Microbiology 6&7 - Prevention, Treatment and Emergence of Viral Disease

Question 1

Define prophylaxis

Answer 1

The prevention of a disease before infection occurs via vaccination/use of drugs

Question 2

Define therapy

Answer 2

Therapy is the treatment of a disease after a host is infected

Question 3

How can eradication of a virus from the planet occur?

Answer 3

• When there is no animal reservoir, and no latent or persistant infection.
• Easy to recognise infection
• Vaccine must be affective against all viral strains
• Vaccines must be low cost, abundant, heat stable and easily administrated.

Question 4

List the different types of vaccine

Answer 4

• Attenuated (generate pathogens in the lab that work in a different animal - eg. Monkeys not humans)
• Inactivation of virus
• Fractionation (a purified subunit)
• Cloning

Question 5

Desribe the types of cloning vaccines

Answer 5

The DNA of a virus cloned and may be inserted into the DNA of a live virus to deliver it to the cell, or DNA could be injected, or proteins may be used in a subunit vaccine or delivered to the cells in a virus like particle

Question 6

Describe how attenuation of a virus occurs

Answer 6

• The pathogenic virus is isolated and grown in human cultured cells
• The cultured virus is used to infect monkey cells or smother pathogen
• Virus acquires mutations
• The virus cant grow in human cells well anymore

Question 7

What are the pros and cons of live attenuated viruses?

Answer 7

They are long lived, rapid, and dont require a large dose. They cause cellular immunity.
However - it requires attenuation and it may revert

Question 8

List the pros and cons of innactivated vaccines

Answer 8

They are safe and can be made from a wild type virus, however they require high doses and boosters.

Question 9

Give an example of a live attenuated virus

Answer 9

Rotarix is used to treat rotavirus - cant be used too early as it causes bowel blockages

Question 10

Give an example of an inactivated vaccine

Answer 10

Influenza and poliovirus have inactivated viruses - polio uses sakk

Question 11

Give an example of a subunit vaccine

Answer 11

The hepatitis B vaccine, and the papillomavirus vaccine (Gardasil or cervarix)

Question 12

Give an example of a toxoid vaccine

Answer 12

Tetnus

Question 13

Give an example of a conjugate vaccine

Answer 13

Influenza Hib vaccine

Question 14

Explain the eradication of smallpox

Answer 14

Smallpox was an easily recognised disease with a vaccine effective against all strains, no animal host and no latent infection. The vaccine is low in cost, has a high heat stabikity and is easily administrated.

Question 15

Give an example of passive immunity and explain what it is.

Answer 15

Passive immunity is where the patient doesnt produce their own antibodies, eg. Zmapp used to treat ebola is a cocktail of 3 antibodies. In ebola treatment blood from survivors was also used.

Question 16

What types of antiviral treatments are there?

Answer 16

• Interferons induce the hosts natural response

- Treatment may alleviate symptoms, though they dont inhibit virus replication

Question 17

How do nucleoside analogues work as antivirals?

Answer 17

They inhibit viral replication by causing the chains to terminate. Drugs include acyclovir and ganciclovir.

Question 18

How is acyclovir specificity maintained?

Answer 18

• It is activated inside the cell by thymidine kinase produced by viruses (phosphorylated).
• The acyclovir has a higher affinity for viral DNA polymerase than host cell polymerase.

Question 19

Give some examples of influenza antivirals.

Answer 19

Amantacine, amantadine and zanamivir.

Question 20

Give examples of neuraminidase inhibitors, and state what they are used for.

Answer 20

Sialic acid, relenza and tamiflu. These are used it flu treatment, preventing replication of influenza.

Question 21

What drug treatments are used for HIV?

Answer 21

HAART highly active antiviral therapy.

Question 22

Why do viruses quickly become resistant?

Answer 22

• RNA doesnt have any checks for mutations, so viruses quickly mutate and multi drug treatments must be used.
• Quasispecies infect one person
• Virus may encounter a bottleneck under limiting conditions

Question 23

What is antigenic drift?

Answer 23

The change in antigens present on a bacterial strain over time.

Question 24

How do new viruses emerge?

Answer 24

• Zoonosis
• Genetic variation
• Increased exposure due to travel and vector spread
• Recombination of multiple viruses

Question 25

What are the global influences on emerging infections?

Answer 25

• Environmental modification
• World population
• Climate change
• Farming practices (monocultures)
• Immunosuppressed humans

Question 26

What processes do antiviral drugs generally target?

Answer 26

Viral enzymes involved in replication of DNA or RNA, transcription or translation, and reverse transcriptase in HIV. Budding, viral assembly or entry to the cell may also be targetted.

Question 27

What are arboviruses? Give examples.

Answer 27

Viruses with a mosquito or insect host. Including:

• Yellow fever, dengue, west nile, zika or chikingunya virus
• Flaviviruses and alphaviruses

Question 28

What can dengue virus antibodies do?

Answer 28

They either increase the infection or neutralise the infection - this is by blocking the binding of viruses to the cell receptor or by enhancing uptake into the cell.

Question 29

What are the two major coronaviruses?

Answer 29

• SARS, transmitted to humans from bats

- MERS is transmitted from camels.