Polat Ceylan, Karataş Ahmet, Sözen Mustafa, Matur Ferhat, Abacıoğlu Hakan, Öktem Mehmet Ali
Dokuz Eylül University Faculty of Medicine, Department of Medical Microbiology, Izmir, Turkey.
Mikrobiyol Bul. 2016 Apr;50(2):245-55. doi: 10.5578/mb.23161.
Hantaviruses infect humans via inhalation of viral particles in infected rodents' secretions such as saliva, urine and faeces or via direct contact with infected rodents. The rodent species that are known as the carriers of Dobrava (DOBV), Puumala (PUUV), Saaremaa (SAAV), Tula (TULV) and Seoul (SEOV) viruses are found in our country. The presence of specific antibodies against hantaviruses have been demonstrated in rodents collected from Black Sea and Aegean Regions of Turkey in 2004 for the first time. The first hantavirus-related hemorrhagic fever with renal syndrome (HFRS) cases were reported in Black Sea region in 2009. The determination of the hantavirus prevalence in wild life and rodent populations in the field is crucial for the information about hantavirus-related cases and to clarify the state of risk. There is no commercial product optimized for the screening of rodent serum samples in terms of HFRS agents like DOBV and PUUV that are widely seen in Eurasia as well as Turkey. In this study, the antigens belonging to the commercial enzyme-linked immunoassay (ELISA) and immunoblot tests that are produced for the screening of human sera were used for the development of antibody screening tests against hantavirus in rodent sera and were optimized. The most appropriate serum and conjugate dilutions were determined for the optimization of ELISA (Anti-Hantavirus Pool ELISA; Euroimmun, Germany) and immunoblot (Euroline Anti-Hanta Profile 1 strips; Euroimmun, Germany) methods. Optimized ELISA method was used for the screening and optimized immunoblot method was used for the confirmation. A total of 84 wild rodent sera that belonged to Apodemus and Microtus species were evaluated with this procedure and the cut-off value, sensitivity and specificity of optimized ELISA method were determined. For the optimization of ELISA 1/50, 1/100 and 1/200 serum dilutions and 1/10.000, 1/20.000 and 1/40.000 conjugate dilutions were tested. For the optimization of immunoblot, 1/50 and 1/100 serum dilutions and 1/5.000 and 1/10.000 conjugate dilutions were tested. The horseradish peroxidase conjugated goat anti-mouse IgG for ELISA and the alkaline phosphatase conjugated goat anti-mouse IgG for immunoblot were used. We followed the manufacturer's recommendations for the incubation parameters, substrate and the number of washes. 1/50 serum dilution and 1/10.000 conjugate dilution for ELISA and 1/100 serum dilution and 1/5.000 conjugate dilution for immunoblot were determined as optimal concentrations. By using the optimized ELISA, 26.2% (22/84) of rodents were found positive for hantavirus antibodies according the determined cut-off value (OD(450/620): 0.325). By using immunoblot as a confirmatory test, 20 out of 22 ELISA positive samples could be studied because of the insufficient amount of sera and 17 of them was found positive in terms of DOBV antibodies. Of these rodents 11 were Apodemus flavicollis, three were Apodemus agrarius, two were Microtus guentheri and one was Apodemus sylvaticus. When the results of ELISA were compared to immunoblot results, the optimized ELISA's sensitivity and specificity were found as 100% and 95%, respectively. In this study, a method that can be used in the screening of rodent sera was constituted which uses commercial antigens that can be provided easily, gives fast and reliable results. Similar serological methods optimized for different types of rodents are of great importance for the realization of active follow-up and monitoring of the studies in the field.
汉坦病毒通过吸入受感染啮齿动物分泌物(如唾液、尿液和粪便)中的病毒颗粒或通过直接接触受感染啮齿动物来感染人类。在我国发现了被认为是多布拉瓦(DOBV)、普马拉(PUUV)、萨雷马(SAAV)、图拉(TULV)和首尔(SEOV)病毒携带者的啮齿动物物种。2004年首次在从土耳其黑海和爱琴海地区采集的啮齿动物中检测到针对汉坦病毒的特异性抗体。2009年在黑海地区报告了首例与汉坦病毒相关的肾综合征出血热(HFRS)病例。确定野生动物和野外啮齿动物种群中的汉坦病毒流行率对于了解汉坦病毒相关病例的信息以及阐明风险状况至关重要。目前没有针对在欧亚大陆以及土耳其广泛存在的诸如DOBV和PUUV等HFRS病原体筛查啮齿动物血清样本进行优化的商业产品。在本研究中,将用于人类血清筛查的商业酶联免疫吸附测定(ELISA)和免疫印迹试验的抗原用于开发针对啮齿动物血清中汉坦病毒的抗体筛查试验并进行了优化。为优化ELISA(抗汉坦病毒混合ELISA;德国欧蒙公司)和免疫印迹(欧蒙抗汉坦病毒1型条带;德国欧蒙公司)方法确定了最合适的血清和缀合物稀释度。使用优化后的ELISA方法进行筛查,使用优化后的免疫印迹方法进行确认。用该方法对总共84份属于姬鼠属和田鼠属的野生啮齿动物血清进行了评估,并确定了优化后ELISA方法的临界值、敏感性和特异性。为优化ELISA,测试了1/50、1/100和1/200的血清稀释度以及1/10000、1/20000和1/40000的缀合物稀释度。为优化免疫印迹,测试了1/50和1/100的血清稀释度以及1/5000和1/10000的缀合物稀释度。ELISA使用辣根过氧化物酶标记的山羊抗小鼠IgG,免疫印迹使用碱性磷酸酶标记的山羊抗小鼠IgG。我们遵循了制造商关于孵育参数、底物和洗涤次数的建议。确定ELISA的最佳浓度为1/50血清稀释度和1/10000缀合物稀释度,免疫印迹的最佳浓度为1/100血清稀释度和1/5000缀合物稀释度。通过使用优化后的ELISA,根据确定的临界值(OD(450/620):0.325),发现26.2%(22/84)的啮齿动物汉坦病毒抗体呈阳性。由于血清量不足,在22份ELISA阳性样本中,有20份可以用免疫印迹作为确证试验进行研究,其中17份在DOBV抗体方面呈阳性。这些啮齿动物中,11只为黄颈姬鼠,3只为黑线姬鼠,2只为 Günther 田鼠,1只为林姬鼠。将ELISA结果与免疫印迹结果进行比较时,优化后ELISA的敏感性和特异性分别为100%和95%。在本研究中,构建了一种可用于筛查啮齿动物血清的方法,该方法使用易于获得的商业抗原,结果快速且可靠。针对不同类型啮齿动物优化的类似血清学方法对于在该领域实现积极的随访和监测研究非常重要。