Vaccine Development and Challenges

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Questions and Answers

What is the primary reason the human body experiences severe damage during a flu infection?

The immune system's reaction is excessively strong. (correct)

The influenza virus directly kills the cells.

The body’s immune response is too weak to fight the virus.

The virus mutates rapidly, evading the immune system.

How does the universal flu vaccine proposed by Chinese researchers differ from traditional vaccines?

It aims to completely eradicate the flu virus from the population.

It uses live mutant virus to elicit a stronger immune response. (correct)

It is designed to target only specific flu strains.

It contains only killed virus particles.

What is the range of annual flu-related deaths worldwide?

Over 1 million

100,000 to 250,000

291,000 to 646,000 (correct)

50,000 to 100,000

What role do T cells play in response to an influenza infection?

They attack and destroy tissues infected by the virus. Signup and view all the answers

Which of the following accurately describes the process of how the flu virus affects the body?

The body’s immune response involves the production of inflammatory molecules and antibodies. Signup and view all the answers

What is one of the primary reasons to store phages with cations, glycerols, and proteins at 4°C?

To ensure high plaque formation and viabilty Signup and view all the answers

What is the significance of the Pithovirus sibericum mentioned in the news?

It was revived from 30,000-year-old ice. Signup and view all the answers

How do autoimmune diseases potentially arise from viral infections?

T cells may mistake viral mimics for body proteins. Signup and view all the answers

What challenge is associated with creating a universal flu vaccine?

Difficulty in predicting yearly strains of the flu virus. Signup and view all the answers

What stage should host bacterial cells be in for effective phage infection?

Healthy, undamaged cells in the log-growth stage Signup and view all the answers

What is generally contained in flu vaccines to combat infection?

Killed strains of the influenza virus Signup and view all the answers

What characterizes the immune response connected to 'molecular mimicry'?

The immune system cannot distinguish between viral and body proteins. Signup and view all the answers

What is the Bacteriophage titre measured in?

pfu/ml Signup and view all the answers

Why do T cells initiate destruction of tissues in autoimmune diseases linked to viral infections?

They mistakenly identify body proteins as foreign. Signup and view all the answers

What does a plaque represent in a plaque assay?

A clear area from the lysis of bacteria originating from a single phage Signup and view all the answers

What does the multiplicity of infection (MOI) refer to?

The number of viral particles per host cell Signup and view all the answers

What is the purpose of the Broth Clearing Assay?

To determine the highest dilution of phage that can cause lysis of bacteria Signup and view all the answers

What can lead to a bacterial host becoming resistant to phages?

Surface mutations that alter bacterial surface receptors Signup and view all the answers

What does a lytic plaque accomplish during its formation?

It produces a clear area by lysing adjacent bacteria. Signup and view all the answers

What historical method did Ellis and Delbrück develop in 1939?

The one step growth curve for observing a single round of virus multiplication Signup and view all the answers

During the life cycle of a lytic phage, what is the primary result of infection?

Phage replication leads to bacterial cell lysis and release of new phage Signup and view all the answers

What occurs during the eclipse phase of a lytic phage?

No infectious phage particles can be found inside or outside the host. Signup and view all the answers

Which proteins are synthesized during the early stage of the phage life cycle?

Early proteins needed for phage DNA synthesis. Signup and view all the answers

During which phase do infectious phage particles accumulate within the host cell?

Latent phase. Signup and view all the answers

What is the primary event that occurs during the rise phase of the phage life cycle?

Bacteria begin to lysing due to the accumulation of phage lysis proteins. Signup and view all the answers

How is the burst size of a phage calculated?

The ratio of the number of progeny phage to the number of input phages. Signup and view all the answers

Which early protein function is essential for phage infection?

Degrading the host chromosome. Signup and view all the answers

What is the significant outcome of the lysis phase for the phage?

Intracellular phages are released into the environment. Signup and view all the answers

What factors contribute to the infectivity rate of phages?

Final concentration of phage particles and the initial concentration. Signup and view all the answers

What is antigenic drift in the context of influenza viruses?

Gradual, small changes in the genes of viruses over time Signup and view all the answers

What was significant about the Ebola vaccine developed in Canada's National Microbiology Laboratory?

It was developed before the 2014 outbreak but remained unused until then Signup and view all the answers

Which of the following is a disadvantage of edible vaccines?

Cooking may destroy the antigen Signup and view all the answers

What structure of a bacteriophage contains the genetic material?

Head Signup and view all the answers

What is a key characteristic of bacteriophages?

They remain dormant when not in contact with a host cell Signup and view all the answers

Which emerging issue complicates vaccine development for certain pathogens?

The rapid mutation rate of some viruses Signup and view all the answers

What is one advantage of using edible vaccines?

They facilitate feeding and immunization simultaneously Signup and view all the answers

What does antigenic shift refer to in viral infections?

The mixing of different virus strains leading to a new subtype Signup and view all the answers

Which factor does NOT necessarily hinder the use of edible vaccines?

Immediate availability in emergency situations Signup and view all the answers

Who first described bacteriophages and when?

Frederick Twort in 1915 Signup and view all the answers

Study Notes

Challenges in Vaccine Development

Certain pathogens, like HIV and malaria, are highly complex, making vaccine development difficult.
Emerging pathogens and pandemics pose a challenge due to limited knowledge about the pathogen involved.
Rapid mutation in viruses, like influenza, necessitates constant adaptation of vaccines due to antigenic drift and shift.
- Antigenic drift: gradual changes in viral genes over time.
- Antigenic shift: combination of different virus strains leading to new subtypes, like H1N1.

Canada’s Ebola Vaccine

Developed at Canada's National Microbiology Laboratory (NML) in 2004, with 100% efficacy.
Delayed commercialization led to its use only during the 2014 Ebola outbreak, which killed 11,000 people.
Merck partnered to produce the vaccine commercially.
Clinical trials were conducted in West Africa (2014-15) and compassionate use protocols implemented in Guinea (2015).

Edible Vaccines

Genetically modified plant or animal products triggering immune responses.
Potato, banana, and tomato are food sources under study for edible vaccines targeting cholera and Hepatitis B.
Advantages:
- Needle-free administration.
- No requirement for skilled professionals.
- No need for adjuvants or chemicals.
- Stimulates both mucosal and systemic immunity.
- Low cost and no need for refrigeration or sterile equipment.
- Simultaneous feeding and immunization.
- Improved safety due to the absence of attenuated pathogens.
Disadvantages:
- Requires raw consumption as cooking might destroy the antigen.
- May require a long time to mature (banana).
- Potential for quick spoilage (tomato and banana).
- Consistency issues between plants and generations.
- Challenges in dosage evaluation.
- Public attitude towards genetically modified food.

Bacteriophages

Viruses infecting bacteria.
First described by Frederick Twort (1915) and Felix d’Herelle (Canadian) (1917).
Obligate intracellular parasites.
Remain dormant as virions outside host cells.
Become active as viruses when in contact with appropriate host cells.

Bacteriophage Structure

Composed of a protein coat (capsid) enclosing genetic material (DNA or RNA).
Head: contains genetic material.

Plaque Assay

A method to quantify bacteriophages.
Infected bacteria lyse, releasing phages that infect nearby bacteria.
The process continues in multiple cycles.
Bacteriophage titre: concentration of infectious viral particles per milliliter of growth medium (pfu/ml).
Multiplicity of infection (MOI): ratio of infectious agents (phages) to infection targets (bacteria).
A plaque is a clear area on an agar plate resulting from the lysis of bacteria, each originating from a single infectious phage.
One plaque represents one plaque-forming unit (pfu).

Lytic Plaques vs. Lysogenic Plaques

Lytic phages destroy the host cell during replication.
Lysogenic phages integrate their DNA into the host's genome, replicating without killing while potentially causing changes in the host.

Broth Clearing Assay

A method to determine bacteriophage concentration.
Involves diluting phage in broth and inoculating with target bacteria.
The highest dilution causing lysis and broth clearing determines the endpoint.

Phage Typing

Identifying bacteria by testing their susceptibility to different bacteriophages.
Bacteriophages bind to specific bacterial surface receptors.
Host cell resistance can arise from surface mutations or lysogenic conversion, which changes surface receptors and protects the host.

One Step Growth or Phage Burst Size Assay

Developed by Ellis and Delbrück in 1939 to study a single round of virus multiplication.
Measures phage burst size, representing the number of progeny phages produced per infected cell.

Phases of Life Cycle of a Lytic Phage

Eclipse Phase:
- No infectious phages inside or outside the host cell.
- Phage nucleic acid takes over host's machinery.
- Early mRNA's and proteins are synthesized.
- Host DNA synthesis is shut down.
- Late mRNA's and proteins, for phage structure and lysis, are produced.
Latent Phase (Intracellular Accumulation Phase):
- Nucleic acid and structural proteins are assembled.
- Infectious phage particles accumulate inside the cell.
Rise Phase (Lysis and Release Phase):
- Host bacteria lyse due to the accumulation of phage lysis protein.
- Intracellular phages are released into the medium.
- Up to 1000 phages can be released per infected bacteria.

Phage Burst Size Calculation

Burst size is the ratio of progeny phage number to input phage number.
Infectivity rate is calculated as the ratio of pfu/ml at a specific time point to the initial bacterial concentration, multiplied by 100.

Phage Handling

Phages are stored with cations, glycerol, and proteins at 4°C to protect from damage, reducing loss of viability.
Healthy, undamaged bacteria in the log-growth phase are needed for successful phage infection.

Virus in the News

Giant virus resurrected from 30,000-year-old ice:
- Scientists revived a giant virus (1.5 µm) from Siberian ice, capable of infecting amoebae.
- Its size allows for visualization with a light microscope.
Virus's similarity to body's proteins may explain Autoimmune Diseases:
- Autoimmune diseases arise from the immune system attacking its own cells.
- "Molecular mimicry" may be involved, where viral fragments mimic human proteins, leading to the destruction of healthy cells by the immune system.
Moving towards a Universal Flu Vaccine:
- Influenza viruses constantly mutate, making vaccine prediction challenging.
- Universal flu vaccines with live mutant virus aim to induce a long-term immune response through T cells.
How Does the Flu Actually Kill People?
- High mortality rates due to the body's immune response.
- Influenza virus replication hijacks human cells, triggering immune system response.
- Immune system reaction can be overly strong, destroying lung tissue and causing hypoxia and death.

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Description

This quiz explores the complexities involved in vaccine development, including the challenges posed by emerging pathogens and the need for rapid adaptation due to virus mutations. It also highlights Canada's Ebola vaccine and innovative concepts like edible vaccines. Test your knowledge on these critical topics in public health!