E N I C C A V Dr

E N I C C A V Dr. Nilansu Das Dept. of Molecular Biology Surendranath College

Clarified syllabus. Clarification shown in blue An overview of immune response : Innate and adaptive immune response, primary and secondary immune response, organs of mammalian immune system Basic concept on molecular structure of immunoglobulins(antibody), humoral and cellular immune responses, antigen presentation, MHC Lymphocytes and immune response: cytotoxic T-cell, helper T-cell, suppressor T-cell Naive B-cell, plasma cell, memory B-cell Basic concept in Autoimmune diseases, Immunodeficiency-AIDS and vaccination. Introduction to immunodiagnostics – RIA, ELISA.

Types of Acquired Immunity

Vaccine A vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease. A vaccine typically contains an agent that resembles either: (a) Weakened (attenuated) or killed forms of the disease-causing microorganism and is often made from (b) The toxins produced by the microbe (c) One of the microbe’s surface proteins. (d) The nucleic acid portion of the microbe that codes for toxins or surface proteins The agent stimulates the body's immune system to recognize it as a threat, destroy it, and develop the ability to further recognize and destroy any encounter of the same microorganisms in future.

Vaccine…. continued Vaccines can be Prophylactic (to prevent the effects of a future infection). Most of the vaccines that we know of, falls into this category or Therapeutic (to fight a disease that has already occurred, such as cancer). The administration of vaccines is called vaccination. Vaccination is the most effective method of preventing the spread of infectious diseases. widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the restriction of diseases such as polio, measles, and tetanus from much of the world.

The Small Pox Story Smallpox was a contagious and deadly disease, causing the deaths of 20– 60% of infected adults and over 80% of infected children. When smallpox was finally eradicated in 1979, it had already killed an estimated 300– 500 million people in the 20 th century. The first disease people tried to prevent by inoculation was most likely smallpox, with the first recorded cases occurring in the 16 th century in China. It smallpox, first recorded cases 16 th century in China was also the first disease for which a vaccine was produced. Although at least six people had used the same principles years earlier, the smallpox vaccine was invented in 1796 by English physician Edward Jenner. The terms vaccine and vaccination are derived from Variolae vaccinae (smallpox of the cow), the term devised by Edward Jenner to (smallpox of the cow) denote cowpox. He used it in 1798 in the long title of his Inquiry into the Variolae vaccinae Known as the Cow Pox, in which he described the protective effect of cowpox against smallpox In 1881, to honor Jenner, Louis Pasteur proposed that the term vaccine should be extended to cover the new protective inoculations then being developed.

Vaccination is one of the most effective ways to prevent diseases. A vaccine helps the body’s immune system to recognize and fight pathogens like viruses or bacteria, which then keeps us safe from the diseases they cause. Vaccines protect against more than 25 debilitating or life-threatening diseases, including measles, polio, tetanus, diphtheria, meningitis, influenza, tetanus, typhoid and cervical cancer. Currently, the majority of children receive their vaccines on time. However, nearly 20 million worldwide still miss out – putting them at risk of serious diseases, death, disability and ill health. Source : WHO

Mechanism of Functioning Vaccines are a way of artificially activating the immune system to protect against infectious disease. The activation occurs through priming the immune system with an immunogen. Stimulating immune responses with an infectious agent is known as immunization. Vaccination includes various ways of administering immunogens. Most vaccines are given by injection as they are not absorbed reliably through the intestines. Live attenuated polio, rotavirus, some typhoid, and some cholera vaccines are given orally to produce immunity in the bowel. While vaccination provides a lasting effect, it usually takes several weeks to develop. This differs from passive immunity (the transfer of antibodies, such as in breastfeeding), which has immediate effect.

Failure of a vaccine A vaccine failure is when an organism contracts a disease in spite of being vaccinated against it. Primary vaccine failure occurs when an organism's immune system does not produce antibodies when first vaccinated. Vaccines can fail when several series are given and fail to produce an immune response. The term "vaccine failure" does not necessarily imply that the vaccine is defective. Most vaccine failures are simply from individual variations in immune response.

Types of Vaccine Several types of vaccines are in use depending on strategies used to try to reduce the risk of illness while retaining the ability to induce a beneficial immune response. Inactivated Some vaccines contain inactivated, but previously virulent, micro-organisms that have been destroyed with chemicals, heat, or radiation. Examples include the polio vaccine, hepatitis A vaccine, rabies vaccine and some influenza vaccines. Modified The live Mycobacterium tuberculosis vaccine developed by Calmette and Guérin is not made of a contagious strain but contains a virulently modified strain called "BCG" used to elicit an immune response to the vaccine.

Types of Vaccine Live Attenuated Some vaccines contain live, attenuated microorganisms. Many of these are active viruses that have been cultivated under conditions that disable their virulent properties, or that use closely related but less dangerous organisms to produce a broad immune response. Although most attenuated vaccines are viral, some are bacterial in nature. Examples include the viral diseases yellow fever, measles, mumps, and rubella, and the bacterial disease typhoid. The live attenuated vaccine containing strain Yersinia pestis EV is used for plague immunization. Attenuated vaccines have some advantages and disadvantages. They typically provoke more durable immunological responses and are the preferred type for healthy adults. But they may not be safe for use in immunocompromised individuals, and on rare occasions mutate to a virulent form and cause disease.

First Generation Vaccines First generation vaccines are whole-organism vaccines – either live and weakened, or killed forms. Live, attenuated vaccines, such as smallpox and polio vaccines, are able to induce killer T-cell (TC or CTL) responses, helper T-cell (TH) responses and antibody immunity. However, attenuated forms of a pathogen can get converted to a dangerous form and may cause disease in immunocompromised vaccine recipients (such as those with AIDS). While killed vaccines do not have this risk, they cannot generate specific killer T cell responses and may not work at all for some diseases.

Second Generation Vaccines Subunit vaccines are the Second generation vaccines and were developed to reduce the risks from live vaccines. These are subunit vaccines, consisting of specific protein antigens (such as tetanus or diphtheria toxoid) or recombinant protein components (such as the hepatitis B surface antigen). They can generate TH and antibody responses, but not killer T cell responses.

Third Generation Vaccines DNA vaccines are third generation vaccines. These vaccines contain DNA that codes for specific proteins (antigens) from a pathogen. The DNA is injected into the body and taken up by cells, whose normal metabolic processes synthesize proteins based on the genetic code in the DNA that they have taken up. Because these proteins contain regions of amino acid sequences that are characteristic of bacteria or viruses, they are recognized as foreign and when they are processed by the host cells and displayed on their surface, to triggers immune responses. Alternatively, the DNA may be encapsulated in protein to facilitate cell entry. If the DNA is encapsulated in the capsid protein, the resulting vaccine can combine the potency of a live vaccine without reversion risks.

Third Generation Vaccines In 1983, Enzo Paoletti and Dennis Panicali at the New York Department of Health devised a strategy to produce recombinant DNA vaccines by using genetic engineering to transform ordinary smallpox vaccine into vaccines that may be able to prevent other diseases. They altered the DNA of cowpox virus by inserting a gene from other viruses (namely Herpes simplex virus, hepatitis B and influenza). In 2016 a DNA vaccine for the Zika virus began testing at the National Institutes of Health. The study was planned to involve up to 120 subjects between 18 and 35. Separately, Inovio Pharmaceuticals and Gene. One Life Science began tests of a different DNA vaccine against Zika in Miami. The NIH vaccine is injected into the upper arm under high pressure. Manufacturing the vaccines in volume remains unsolved. Clinical trials for DNA vaccines to prevent HIV are underway.

u o Y k n a h T Dr. Nilansu Das Dept. of Molecular Biology Surendranath College