All Types of Vaccines, How They Work, Animation.

Summary

This 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.