Department of Pathobiology, College of Veterinary Medicine, Auburn University, 166 Greene Hall, Auburn, AL 36849, United States.
Department of Pathobiology, College of Veterinary Medicine, Auburn University, 166 Greene Hall, Auburn, AL 36849, United States.
Vet Parasitol. 2020 Jun;282:109134. doi: 10.1016/j.vetpar.2020.109134. Epub 2020 May 20.
Annual antigen testing is a mainstay for diagnosing infection with Dirofiliaria immitis in dogs; yet, it has been documented that some heartworm-infected dogs and cats test false-negative for antigen due to the presence of antigen-antibody complexes. Several studies have reported the use of heat as a reliable means of immune-complex dissociation (ICD) in recent years; however, the data regarding the use of acid as a reliable method of ICD for D. immitis detection are limited. The objective of this study was to compare an acid-based form of ICD to the more established and evaluated method of heat-based ICD in experimentally infected and non-infected dogs. Plasma from class A dogs experimentally infected ∼4 months prior with D. immitis (infected; n = 24) and dogs reared indoors with no history of exposure to mosquitoes (non-infected; n = 75) were evaluated for presence of D. immitis antigen (DiroCHEK® Heartworm antigen test kit). Each sample was divided into three aliquots for testing: [1] Control plasma (no acid- or heat-treatment), [2] acid-treated plasma (trichloroacetic acid (TCA), incubation, centrifugation for 5 min at 16,000 X g, buffer), and [3] heat-treated plasma (104 °C followed by centrifugation at 16,000 X g). Treatments for each aliquot were performed and tested in triplicate; results were determined both visually (color change) and by spectrophotometric analysis (optical density [OD] value). Of the 24 infected dogs, 0/24 tested positive for antigen in the absence of acid- or heat-treatment. Those same plasma samples following processing by either acid- or heat-treatment yielded 18/24 (75.0%) and 19/24 (79.2%) antigen-positive results, respectively. Of the 75 plasma samples from non-infected dogs, neither acid- nor heat-treatment of plasma caused any false-positive color changes or spectrophotometric values. These results indicate that acid as a means of ICD reliably allowed for the detection of D. immitis antigen in infected plasma while not inducing false-positive results in non-infected plasma samples.
年度抗原检测是诊断犬心丝虫感染的主要方法；然而，已有文献记录表明，由于存在抗原-抗体复合物，一些感染心丝虫的犬和猫的抗原检测结果可能呈假阴性。近年来，已有多项研究报告了使用热作为一种可靠的免疫复合物解离（ICD）方法；然而，关于酸作为一种可靠的 D. immitis 检测 ICD 方法的数据有限。本研究的目的是比较基于酸的 ICD 方法与更成熟和经过评估的基于热的 ICD 方法在实验感染和非感染犬中的应用。从 A 级犬（约 4 个月前感染心丝虫）和室内饲养、无蚊虫接触史的犬（非感染）的血浆中检测 D. immitis 抗原（DiroCHEK® 心丝虫抗原检测试剂盒）。每个样本分为三份进行检测：[1] 对照血浆（未进行酸或热处理）、[2] 酸处理血浆（三氯乙酸（TCA），孵育，16000 X g 离心 5 分钟，缓冲液）和[3] 热处理血浆（104°C 后 16000 X g 离心）。每份样本均进行处理并重复检测 3 次；通过目测（颜色变化）和分光光度分析（光密度[OD]值）确定结果。在 24 只感染犬中，0/24 在未进行酸或热处理的情况下检测到抗原呈阳性。经酸或热处理后的相同血浆样本分别产生 18/24（75.0%）和 19/24（79.2%）的抗原阳性结果。在 75 份非感染犬的血浆样本中，无论是酸处理还是热处理均未导致任何假阳性颜色变化或分光光度值。这些结果表明，酸作为 ICD 的一种方法可在感染的血浆中可靠地检测到 D. immitis 抗原，而不会在非感染的血浆样本中引起假阳性结果。
