Applications of ImmunologyChapter 18

ObjectivesKnow some terms Immunization, vaccination, vaccine, etc Explain why vaccination worksCompare and contrast different vaccine typesKnow some serological tests

Adaptive Immunity

Vaccination and ImmunizationTerms often used interchangeablyVaccinationProcess of introducing vaccine into the bodyRoute of administration may be oral, subcutaneous or intramuscularImmunizationResult obtained when vaccine stimulates immunityVaccines induce Abs and activated immune cells to protect host from future infection

Booster DosesRepeated vaccinations for the same diseasesAllow body to build up defence to particular level Schedule for infant and childhood immunizations includes booster doses for tetanus, diphtheria, whooping cough and polio- Immunization begins at infancy - Boosters start in kindergarten- Adults need booster doses against tetanus every ten years - Booster tetanus toxoid also given following any deep injury

Primary and Secondary Immune Response to an Ag

IgM appears first and IgG follows and provide longer-term immunityGreater immune response following repeated exposure(s) to the same Ag Fig. 17.16

Types of VaccinesVaccinesPreparation of microbial antigens (Ags) used to induce protective immunity4 major typesWhole cells (live attenuated or inactivated-killed)Acellular or subunit (toxoid, recombinant vaccine)Conjugated (capsule + protein)- Haemophilus influenzae type b vaccine DNA or nucleic acid

Whole Cell VaccinesAttenuated (live but avirulent): longer term, w/o booster, effective, closely mimic actual infectionViral vaccines: Measles, rubella, polio (Sabin), chickenpoxBacterial vaccines: TB (BCG) and typhoidWhat are the disadvantages?

Inactivated/killed: (inactivatedviruses; killed-bacteria) Heat or chemical killing/inactivation (chemicals: formalin or phenol). Less effective, required boosters.Killed by heat, Viral vaccines: Rabies (original), polio (Salk), influenzaBacterial vaccine: Whooping cough (pertussis) vaccine, cholera, pneumococcal pneumonia

Acellular or Subunit VaccinesAntigenic fragments of a pathogen that best stimulates an immune responseCapsular polysaccharide (part of capsule)Surface antigenic proteinsToxoids (inactivated toxin)

Recombinant: Subunit vaccines that are produced by genetic modification techniquesE.g. hepatitis B virus vaccine Hepatisis B surface antigen (HBsAg)

Acellular or Subunit Vaccines

Conjugated VaccinesCapsular polysaccharides elicit poor immune responsesT-independent Ags do not effectively stimulate the immune system especially in children < 24 months.Conjugated vaccines covalently attach antigen to carrier protein (from same organism)This conferring immunological properties on carrier protein (can activate B-cells)Example:Hib vaccine (Haemophilias influenzae type b) combined with DT toxoidsMenengicocal vaccine (Neisseria menengitidis)Pneumococcal vaccine (Streptococcus pneumoniae)

DNA VaccinesDNA directly introduced into host cellDNA fragment is expressed (protein produced) host immune system (humoral and cellular) responds to foreign proteins producedAdvantagesDNA is artificial and purity can be assuredExpressed for extended times with good immunological memorySeveral genes can be mixed and injected as oneDNA sequences can be produced cheaplyNot for non-protein AgsApproved in animals but not yet in humansProtects horses from West Nile virus and salmon from viral disease

DNA VaccinesPart of gene encoding pathogens protein is introduced into the bodyInside the cell, this protein (fragment) is produced it exists the cells and stimulates the immune system

Multivalent VaccinesIndividual vaccines often combinedReduces number of injections children are subjected to.Diphtheria (D) and acellular Pertussis and Tetanus toxoids (T) vaccine DaPT Salk polio vaccine added to above DaPTpolio vaccine Pentavalent vaccine - DaPT-polio-Hib (with Haemophilus influenzae type b) has been adopted in Canada

Adjuvants Any nontoxic materials (chemical additives) that prolongs antigen interaction with immune cells Increase the effectiveness of a vaccine Several types are availableAluminum salts, phosphates, oil-and-water emulsion Multivalent DPT or DPT-polio vaccine onto aluminum salts

Vaccines Used to Prevent Bacterial Diseases

DiseaseVaccineDiphtheria Purified diphtheria toxoid Meningococcal meningitis Purified polysaccharide from Neisseria meningitidis Pertussis (whooping cough) Inactivated toxin plus acellular fragments of Bordetella pertussis Pneumococcal pneumonia Purified polysaccharide from seven strains of Streptococcus pneumoniae Tetanus Purified tetanus toxoid Haemophilus influenzae type b meningitis Polysaccharide from Haemophilus influenzae type b conjugated with protein to enhance effectiveness

Vaccines Used to Prevent Viral Diseases

DiseaseVaccineInfluenza Injected vaccine: inactivated virus (Nasally administered: attenuated virus) Measles Attenuated virus Mumps Attenuated virus Rubella Attenuated virus Chickenpox Attenuated virus Poliomyelitis Inactivated virus (Salk) (IPV)Attenuated virus (Sabin) (OPV)

Vaccines Used to Prevent Viral Diseases

DiseaseVaccineRabies Inactivated virus Hepatitis B Antigenic fragments of virus Hepatitis A Inactivated virus Smallpox Live vaccinia virus Herpes zoster Attenuated virus Human papillomavirus Antigenic fragments of virus

Advantages:Easy to administer (Save the lives of 3-5 million children who die each year from diseases like bacterial diarrhea)Easily harvested in large quantitiesNo refrigeration or expiry date

Transgenic Plants - Engineered to Produce Vaccines

Qs & AsSome diseases such as diphtheria and tetanus are rare in countries like Canada, why are vaccination against these diseases still required?

Why are annual vaccinations against influenza required whereas only one or two vaccinations over the course of ones life may be required for some diseases?

Why is there need for more than one vaccinations of infants/children against diseases such as diphtheria, tetanus, polio and whooping cough (pertussis)?

The following is for your information only.

Monoclonal AntibodiesFig. 18.2Monoclonal antibodies:UniformHighly specificProduced readilyUseful in diagnosticsBacteria pathogensPregnancy testsTreatment of diseasesLeukemiaRheumatoid arthritisAsthma

Diagnostic ImmunologyAntiserum is specific for bacterium and protein recognition and is used in diagnostic microbiology & medicine Slide agglutination test, enzyme-linked immunosorbent assay (ELISA), direct fluorescent-antibody testMonoclonal vs polyclonal Abs

Fig. 18.11

Figure 18.11 Fluorescent-antibody (FA) techniques.Group A streptococci from patients throatFluorescent dyelabeled antibodies to group A streptococciFluorescentstreptococciReactions in a positive direct fluorescent-antibody testReactions in a positive indirect fluorescent-antibody testT. pallidum fromlaboratory stockSpecific antibodies in serum of patientAntibodies bindingto T. pallidumFluorescent dyelabeledanti-human immuneserum globulin(will react withany immunoglobulin)Fluorescent spirochetes(see Figure 3.6b)

Enzyme-Linked Immunosorbent Assay Direct ELISA to detect Ags & indirect ELISA to detect AbsUse of microtiter plate

E.g. Measurement of drugs using direct ELISA (A):

Anti-drug Abs are absorbed to wellPatients urine is added to wellDrug is captured by AbsWells are rinsedEnzyme-linked Abs are added to form a sandwichAdd a substrate for the linked enzyme to produce a color

ELISA (Example)Fig. 18.13Pregnancy testDetects human chorionic gonadotropin (hCG) hormone in urine of pregnant women

Reactions in Neutralization Tests

Immune DisordersC. 19

Self-ToleranceThe human immune system is capable of recognizing a minimum of 1015 AgsBody doesn't make Ab or CTL against selfClonal deletion (B cells) and thymic selection (T cells)Process of destroying B and T cells that react to self antigensHappens at the immature lymphocyte stage

Autoimmune DiseasesClonal deletion and thymic selection usually ensures self-toleranceAutoimmunity responses result from loss of self-toleranceMay or may not be associated with diseaseAbout 30% of population will have autoimmune lymphocytes by age 65 (but not exhibit disease symptoms)Can also be induced by infectious organisms and drugsDisease results when autoimmune lymphocytes damage tissue componentsAutoimmune diseases more common in women (75%)

Cytoxic Autoimmune ReactionsAntibodies react against cell surface antigens

Graves diseaseAntibodies against thyroid-stimulating hormone receptor Stimulate production of thyroid hormone hyperthyroidismThyroid gland greatly enlarged and markedly bulging, staring eyes

Immune Complex Autoimmune Reactions Abs form complexes that are deposited in tissues/organsSystemic lupus erythematosusProduce Abs that complex with own cells, DNA, histones, ribosomesComplexes deposited in blood vessels and kidney glomeruliRheumatoid arthritis- Immune complexes of IgM, IgG and complement are deposited in joints- Cause severe damage to the cartilage and bone of the joint

Cell Mediated Autoimmune ReactionsT-cells attack specific cells/tissuesType I diabetes (Insulin dependent diabetes)T-cells attack the pancreatic b-cellsResults in destruction of b-cells and loss of insulin production Multiple sclerosisT-cells attack myelin protein of nervesResults in demyelination of axons that leads to fatigue, weakness and may eventually lead to paralysis

Immune DeficienciesCongenital: Due to defective or missing genesSelective IgA immunodeficiencySevere combined immunodeficiencyAcquired: Develop during an individual's life, due to drugs, cancers, and infectionsArtificial: Immunosuppression drugsNatural: HIV infections

*Acellular- taking a piece of the organismProteins stimulate T cell dependent. Independent simulated by carbs and lipids*********Diphtheria and tetanus are always present in the environment, cant get rid of themInfluenza virus is constantly changing. Strains of this year wont be the same the next year*********