B8. Passive Immunization Flashcards
B8. Passive Immunization
• Natural (maternal) or artificial (homologous 2-3w, heterologous 1-2 weeks). Prevention before infection, or after infection to prevent symptoms.
• Convalescent serum, immune serum, hyper immune serum, Ig fraction, Mab can be used.
• Passive immunisation provides direct immunity. Can be used if no time for active immunisation or immune suppressed animals.
• Artificial: always atb, no cells are involved - big difference btw maternal and artificial immunity.
o Atb from same sp - homologous - this is preferred! 2w protection. Can be given repeatedly with same efficiency.
o Atb from different sp - heterologous - limitations compare to homologous, 1w protection. Can’t be repeated, it will have no effect in case it has to be repeated (even if other disease).
• If time is available, immunise the mother! A natural immunity is longer lasting than artificial. Several months protection can be offered depending on vaccine etc.
• Atb injected into the animal will give an immediate protection and protect from clinical signs of a disease – it will block the pathogenesis of the disease, but they will never protect the enterocytes of the organism!!
• Do not wait for the clinical signs if you almost know for certain the animal have been infected. It will not cause harm if they are used, it will only cost money.
• If the clinical signs are present already, atb have to be used, especially in viruses (or sometimes INF).
Routes of vaccination
• Parenteral o Protects from clinical signs and not from infection (only certain cases, may be small local effect). o Always the first immune response near the site of infection, memory cells in these areas will circulate and be stored mostly in the bone marrow. o Best response after iv injection: first lymphoid organ will be the spleen, full of inducible cells. Similar effect ip, full of MPS cells - systemic response in different areas of the body. o Im or sc are most common and easy to use but not very efficient. o Intra dermal injection (hard if skin is not thick enough) may provide local protection on site of injection and also some mucosal surfaces. o May still be infected and shed organisms even if no clinical signs • Local o Immune response induced on body surface, infection may be blocked. o Usually live vaccines are needed for local immunisation, inactivated vaccine may protect locally if injected into the mucosal membrane (otherwise washed away etc.) o Apply vaccine in food, water, nasal etc. o Weak systemic response
Limits of vaccination
• Animals will not give a uniform reaction due to differences in age, gender, immune status etc. Even if the animals are almost identical, there will always be individuals that do not respond to the vaccine as expected. • Over or no response at all even if no immunodeficiency etc. • Overreaction is the most dangerous - may generate tumours when development of the cells are stopped and atg/atb complexes can be deposited in organs and cause damage. • Weak or no response: not enough protection the animal will get the disease. • Every protection can be broken by superinfection of pathogens - vaccination only offers immunity against average amount of atg. Normally immunised animals may sometimes shed so many organisms that they break through the protection offered by the vaccine. Not only a danger of unvaccinated animals! • Adjuvants can be used to link with BCR - Immune stimulated complexes are formed that holds the atg • together to easy the cross linking of the BCR. • If atg are mixed with oil droplets and injected (tissue irritant), some of the proteins are immediately released from the droplet and some later - helps immune response to produce the specify atb. • Aluminium adjuvants: immune response does not know what to do with it, and a lot of danger signals are produced as it cannot be broken down. Not widely used anymore, allergy are more often observed with aluminium as an adjuvant. • Freund adjuvant: best adjuvant composed of mineral oils and inactivated mycobacterium - very irritating! • Excellent response, but massive tissue damage at the site of injection. No longer used, not allowed in most countries. Incomplete version with mineral oil only are still used in some countries.
Duration of immunity/protection
• Compromise between vaccine companies and customers is at least one year protection of the vaccines. Even with one year vaccines a long lasting protection can be given. • Early vaccination in presence of maternal atb there will be a blockage of the atb!!! o Note parvo virus vaccination, even 6 or 8w. Even if hem agglutination test is negative, there will still be protection! The test is not very sensitive. Maternal atb have been recognised 34months after birth. o Follow professional recommendations! Not pharmaceutical! • Note that vaccines registered decades ago may not be relevant anymore due to changed atg structure of the pathogen! This problem emerged 2-3 years ago.
o Note canine parvo virus and canine distemper both have new strains making the old vaccines irrelevant.
Types of Atb
- The atb will save the animal, but one problem: injecting the atb in an animal with already a lot of atb• immune complexes will be formed and deposit in blood vessels, vital organs and cause a hypersensitivity problem and chronic diseases may develop. USE ATB AS EARLY AS POSSIBLE!
- Derzy’s disease: parvo virus of geese
- If a patient doesn’t have atb against a disease and isn’t infected, passive immunisation should be provided in case of dangerous diseases in infected areas (parvo, distemper). Homologous atb will provide protection 2 w - during this time the virus will enter the animal and replicate and stimulate an active immunity.
- Calici and herpes viruses are hard to tell apart - atb are usually provided together in the same bottle
- Ig fraction = purified atb, this is the best one. Not available for every important disease. Use from same species to ensure no contamination. Safe to use.
- Hyper immune serum: also excellent. Animals are vaccinated repeatedly until max level of atb is reached → animals are killed, serum collected and sold. These preparations have to be checked for toxins, infectious organism - they are usually very safe. Accidents has happened: diseases and epidemics have started due to this method, but today very unlikely.
- Immune serum: not always safe to use. Companies selling them cannot always guarantee safe products with known origin - make sure they are properly sterilised (gamma radiation) and always buy form known companies!!
- Mab: not very good. Problems when using them for passive immunisation (but perfect against tumours) → usually mouse atb, they come from a different species, cannot be used repeatedly. They only target a single epitope, bacteria/viruses have hundreds of different epitopes and all pathogens may not be neutralized (mutant viruses!) Pab are found in hyper immune serum or Ig fraction.
- If there are no vaccine or immune serum available, e.g. new diseases or narrow market, convalescent serum can be used from animals that already have survived the infection. This is very risky! Diseases have been spread this way, make sure they are sterilised! If not sure, do not use them!
