Retrospective Study
Copyright ©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Virol. Dec 25, 2024; 13(4): 95986
Published online Dec 25, 2024. doi: 10.5501/wjv.v13.i4.95986
Diagnosis of West Nile virus infections: Evaluation of different laboratory methods
Tatjana Vilibic-Cavlek, Maja Bogdanic, Vladimir Savic, Zeljka Hruskar, Ljubo Barbic, Vladimir Stevanovic, Ljiljana Antolasic, Ljiljana Milasincic, Dario Sabadi, Gorana Miletic, Ivona Coric, Anna Mrzljak, Eddy Listes, Giovanni Savini
Tatjana Vilibic-Cavlek, Maja Bogdanic, Zeljka Hruskar, Ljiljana Antolasic, Ljiljana Milasincic, Department of Virology, Croatian Institute of Public Health, Zagreb 10000, Croatia
Tatjana Vilibic-Cavlek, Maja Bogdanic, Anna Mrzljak, School of Medicine, University of Zagreb, Zagreb 10000, Croatia
Vladimir Savic, Poultry Center, Croatian Veterinary Institute, Zagreb 10000, Croatia
Ljubo Barbic, Vladimir Stevanovic, Gorana Miletic, Ivona Coric, Department of Microbiology and Infectious Diseases with Clinic, Faculty of Veterinary Medicine University of Zagreb, Zagreb 10000, Croatia
Dario Sabadi, Department of Infectious Diseases, Clinical Hospital Center Osijek, Osijek 31000, Croatia
Dario Sabadi, Medical Faculty, Josip Juraj Strossmayer University of Osijek, Osijek 31000, Croatia
Anna Mrzljak, Department of Gastroenterology and Hepatology, University Hospital Center Zagreb, Zagreb 10000, Croatia
Eddy Listes, Croatian Veterinary Institute, Veterinary Institute Split, Split 21000, Croatia
Giovanni Savini, OIE Reference Center for West Nile Disease, Istituto Zooprofilattico Sperimentale, G. Caporale, Teramo 64100, Italy
Author contributions: Vilibic-Cavlek T and Bogdanic M conceptualized and designed the research; Vilibic-Cavlek T, Bogdanic M and Sabadi D acquired clinical data; Antolasic Lj and Milasincic L and Hruskar Z performed laboratory analysis; Savic V, Barbic Lj, Stevanovic V, Miletic G, Coric I, Mrzljak A, and Listes E performed data collection, and analysis of the results; Vilibic-Cavlek T, Bogdanic M and Savic V wrote the manuscript; Savini G critically revised the manuscript; Vilibic-Cavlek T and Savic V obtained the funds for this research; All authors have read and approved the final version of the manuscript.
Supported by the Croatian Science Foundation, No. IP-2016-06-7456: CRONEUROARBO; and the European Union NextGenerationEU project supported by the Ministry of Science and Education of the Republic of Croatia, No. NPOO 1 of Croatian Veterinary Institute: FLAVIR.
Institutional review board statement: The study was approved by the Ethics Committee of the Croatian Institute of Public Health (protocol code 80-1092/1-16, approved on 3 June 2016).
Informed consent statement: Informed consent was obtained from all participants included in the study.
Conflict-of-interest statement: All authors reported no conflicts of interest.
Data sharing statement: Technical appendix, statistical code, and dataset available from the corresponding author at tatjana.vilibic-cavlek@hzjz.hr. Consent for data sharing was not obtained but the presented data are anonymized and the risk of identification is low. No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Tatjana Vilibic-Cavlek, MD, PhD, Associate Professor, Department of Virology, Croatian Institute of Public Health, Zagreb 10000, Zagreb 10000, Croatia. tatjana.vilibic-cavlek@hzjz.hr
Received: April 23, 2024
Revised: August 14, 2024
Accepted: August 27, 2024
Published online: December 25, 2024
Processing time: 177 Days and 6.9 Hours
Abstract
BACKGROUND

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.

AIM

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.

METHODS

The study included patients with confirmed WNV neuroinvasive infection (n = 62), asymptomatic WNV seropositive individuals (n = 22), and individuals with false-positive WNV IgM antibodies (n = 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.

RESULTS

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% (P = 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.

CONCLUSION

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.

Keywords: West Nile virus; Reverse transcription-polymerase chain reaction; Serology; IgG avidity; Cross-reactivity

Core Tip: We analyzed different diagnostic methods in patients with West Nile virus (WNV) neuroinvasive disease and asymptomatic seropositive individuals. The WNV RNA detection rate was significantly higher in the urine/serum than in cerebrospinal fluid (CSF). The RT-PCR cycle threshold (Ct) values were significantly lower in urine than in CSF and serum samples. The frequency of WNV RNA and IgM/IgG antibody detection rates depends on the sampling time and type of clinical samples (CSF or serum). The correlation between ELISA and IgG avidity was negative for IgM and positive for IgG. No correlation was observed between ELISA IgG and virus neutralization test.