All Types of Vaccines, How They Work, Animation.

Alila Medical Media

27 Jan 202105:55

Summary

TLDRThis video explains the process of how viruses infect human cells and how the immune system responds. It covers how viruses use host cells to replicate, the role of dendritic cells and T-cells in activating immune responses, and the different types of immunity. The script also discusses how vaccines work, comparing attenuated, inactivated, subunit, DNA, and mRNA vaccines, while highlighting their benefits, risks, and mechanisms of action. Special attention is given to the role of viral vectors and concerns surrounding DNA vaccines.

Takeaways

🦠 During a viral infection, the virus attaches to a human cell and uses the host cell’s machinery to replicate, producing new viral particles.
💥 The infected host cell dies, releasing new viral particles that infect more cells, causing tissue damage and symptoms.
🛡️ Infected cells present viral antigens on their surface, alerting the immune system and activating cytotoxic T-cells.
🌍 Dendritic cells act as professional antigen-presenting cells, capturing antigens and presenting them to helper T-cells in lymph nodes.
🤝 The immune system mounts two types of immunity: cell-mediated immunity and antibody-mediated immunity, but this process takes time.
💉 Vaccines introduce viral antigens to trigger immune responses without causing the disease, mimicking the natural infection response.
⚖️ Different types of vaccines exist, such as inactivated (Sinovac), subunit (EpiVacCorona), and nucleic acid (Pfizer, Moderna) vaccines, each with distinct mechanisms.
🧬 DNA vaccines introduce viral DNA into the cell's nucleus to generate viral antigens, while mRNA vaccines deliver mRNA that is translated into viral proteins in the cytoplasm.
🚫 Subunit vaccines cannot cause disease but may require adjuvants to stimulate the immune system, while nucleic acid vaccines raise concerns about DNA integration, though risks are minimal.
🔬 mRNA vaccines are less likely to integrate into the human genome and are delivered within a lipid covering that fuses with cell membranes.

Q & A

How does a virus enter and replicate within a human cell?
-A virus attaches to a human cell using its spikes, enters the cell, and uses the host cell’s machinery to replicate, producing viral proteins and genetic material. These are assembled into new viral particles, which are released as the host cell dies.
How does the immune system recognize an infected cell?
-Infected cells display pieces of viral proteins on their surface, which act as viral antigens. These antigens are recognized by cytotoxic T-cells, activating the immune system.
What role do dendritic cells play in the immune response?
-Dendritic cells, as professional antigen-presenting cells, patrol body tissues and capture viral antigens. They then travel to lymph nodes to present these antigens to helper T-cells, aiding in the immune response.
What are the two types of immunity triggered by viral antigens?
-Viral antigens trigger two types of immunity: cell-mediated immunity and antibody-mediated immunity.
How do vaccines induce an immune response without causing disease?
-Vaccines deliver viral antigens to the body, triggering an immune response similar to natural infection. This response includes the production of antibodies and other immune defenses, but without the disease symptoms.
Why might vaccines cause mild symptoms similar to an infection?
-As lymph nodes near the injection site start producing antibodies, they may become swollen and tender, which are signs of the vaccine working and can cause mild symptoms similar to infection.
What is the difference between attenuated and inactivated vaccines?
-Attenuated vaccines contain weakened viruses that can cause disease in people with compromised immune systems. Inactivated vaccines, such as Sinovac and Covaxin, use dead viruses and only induce antibody-mediated immunity.
What are subunit vaccines, and how do they work?
-Subunit vaccines contain only parts of the virus, usually a spike protein. They cannot cause disease but may not always trigger a strong immune response, so adjuvants are added to stimulate the immune system.
How do DNA and mRNA vaccines differ in their mechanism of action?
-DNA vaccines deliver viral DNA into the cell’s nucleus, where it is transcribed into mRNA and then translated into viral protein. mRNA vaccines, such as Pfizer and Moderna, deliver mRNA directly into the cytoplasm to produce viral proteins without entering the nucleus.
Why are non-human adenoviruses used in viral vector vaccines?
-Non-human adenoviruses are used because many people may have immunity to human adenoviruses, which could destroy the viral vector before it can deliver the DNA, reducing the vaccine’s effectiveness.

Outlines

00:00

🦠 Viral Infection and Immune Response Activation

The paragraph describes the process of how a virus infects human cells. The virus uses its spikes to enter the cell and hijacks the host cell's machinery to replicate itself, producing viral proteins and genetic material. As infected cells die, new viral particles are released, further infecting more cells. The infected cells alert the immune system by presenting viral antigens to immune cells, specifically cytotoxic T-cells. Professional antigen-presenting cells, like dendritic cells, also capture viral debris and transport it to lymph nodes where helper T-cells and B-cells are activated. These cells work together to mount both cell-mediated and antibody-mediated immune responses. The process takes time, during which the person experiences symptoms.

05:02

💉 Vaccines and Their Mechanisms

Vaccines trigger an immune response similar to a natural infection by delivering viral antigens without causing the disease. The immune response may sometimes cause mild symptoms as the body starts producing antibodies. Traditional vaccines contain weakened or inactivated viruses, but they require rigorous safety testing as attenuated vaccines may cause disease in immunocompromised people. Inactivated vaccines mainly induce antibody-mediated immunity. Subunit vaccines only use parts of the virus, like spike proteins, and usually need adjuvants to boost the immune response. Nucleic acid vaccines deliver genetic instructions for creating viral antigens, with DNA vaccines introducing viral DNA to the cell's nucleus and mRNA vaccines delivering mRNA into the cytoplasm to produce viral proteins.

Mindmap

Keywords

💡Viral infection

A viral infection occurs when a virus invades a human cell, using the host’s machinery to replicate itself, which leads to the production of new viral particles. In the script, this concept is essential as it describes the virus's life cycle—starting from attachment to the host cell, replicating, and then spreading to destroy body tissues, producing symptoms.

💡Antigen-presenting cells

Antigen-presenting cells (APCs), such as dendritic cells, capture and display viral antigens on their surface to alert the immune system. The video explains their role in identifying intruders like viruses and triggering immune responses by presenting the antigen to T-cells, initiating either cell-mediated or antibody-mediated immunity.

💡Cytotoxic T-cells

Cytotoxic T-cells are immune cells that recognize and destroy virus-infected cells. They are activated when an infected cell presents viral antigens on its surface. In the video, they play a key role in the body's defense mechanism by killing cells that harbor the virus.

💡Helper T-cells

Helper T-cells assist other immune cells in their responses. They are activated when antigen-presenting cells, such as dendritic cells, present viral antigens to them in lymph nodes. These cells help coordinate both cell-mediated and antibody-mediated immune responses, as explained in the video.

💡B-cells

B-cells are immune cells that produce antibodies when activated by viral antigens. The video mentions B-cells working in lymph nodes to produce antibodies, which are part of the body’s defense mechanism against viral infections.

💡Antibody-mediated immunity

Antibody-mediated immunity involves the production of antibodies by B-cells in response to a viral infection. These antibodies neutralize viruses or mark them for destruction. The video explains that vaccines often induce this type of immunity to prevent disease without causing an actual infection.

💡Cell-mediated immunity

Cell-mediated immunity involves T-cells, especially cytotoxic T-cells, directly attacking virus-infected cells. In the video, this is one of the two key immune responses triggered by an infection or a vaccine, playing a vital role in limiting the spread of the virus.

💡Vaccines

Vaccines are substances that introduce viral antigens into the body to trigger an immune response without causing illness. The video discusses various types of vaccines, such as attenuated, inactivated, subunit, and nucleic acid vaccines, highlighting how they work by simulating natural infections to build immunity.

💡mRNA vaccines

mRNA vaccines, like Pfizer and Moderna's COVID-19 vaccines, deliver mRNA that instructs cells to produce viral proteins, triggering an immune response. The video explains that mRNA vaccines are unlikely to integrate into human DNA and highlights their efficiency in teaching the immune system to recognize and combat viruses.

💡Subunit vaccines

Subunit vaccines contain only parts of the virus, usually a protein, rather than the whole virus. The video describes how these vaccines, such as EpiVacCorona, cannot cause disease but may require adjuvants to stimulate an effective immune response, as they may not be perceived as a threat by the immune system.

Highlights

Viruses attach to human cells using their spike proteins to initiate infection.

Once inside the cell, viruses hijack the host's machinery to replicate and produce viral particles.

Infected cells present viral antigens to cytotoxic T-cells, activating the immune response.

Dendritic cells act as professional antigen-presenting cells by collecting viral debris and presenting it to helper T-cells.

The immune system mounts both cell-mediated and antibody-mediated immunity to target the viral antigen.

Vaccines deliver viral antigens to trigger immune responses without causing the disease.

Some vaccines, like inactivated ones, only induce antibody-mediated immunity and require extensive safety testing.

Subunit vaccines contain parts of the virus, such as the spike protein, and often require adjuvants to enhance the immune response.

Nucleic acid vaccines use genetic material, such as DNA or mRNA, to make viral proteins and trigger an immune response.

DNA vaccines deliver viral DNA into the cell nucleus, where it is transcribed into mRNA and then into viral proteins.

mRNA vaccines introduce mRNA into the cytoplasm, where it is translated into viral proteins, without integrating into the human genome.

Viral-vector vaccines use a harmless virus, such as a modified adenovirus, to deliver viral DNA, as seen with Sputnik V and Johnson & Johnson.

Non-human adenoviruses are often used in viral-vector vaccines to avoid pre-existing immunity in humans.

Concerns about DNA vaccines potentially integrating into the human genome have been largely dispelled by animal studies.

mRNA vaccines, like Pfizer and Moderna, are less likely to integrate into the human genome compared to DNA vaccines.