Značaj određivanja aviditeta protutijela IgG u dijagnostici infekcije uzrokovane virusom Zapadnog Nila

master's thesis

• Title (english): Value of IgG avidity determination in diagnosis of West Nile virus infection
• Author: Branimir Krištofić
• Mentor: Tatjana Vilibić Čavlek (mentor)
• Committee member: Sunčanica Ljubin Sternak (predsjednik povjerenstva)
• Committee member: Goran Tešović (član povjerenstva)
• Committee member: Godrana Mlinarić-Galinović (član povjerenstva)
• Granter: University of Zagreb; School of Medicine; (Department of Medical Microbiology and Parasitology); Zagreb
• Defense date and country: 2015-07-15, Croatia
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Public Health and Health Care; Epidemiology
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Clinical Medical Sciences; Infectology
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Clinical Medical Sciences; Medical Microbiology

Abstract

Dijagnoza infekcije virusom Zapadnog Nila (VZN) najčešće temelji na serološkim metodama. IgM protutijela uobičajeno se smatraju biljegom akutne infekcije, međutim dokazano je da IgM protutijela u nekih bolesnikaa s VZN infekcijom mogu perzistirati i do 500 dana. Određivanje IgG aviditeta koristi se za razlikovanje akutne/nedavne od prošle infekcije u serološkoj dijagnostici raznih virusa te bi se moglo koristiti i u dijagnostici VZN infekcije. Kako bi utvrdili značaj aviditeta IgG protutijela u dijagnostici VZN infekcije, analizirali smo ukupno 42 IgM i/ili IgG pozitivna uzorka seruma. Uzorci su dobiveni od 27 bolesnika u kojih je potvrđena VZN neuroinvazivna bolest i 15 asimptomatskih osoba. VZN IgM/IgG protutijela te aviditet IgG protutijela određeni su pomoću komercijalnog imunoenzimnog testa. IgM protutijela detektirana su u 35 (83,3%) uzoraka seruma. Akutna/nedavna VZN infekcija dokazana je na temelju niske/granične vrijednosti indeksa aviditeta (AI) u 32 (91,4%) IgM pozitivna uzorka. U 3 IgM pozitivna uzorka (8,6%), dokazan je je visok AI što je ukazivalo na perzistentna VZN IgM protutijela. Akutna infekcija je potvrđena pomoću aviditeta IgG protutijela u 27/27 (100%) bolesnika s neuroinvazivnom VZN infekcijom te u 5/15 (33,3%) asimptomatskih ispitanika. U svih su bila detektabilna IgM protutijela. U 3 (20,0%) IgM pozitivna kao i 7 (46,7%) IgM negativnih asimptomatskih ispitanika, detektirana su IgG protutijela visokog AI, što je upućivalo na raniju VZN infekciju. Dokazana je značajna korelacija između vrijednosti IgM protutijela i AI (više vrijednosti IgM protutijela bile su povezane sa značajno nižim AI; p<0,001). Niske vrijednosti AI ukazivale su na VZN infekciju nastalu unutar 32 dana. Rezultati ovog istraživanja pokazali su da je određivanjem IgG aviditeta moguće razlikovati akutnu/nedavnu od ranije VZN infekcije u osoba sa simptomatskom i asimptomatskom VZN infekcijom. Aviditet IgG protutijela predstavlja značajan serološki biljeg za potvrdu primarne VZN infekcije, osobito u slučajevima atipičnog serološkog odgovora (graničnih ili perzistentnih IgM protutijela).

Abstract (english)

Diagnosis of WNV infection is usually based on serologic methods. Classically, IgM is considered as a marker of acute infection. However, IgM antibodies to WNV have been shown to persist for up to 500 days in some patients. Avidity testing for the differentiation between acute/recent and past antibody response has been used in the serologic diagnosis of several viruses and could be used in diagnosis of WNV infection. To evaluate the value of IgG avidity determination in diagnosis of WNV infection we analyzed a total of 42 WNV IgM and/or IgG positive serum samples. Samples were obtained from 27 patients with confirmed WNV neuroinvasive disease and 15 asymptomatic cases. WNV IgM/IgG and IgG avidity testing were performed using a commercial enzyme-linked immunosorbant assay. IgM antibodies were detected in 35 (83.3%) samples. Acute/recent WNV infection was documented by low/borderline avidity index (AI) in 32 (91.4%) IgM positive samples. In 3 IgM positive samples (8.6%), high AI was detected indicating persisting IgM antibodies from previous infection. According to clinical symptoms, acute infection was confirmed using IgG avidity in 27/27 (100%) patients with neuroinvasive WNV infection and 5/15 (33.3%) asymptomatic subjects. All of them had detectable IgM antibodies. In 3 (20.0%) IgM positive as well as 7 (46.7%) IgM negative asymptomatic subjects, IgG antibodies of high AI were detected indicating past WNV infection. There was a significant correlation between value of IgM antibodies and AI (higher IgM value was associated with lower AI; p<0.001). Low AI values were indicative of WNV infection in the period of less than 32 days.
Results of this study indicate that IgG avidity could differentiate acute/recent from past WNV infection in both symptomatic and asymptomatic persons. IgG avidity represents a valuable serologic marker for confirmation of primary WNV infection, especially in cases of atypical serologic response (borderline or persisting IgM antibodies).

• Keywords: virus Zapadnog Nila; serologija; IgG aviditet
• Keywords (english): West Nile virus; serology; IgG avidity
• Language: croatian
• URN:NBN: urn:nbn:hr:105:592663
• Study programme: Title: Medicine; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: doktor/doktorica medicine (doktor/doktorica medicine)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2016-11-23 13:05:55