Vilibic-Cavlek Tatjana, Kristofic Branimir, Savic Vladimir, Kolaric Branko, Barbic Ljubo, Tabain Irena, Peric Ljiljana, Sabadi Dario, Miklausic Bozana, Potocnik-Hunjadi Tanja, Zember Sanja, Stevanovic Vladimir, Listes Eddy, Savini Giovanni
Department of Virology, Croatian Institute of Public Health, Zagreb, Croatia.
School of Medicine University of Zagreb, Zagreb, Croatia.
Rev Soc Bras Med Trop. 2018 Sep-Oct;51(5):591-595. doi: 10.1590/0037-8682-0482-2017.
West Nile virus (WNV) immunoglobulin M (IgM) antibodies have been shown to persist for up to 500 days in certain patients. To evaluate the usefulness of immunoglobulin G (IgG) avidity assessment in the diagnosis of WNV infection, we analyzed 54 WNV IgM- and/or IgG-positive serum samples from 39 patients with neuroinvasive disease and 15 asymptomatic cases tested during a seroprevalence investigation.
Serological tests (WNV IgM/IgG antibody detection, IgG avidity) were performed using commercially available enzyme-linked immunosorbent assays.
WNV IgM antibodies were detected in 47 (87%) samples. Acute/recent WNV infection was confirmed based on low/borderline avidity index (AI) in 44 IgM-positive samples (93.6%). In three IgM-positive samples (6.4%), high IgG AIs were detected, thus indicating persisting IgM antibodies from previous infections. All IgM-negative samples showed high AIs. Patients with WNV neuroinvasive disease tested within 30 days showed low AIs. In six patients tested 34-50 days after disease onset, AI was borderline (42%-60%), suggesting earlier WNV IgG maturation. Samples with the highest IgM values were associated with the lowest AIs (Spearman's rho coefficient -0.767, p < 0.001).
Our results indicate that IgG avidity differentiates current/recent WNV infection from persistent IgM seropositivity from the previous WNV transmission season both in patients with WNV neuroinvasive disease and in asymptomatic persons. A strong negative correlation between IgM antibody levels and AI indicates that in cases with very high IgM levels, determination of IgG avidity may not be necessary. As many patients showed rapid avidity maturation, low IgG avidity is indicative of WNV infection within the previous month.
已证明西尼罗河病毒（WNV）免疫球蛋白M（IgM）抗体在某些患者体内可持续长达500天。为评估免疫球蛋白G（IgG）亲和力评估在WNV感染诊断中的作用，我们分析了在血清流行率调查期间检测的39例神经侵袭性疾病患者和15例无症状病例的54份WNV IgM和/或IgG阳性血清样本。
使用市售酶联免疫吸附试验进行血清学检测（WNV IgM/IgG抗体检测、IgG亲和力）。
47份（87%）样本中检测到WNV IgM抗体。根据44份IgM阳性样本（93.6%）的低/临界亲和力指数（AI）确诊急性/近期WNV感染。在3份IgM阳性样本（6.4%）中检测到高IgG AI，表明存在既往感染持续的IgM抗体。所有IgM阴性样本均显示高AI。发病30天内检测的WNV神经侵袭性疾病患者显示低AI。在发病后34 - 50天检测的6例患者中，AI处于临界值（42% - 60%），提示WNV IgG成熟较早。IgM值最高的样本与最低的AI相关（斯皮尔曼等级相关系数-0.767，p < 0.001）。
我们的结果表明，IgG亲和力可区分WNV神经侵袭性疾病患者和无症状者当前/近期的WNV感染与既往WNV传播季节持续的IgM血清阳性。IgM抗体水平与AI之间存在强烈的负相关，表明在IgM水平非常高的情况下，可能无需测定IgG亲和力。由于许多患者显示出快速的亲和力成熟，低IgG亲和力表明在前一个月内感染了WNV。
