Veterinary Medicine - August 2007 - (Page Insert2)

Immunology Bulletin the initial series. A second indication is to assess antibody levels in a dog or cat that is considered to be at risk as a nonresponder. Historically, Doberman pinschers and Rottweilers were identified as breeds remaining susceptible to certain infections, especially parvovirus, despite having received appropriate vaccines. However, no vaccine can be expected to provide 100% protection to 100% of vaccinates. Third, in patients with a history of having experienced a known or suspected adverse postvaccinal reaction, performing an antibody titer may provide some assurance that the patient is immune if vaccination is deemed inappropriate. For example, any patient having experienced an acute-onset adverse event (e.g., acute anaphylaxis) should not be subjected to vaccination when feasible. Also, antibody titer determination is indicated in any patient that has recovered from a serious immune-mediated disorder (e.g., immunemediated hemolytic anemia). clones of B-lymphocytes can be sustained for many years. These antibody-producing cells retain the ability to recognize discrete antigenic epitopes and can rapidly produce significant levels of antibody subsequent to re-exposure. In effect, the immunologic memory associated with B-lymphocytes serves to boost the patient’s antibody level from nondetectable levels to protective levels in a matter of hours to days.2 A negative antibody titer for one of the core vaccines only reflects susceptibility to infection if the patient has never experienced infection, has never been vaccinated, or (rarely) failed to respond to previous vaccination. Do all vaccines result in a comparable antibody response? No. Bacterial vaccines (bacterins) typically induce a poorer immune response than viral vaccines. Killed vaccines generally induce a poorer antibody response than modified-live vaccines. Recombinantvectored vaccines induce an immune response similar to that of modified-live vaccines. Using defined portions of DNA isolated from pathogenic viruses, recombinant-vectored vaccines induce the expression of discrete immunogenic proteins in the absence of the infectious pathogen. The immune response is robust and typically includes both humoral immunity (antibody) and cell-mediated immunity. While some recombinantvectored vaccines produce a significant level of antibody, inoculation of patients with discrete genes that encode protein antigens can result in lower antibody titers than those resulting from vaccines containing live, attenuated organisms. Animals vaccinated with a recombinant-vectored vaccine may normally have low to even undetectable titers yet still mount a sustained, protective immune response subsequent to exposure. Does a positive titer correlate with protection from disease? The reference range for antibody titers to specific antigens is established by the individual laboratory that performs the assay. In the case of the canine core antigens CDV and CPV and the feline core antigen FPV, a positive antibody titer is expected to correlate well with protective immunity. For several years, however, veterinarians have used—and continue to use—coronavirus antibody titers to establish FIP diagnoses. In the case of feline coronavirus, an antibody titer cannot prompt an FIP diagnosis nor does it correlate with immunity against developing FIP. Does a negative titer correlate with susceptibility to disease? Not necessarily—using antibody titers to decide that an individual patient requires vaccination can be problematic. While a positive titer to CDV, CPV, and FPV generally correlates with protection, a negative titer to these antigens does not necessarily correlate with susceptibility.1* Immunoglobulin (antibody) is subject to catabolism. Over time, antibody titers may fall to levels below the threshold for detection. However, the B-lymphocyte, which produces the humoral immune response to specific antigens, has immunologic memory. Once activated by antigen, Conclusion Whether a practitioner administers booster vaccines annually or triennially, there are few indications for routinely substituting antibody titers for vaccination. Differences in test methodologies and vaccine types and the ability of the individual patient to mount a protective immune response are significant variables in defining the value of antibody titers in assessing vaccination response. *To view this publication and a reference list online, visit www.advanstarvhc.com/c8. ©2007 Merial Limited Duluth, Ga. All rights reserved VAC07PBAUGIMMBULL http://www.advanstarvhc.com/c8 http://www.advanstarvhc.com/c8

Table of Contents Feed for the Digital Edition of Veterinary Medicine - August 2007

Contents A Veterinary Medicine Interview Veterinary Voices Idea Exchange Diagnosis and Treatment of Solar Dermatitis in Dogs Diagnostic Imaging for Linear Foreign Bodies in Cats Overcoming the Diagnostic and Therapeutic Challenges of Canine Immune-Mediated Thrombocytopenia Ophthalmic drugs: What’s new? CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - August 2007

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