Chapter 29 Types of Vaccines Flashcards
What is active immunization in equine medicine?
The use of antigens formulated as a vaccine to stimulate an immune response.
What is re-immunization in horses?
Natural exposure to the pathogen in the vaccinated animal, resulting in a secondary immune response and enhanced immunity.
What is the ideal characteristic of a vaccine?
It should be safe, induce a potent and long-lasting immune response, not cause clinical signs of the disease, and have minimal or no adverse side effects.
What are the types of vaccines licensed for use in horses?
Attenuated or modified live vaccines (MLV), killed or inactivated vaccines, subunit vaccines, nucleic acid-based vaccines, and chimera vaccines.
What is an attenuated or modified live vaccine (MLV)?
A vaccine composed of viable attenuated organisms that replicate in host cells and stimulate an immune response without causing disease.
What are the principal advantages of MLVs?
They are usually more effective than killed or inactivated vaccines, stimulate both innate and adaptive immune responses, and elicit a greater number of effector mechanisms.
What are the disadvantages of MLVs?
Potential for virulence reversion, opportunistic infections in immunodeficient patients, challenging manufacturing, storage, handling, safety, and phenotypic stability issues.
What is an example of an intranasal MLV for equine influenza virus?
Flu Avert, attenuated by cold adaptation in embryonated eggs.
What is a killed or inactivated vaccine?
A vaccine prepared with microorganisms that are rendered unable to replicate in the host through chemical, heat, or irradiation methods.
What are the advantages of killed or inactivated vaccines?
Easier to manufacture, more stable than live vaccines, cannot revert to virulent form, and safer for immunosuppressed animals.
What is the main disadvantage of killed or inactivated vaccines?
They usually require multiple injections to elicit an immune response and generally induce less adverse reactions.
What is an example of a killed vaccine against West Nile virus?
West Nile Innovator, shown to provide protection against severe disease.
What is a protein or subunit vaccine?
A vaccine that combines a portion of the pathogen, such as purified antigens or inactivated toxins, usually combined with an adjuvant.
What are the advantages of subunit vaccines?
Increased safety without risk of reverting to virulence, reduced antigenic competition, and potential to differentiate vaccinated from infected animals.
What are the disadvantages of subunit vaccines?
Require strong adjuvants, may cause tissue adverse reactions, generally shorter duration of immunity, do not generate mucosal antibodies, and do not replicate intracellularly.
What is an example of a subunit vaccine for Streptococcus equi?
Strepvax II, made with a purified M-protein.
What is a recombinant vectored vaccine?
A vaccine that uses a virus or bacterium vector to express selected genes from the target pathogen coding for protective antigens.
What is the advantage of viral vector vaccines?
Induction of a full range of immune responses, including cytotoxic T lymphocytes (CTLs).
What is the main concern with vectored vaccines?
Pre-existing immunity against the vector or potential immune response against the vector limiting response to the target pathogen.
What is an example of a canary pox-vectored vaccine for equine influenza virus?
Recombitek rFLU, expressing genes for the hemagglutinin of two influenza virus lineages.
What is a DNA-based vaccine?
A vaccine produced by inserting genes coding for protective antigens into bacterial plasmids that enter host cells and direct the synthesis of the vaccine protein.
What are the advantages of DNA vaccines?
Safe, stable, easy and inexpensive to manufacture, elicit strong CTL responses, and have intrinsic adjuvant-like activities.
What are the disadvantages of DNA vaccines?
Decreased DNA uptake with increased body size, potential for chronic inflammation or autoantibody production, limited to protein immunogens, and potential to affect genes responsible for cell growth.
What was the first USDA-approved DNA vaccine for horses?
West Nile-Innovator DNA, for West Nile virus.
What is a chimera vaccine?
A hybrid organism created by combining nucleic acid fragments from two or more different organisms, with at least two fragments containing essential genes necessary for replication.
What is an example of a chimera vaccine for West Nile virus?
PreveNile, a live West Nile virus flavivirus chimera.
What is a marker vaccine (DIVA)?
A vaccine that lacks one or more proteins of the virulent organism, enabling differentiation of vaccinated animals from those infected naturally.
What is an example of a marker vaccine for equine arteritis virus?
A recombinant EAV with a silent nucleotide substitution in the nucleocapsid gene.
What type of immune responses do vaccines induce?
Development of antibodies, long-lived effector cells, and memory cells.
What influences the type of immune response elicited by a vaccine?
The type of vaccine, antigen load, adjuvant or delivery system, and host factors such as genetics, existing immunity, age, immune status, presence of maternal antibodies, and pregnancy status.
What is the role of innate immunity in vaccination?
Sending danger signals to the host through stimulation of pathogen recognition receptors (PRRs) of the innate immune cells.
What are examples of pathogen recognition receptors (PRRs)?
Toll-like receptors (TLRs) and NOD-like receptors (NLRs).
How do live vaccines stimulate the innate immune system?
By containing pathogen-associated molecular patterns (PAMPs) regardless of attenuation.
What is the role of adjuvants in inactivated, subunit, or DNA vaccines?
To promote inflammation at the site of vaccination and attract antigen-presenting cells (APCs) that initiate T and B cell activation.
What is humoral immunity?
An immune response involving the production of antibodies that control extracellular infections.
What happens to antigens after injection of a vaccine?
They reach the regional lymph nodes or spleen, where they are stored on the surface of follicular cells of lymphoid tissues.
What are the two signals required for B cell activation?
Binding of antigens to the B cell receptor (BCR) and subsequent interaction with CD4+ T helper cells.
What are T cell-independent antigens?
Antigens that induce strong B cell activation without the need of T cell interaction.
What is cell-mediated immunity (CMI)?
An immune response involving the activation of T cells to control intracellular pathogens.
What is the advantage of modified-live vaccines in inducing CMI responses?
They are effective at inducing CMI responses by activating CD4+ T helper cells and cytotoxic CD8+ T cells.
What is the role of antigen-presenting cells (APCs) in vaccination?
To migrate to lymphoid tissues from the site of injection, process the vaccine antigen, and present it to CD4+ T cells via MHC class II molecules.
What happens to T cells after activation by APCs?
They undergo clonal expansion and differentiation into effector cells.
What is the role of CD4+ T helper effector cells?
To produce cytokines that activate B cells, CD8+ T cells, and macrophages.
What is the role of CD8+ T cells (CTLs)?
To mediate cytotoxicity of host cells containing intracellular pathogens.
What are the different routes of vaccination?
Intramuscular, subcutaneous, intranasal, oral, sublingual, vaginal, ocular, and aerosol.
Why is the route of administration important in vaccine development?
To reach local APCs and induce immunity similar to a natural challenge.
What are mucosal vaccines?
Vaccines designed to generate mucosal immunity by mimicking natural infection at the site of pathogen entry.
What are examples of mucosal pathogens?
Equine influenza virus (EIV), equine herpesvirus-1 (EHV-1), Streptococcus equi, Rhodococcus equi, Salmonella enterica, and Escherichia coli.
What are the advantages of needle-free vaccine delivery?
Efficiency and effectiveness comparable to parenteral administration with a syringe and needle.
What are adjuvants?
Substances added to vaccines to enhance and modulate protective immunity.
What are the proposed mechanisms of action of adjuvants?
Formation of depot, induction of inflammatory cytokines and chemokines, recruitment of immune cells, enhancement of antigen uptake and presentation, and increased expression of costimulatory molecules and cytokines.
