Immunisation - Vaccines PDF

IMMUNISATION VACCINES Noman Naseem VETS2007 [email protected] Learning objective Discuss the difference between passive and active immunization List the requirements of an ideal vaccine Discuss the difference between infectious and non-infectious vaccines List some possible vaccine side-effects...

IMMUNISATION VACCINES Noman Naseem VETS2007 [email protected] Learning objective Discuss the difference between passive and active immunization List the requirements of an ideal vaccine Discuss the difference between infectious and non-infectious vaccines List some possible vaccine side-effects IMMUNISATION PASSIVE IMMUNISATION • Transfer of antibodies • Temporary immunity E.g., tetanus antitoxin, antivenoms ACTIVE IMMUNISATION • Administration of an antigen > development of an immune response • Immunity is not immediate • Immunity is long-lasting and can be re-stimulated • Vaccine ACTIVE IMMUNISATION No vaccine is perfect, but the ideal vaccine should: • • • • • • • • • Be inexpensive Be consistent in formulation Be stable Have a long shelf-life Be able to induce the most appropriate type of immune response Incorporate a range of epitopes from the target organism Be able to induce a long-lived immune response Be able to induce memory Have no adverse effects Vaccines Infectious vaccines • Infecting an animal w/o producing disease • A single dose is effective • Live virulent, live attenuated, recombinant, marker Non-infectious vaccines • Less efficacious • Requiring up to 3 doses (priming, immunisation, boosting) • Killed whole, subunit, naked DNA INFECTIOUS VACCINES LIVE VIRULENT VACCINES • Injection of a live and virulent infectious agent • Quite uncommon (why?) ORF (contagious ecthyma) in sheep INFECTIOUS VACCINES LIVE ATTENUATED VACCINES • Most commonly used • Intact and viable organism but with reduced virulence (replication but no disease) Blue eye induced by CAV-1 vaccination in dogs Means of attenuation Multiple Passaging Heating Antigenically Deletion of similar organisms virulence factor INFECTIOUS VACCINES What are the disadvantages? • Reversion of virulence • Wrong route of administration > disease • Contamination • Less stability • Specialised storage conditions INFECTIOUS VACCINES RECOMBINANT ORGANISM VACCINES Viral gene Non-virulent virus Recombinant virus with inserted target virus gene E.g., canarypox virus used as a carrier for genes derived from FeLV, CDV, rabies virus Carrier virus expressing product of inserted gene After injection: recombinant virus entering DCs > activation of the immune response INFECTIOUS VACCINES MARKER VACCINES If serum antibodies in an animal are due to an actual infection or secondary to vaccination? Does the cow have serum anti-GpE? Natural IBR virus expressing GpE YES Field exposure/infection Vaccine IBR strain w/o GpE NO Seropositive due to vaccine NON-INFECTIOUS VACCINES KILLED WHOLE ORGANISM VACCINES Live attenuated vaccine More effective immunity Virus treated with chemicals (formalin, alcohol, alkylating agents) Fewer doses required More stability on storage More risk of disease Risk of spreading to other animals Killing (but the antigenicity is preserved) More risk of containing contaminating organisms More risk of reversion Adjuvants required (with more adverse effects) Can be given by natural route Easy storage conditions No replication and no pathology Lower costs Higher doses required Killed vaccine NON-INFECTIOUS VACCINES SUBUNIT VACCINES Not containing the entire organism, but only the immunogenic structural protein Two methods of production e.g. FeLV vaccine incorporating gp70 NON-INFECTIOUS VACCINES NAKED DNA VACCINES • Gene inserted into a bacterial plasmid > direct injection into the animal • Plasmid transfecting local host cells, including APCs that migrate to regional lymphoid tissue • Ready access of the protein to the antigen processing pathway (potent immune response) • E.g., experimental injection of the plasmid containing the gene for rabies glycoprotein G into the pinna of dogs ADJUVANTS Substances added to the vaccine to maximise its effectiveness Advantages • Increased speed or magnitude of the immune response • Reduction of the amount of antigen or number of doses • Establishment of long-term memory Disadvantages: may cause tissue irritation/lesion Hallmarks of an ideal adjuvant ADJUVANTS (1) DEPOT ADJUVANTS • Aluminium salts (insoluble) mixed with the Ag > injection > formation of a granuloma > slow leakage of the Ag into the body > prolonged antigenic stimulation • Freud’s incomplete adjuvant (water-in-oil emulsion) mixed with the Ag > local chronic inflammation (granuloma or abscess) (2) PARTICULATE ADJUVANTS • Readily phagocytosable particles incorporating the Ag > more effective delivery to APCs • Emulsion, microparticles, liposomes (3) IMMUNOSTIMULATORY ADJUVANTS • Enhanced cytokine production and selective stimulation of Th1 or Th2 cells • E.g., synthetic bacterial products ADVERSE CONSEQUENCES OF VACCINES 1) 2) 3) 4) Transient pyrexia and lethargy (a few days post-vaccination) Type I hypersensitivity response (pruritus, oedema) Type II (IMHA) or III (vasculitis) hypersensitivity reactions Feline injection site sarcoma: especially with FeLV and rabies vaccines; poor prognosis Feline injection site sarcoma Rare (0.1-0.01%) side effect of vaccine injection, occurs most commonly with killed vaccines (FeLV, Rabies) containing adjuvant Increased risk with multiple injections Adjuvant in induces of chronic inflammation, which may be linked to the carcinogenesis of FISS Injections of other drugs including meloxicam, cisplatin, long-acting penicillin, methylprednisolone and lufenuron may also induce sarcomas A dog is developing the disease for which was vaccinated: Why??? VACCINE FACTORS • Improper storage of vaccine • Improper administration (wrong route, wrong dose) • Reversal to virulence • Using a vaccine past its expiry date HOST FACTORS • The animal was incubating disease at the time of vaccination or was infected immediately after vaccination • Maternal antibody interference • Immunosuppressed dog