Lecture 22. Controlling Viral Infections Flashcards
What two points underpin the concept of vaccination?
Infection often leads to life-long immunity
The virulence of different strains of a pathogen may vary
What is a vaccine?
A vaccine is a biological product that can be used to safely induce an immune response that confers protection against infection and/or disease on subsequent exposure to a pathogen
What are live/attenuated vaccines?
Contains the whole virus that has been weakened or attenuated to produce an immune response similar to that seen during natural infection
What are examples of live attenuated vaccines?
Measles, mumps, rubella
Rotavirus
Oral polio vaccine
Live attenuated influenza vaccine
What are features of live/attenuated vaccines?
Tend to create a strong and lasting immune response
May not be suitable for immunocompromised individuals
What are killed/inactivated viral vaccines?
Contain whole virus which has been killed or have been altered, so that they cannot replicate
What are examples of killed/inactivated viral vaccines?
Inactivated polio vaccine or IPV
Inactivated flu vaccines
Hepatitis A vaccine
Rabies vaccine
What are features of killed/inactivated viral vaccines?
Don’t create a strong and lasting immune response
May be suitable for immunocompromised individuals
What are subunit viral vaccines?
Do not contain the whole virus at all, they contain one or more specific component/unit/antigens usually from the surface of the virus
What are examples of subunit viral vaccines?
Hepatitis B Virus vaccine
Human Papillomavirus vaccine
What are the features of subunit viral vaccines?
Don’t create a strong and lasting immune response
May be suitable for immunocompromised individuals
What are nucleic acid-based vaccines?
Do not provide the viral protein/antigen. Instead they provide the genetic instructions/genes that encode for that specific viral antigen to host cells. These genes are then expressed by the host cells to produce the viral antigen, which stimulates an immune response against it.
What are features of nucleic acid-based vaccines?
Quick and easy to develop
Provide significant promise for the development of vaccines in the future
What are examples of RNA vaccines?
mRNA
Pfizer BioNTech COVID-19 vaccine
Moderna COVID-19 vaccine
What creates an effective vaccination program?
Vaccine must be cheap (polio a few pence, HBV around £100), safe and acceptable
The virus/disease must show antigenic stability, ease of diagnosis and follow up of contacts and no animal reservoirs
What are the properties of antiviral drugs?
Vaccines have limited or no therapeutic effect if someone already infected
Antivirals can stop infection once it has started
Why do we have a limited number of antiviral drugs?
Many compounds that interfere with virus growth cause
adverse effects in the host
Some medically important viruses can’t be propagated,
have no animal models, or are dangerous
An antiviral drug (compound) must be potent-completely inhibit viral replication
Many acute viral infections are short-lived
What is an example of an antivirals-binding inhibitor?
Maraviroc (Selzentry), anti-HIV
What is the mode of action of maraviroc?
Maraviroc blocks the chemokine receptor CCR5
What are examples of antivirals-entry inhibitors?
Amantadine & Rimantadine, anti-influenza
What is the mode of action in amantadine & rimantadine?
Inhibit entry and NA release: blockage of the M2 ion channel
Why did hydroxychloroquinolone fail?
Licensed drug (for Malaria)
HCQ known to inhibit replication of multiple viruses by inhibiting endosomal acidification
Found to inhibits SARS-CoV-2 replication in cell culture
Given emergency approval by FDA (EUA in US)
But then failed
EUA was withdrawn
What do anti-HIV drugs do?
Control viral replication prolonging survival
Anti-HIV drugs inhibit viral replication at many different phases of the HIV replicative cycle
What is HAART?
Highly-Active Anti-Retroviral Therapy)
Administration of a mixture of different drugs (drug “cocktail”)
