Journal of Feline Medicine and Surgery (2013) 15 , Supplementary File FACT SHEET

THE IMMUNE RESPONSE TO A brief review

This Fact Sheet accompanies the 2013 AAFP Feline Vaccination Advisory Panel Report published in the Journal of Feline Medicine and Surgery (2013), Volume 15, pp 785 –808.

AAFP FELINE VACCINATION ADVISORY PANEL Margie A Scherk The ’s DVM Dip ABVP The 2013 Report of the Feline Vaccination (Feline Practice) Advisory Panel of the American Association of Advisory Panel Chair* The cat’s immune system prevents or limits Feline Practitioners (AAFP) provides practical Richard B Ford infectious diseases with three layers of defense: recommendations to help clinicians select DVM MS Dip ACVIM < DACVPM (Hon) The physical barrier of the skin and appropriate vaccination schedules for their mucosal epithelium; feline patients based on risk assessment. Rosalind M Gaskell < BVSc PhD MRCVS The innate immune system; The recommendations rely on published data < The adaptive immune system. as much as possible, as well as consensus of a Katrin Hartmann multidisciplinary panel of experts in immunology, Dr Med Vet Dr Med Vet Habil Physical barrier Dip ECVIM-CA infectious disease, internal medicine and clinical practice. The Report is endorsed by the Kate F Hurley The physical barrier provided by the skin and DVM MPVM mucosal epithelium prevents invasion via International Society of Feline Medicine (ISFM). many mechanisms, including cilia that flush Michael R Lappin DVM PhD Dip ACVIM away and proteins that degrade Julie K Levy invading organisms. Once the barrier is DVM PhD Dip ACVIM breached, all aspects of immunity are highly provide innate immune activation Susan E Little specific and coordinated. via the vector or modified-live DVM Dip ABVP (Feline Practice) itself as they are recognized as foreign by the Innate immune system Shila K Nordone innate immune system. MS PhD The innate immune system includes Adaptive immune system Andrew H Sparkes neutrophils, macrophages, dendritic cells and BVetMed PhD DipECVIM natural killer cells that prevent many pathogens Acquired immunity is characterized by MRCVS from infecting and/or causing disease in specificity and memory. It is *Corresponding author: animals. These cells respond to pathogens by stimulated when an animal is vaccinated or Email: [email protected] recognizing molecules that are broadly shared exposed to an infectious agent or . 1 by pathogens but are distinct from self-tissue. The acquired immune system consists of The innate immune system is the first line of humoral immunity and cell-mediated immunological defense and is the arm of the immunity (CMI). In humoral immunity, immune response that is activated by adjuvants differentiated B lymphocytes, called plasma in vaccines. Activation of this innate system is cells, produce the primary feline immuno - 2 3 required for effective vaccination. Some globulin classes IgG, IgM, IgA and IgE. commonly used adjuvants include bacterial CMI comprises T lymphocytes, including products added to vaccine preparations, as well T helper, T regulatory and T cytotoxic as modified-live and vaccine vectors cells, which all contribute to vaccinal 4 such as . So-called ‘adjuvant-free’ immunity.

© ISFM and AAFP 2013 Reprints and permission: sagepub.co.uk/journalsPermissions.nav FACT SHEET / Immune response to vaccination

Immunocompromise and When an animal is infected or vaccinated, immunosenescence B and T lymphocytes specific for a multitude of antigenic epitopes on viruses, 12,14 –18 and/or parasites are stimulated to proliferate While only limited feline-specific data exist, and differentiate into effector and memory we know collectively from other that, cells. Effector cells are short lived (days to with age, the immune system undergoes weeks), whereas memory B and T cells pro - profound changes resulting in an overall decline vide long term immunity and are able to dif - in immune function known as immuno - ferentiate into effector cells during subsequent senescence. There is no single cell type or organ challenge with the same pathogen. Memory responsible for immunosenescence. Rather, in a cells are not maintained by constant exposure system reliant on absolute coordination of all to their specific pathogen but, rather, by non- parts to function effectively, there is a loss of specific activation (eg, commensal bacteria or multiple levels of control, including the barrier, environmental irritants) that induces low- innate and adaptive arms of the immune system. level cellular proliferation. Memory B and T Age-related declines in immune function directly cells cooperate to provide protection from translate into increased susceptibility of aged infection at a later time in the life of the vacci - patients to infection, autoimmune disease and nated animal. Immunologic memory is the . Memory responses to vaccine in 5 basis for protective vaccines. CMI and aged patients, while less robust than in young humoral immunity are stimulated within adults, appear to be sufficient enough to maintain minutes to hours when a vaccinated animal is protective levels of antigen-specific antibody 19 exposed to an infectious agent (anamnestic in the majority of cases. If a cat is routinely response), whereas it often takes days to immunized through its adult years then weeks (primary response) for immunity to be maintaining vaccination protocols at stimulated in a non-vaccinated, immunologi - recommended intervals is warranted in senior 4,6 –9 cally naive cat. . Intervals do not need to be decreased Whether cell-mediated or humoral respons - because titers are likely to be maintained between es are most important for mediation of protec - boosts; however, intervals should not be 17,18,20 tion varies with the specific pathogen, the increased either due to immunoscenes cence. route of infection, and the colonization and One of our greatest gaps in knowledge is replication of the infectious agent. For what immunization schedule to recommend for instance, many pathogens of the respiratory aged cats with an unknown vaccination history 16 or gastrointestinal tract require generation of or that are receiving their first doses. At the mucosal cellular and/or humoral immune current time, two to three immunizations given responses, with IgA being the most effective at 3 –4 week intervals are likely to establish suf - and abundant antibody class on the mucosal ficient protection against the core vaccine 10 surfaces of the cat. As such, mucosal immu - antigens. When other vaccines are deemed nec - nization is a highly effective means of induc - essary, a parallel situation could be drawn from ing long-lasting antigen-specific IgA and human geriatric patients immunized yearly 11 21,22 mucosal CMI. Systemic infections are con - against new strains of influenza virus. These trolled or prevented primarily by IgG and cir - studies suggest that while immunization with 2 culating effector T cells. new antigens is not as effective in the elderly as If vaccination prevents subsequent infec - it is in healthy adults, it is beneficial at reducing tion, the animal is considered to have steriliz - the deleterious effects of infectious disease. ing immunity, the ultimate form of immunity since disease cannot develop. This form of Immunocompromised patients immunity may occur after immunization Cats presumed to have an impaired immune response are not uncommon. In against feline panleukopenia virus and 12,13 particular, cats infected with feline immunodeficiency virus or virus. When vaccination does not prevent or those receiving ongoing immunosuppressive therapies, are at an increased risk infection (eg, feline herpesvirus-1 and feline 6 of infection. Although data is limited, immuno suppression with retroviral infections calicivirus), systemic and local CMI, along has been associated with development of clinical disease following the use of live with humoral immunity including local IgA vaccines. In the face of immunosuppression, killed vaccines may theoretically antibodies, provide protective, but non- be preferable. Because immune responses can be hampered, vaccination should sterilizing immunity that only reduces the 4 be updated before immunosuppressive therapies are started wherever possible. severity of disease.

Journal of Feline Medicine and Surgery (2013) 15 , Supplementary File FACT SHEET / Immune response to vaccination

References

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DISEASE INFORMATION FACT SHEETS SUPPLEMENTARY FILES < Feline herpesvirus 1 Fact Sheets accompanying the < Feline calicivirus 2013 AAFP Feline Vaccination Advisory < Feline panleukopenia Panel Report are available, Rabies together with the Owner Guide < included in Appendix 2, at < Feline leukemia virus http://jfms.com < Feline immunodeficiency virus DOI: 10.1177/1098612X13495235 < Feline infectious peritonitis < Chlamydophila felis < Bordetella bronchiseptica

GENERAL INFORMATION FACT SHEET PET OWNER GUIDE < The immune response to (APPENDIX 2, pp 807 –808) vaccination: a brief review < Vaccinations for Your Cat

Journal of Feline Medicine and Surgery (2013) 15 , Supplementary File