35.6 Population Virology Flashcards
What factors can influence persistence and transmission of a virus?
Availability of hosts. population density, multiple different hosts.
What are the different routs of transmission?
*Feco-oral route
*Respiratory droplets or aerosol
*Saliva
*Genito-urinary transmission
*Transfusion, blood products (e.g. drug abuse)
Give an example of a virus transmitted through the feco-oral route.
Polio
Give an example of viruses transmitted via respiratory droplets or aerosol.
Influenza, SARS-CoV-2
Give an example of a virus transmitted via saliva
EBV
Give an example of a virus with Genito-urinary transmission.
HIV
Give an example of viruses transmitted through transfusion and blood products.
HIV/ HBV
How can viral infections be prevented/ treated?
*Vaccination (e..g. smallpox eradication)
*Antiviral drugs
Why do viruses have a high mutability of their genome?
*RNA-dependent RNA polymerases and reverse transcriptase are used in replication - they have a very low fidelity rate.
*Especially RNA viruses (Blatimore 3-7)
Why do the enzymes involved in virus replication have a low fidelity rate, what is the fidelity rate?
these enzymes have a very low fidelity rate compared to eukaryotic counterparts due to lower affinity threshold + lack of proofreading mechanism.
What introduces a selection pressure on the viruses?
Neutralizing Abs and T-cells
What is antigenic drift?
Small changes in the antigenic structure due to random mutations within the antigen gene, caused for example by the error-prone RNA polymerase
* Lead to epidemics (i.e. yearly seasonal outbreaks of the flu)
Which viruses commonly display antigenic drift?
Influenza/ SARS-CoV-2/ HIV
What is antigenic shift?
Large changes in the antigens due to obtaining a new gene for the antigens (haemagglutinin and neuraminidase) from e.g. swine flu
* Lead to pandemics
Which virus often displays antigenic shift?
influenza
What is antigenic conservatism?
Conservation of a core component needed for normal functioning.
*e.g. VP1/2/3 surface capsid proteins used for engagement of host CD155 and entry all have conserved core in polio virus.
Why are there less available treatments for viruses compared to bacteria?
Limited choice of targets, often due to viruses inhabiting host cells. Many antiviral therapies target viral enzymes, however there is still a risk of development of resistance.
What are the different anti-viral therapies available for HIV?
*HIV reverse transcriptase inhibitors
*HIV protease inhibitors
*HIV entry inhibitors
*HIV integrase inhibitors
What are the 2 different classes of HIV reverse transcriptase inhibitors?
*chain terminators - inhibit the synthesis of new viral DNA molecules in a similar way to sanger sequences.
*Direct RT inhibitors - competitively inhibit RT action on +ssRNA
Give an example of a chain terminator (anti-HIV)
Zidovudine
Give an example of a direct RT inhibitor (anti-HIV)
Nevirapine
Give an example of a HIV protease inhibitor and its mechanism of function
saquinavir
*to prevent the cleavage of gag, pol and env precursors into functional forms
Give an example of a HIV integrase inhibitor and its mechanism of function.
Raltegravir
*prevent the effective insertion of viral DNA into the host cell chromosomes
Give an example of a HIV entry inhibitor and its mechanism of action.
Maraviroc
*binds to CCR5 on the surface of T-cells preventing HIV env protein gp120 from doing so.
What is ART (Anti-retroviral therapy)?
The use of combinations of 2 or 3 anti-retroviral drugs to minimise drug resistance that result from high HIV mutation rate.
State the two main types of antineuraminidase drugs (used to treat influenza).
- zanamifir (Relenza)
- oseltamivir (Tamiflu)
How can the release of new influenza viruses from host cells be targeted by antiviral drugs?
Neuramidinidase inhibitors are used as antiviral drugs, since neuraminidase is required to cleave sialic acid, releasing new viruses.
How can herpes be treated?
- Aciclovir and ganciclovir
- Herpes viruses have thymidine kinase (TK) genes
- These convert the aciclovir and ganciclovir into triphosphates that act as chain terminators in DNA replication
- They can be used against HHV-1, HHV-3 and HHV-5, but they are not effective in latency because TK is not expressed
What issues are there with viruses in palliative care?
*Lack of effective drugs
- sometimes anti-viral drugs used to alleviate symptoms + suffering
*Lack of specific diagnosis due to similarity of symptoms
- difficult to make specific diagnosis early enough to give effective treatment.
What is the role of anti-inflammatory drugs in palliative care?
They can be used to reduce symptoms of an infection to improve quality of life and alleviate suffering, however they can make it easier for the virus to damage cells and lead to lytic changes.
Therefore, not an ideal treatment option.
