What They Are How They Work VACCINES What They Are How They Work Topics in nanobiotechnology Ph.D. Student: Aleksandra Różek

What Is a Vaccine? Traditional vaccines contain either parts of microbes or whole microbes that have been killed or weakened so that they don’t cause the disease. - take advantage of the body’s to learn how to eliminate almost any disease causing germ, or microbe, that attacks it. Immune system takes > 1 week to learn how to fight off an unfamiliar microbe. Stronger microbes can spread through the body faster than the immune system can fend them off.

Vaccine Benefits Naturally acquired immunity – immunity produced by antibodies passed from mother to fetus (passive), or by the body’s own antibody and cellular immune response to a disease causing organism (active). Artificially acquired immunity – immunity provided by vaccines, as opposed to naturally acquired immunity, which is acquired from exposure to a disease-causing organism. Herd immunity – the resistance to a particular disease gained by a community when a critical number of people are vaccinated against that disease.

How Vaccines Work? Immune system – a collection of specialized cells and organs that protect the body against infectious diseases.

Lymphocytes: T Cells & B Cells Macrophages – large and versatile immune cells that devour and kill invading microbes and other intruders. - stimulate other immune cells by presenting them with small pieces of the invaders. Lymphocytes - white blood cells that are central to the immune system’s response to foreign microbes. B Cells – white blood cells crucial to the immune defenses. They come from bone marrow and develop into blood cells called plasma cells, which are the source of antibodies. T Cells – white blood cells that direct or participate in immune defenses.

Memory Cells and natural immunity After body eliminated the disease some of the B cells and T cells are converted into memory cells. Memory B cells can quickly divide into plasma cells and make more antibody if needed. Memory T cells can divide and grow into disease-fighting army.

Different Types of Vaccines Live, attenuated vaccines A vaccine made from microbes that have been weakened in the laboratory so that they can’t cause disease. Disease: Measles, mumps, rubella, polio (Sabin vaccine), yellow fever Inactivated or „killed” vaccines A vaccine made from a whole viruses or bacteria that has been inactivated with chemicals or heat. Disease: Cholera, flu, hepatitis A, Japanese encephalitis, plague, polio (Salk Vaccine), rabies Toxoid vaccine A vaccine containing a toxoid, used to protect against toxins produced by certain bacteria. Disease: Diphtheria, tetanus Subunit vaccines A vaccine that uses one or more components of a disease – causing organism, rather than the whole, to stimulate an immune response. Disease: Hepatitis B, pertussis, pneumonia caused by Streptococcus pneumoniae

Different Types of Vaccines Conjugate vaccines A vaccine in which proteins that are easily recognizable to the immune system are linked to the molecules that form the outer coat of disease – causing bacteria to promote an immune response. Conjugate vaccines are designed primarily for very young children because their immune systems can’t recognize the outer coats of certain bacteria. Disease: Haemophilus influenzae type B, pneumonia Caused by Streptococcus pneumoniae DNA vaccines A vaccine that uses a microbe’s genetic material, rather than the whole organism or its parts, to stimulate an immune response. Disease: In clinical testing Recombinat vector vaccines Vaccines that use modified viruses or bacteria to deliver genes that code for microbial antigens to cells of the body. Disease: In clinical testing

Advantages Disadvantages 1 2 3 4 5 6 7 Produce a strong immune response Often give livelong immunity with one or two doses Safer and more stable than live vaccines Don’t require refrigeration: more easily stored and transported Teaches the immune system to fight off bacterial toxins Targeted to very specific parts of the microbe Fewer antigens, so lower chance of adverse reactions Allow infant immune systems to recognize certain bacteria Produce a strong antibody and cellular immune response Relatively easy and inexpensive to produce Closely mimic a natural infection, stimulating a strong immune response Remote possibility that the live microbe could mutate back to a virulent form Must be refrigerated to stay potent Produce a weaker immune response than live vaccines Usually require additional doses, or booster shots When developing a new vaccine, identifying the best antigens can be difficult and time consuming Still in expertimental stages