MICROBIOLOGY AND IMMUNOLOGY (BIOL200/343), SUMMER, 2017 Lecture:9 MICROBIOLOGY AND IMMUNOLOGY (BIOL200/343), SUMMER, 2017 Dr.Q.M.I.Haq

Vaccines A vaccine is a biological preparation that improves immunity to a particular disease. How vaccines work

Vaccines can only be used to prevent infections (both viral and bacterial). Made from a an attenuated, less virulent strain of the virus, inactivated virus or by using only part of the virus/bacteria itself. An attenuated virus is a weakened, less vigorous virus. “Attenuate" refers to procedures that weaken an agent of disease (heating). Vaccines can be prophylactic (example: to prevent or ameliorate the effects of a future infection by any natural or "wild" pathogen), or therapeutic (e.g., vaccines against cancer are also being investigated).

Center for Disease Control and Prevention (CDCP): Immunization efforts have lowered incidence rates of several serious illnesses by more than 95% since the beginning of the twentieth century. Includes: diphtheria, polio, measles, and tetanus.

Types of Vaccine: 1-Inactivated Some vaccines contain inactivated, but previously virulent, micro-organisms that have been destroyed with chemicals, heat,radioactivity, or antibiotics. Examples are influenza, cholera, polio, hepatitis A, and rabies etc. 2-Attenuated Some vaccines contain live, attenuated microorganisms. Although most attenuated vaccines are viral, some are bacterial in nature. Examples include the viral diseases yellow fever, measles, rubella, and mumps, and the bacterial disease typhoid. Attenuated vaccines have some advantages and disadvantages. They may not be safe for use in immunocompromised individuals, and may rarely mutate to a virulent form and cause disease.

3-Toxoid Toxoid vaccines are made from inactivated toxic compounds that cause illness rather than the micro-organism. Toxoid vaccines are known for their efficacy. Examples Tetanus and diphtheria. Not all toxoids are for micro-organisms; for example, Crotalus atrox toxoid is used to vaccinate dogs against rattlesnake bites. 4-Subunit Protein subunit – rather than introducing an inactivated or attenuated micro-organism to an immune system (which would constitute a "whole-agent" vaccine), a fragment of it can create an immune response. Examples include the subunit vaccine against Hepatitis B virus that is composed of only the surface proteins of the virus.

5- Conjugate Certain bacteria have polysaccharide outer coats that are poorly immunogenic. By linking these outer coats to proteins (e.g., toxins), the immune system can be led to recognize the polysaccharide as if it were a protein antigen. Examples-this approach is used in the Haemophilus influenzae type B vaccine. 6-Valence Vaccines may be monovalent (also called univalent) or multivalent (also called polyvalent). A monovalent vaccine is designed to immunize against a single antigen or single microorganism. A multivalent or polyvalent vaccine is designed to immunize against two or more strains of the same microorganism, or against two or more microorganisms. 

Production: Vaccine production has several stages. First, the antigen itself is generated.   Antigen is isolated from the cells used to generate it.   A virus may need to be inactivated.   Finally, the vaccine is formulated by adding adjuvant, stabilizers, and preservatives. The adjuvant enhances the immune response of the antigen, stabilizers increase the storage life, and preservatives allow the use of multidose vials. Note: In 2010, India produced 60 percent of the world's vaccine worth about $900 million(€670 million).

DIVA vaccines: DIVA (Differentiating Infected from Vaccinated Animals) vaccines make it possible to differentiate between infected and vaccinated animals. DIVA vaccines carry at least one epitope less than the microorganisms circulating in the field. Use in practice: The DIVA strategy has been applied in various countries. Note: the part of an antigen molecule to which an antibody attaches itself.

Trends: Vaccine development has several trends: Until recently, most vaccines were aimed at infants and children, but adolescents and adults are increasingly being targeted. Combinations of vaccines are becoming more common; vaccines containing five or more components are used in many parts of the world.  In 2013, Biofarma has released a new product called Pentabio, which is combination vaccine of Diphtheria, Tetanus, Pertussis, Hepatitis B, and Haemophilus Influenzae Type B for baby/infant in Indonesia’s Immunization Program. New methods of administering vaccines are being developed, such as skin patches, aerosols via inhalation devices, and eating genetically engineered plants.

Vaccines are being designed to stimulate innate immune responses, as well as adaptive. Vaccines are being developed to defend against bioterrorist attacks such as anthrax, plague, and smallpox. Scientists are now trying to develop synthetic vaccines by reconstructing the outside structure of a virus.

Plants as bioreactors for vaccine production: Transgenic plants have been identified as promising expression systems for vaccine production. Complex plants such as tobacco, potato, tomato, and banana can have genes inserted that cause them to produce vaccines usable for humans. Bananas have been developed that produce a human vaccine against Hepatitis B. 

Why aren’t they always effective? Less effective vaccines need booster injections to stimulate secondary responses. Some people don’t respond well/at all to vaccinations. Defective immune systems. Malnutrition particularly protein. Antigenic variation caused by mutation No vaccines against protoctists (malaria and sleeping sickness). Sleeping sickness caused by Trypanosoma has a thousand different ags and changes them every 4-5 days. Antigenic concealment parasites live inside body cells. Like Plasmodium live in liver and blood cells, HIV live inside T-helper cells. Parasitic worms – cover themselves in host proteins.

HIV: Where’s the vaccine? Several challenges arise with development: HIV continually mutates and recombines HIV infects Helper T cells and live inside the T-helper cells. Helper T cell infection causes problems because it is infecting the same cell needed for immune response! Studies have been done to question the causal association between HIV and AIDS, as there have been cases of AIDS without HIV. (Blattner et al., 1988a,b; Ginsberg, 1988; Evans, 1989a,b, 1992; Weiss and Jaffe, 1990; Gallo, 1991; Goudsmit, 1992; Groopman, 1992; Kurth, 1990; Ascher et al., 1993a,b; Schechter et al., 1993a,b; Lowenstein, 1994; Nicoll and Brown, 1994; Harris, 1995 )