune response
• It is possible reinfection as the immune response triggered is not long-lasting and the virus
  rapidly change

Question 7

Latent infection

Answer 7

• Latent virus remains in asymptomatic
  host cell for long periods
• No symptoms or viruses are detectable/active
• May reactivate due to changes in immunity
• Cold sores and herpes

Question 8

Persistent infection

Answer 8

• A persistent viral infection occurs
  gradually over a long period
• Where the virus continue to replicate over time a low level Hep B
• Not always becoming chronic

Question 9

Herpesvirus

Answer 9

• Remain latent in a quiescent but persistent form in neutral ganglia cells
• Primary infection - Cold sores HSV-1 and chicken pox for vzv
• Innervating sensory neurons, and viruses are transported to the neuronal cell body.

Question 10

Viral DNA episomal state

Answer 10

• Released into the neuronal nucleus
  and circularizes

Question 11

Circular viral DNA

Answer 11

• Persists in the neuronal cell
  nucleus

Question 12

Reactivation of herpes virus HSV-1

Answer 12

• Periodically reactivate to cause cold sores, in response exposure to sunlight, psychological stress, fever, menstruation and surgical resection
• Reactivation in the neuronal cell body
• Newly formed capsids are transported to the axonal termini
• Infectious virus is released from the axon and infects epithelial cells, resulting in recurrent infection and virus shedding

Question 13

Varicella Zooster Virus

Answer 13

• VZV after years of inactivity may produce skin disease shingles
• Localised and painful
• One or two adjacent dermatomes, usually on the trunk

Question 14

Cancers caused by virus (oncoviruses)

Answer 14

• Non contagious occour later in time
• Become integrated into the host cell’s DNA
  and induce tumours

Question 15

Oncoviruses Mechanisms

Answer 15

• Encode proteins that act as oncogenes themselves
• Activate cellular proto-oncogenes (normal) to oncogenes
• Inactivate tumour suppressor genes
• Cell cycles are no longer regulated at checkpoints
• Unregulated cell proliferation
• Chromosome instability - Mutation accumulation

Question 16

Examples of viruses that caus cancer

Answer 16

• Hep-B and C
• HIV and HPV
• Human T-cell

Question 17

Isolation and Cultivation of Viruses

Answer 17

• The study and isolation of viruses
• Propagated using different systems in laboratory settings
• Animals
• Embryonated eggs
• Cell cultures

Question 18

Continuous eukaryotic cell lines

Answer 18

• Cells commercially available
  to divide in a laboratory

Question 19

Isolation and Cultivation of Viruses

Answer 19

• Grow in plates sample containing viruses are added to allow virus to attach to the cells and then removed
• Cell are then covered with Agar block diffusion of viruses. Virions infect surrounding cells
• Localised area of cell destroyed
• Detected by using a dye to stain just the viable
  cell. The dead cells of the plaque do not retain the dye
• Each plaque corresponds to an area of cells infected and dead by single virus

Question 20

Vaccinations

Answer 20

• Prevent viral infections
• Protection from possible infection illness when coming into contact with respective pathogen
• Attenuated viruses or proteins or mRNA to trigger a specific immune response
• Viral diseases, often deadly have been eradicated or almost eradicated

Question 21

Antiviral drugs

Answer 21

• Antiviral chemotherapy to treat specific viral infectionsselectively
• Virus replication with low effects on the host cell activity
• Inhibiting intital viral life cycle
• Target machanism of action to treat infections

Question 22

HIV

Answer 22

• Retroviridae family - subtypes HIV-1 and HIV-2
• Insert a copy of its RNA genome into the host
  cell’s genome

Question 23

HIV turning into AIDS

Answer 23

• Causes acquired immunodeficiency syndrome - progressive failure of immune system
• Decrease CD4+ and T-lyphocyte life-threatening opportunistic infections and cancers

Question 24

Acute HIV

Answer 24

• Flu-like symptoms that occur
  days to weeks after contracting HIV

Question 25

Chronic HIV

Answer 25

• The latent and asymptomatic
  stage that can last several years

Question 26

AIDS

Answer 26

• Occurs when CD4 cell count falls
  below 200 cell/mm3. This makes people
  vulnerable to opportunistic infections and
  AIDS-defining conditions

Question 27

HIV Combinational therapy

Answer 27

• The highly active antiretroviral therapy regimene typically a combination of two/three antiretroviral drugs with different mechanisms of action
• Different mutations are required to develop drug resistance to all drugs
• Reduced risk of drug resistance

Question 28

Principle of combination therapy

Answer 28

• Different antiviral drugs with distinct mechanisms of action having a proved synergistic activity against HIV

Question 29

HIV Combinational therapy goals

Answer 29

• Reduce plasma viral RNA to an undetectable level
• Prevent or reduce drug resistance
• Reduce morbidity and mortality
• Prevent HIV transmission - Undetectable therefore untransmittable