Molecular Virology Unit, Microbiology and Virology Department, IRCCS Policlinico San Matteo, Via Taramelli 5, 27100 Pavia, Italy.
SIMT, Centro Lavorazione e Validazione, Ospedale di Cremona, 26100 Cremona, Italy.
Viruses. 2020 Jan 29;12(2):157. doi: 10.3390/v12020157.
West Nile virus (WNV) and Usutu virus (USUV) are two related arboviruses (genus , family ), with birds as a reservoir and mosquitoes as transmitting vectors. In recent years, WNV epidemiology changed in many European countries with increased frequency of outbreaks posing the issue of virus transmission risks by blood transfusion. USUV emerged for the first time in birds of the Tuscany region (Italy) in 1996 and in 2001 in Austria. While WNV is responsible for both mild and neuroinvasive diseases, USUV infection is usually asymptomatic and neuroinvasive symptoms are rare. Since WNV and USUV co-circulate, the surveillance of WNV allows also the detection of USUV. Due to the great similarity in amino-acid sequence of major surface proteins of the two viruses, a high cross-reactivity can lead to misinterpretation of serological results. Here, we report the results obtained from 54 asymptomatic blood donors during a three-year follow-up showing an unexpected high positivity (46.3%) for USUV. The major obstacle encountered in the differential diagnosis between these two viruses was the high cross-reactivity found in neutralizing antibodies (NT Abs) and, in some cases, a long follow-up was mandatory for a correct diagnosis. Moreover, two new ELISpot assays were developed for a more rapid and specific differential diagnosis, especially in those cases in which NT Abs were not determinant. Using a combination of Enzyme-linked immunospot (ELISpot), molecular, and serological tests, we could identify 25 true positive WNV and 25 true positive USUV blood donors. Our data highlight the importance of raising awareness for increasing USUV infections in endemic countries involved in blood transfusion and organ donation.
西尼罗河病毒（WNV）和乌苏图病毒（USUV）是两种相关的虫媒病毒（属，科），鸟类是其储存宿主，蚊子是传播媒介。近年来，WNV 在许多欧洲国家的流行情况发生了变化，暴发频率增加，这引发了通过输血传播病毒的风险问题。USUV 于 1996 年首次在托斯卡纳地区（意大利）的鸟类中出现，2001 年在奥地利出现。虽然 WNV 可引起轻度和神经侵袭性疾病，但 USUV 感染通常无症状，且神经侵袭性症状很少见。由于 WNV 和 USUV 共同流行，WNV 的监测也可检测到 USUV。由于两种病毒主要表面蛋白的氨基酸序列非常相似，高交叉反应性可能导致血清学结果的错误解读。在此，我们报告了在为期三年的随访中，54 名无症状献血者的结果，显示出出人意料的高 USUV 阳性率（46.3%）。在这两种病毒的鉴别诊断中遇到的主要障碍是中和抗体（NT Abs）中发现的高交叉反应性，在某些情况下，需要进行长期随访才能做出正确诊断。此外，还开发了两种新的 ELISpot 检测方法，用于更快速和特异性的鉴别诊断，尤其是在 NT Abs 不确定的情况下。使用酶联免疫斑点（ELISpot）、分子和血清学检测相结合的方法，我们可以鉴定出 25 名真正的 WNV 阳性和 25 名真正的 USUV 阳性献血者。我们的数据强调了提高对在涉及输血和器官捐赠的虫媒病毒流行国家中不断增加的 USUV 感染的认识的重要性。
