Vilibic-Cavlek Tatjana, Bogdanic Maja, Savic Vladimir, Hruskar Zeljka, Barbic Ljubo, Stevanovic Vladimir, Antolasic Ljiljana, Milasincic Ljiljana, Sabadi Dario, Miletic Gorana, Coric Ivona, Mrzljak Anna, Listes Eddy, Savini Giovanni
Department of Virology, Croatian Institute of Public Health, Zagreb 10000, Croatia.
School of Medicine, University of Zagreb, Zagreb 10000, Croatia.
World J Virol. 2024 Dec 25;13(4):95986. doi: 10.5501/wjv.v13.i4.95986.
The diagnosis of West Nile virus (WNV) is challenging due to short-term and low-level viremia, flavivirus cross-reactivity, and long immunoglobulin M (IgM) persistence.
To evaluate different methods for WNV detection [reverse transcription-polymerase chain reaction (RT-PCR), IgM/IgG antibodies, IgG avidity] in serum, cerebrospinal fluid (CSF), and urine samples of patients with confirmed WNV infection.
The study included patients with confirmed WNV neuroinvasive infection ( = 62), asymptomatic WNV seropositive individuals ( = 22), and individuals with false-positive WNV IgM antibodies ( = 30). WNV RNA was detected using RT-PCR. A commercial ELISA was used to detect WNV IgM/IgG antibodies with confirmation of cross-reactive samples using a virus neutralization test (VNT). IgG-positive samples were tested for IgG avidity.
The WNV-RNA detection rates were significantly higher in the urine (54.5%)/serum (46.4%) than in CSF (32.2%). According to the sampling time, the WNV-RNA detection rates in urine collected within 7 days/8-14/≥ 15 days were 29.4/66.6/62.5% ( = 0.042). However, these differences were not observed in the CSF. The median RT-PCR cycle threshold values were significantly lower in urine (32.5, IQR = 28-34) than in CSF (34.5, IQR = 33-36). The frequency of positive WNV IgM and IgG significantly differed according to the sampling time in serum but not in CSF. Positive IgM/IgG antibodies were detected in 84.3/9.3% of serum samples collected within 7 days, 100/71.1% of samples collected 8-14, and 100% samples collected after ≥ 15 days. Recent WNV infection was confirmed by low/borderline avidity index (AI) in 13.6% of asymptomatic individuals. A correlation between ELISA and AI was strong negative for IgM and strong positive for IgG. No significant correlation between ELISA IgG and VNT was found.
The frequency of WNV RNA and antibody detection depends on the sampling time and type of clinical samples. IgG avidity could differentiate recent WNV infections from long-persisting IgM antibodies.
由于西尼罗河病毒（WNV）存在短期和低水平病毒血症、黄病毒交叉反应以及免疫球蛋白M（IgM）持续时间长等情况，其诊断具有挑战性。
评估在确诊WNV感染患者的血清、脑脊液（CSF）和尿液样本中检测WNV的不同方法[逆转录-聚合酶链反应（RT-PCR）、IgM/IgG抗体、IgG亲和力]。
该研究纳入了确诊WNV神经侵袭性感染的患者（n = 62）、无症状WNV血清阳性个体（n = 22）以及WNV IgM抗体假阳性个体（n = 30）。使用RT-PCR检测WNV RNA。采用商业酶联免疫吸附测定（ELISA）检测WNV IgM/IgG抗体，并通过病毒中和试验（VNT）对交叉反应样本进行确认。对IgG阳性样本检测IgG亲和力。
尿液（54.5%）/血清（46.4%）中WNV-RNA的检出率显著高于脑脊液（32.2%）。根据采样时间，在7天内/8 - 14天/≥15天采集的尿液中WNV-RNA检出率分别为29.4%/66.6%/62.5%（P = 0.042）。然而，在脑脊液中未观察到这些差异。尿液中RT-PCR的中位循环阈值（32.5，四分位间距 = 28 - 34）显著低于脑脊液（34.5，四分位间距 = 33 - 36）。血清中WNV IgM和IgG阳性频率根据采样时间有显著差异，但在脑脊液中无差异。在7天内采集的血清样本中，84.3%/9.3%检测到阳性IgM/IgG抗体，8 - 14天采集的样本中为100%/71.1%，≥15天采集的样本中为100%。13.6%的无症状个体通过低/临界亲和力指数（AI）确诊为近期WNV感染。ELISA与AI之间，IgM呈强负相关，IgG呈强正相关。未发现ELISA IgG与VNT之间存在显著相关性。
WNV RNA和抗体的检测频率取决于采样时间和临床样本类型。IgG亲和力可区分近期WNV感染与持续存在的IgM抗体。
