Chapter 21 Vaccines Copyright © 2011 Delmar, Cengage Learning

Immunity Nonspecific immunity –Includes things such as physical barriers, mucus production, inflammation, fever, and phagocytosis –Directed against all pathogens; is the initial defense against invading agents Specific immunity –Takes over when the nonspecific mechanisms fail –Targeted for a specific antigen; has memory –Arises from B- and T-lymphocytes Copyright © 2011 Delmar, Cengage Learning

Types of Immunity Cell-mediated immunity –T-lymphocytes directly attack the invading antigen –Important for protecting against intracellular bacterial or viral infections, fungal diseases, and protozoal diseases Antibody-mediated immunity –B-lymphocytes produce antibodies that react to antigen –Important for extracellular phases of systemic viral and bacterial infections and protection against endotoxin and exotoxin-induced disease Copyright © 2011 Delmar, Cengage Learning

Ways to Acquire Specific Immunity Active immunity –Arises when an animal receives an antigen that activates B- and T-lymphocytes –Creates memory Passive immunity –Arises when an animal receives antibodies from another animal –Provides immediate onset of immunity, but the animal is protected for a shorter time (no memory) Natural immunity –Acquired during normal biological experiences Artificial immunity –Acquired through medical procedures Copyright © 2011 Delmar, Cengage Learning

Vaccines A vaccine is a suspension of weakened, live, or killed microorganisms administered to prevent, improve, or treat an infectious disease Types of vaccines: –Inactivated (killed): made from microbes, microbe parts, or microbe by-products that have been chemically treated or heated to kill the microbe Contain adjuvants (substances that enhance the immune response by increasing the stability of the vaccine in the body); may cause vaccine reactions Advantages: safe; stable; unlikely to cause disease Disadvantages: need repeated doses; possible reactions Copyright © 2011 Delmar, Cengage Learning

Vaccines Types of vaccines (cont.): –Attenuated (modified-live): microorganisms go through a process of losing their virulence (called attenuation), but must be able to replicate within the patient to provide immunity Advantages: immunity lasts longer; has better efficacy and quicker stimulation of cell-mediated immunity than killed vaccines Disadvantages: possible abortion; can produce mild forms of the disease; can shed into the environment; proper handling/storage is critical Copyright © 2011 Delmar, Cengage Learning

Vaccines Types of vaccines (cont.): –Live: made from live microorganisms that may be fully virulent Advantages: fewer doses needed; last longer; inexpensive; adjuvants not needed Disadvantages: residual virulence that requires carefully handling –Recombinant: a gene or part of a microorganism is removed from one organism (usually the pathogen) and inserted into another microorganism Advantages: fewer side effects; effective immunity; varied routes of administration Disadvantage: increased cost Copyright © 2011 Delmar, Cengage Learning

Vaccines Types of vaccines (cont.): –Adjuvants: substances that enhance the immune response –There are four types of adjuvants: Depot Particulate Immunostimulatory Mixed –Depot adjuvants protect antigens from rapid degradation which contributes to a prolonged immune response Copyright © 2011 Delmar, Cengage Learning

Vaccines Types of vaccines (cont.): –Particulate adjuvants deliver antigen in such a way that both cell-mediated and humoral immunity are enhanced by stimulation of antigen processing –Immunostimulatory adjuvants promote cytokine production –Mixed adjuvants combine a particulate or depot adjuvant with an immunostimulatory agent Copyright © 2011 Delmar, Cengage Learning

Vaccines Types of vaccines (cont.): –Polyneucleotides: or DNA vaccines injects DNA that encodes for foreign antigens is another type of vaccine Advantage: that it is possible to select only the genes for the antigen of interest Copyright © 2011 Delmar, Cengage Learning

Vaccines Types of vaccines (cont.): –Toxoids: “vaccine” used against a toxin that has been deactivated by heat or chemicals, but is still able to stimulate antibody production Advantage: provides protection against toxin Disadvantages: shorter duration of effectiveness; may contain adjuvants –Antitoxins: substances that contain antibodies obtained from an animal that has been hypersensitized to neutralize toxins Advantage: quick protection against a toxin Disadvantages: short-lived protection; may contain preservatives that can cause reactions Copyright © 2011 Delmar, Cengage Learning

Vaccines Types of vaccines (cont.): –Antiserum: antibody-rich serum obtained from a hypersensitized or actually infected animal Advantage: provides quick protection against a microorganism Disadvantages: shorter duration of effectiveness; may contain adjuvants –Autogenous: vaccine produced for a specific disease in a specific area from a sick animal Advantage: provides protection against the specific organism in a specific area Disadvantage: may contain endotoxin and other by-products found in the culture Copyright © 2011 Delmar, Cengage Learning

Vaccines Types of vaccines (cont.): –Multiple-antigen vaccines are called polyvalent –Polyvalent vaccines contain more than one antigen Contain a mixture of different antigens and are more convenient to administer because fewer injections are needed Adverse reaction increases as the number of antigens increases –To be approved, must show that each part of the polyvalent vaccine induces the same level of immunity as does the single- antigen vaccine –Monovalent vaccines are vaccines with only a single antigen present Using several monovalent vaccines may expose the animal to higher levels of adjuvants Must give more injections Copyright © 2011 Delmar, Cengage Learning

Maternally Derived Antibodies Maternally derived antibodies are antibodies that offspring receive passively from their mothers, either from colostrum or via the placenta Maternally derived antibodies give the offspring disease resistance for a few days and provide variable antibody levels for up to nine weeks To enhance this protection, young animals receive vaccinations and booster vaccinations to ensure appropriate immunity –Booster vaccines are needed because effective vaccination varies among individuals, because of variable levels of maternal antibodies –Booster vaccines also allow antibody levels to rise to satisfactory levels Copyright © 2011 Delmar, Cengage Learning

Vaccine Reactions Although vaccines are considered safe, vaccine reactions can occur All vaccine reactions must be recorded in the medical record Typical vaccine reactions: –Location reactions at the injection site –Fever –Lethargy –Vomiting –Salivation –Difficulty breathing –Vaccine-associated sarcomas in cats –Autoimmune hemolytic anemia in dogs Copyright © 2011 Delmar, Cengage Learning

Issues in Vaccine Use Consider the following with all vaccine protocols: –Vaccine issues Proper care and handling Proper route of administration Proper use (do not mix vaccine products) Proper dose –Patient issues Animal age Freedom from disease Concurrent use of medication Pregnancy Environment Copyright © 2011 Delmar, Cengage Learning

Vaccine Protocols Practice of annual vaccination is now under debate One way to discover when revaccination is necessary is via the antibody titer –An antibody titer is a serum test that reveals the level of antibody to a particular antigen in a particular individual –Antibody titers are expressed as 1:2, 1:4, etc., a ratio that represents the dilution at which the immune response is still adequate Core vaccines are recommended for all individual animals Noncore vaccines are recommended only for individual animals deemed to be at high risk for contact with the organism Copyright © 2011 Delmar, Cengage Learning

Species-Specific Vaccine Protocols Examples of vaccines available for a variety of species are listed in the textbook Copyright © 2011 Delmar, Cengage Learning