Microbiology 6&7 - Prevention, Treatment and Emergence of Viral Disease Flashcards
Define prophylaxis
The prevention of a disease before infection occurs via vaccination/use of drugs
Define therapy
Therapy is the treatment of a disease after a host is infected
How can eradication of a virus from the planet occur?
- 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.
List the different types of vaccine
- Attenuated (generate pathogens in the lab that work in a different animal - eg. Monkeys not humans)
- Inactivation of virus
- Fractionation (a purified subunit)
- Cloning
Desribe the types of cloning vaccines
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
Describe how attenuation of a virus occurs
- 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
What are the pros and cons of live attenuated viruses?
They are long lived, rapid, and dont require a large dose. They cause cellular immunity.
However - it requires attenuation and it may revert
List the pros and cons of innactivated vaccines
They are safe and can be made from a wild type virus, however they require high doses and boosters.
Give an example of a live attenuated virus
Rotarix is used to treat rotavirus - cant be used too early as it causes bowel blockages
Give an example of an inactivated vaccine
Influenza and poliovirus have inactivated viruses - polio uses sakk
Give an example of a subunit vaccine
The hepatitis B vaccine, and the papillomavirus vaccine (Gardasil or cervarix)
Give an example of a toxoid vaccine
Tetnus
Give an example of a conjugate vaccine
Influenza Hib vaccine
Explain the eradication of smallpox
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.
Give an example of passive immunity and explain what it is.
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.
What types of antiviral treatments are there?
- Interferons induce the hosts natural response
- Treatment may alleviate symptoms, though they dont inhibit virus replication
How do nucleoside analogues work as antivirals?
They inhibit viral replication by causing the chains to terminate. Drugs include acyclovir and ganciclovir.
How is acyclovir specificity maintained?
- 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.
Give some examples of influenza antivirals.
Amantacine, amantadine and zanamivir.
Give examples of neuraminidase inhibitors, and state what they are used for.
Sialic acid, relenza and tamiflu. These are used it flu treatment, preventing replication of influenza.
What drug treatments are used for HIV?
HAART highly active antiviral therapy.
Why do viruses quickly become resistant?
- 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
What is antigenic drift?
The change in antigens present on a bacterial strain over time.
How do new viruses emerge?
- Zoonosis
- Genetic variation
- Increased exposure due to travel and vector spread
- Recombination of multiple viruses
What are the global influences on emerging infections?
- Environmental modification
- World population
- Climate change
- Farming practices (monocultures)
- Immunosuppressed humans
What processes do antiviral drugs generally target?
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.
What are arboviruses? Give examples.
Viruses with a mosquito or insect host. Including:
- Yellow fever, dengue, west nile, zika or chikingunya virus
- Flaviviruses and alphaviruses
What can dengue virus antibodies do?
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.
What are the two major coronaviruses?
- SARS, transmitted to humans from bats
- MERS is transmitted from camels.
