COVID-19

Vaccine: A permanent solution against viral and bacterial diseases (Part-1)

by Abdullah Al Mamun

There are mainly two types of diseases-Communicable and non-communicable diseases. Communicable diseases are bacterial or viral diseases. Communicable diseases are the most dangerous diseases for human beings. There is much treatment invented to prevent communicable diseases but the vaccine is the most important and useful discovery.

What is a vaccine?

 A vaccine is a substance which is made by any kind of pathogenic part(without infectious active part) which inject to our body for activating our immune system that our immune system destroys the antigen by produce specific antibody & get our body in a healthy condition and memorize the same antigen that If the same antigen or related antigen attacks again in future on our body that our body can produce the same & specific antibody against it for prevention.

The main agenda of the vaccine is ‘it doesn’t make diseases. It just makes a strong immune system forever. 

When and how was the vaccine first discovered?

  In the 18th century, there was a virus that created a pandemic worldwide called Smallpox. About 4,00,000 people were dying every year. There was a method for controlling the spread of smallpox named variolation. The method named after the virus that causes smallpox (variola virus), variation is used to immunize our body from smallpox. It is the process by which material from smallpox patients was given to people who had never had smallpox. This was done either by scratching the material into the arm or inhaling it through the nose. With both types of variation, people usually went on to develop the symptoms associated with smallpox, such as fever and a rash. However, fewer people died from variation than if they had acquired smallpox naturally.

In 1796 English doctor called Edward Jenner noticed that If a person once infected by that virus and recovered from smallpox then that person recovered for a lifetime. And Dr.Edward Jenner also noticed that there was another virus called Cowpox which was closely similar to smallpox and if A person had gotten cowpox did not show any symptoms of smallpox. Then he experimented on a 9 years old boy.Dr.Edward Jenner took the cow pus from that cow which was infected with the cowpox virus and injected into that boy and months later Jenner injected smallpox into that boy several times but that boy never developed smallpox. After more experiments, Dr.Jenner finally published his discovery in 1801 and stated that Vaccination is the final solution for smallpox and replaced it with the violation process.

How does the vaccine work in our bodies?

           Before we know how vaccines work, we have to know how the immune system works first. the immune system works in three stages:

  1. Recognizing the antigen: An antigen contains hemagglutinin proteins(HA). When an antigen is injected into our body’s bloodstream there are three types of cells mainly found such as macrophages, B- lymphocytes, and T-lymphocytes which work as immune cells.

At first, the macrophages trapped the antigen in lymphoid organs. The phagocytic cells which are guarding the body, engulf and digest the foreign substances and show the HA on its surfaces. Now the T-cell can recognize and bind with it and get activated. After activation T-cells proliferate into different T-cells like Cytotoxic T-cell, Induce T-cell, Helper T-cell, and Suppressor T-cell. The activated helper T-cell also contains HA on its surface associated with MHC( major histocompatibility complex) for recognition of antigen.

  1. Killing The Antigen: Unlike T-cell, B-cell can also ingest HA of antigen and present on its surfaces associated with MHC. When the T-cell interacts with activated B-cell with exposing the MHC receptor, it starts secret lymphokines. Lymphokines are cytokines which are a group of proteins that bring about communication between different cells.

The lymphokines have several functions. Their one function is to stimulate B-cells to produce plasma cells. Then the cell produces specific antibodies against the antigen. 

  1. Memorize the antigen: The lymphokines also trigger B-cell to produce memory B-cell. The Memory B-cell can memorize the antigen for further infection.

The main agenda to Produce memory cell is,

      If the same antigen attacks the body against them the T-cell can easily recognize the antigen and produce the antibody against it quickly. This agenda is used in the vaccine mechanism. A vaccine contains inactivated antigen which goes through the same immune response and the B-cell also stores the inactivated form of antigen as a memory. Since B-cell already stored the inactivated form of antigen, then the immune system can easily immunize the body if the activated or whole antigen attacks the body again.

Are there any common or basic strategies to develop a vaccine?

     In modern times, there is no basic strategy for vaccine development. There are several types of strategies for several types of vaccines. Vaccine development depends on many factors like the area’s people’s immune system, pathogen activity, etc. 

What are the types of a vaccine?

    The main agenda for vaccine development is injecting antigen without causing illness.That’s why scientists made different types of vaccines for people’s welfare.There are some main types of vaccine discussed below:

Live Attenuated Vaccines: It is a vaccine composed of a complete living bacteria or virus which are so weaker, asymptomatic that these pathogens can’t get multiply and spread. But the immune system will still recognize its antigens as a memory for a lifetime.

  • Advantages: It is one of the best vaccines compared to others.It introduces complete living pathogens to the body that the body’s immune system gets excellent stimulation. That’s why this vaccine needs fewer doses than others for life long immunity. 
  • Disadvantages: This type of vaccine is a big risk for those people who have weak immunity or going through some treatment like HIV or chemotherapy.Because of these, there are many chances of pathogens could get stronger and occur sickness. 
  • Specific Vaccines:
    • Measles
    • Mumps
    • Rubella (MMR combined vaccine)
    • Varicella (chickenpox)
    • Influenza (nasal spray)
    • Rotavirus

Inactivated Vaccines: It is composed of specific whole kill pathogens or small fragments of the pathogen( like protein or sugar) which loses its activity that it can’t occur diseases. Though the pathogen is date dead the immune system can still recognize it and learn from it how to fight against a live version of it later.

  • Advantages: This vaccine can take anyone.Even those people can also take this vaccine who has weak immunity because it can’t cause sickness. It can also easily be stored because they can’t get spread and mutated. 
  • Disadvantages: Since the virus or bacteria is dead, it can’t be that much specific as a live attenuated vaccine.  So it has to be given several doses and booster shots also for making the immune system strong. 
  • Specific Vaccines:
    • Polio (IPV)
    • Hepatitis A
    • Rabies

Subunit/conjugate Vaccines: It is composed of polysaccharides molecules from the surface of other bacteria which is attached to something else that the immune system will give a strong response.In most of the conjugated vaccine, the polysaccharide is attached to diphtheria or tetanus toxoid proteins.And the immune system recognizes these proteins so easily that the immune system gives a stronger response to these polysaccharides. 

  • Advantages: Conjugated vaccines can show immunological memory and minimize asymptomatic carriage of bacteria.It builds herd immunity also.
  • Disadvantages: It is more complicated to prepare.During conjugation, this vaccine loses its immunogenicity.The major disadvantages are it shows very low immune responses in young children.
  • Specific Vaccines:
    • Hepatitis B
    • Influenza
    • Haemophilus Influenzae Type B (Hib)
    • Pertussis (part of DTaP combined immunization)
    • Pneumococcal
    • Human Papillomavirus (HPV)
    • Meningococcal

Toxoid Vaccines: Some bacteria secrets some toxins that are poisonous proteins for causing diseases in our body.Our immune system can recognize those toxins as like as the carbohydrate or protein subunits on the surface of bacteria. So scientists made a chemical which is a mixture of formaldehyde and water.This chemical composition acts as bacterial toxins but doesn’t cause diseases that the immune system can recognize and learn from it how to fight with these toxins.

  • Advantages: It stimulates strong antibody production and also generates long-lasting memory cell production.It’s very safe to store also.
  • Disadvantages: It’s not highly immunogenic.That’s why this vaccine requires a series of doses and must be given a booster dose every 10 years. 
  • Specific Vaccines:
  • Diphtheria
  • Tetanus

DNA Vaccines: DNA vaccine is one of the most promising and newest vaccines and still in experimental stages.It is composed of a few parts of the pathogen’s DNA instead of all unnecessary parts of a bacteria or virus.These DNA parts instruct the immune system to produce antigens for fighting against the pathogens all by itself.As a result, these vaccines would be very efficient immune system trainers.

  • Advantages: It is a non-infectious vaccine.It Stimulates the innate immune response.It is easy to develop.
  • Disadvantages: It has a limitation for protein immunogens. there is a risk of affecting gene controlling cell growth. A DNA vaccine can induce antibody production DNA.
  • Specific Vaccines:
  • pVAC

Recombinant Vector Vaccines: It is similar to the DNA vaccine. It is composed of DNA that is taken from a harmful pathogen and inserted into the bacterial or yeast cells to develop the vaccine. The DNA is taken from the virus or bacterium against which we want to protect. This injection into other cells helps to produce quantities of active ingredients which helps to manufacture the vaccine.

  • Advantages: It is not costly, it can be produced much faster than traditional vaccines, it is safer than a normal attenuated vaccine because it is impossible to transmit the disease.
  • Disadvantages: There is some possibility of reversion to buy Reliance by secondary mutation or reassortant. it has the limitation of use in immunocompromised patients. its immune response to virus-infected cells may cause a pathological problem 
  • Specific Vaccines:
  •  hepatitis B vaccine

If vaccine production needs time then how to fight against antigens?

    We can immunize our body in two ways:

          1.Active immunization: Vaccination process

          2. Passive immunization: Antibody(Antibiotic), which is a medicine.

If antibiotics can also immunize our body then why should we take vaccines over antibiotics?

    The vaccine is related to the immune system which makes our immune system for a long time. There are no side effects on our body. 

   But Medicine is related to only a specific pathogen that works as a specific immune system for a short time. There are major side effects in our body which is called antibiotic resistance that make our immune system weak. 

References:

  1. https://pubmed.ncbi.nlm.nih.gov/21739679/
  2. https://youtu.be/Atrx1P2EkiQ
  3. https://youtu.be/YlKLpQEWILg
  4.  http://vk.ovg.ox.ac.uk/vk/types-of-vaccine
  1. https://www.immunology.org/celebrate-vaccines/public-engagement/guide-childhood-vaccinations/how-vaccineswork#:~:text=Vaccines%20contain%20a%20harmless%20form,response%20without%20making%20you%20sick

Abdullah Al Mamun

Biochemistry & Biotechnology

University of Science & Technology, Chittagong

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